IMPACT OF SEEDING RATE AND FERTILIZER APPLICATION, PLACEMENT, AND TIMING ON SOYBEAN AND CORN PLANT GROWTH AND GRAIN YIELD By Taylor Scott Purucker A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of Crop and Soil Sciences – Master of Science 2019 IMPACT OF SEEDING RATE AND FERTILIZER APPLICATION, PLACEMENT, AND TIMING ON SOYBEAN AND CORN PLANT GROWTH AND GRAIN YIELD ABSTRACT By Taylor Scott Purucker Greater soybean (Glycine max L. Merr.) dry matter found in current soybean varieties and reduced seeding rates can impact nutrient uptake and grain yield potential and may influence grain yield response to fertilizer applications. Field experiments were initiated in Richville and Lansing, MI to determine the effects of seeding rate and fertilizer applications on plant growth, nutrient accumulation, grain yield, and profit. Increasing seeding rate from 123,500 to 222,400 seeds ha-1 increased grain yield 304 kg ha-1 but no statistical differences were observed above 222,400 seeds ha-1. Subsurface MESZ applications increased grain yield 241 to 261 kg ha-1 but did not interact with seeding rate. The influence of soil nutrient concentrations and environmental conditions on grain yield may take precedence over reduced interplant competition in decreased seeding rates. Weather volatility and closer synchronization of nitrogen (N) application with peak corn (Zea mays) uptake may provide opportunity for enhanced N use efficiency and grain yield with sidedress N placement closer to the plant. Field studies were initiated in Richville and Lansing, MI to assess the effects of multiple N timing and sidedress (SD) placement strategies on corn growth, grain yield, agronomy efficiency (AE) of applied N, and profit. Grain yield was not influenced by N strategy during dry soil conditions but AE increased with V4-6 N applications and coulter-inject SD N placement. Corn N response may be influenced by environmental conditions therefore weather forecasts and environmental trends should be considered when deliberating N timing and SD placement strategies. Copyright by TAYLOR SCOTT PURUCKER 2019 Dedicated to my family, friends and colleagues whom have offered their love, wisdom and support along the way. iv ACKNOWLEDGEMENTS Being a part of the soil fertility and nutrient management program at Michigan State University has been an invaluable experience. First and foremost, I would like to thank my advisor Dr. Kurt Steinke for this opportunity. I will always reflect on my time spent in your program and appreciate your guidance, support, and encouragement. I will continue to draw on my knowledge-base in future endeavors and forever be grateful for your contributions. I would also like to thank my committee members Dr. Martin Chilvers and Dr. Zachary Hayden for their advice and suggestions with my projects. Thank you to the soil fertility research technician Andrew Chomas for your mentoring, guidance, and assistance with field work. From one brother of Alpha Gamma Rho to another, I thank you for making me a better man, and through me a better and broader agriculture. Thank you to the MSU Agronomy Farm staff Mike Particka and Tom Galecka, and to Paul Horny and Dennis Fleischmann of the MSU Saginaw Valley Research and Extension Center for your assistance and coordination of field projects. Thank you to Bill Widdicombe and Lori Williams for your assistance with corn harvest. I would also like to thank Evan Williams and Joe Paling for their wisdom and guidance in data collection. Thank you to fellow graduate students Dan Quinn, Dr. Jeff Rutan, and Seth Purucker for field assistance and friendships. I would like to thank the Purucker, Smuda, and Rizzolo families for their unparalleled encouragement and support. I will truly forever be grateful for everything you have done for me. Last, but certainly not least, I would like to thank Kellie Rizzolo for your continued love and support. I cannot put into words the courage and significance you have given me. Thank you for your patience and understanding in everything I do. v TABLE OF CONTENTS LIST OF TABLES ....................................................................................................................... viii CHAPTER 1 LITERATURE REVIEW ................................................................................................................1 Soybean ................................................................................................................................1 Global and Domestic Soybean Production ..............................................................1 Seeding Rate and Plant Density ...............................................................................2 Nutrient Uptake, Partitioning, and Remobilization .................................................4 Nitrogen: ......................................................................................................4 Phosphorus: ..................................................................................................5 Potassium: ....................................................................................................5 Sulfur: ..........................................................................................................6 Zinc: .............................................................................................................6 Dry Matter Accumulation, Partitioning, and Remobilization ..................................7 Seeding rate:.................................................................................................8 Nutrient application: ....................................................................................8 Nutrient Management ............................................................................................10 Nitrogen: ....................................................................................................10 Phosphorus: ................................................................................................11 Potassium: ..................................................................................................12 Sulfur: ........................................................................................................13 Zinc: ...........................................................................................................14 Corn....................................................................................................................................15 Global and Domestic Corn Production ..................................................................15 Nitrogen Uptake and Removal...............................................................................15 Nitrogen Timing.....................................................................................................16 Nitrogen Placement ................................................................................................17 Spring surface applied: ..............................................................................17 Subsurface band: ........................................................................................17 Coulter-inject: ............................................................................................18 Surface band: .............................................................................................18 Corn Root Growth..................................................................................................19 Nitrogen Volatilization and Urease Inhibitors .......................................................20 Nitrogen Use Efficiency ........................................................................................21 LITERATURE CITED ......................................................................................................22 CHAPTER 2 SOYBEAN SEEDING RATE AND FERTILIZER APPLICATION INTERACTIONS ON PLANT GROWTH AND GRAIN YIELD ...................................................................................35 Abstract ..............................................................................................................................35 Introduction ........................................................................................................................36 Materials and Methods .......................................................................................................40 Results and Discussion ......................................................................................................43 vi Environmental Conditions .....................................................................................43 Dry Matter and Nutrient Accumulation .................................................................43 Dry Matter Partitioning ..........................................................................................49 Grain Yield.............................................................................................................51 Economic Analysis ................................................................................................55 Conclusions ........................................................................................................................56 Acknowledgements ............................................................................................................57 APPENDICES ...................................................................................................................58 APPENDIX A: CHAPTER 2 TABLES ...............................................................59 APPENDIX B: CHAPTER 2 DATA COLLECTED BUT NOT INCLUDED IN PUBLICATION ....................................................................................................67 LITERATURE CITED ......................................................................................................73 CHAPTER 3 CORN NITROGEN TIMING AND SIDEDRESS PLACEMENT STRATEGIES......................81 Abstract ..............................................................................................................................81 Introduction ........................................................................................................................82 Materials and Methods .......................................................................................................85 Results and Discussion ......................................................................................................88 Environmental Conditions .....................................................................................88 Grain Yield.............................................................................................................89 Economic Analysis ................................................................................................91 Agronomic Efficiency ............................................................................................92 Normalized Difference Vegetation Index ..............................................................93 Chlorophyll Meter ..................................................................................................94 Conclusions ........................................................................................................................95 Acknowledgements ............................................................................................................97 APPENDICES ...................................................................................................................98 APPENDIX A: CHAPTER 3 TABLES ...............................................................99 APPENDIX B: CHAPTER 3 DATA COLLECTED BUT NOT INCLUDED IN PUBLICATION ..................................................................................................106 LITERATURE CITED ....................................................................................................111 vii LIST OF TABLES Table 2.01. Soil chemical properties and mean nutrient concentrations (0 to 20-cm depth), Richville and Lansing, MI, 2017 to 2018 ......................................................................................59 Table 2.02. Monthly and 30-yr mean temperature and precipitation data for the soybean growing season, Richville and Lansing, MI, 2017 to 2018..........................................................................60 Table 2.03. Interaction between soybean seeding rate and fertilizer application (P < 0.01) on V4 individual plant dry matter (DM) production, across locations and years, Richville and Lansing, MI, 2017 to 2018. All values reported on a dry weight (0% moisture) basis ................................61 Table 2.04. Soybean seeding rate and fertilizer application effects on V4 aboveground dry matter accumulation across years, Richville and Lansing, MI, 2017 to 2018. All values reported on a dry weight (0% moisture) basis .....................................................................................................62 Table 2.05. Soybean seeding rate and fertilizer application effects on V4 total nutrient accumulation, Richville and Lansing, MI, 2017 and 2018 ............................................................63 Table 2.06. Soybean grain nutrient accumulation at physiological maturity (R8) as affected by seeding rate and fertilizer application presented across locations and years, Richville and Lansing, MI, 2017 to 2018 .............................................................................................................64 Table 2.07. Influence of soybean seeding rate and fertilizer application on R8 total dry matter partitioning presented across locations and years, Richville and Lansing, MI, 2017 to 2018 .......65 Table 2.08. Seeding rate and fertilizer application effects on soybean grain yield and economic return, across locations and years, Richville and Lansing, MI, 2017 to 2018. ..............................66 Table 2.09. Influence of soybean seeding rate and fertilizer application on V4 dry matter partitioning, across locations and years, Richville and Lansing, MI, 2017 to 2018. .....................67 Table 2.10. Soybean seeding rate and fertilizer application effect on R2 dry matter partitioning, across locations and years, Richville and Lansing, MI, 2017 to 2018 ...........................................68 Table 2.11. Impact of seeding rate and fertilizer application on soybean dry matter partitioning across locations and years, Richville and Lansing, MI, 2017 to 2018 ...........................................69 Table 2.12. Seeding rate and fertilizer application effects on soybean grain yield and machine- harvest loss, across locations and years, Richville and Lansing, MI, 2017 to 2018 ......................70 Table 2.13. Impact of soybean seeding rate and fertilizer application on R1 uppermost trifoliate nutrient concentrations, Richville and Lansing, MI, 2017 to 2018 ...............................................71 viii Table 2.14. Influence of soybean seeding rate and fertilizer application on R8 grain secondary and micronutrient accumulation, across locations and years, Richville and Lansing, MI 2017 to 2018................................................................................................................................................72 Table 3.01. Overview of corn nitrogen (N) timing and sidedress placement treatments, Richville and Lansing, MI, 2017 to 2018 ......................................................................................................99 Table 3.02. Mean monthly precipitation and temperature for the corn growing season, Richville and Lansing, MI, 2017 to 2018 ....................................................................................................100 Table 3.03. Corn grain yield and net economic return as affected by pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed V4-6 (SD), 0/100 PPI and SD, and 5x5 N strategies in combination with SD placements of coulter-inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI), across locations and years in Richville and Lansing, MI, 2017 to 2018 .........................................................................................................................................101 Table 3.04. Mean soil moisture (cm3 cm-3) and cumulative precipitation (mm) three weeks following corn nitrogen (N) applications, Richville and Lansing, MI, 2017 to 2018 .................102 Table 3.05. Agronomic efficiency (AE) of applied corn nitrogen (N) fertilizer compared across main effects of N timing strategy including pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed V4-6 (SD), 0/100 PPI and SD, and 5x5 N strategies, SD placement including coulter-inject (CI) and Y-drop surface application (YD), and addition of a urease inhibitor (UI) using multiple degree of freedom contrasts, across locations and years in Richville and Lansing, MI, 2017 to 2018 ....................................................................................................103 Table 3.06. Multiple degree of freedom contrasts comparing pre-emergence (PRE), 50/50 pre- plant incorporated (PPI) and sidedressed V4-6 (SD), 0/100 PPI and SD, and 5x5 N strategies on mean canopy normalized difference vegetation index (NDVI) measurements at V6 across locations in 2017 and 2018 and at V10 across years and locations in Richville and Lansing, MI, 2017 to 2018 ................................................................................................................................104 Table 3.07. Corn SPAD chlorophyll as affected by pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed V4-6 (SD), 0/100 PPI and SD, and 5x5 N strategies in combination with SD placements of coulter-inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI) at R1 across locations in 2017 and 2018 and at R4 across years and locations in Richville and Lansing, MI, 2017 to 2018 ..........................................................105 Table 3.08. Corn V4 normalized difference vegetation index (NDVI) measurements as affected by pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed (SD), 0/100 PPI and SD, and 5x5 N strategies in combination with SD placements of coulter-inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI), across locations and years in Richville and Lansing, MI, 2017 to 2018 ....................................................................................106 Table 3.09. Corn V6 SPAD chlorophyll as affected by pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed (SD), 0/100 PPI and SD, and 5x5 N strategies in combination ix with SD placements of coulter-inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI), across years and locations in Richville and Lansing, MI, 2017 to 2018 ...107 Table 3.10. Impact of pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed (SD), 0/100 PPI and SD, and 5x5 N strategies in combination with SD placements of coulter- inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI) on V6 corn plant height presented by year and location, Richville and Lansing, MI, 2017 to 2018 .............108 Table 3.11. Impact of pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed (SD), 0/100 PPI and SD, and 5x5 N strategies in combination with SD placements of coulter- inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI) on R1 corn plant height across years and locations, Richville and Lansing, MI, 2017 to 2018 .....................109 Table 3.12. Post-harvest soil residual nitrate (NO3-N) concentration as affected by pre- emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed (SD), 0/100 PPI and SD, and 5x5 N strategies in combination with SD placements of coulter-inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI) across locations and years, Richville and Lansing, MI, 2017 to 2018 ....................................................................................................110 x CHAPTER 1 LITERATURE REVIEW Soybean Global and Domestic Soybean Production Soybean (Glycine max L. Merr.) production serves its primary purpose as an annual field crop that produces a high protein grain used for human consumption and animal feed (Hungria et al, 2006). Domestically introduced in 1765 by Samuel Bowen, soybeans were predominantly used as a supplemental forage crop in the eastern half of the United States (U.S.) until grain production became prevalent in the 1940s (Morse et al., 1950; Hymowitz and Shurtleff, 2005). The adaptability to mechanized farming practices and the use of soybeans manufactured for oil, meal and food products fueled the market for grain production, causing a decline in the number of acres used to produce hay (Morse et al., 1950). Regardless of its end use, soybeans can be grown on unproductive soils with low pH (Borst and Thatcher, 1931) and have proven useful to succeeding crops by providing a major nutrient source through residue mineralization (Bender et al., 2015). Historical human consumption of soybean by-products was concentrated in Asia but was used as swine and poultry nutrition in other parts of the world (Wilson, 2004; Lusas, 2004). Since 2000, global markets have expanded due to the high protein content found in soybean meal (Wilson, 2004). In 2017, the U.S. produced approximately 33% of world soybean production and exported over 59 million metric tons (USDA-FAS, 2017b). The U.S. was the world’s largest soybean producer in 2017 and second largest exporter (USDA-FAS, 2017b). Combined with the 1 U.S., Brazil, Argentina, China, India, Paraguay, and Canada, produced 94% of the world’s soybeans in 2017 (USDA-FAS, 2017b). Soybean production in Michigan varies by region due to climatic variability and the many high-value crops produced. Since 2012 Michigan average soybean yields were 3087 kg ha-1 and contributed US$1.01 billion to the economy (USDA-NASS, 2017d,f). United States’ average soybean grain yields were 3114 kg ha-1 during the same time period (USDA-NASS, 2017e). Since 1998 U.S. average yields increased 35% likely due to earlier planting dates, increased weed control, reduced government subsidies for corn (Zea Mays L.) production, and increased harvestable yield (Specht et al., 1999; USDA-NASS, 2017e). Seeding Rate and Plant Density Producers in the U.S. benefited from increased seeding rates through greater weed suppression and quicker canopy closure (Shibles and Weber, 1966; Devlin et al., 1995; Harder et al., 2007; Assefa et al., 2016). Decreased seeding rates may produce comparable grain yields as increased seeding rates due to reduced interplant competition (Suhre et al., 2014). Seeding rates that produced optimal yields varied by agronomic practices and environmental conditions (Walker et al., 2010; Isidro-Sánchez et al., 2017) and ranged between 179,100 seeds ha-1 (Chen and Wiatrak, 2011) and 988,000 seeds ha-1 (Norsworthy and Oliver, 2001). In modern soybean varieties, increased seeding rates may increase yield potential but can negatively influence yield through greater interplant competition (Suhre et al., 2014). In New York, Cox et al. (2010) found no grain yield differences between seeding rates of 358,000 and 580,000 seeds ha-1 and attributed the lack of differences to increased plant dry matter (DM) and pods plant-1 at decreased seeding rates. A study in Michigan evaluating the effect of row width and plant populations on weed control and grain yield reported similar grain yields in plant 2 populations between 185,000 plants ha-1 to 445,000 plants ha-1 (Harder et al., 2007). In Ontario, Ablett et al. (1991) reported similar yields in indeterminate cultivars seeded between 395,000 to 790,000 seeds ha-1. Studies in Iowa indicated maximum yield was achieved at 462,200 seeds ha-1 but 258,600 plants ha-1 achieved 95% of maximum yield (De Bruin and Pedersen, 2008a). Greater interplant competition likely limited positive grain yield responses at increased seeding rates. Environmental conditions may influence optimal seeding rates (Walker et al., 2010). Alessi and Power (1982) suggested increased plant densities absorb greater quantities of water and may deplete early-season water reserves during dry soil conditions. Devlin et al. (1995) reported similar yields between seeding rates of 129,200 and 645,800 seeds ha-1 under drought conditions, but yield was maximized at 284,200 seeds ha-1 when moisture was non-limiting. Similarly, Walker et al. (2010) found optimal yield was produced at 90,000 plants ha-1 under drought condition but increased to 222,000 plants ha-1 when moisture was adequate. Benefit of increased seeding rates may only be realized when moisture does not limit grain yield. Due to the greater cost of seed at increased seeding rate, De Bruin and Pedersen (2008b) suggested greater emphasis be placed on optimal economic return as opposed to maximum grain yield. Results in Kentucky indicated economically optimal seeding rates were 7 to 33% less than seeding rates maximizing yield (Lee et al., 2008). Economically optimal seeding rates ranged between 76,000 to 241,000 plants ha-1 but plant populations required for maximum yield were 338,000 to 473,000 plants ha-1 (Lee et al., 2008). Similar results were reported by Norsworthy and Oliver (2001) but decreased seeding rates were associated with a greater herbicide cost. In Michigan, economic return was not affected by crop price and optimized at plant populations of 185,000 and 296,000 seeds ha-1 (Harder et al., 2007). 3 Nutrient Uptake, Partitioning and Remobilization Increased DM in current soybean varieties simultaneously increased grain yield and total nutrient requirements (Bender et al., 2015; Balboa et al., 2018). Grain nutrient requirements can be satisfied through direct nutrient partitioning or remobilization from existing vegetative DM (Hammond et al., 1951). Up to 80% of total grain nutrient content may be accumulated by R6 (Sale and Campbell, 1980; Bender et al., 2015). Approximately 30 to 40% of grain nutrients can be remobilized from aboveground vegetative DM despite reduced nutrient accumulation rates between R4 and physiological maturity (Borst and Thatcher, 1931; Hanway and Weber, 1971c; Bender et al., 2015; Gaspar et al., 2017a, 2017b). The importance of continued soil uptake and nutrient vegetative remobilization for grain nutrient accumulation emphasize maintenance of soil nutrient levels (Gaspar et al., 2018). Nitrogen: Soybeans can reach peak nitrogen (N) uptake rates by R4 and remove approximately 58 to 63 g N kg-1 (Warncke et al., 2009; Bender et al., 2015). Maximum accumulation rates may be between 3.6 and 4.9 kg N ha-1 d-1 and remove approximately 232 kg N ha-1 (Hammond et al., 1951; Bender et al., 2015; Gaspar et al., 2017a). At physiological maturity, Bender et al. (2015) reported a N harvest index (i.e., percent of total plant N in grain tissues [HI]) of 73%. Soybean may remove large quantities of N in grain tissues and leave a negative soil N balance in soybean production systems (Tamagno et al., 2018). Vegetative remobilization is a large grain nutrient source and can account for up to 39 to 50% of total grain N (Gaspar et al., 2017a). Hammond et al. (1951) reported 58 to 64% of grain N was remobilized from vegetative tissues with the remainder accumulated from the soil. Similarly, Bender et al. (2015) reported 53% of grain N was satisfied through remobilization. Results of Gaspar et al. (2017a) suggested increased grain 4 yields were more associated with soil N uptake during grain-fill rather than vegetative remobilization. At physiological maturity, Hammond et al. (1951) reported N was distributed throughout leaves, stems and roots, pods, and grain by 12%, 4%, 4%, and 80%, respectively. Phosphorus: Gaspar et al. (2017b) reported peak phosphorus (P) accumulation at R4 at a rate between 0.42 to 0.56 kg P ha-1 d-1, and total P accumulation ranging from 24.4 to 36.6 kg P ha-1. Soybean grain P removal (81% of total plant P) can be the highest of all essential nutrients (Bender et al., 2015). Phosphorus HI has increased from 68% in soybean cultivars from the 1930s (Borst and Thatcher, 1931) to 80% in current soybean varieties (Gaspar et al., 2017b). Improvements in soybean genetics concomitantly increased soybean grain P removal and indicated soil P levels should be maintained for soybean grain production. Similar to N, soil P accumulation past R5 must be supplemented by vegetative remobilization to supply grain P requirements. Gaspar et al. (2017b) reported 68 to 78% of grain P relied on continued soil uptake past R5.5 and higher yield levels (5500 kg ha-1) satisfied grain P requirements through increased late-season nutrient accumulation. Potassium: In Wisconsin and Minnesota, potassium (K) accumulation was slow within 20 days of planting but rapidly increased by R1 and peaked by R3 (Gaspar et al., 2017b). In current soybean varieties, maximum accumulation rates were between 1.7 and 2.8 kg K ha-1 d-1 (Bender et al., 2015; Gaspar et al., 2017b) and are slightly higher than K accumulation rates reported in the 1950s and 1970s (Hammond et al., 1951; Hanway and Weber, 1971a). Total soybean K accumulation can range between 90 and 100% which emphasizes the importance of pre-plant and early-season K availability (Hanway and Weber, 1971a; Bender et al., 2015; Gaspar et al., 5 2017b). Due to < 10% of total K uptake occurring past R5, grain K requirements heavily rely on vegetative remobilization as opposed to continued soil uptake (Gaspar et al., 2017b). Relatively low soybean K HI (46 to 49%) indicated soybean residue return to the soil may be a major K source for subsequent crops (Bender et al., 2015; Gaspar et al., 2017b). Soybean grain K uptake equaled 131 to 192 kg K ha-1 while K removal was 63 to 94 kg K ha-1 (Bender et al., 2015; Gaspar et al., 2017b). Sulfur: Soybean sulfur (S) uptake occurred primarily after R1 with an initial phase of minimal S accumulation (Bender et al., 2015; Gaspar et al., 2018). Gaspar et al. (2018) reported S accumulation prior to R1 was < 17% of total S uptake while S accumulation after R5.5 ranged between 25 to 32%. Bender et al. (2015) reported peak S accumulation occurred at R4 at a rate of 0.29 kg S ha-1 d-1. However, Gaspar et al. (2018) reported peak uptake occurred earlier at R2.5 and ranged from 0.26 to 0.33 kg ha-1 d-1. Soil S uptake past R5.5 may supply up to 52% of grain S and contribute greater to grain S requirements than vegetative remobilization (Gaspar et al., 2018). Naeve and Shibles (2005) and Bender et al. (2015) both reported vegetative remobilization supplied approximately 40% of grain S requirements. At maturity, S HI can range between 61 to 69% (Sexton et al., 1998; Bender et al., 2015; Gaspar et al., 2018). Zinc: Zinc (Zn) accumulation in soybean was evenly distributed throughout the growing season with a peak uptake rate of 3.57 to 3.99 g ha-1 d-1 occurring at approximately R4 (Bender et al., 2015). Gaspar et al. (2018) found approximately 25% of Zn accumulation occurred following R5.5 which supplied 51% of grain Zn. Leaves may serve as a large storage sink of Zn with the purpose of remobilization to grain (Gaspar et al., 2018). At a 4421 kg ha-1 yield level, Gaspar et 6 al. (2018) reported a removal rate of 0.23 kg Zn ha-1. In current soybean varieties, Bender et al. (2015) reported soybean Zn HI was 44%. Dry Matter Accumulation, Partitioning, and Remobilization Total DM accumulation has increased approximately 134% over the past 80 years and may be a primary factor responsible for increased nutrient uptake and grain yield in modern soybean varieties (Borst and Thatcher, 1931, Hammond et al., 1951; Hanway and Weber, 1971b; Bender et al., 2015; Gaspar et al., 2017a; Balboa et al., 2018). Gaspar et al. (2017a) suggested increased soybean grain yields were achieved through greater late-season DM accumulation rate and total DM. However, other studies found poor relationship between DM at maturity and soybean grain yield (Shibles and Weber, 1966; Bender et al., 2015). Dry matter partitioning and remobilization is a critical component of soybean grain yield that may simultaneously influence nutrient allocation patterns (Gaspar et al., 2017a). In Illinois, Bender et al. (2015) reported final DM partitioning was distributed among leaves, stems, pods, and grain tissues by 16, 33, 14, and 37%, respectively. In Ohio, Borst and Thatcher (1931) reported DM was dispersed by 25, 27, 19, and 29% among leaves, stems, pods, and grain tissues. In Iowa, Hanway and Weber (1971b) reported total DM was partitioned into grain (29%), leaves (28%), stems (17%), petioles (15%), and pods (11%). Increased grain DM partitioning in modern soybean varieties may have been due to the transition from soybean as a forage crop to grain production (Borst and Thatcher, 1931; Hanway and Weber 1971c; Bender et al., 2015). A peak DM accumulation rate of 161 kg ha-1 d-1 was reported by Bender et al. (2015) and occurred at R4. 7 Seeding rate: Increased plant DM is critical for soybean’s compensation ability of reduced plant densities (Lueschen and Hicks, 1977). As plant density decreased from 234,000 to 70,000 plants ha-1, Carpenter and Board (1997a) reported individual plant DM increased from 19.3 to 63.3 g plant-1. However, total DM remained similar within 30 days of emergence despite increased plant size at decreased plant densities. Cox et al. (2010) reported similar results where seeding rates between 231,000 and 469,000 seeds ha-1 produced similar total DM (4970 kg ha-1). Greater DM plant-1 provides potential for increased pod and grain production plant-1 at decreased seeding rates. Despite varying plant sizes, DM partitioning ratios may be constant across plant densities, planting dates, and growth habits (Egli, 1988; Board, 2000). However, Carpenter and Board (1997a) and Rigsby and Board (2003) found decreased seeding rates increased stem DM partitioning to support grain production on plant branches. Compared to increased seeding rates, Wells (1993) demonstrated reduced plant densities increased crops growth rate earlier in the growing season and suggested crop growth rates varied by seeding rate. Results agreed with Board (2000) who reported reduced plant densities increased crop growth rate 35 to 50% 21 days after soybean emergence, but crop growth rates across plant densities were similar by R1. Carpenter and Board (1997b) reported a 9% yield difference between plant populations of 70,000 and 234,000 plants ha-1 and related the lack of yield difference to increased branching and crop growth rates at reduced plant densities. Greater interplant competition in increased plant densities may limit crop growth and contribute to grain yield plateaus. Nutrient application: Nitrogen applications may increase early-season DM accumulation and translate into increased yields when crop growth rates are maintained throughout reproduction 8 (Kaiser and Kim, 2013; Cigelske, 2016; Gaspar et al., 2017a). Osborne and Riedell (2006) reported an N application of 16 kg N ha-1 increased early-season (V3/4 and R1) DM and grain yield 7.0% and 5.3 to 7.2%, respectively. In a double-cropping system following corn, Starling et al. (1998) reported a starter N application of 50 kg N ha-1 broadcast and incorporated prior to planting (PPI) increased R1 DM and grain yield 0.50 and 0.15 Mg ha-1, respectively. Taylor et al. (2005) reported DM accumulation at R1 was maximized with an application of 60 to 70 kg N ha- 1 broadcast immediately after soybean planting regardless of planting date or cultivar. Averaged across irrigated production systems in Argentina and Nebraska, Cafaro La Menza et al. (2017) reported split N applications increased final DM and grain yield 9 and 11%, respectively. Phosphorus applications may increase early-season soybean growth during cool, wet springs or when soils are deficient (Warncke et al., 2009). At sites with soil P ranging from 10 to 29 mg P kg-1, Kaiser and Kim (2013) reported increased early-season (V5) DM with P application but suggested the observed response may have been due to the N and S components in the fertilizer. In Ohio, the combination of 45 kg P2O5 ha-1 and 18 kg N ha-1 increased shoot DM in two of three years but differences diminished by R1 and did not increase grain yield (Hankinson et al., 2015). In the Humid Argentine Pampas, Boem et al. (2007) reported increased yield with subsurface S application and related the increase to greater DM accumulation between R5 to R8. However, DM production was not affected prior to R5, and S applications may not influence grain yield until during grain-fill (Boem et al., 2007). Dry matter and grain yield response to nutrient applications may be dependent on soil test values (Warncke et al., 2009). 9 Nutrient Management Nitrogen: Nitrogen is used in excess of any other essential nutrient in modern crop production but is also commonly the most limiting (Schlegel and Grant, 2006). Soybean’s large N requirement is driven by the high protein content in grain (Wesley et al., 1998). Three primary sources provide N to a growing soybean crop including: soil mineralization, synthetic N fertilizer, and biological N fixation (Barker and Sawyer, 2005; Salvagiotti et al., 2008). Biological N fixation can provide 50 to 60% of the soybean’s total N requirement (Salvagiotti et al., 2008; Tamagno et al., 2017) but may not occur until 16 days after planting and considerably contribute to N availability until R1 (Harper and Hageman, 1972; Havelka et al., 1982; Zapata et al., 1987). Salvagiotti et al. (2008) suggested biological N fixation supplied adequate N in grain yields up to 4000 to 4500 kg ha-1 but additional N may be needed when yields exceed this level. Soybean N applications in Michigan are not recommended due to inconsistent responses at current yield levels (<3800 kg ha-1) and the high native Rhizobium bacterial populations in Michigan soils involved in N fixation (Warncke et al., 2009). Current high-yielding cultivars have gained interest in applying additional N fertilizer to reach maximum yield potential (Barker and Sawyer, 2005). However, positive yield and economic return response to N applications are variable (Salvagiotti et al., 2008). Reviewed literature ranges from early-season to late-reproductive foliar N applications, with the general consensus of no significant yield increases to N fertilizer or no additional partitioning of N to the seed (Hanway and Weber, 1971d; Stone et al., 1985; Schmitt et al., 2001; Salvagiotti et al., 2008; Orlowski et al., 2016; Mourtzinis et al., 2017). Afza et al. (1987) reported increased grain yield with N application due to limited N supply during grain-fill. Broadcast N at planting may 10 increase grain yield due to inadequate early-season N supply from biological N fixation (Ham et al., 1975). Nitrogen application on the soil surface or in the zone of nodulation may reduce biological N fixation contribution to N supply (Salvagiotti et al., 2008). Regardless of pre-plant soil N levels, Starling et al. (1998) observed decreased soybean nodulation from 50 kg ha-1 PPI N applications. Hungria et al. (2006) reported decreased nodulation and N fixation when 30 kg N ha-1 was placed with the seed at planting. To reduce the effects of N application on biological fixation, Salvagiotti et al. (2008) recommended placing N fertilizer below the nodulation zone but N applications would be limited to before planting. Phosphorus: Phosphorus is the second most limiting nutrient to crop production and is important in respiration, root growth, crop maturity date, and drought tolerance (Bundy et al., 2005; Schlegel and Grant, 2006; Havlin et al., 2014). Phosphorus availability may be influenced by low mobility in the soil and interactions with soil chemical properties (Randall and Hoeft, 1988). Michigan soils > 15 mg P kg-1 supply sufficient P needed for soybean production but soil test levels may decline when not replenished with P fertilizer (Warncke et al., 2009). Additionally, the high P content in soybean seed (80% HI) may supply sufficient P needed for early-season growth and restrict plant growth response to pre- and at-plant P applications (Hammond et al., 1951). Subsurface banded P applications are recommended in Michigan due to greater potential for P adsorption with broadcast applications (Warncke et al., 2009). Warncke et al. (2009) recommended maximum P application should not exceed 224 kg P2O5 ha-1 yr-1 in any cropping system (Warncke et al., 2009). Soil test values may dictate grain yield response to nutrient 11 applications and be unlikely when soil P levels exceed 15 mg P kg-1 (Warncke et al., 2009). Brooker et al. (2017) found grain yield decreased 498 kg ha-1 when soil P levels were < 15 mg P kg-1. Sutradhar et al. (2017) reported a positive yield response to P applications when soil P was < 8 mg kg-1. In 7 of 20 sites, Borges and Mallarino (2000) reported increased grain yield to P application when soil levels were < 9 mg kg-1 but a positive grain yield response was not observed at all sites considered deficient (i.e., < 9 mg kg-1). Starter P applications in Ohio did not increase grain yield due to soil P levels 33 to 84 mg kg-1 and environmental conditions promoting nutrient mineralization from soil organic matter (Hankinson et al., 2015). A greater chance for a positive yield response to P applications can occur when soil levels are deficient or during cool, wet springs where root growth is reduced (Havlin et al., 2014). Potassium: Potassium is essential for enzyme activation, photosynthesis, assimilate processes, and crop quality (Pettigrew, 2008). Plants accumulate K by diffusion which can be inhibited by dry soil conditions, cool temperatures, and high soil moisture that restrict aeration (Hanway and Johnson, 1985). Because of cool spring temperatures in the Upper Midwest, K must be readily available at planting to support early-season DM and grain yield (Hanway and Johnson, 1985). In a review on K and its interaction with other nutrients, Dibb and Thompson Jr. (1985) concluded K may promote N and P uptake. However, maintaining high K levels may result in luxury consumption and reduced K efficiency (Parvej et al., 2016). In a no-till production system, Borges and Mallarino (2000) observed similar plant responses to K applications in soils ranging from 90 to 262 mg K kg-1 but suggested soil K levels may not directly influence plant K uptake. Clover and Mallarino (2013) observed signs of K luxury consumption in sites and increased K uptake did not result in increased DM. However, the authors reported increased 12 yield from K fertilization when soil K levels were below 173 mg K ha-1 (Clover and Mallarino, 2013). Brooker et al. (2017) reported a 269 kg ha-1 yield reduction when soil K levels were deficient. In a 14 year corn-soybean rotation study, Mallarino et al. (1991) observed grain yield increases at 26 of 49 sites in soils ranging between 69 and 100 mg K ha-1. However, yield increases were not observed when soil K levels were > 100 mg kg-1 (Mallarino et al., 1991). In Michigan, K recommendations are based on soil test values, cation exchange capacity (CEC), and critical levels for the specific crop (Warncke et al., 2009). Sulfur: Sulfur is important to crop production because it can aid in amino acid synthesis, increase cold resistance, and promote soybean nodulation (Coleman, 1966). Reduced S in pesticides, incidental S in fertilizer, atmospheric deposition from industrial operations, and increased crop yields have increased perceived S deficiency in Michigan grain crops (Coleman, 1966; Hitsuda et al., 2008; Chien et al., 2016). As a result, multi-nutrient fertilizers utilize S and are marketed for their S component. Elemental S may fulfill late-season S requirements by delaying S availability but must be oxidized for plant available uptake (Chien et al., 2016). Lack of S mobility in plants emphasizes the importance of maintaining S availability as plants cannot mobilize S to young leaves when deficient (Sunarpi and Anderson, 1997). Sulfur deficiency symptoms include chlorotic and stunted plants and commonly mistaken for N deficiency (Zhao et al., 1996; Hitsuda et al., 2005; 2008). Plants may also appear stunted and “spindly” with decreased stem and leaf production (Ceccotti, 1996; Hitsuda et al., 2008). Sulfur deficiency may occur during excessive precipitation on well-drained, sandy soils due to leaching potential (Coleman, 1966). Soil S testing may be a poor indicator of S availability due to variable S levels in the soil and accumulation of S in subsoil layers (Hitsuda et al., 2005). In a review on 13 agronomic effectiveness of S fertilizers, Chien et al. (2016) suggested the effectiveness of S applications were variable and dependent on environmental factors (e.g., soil organic matter, precipitation and leaching potential, and rate of elemental S oxidation). Results of Kaiser and Kim (2013) and Steinke et al. (2015) suggested soil organic matters > 20 g kg-1 and 28 g kg-1 were sufficient for soybean and corn growth, respectively. Cropping systems with recent (i.e., ≤ 3 yrs) manure or S application may reduce potential for a grain yield response to S application (Warncke et al., 2009). Zinc: Increased yields in recent soybean cultivars have concomitantly increased total nutrient requirements and perceived micronutrient deficiencies (Bender et al., 2015; Sutradhar et al., 2017). Soybean is moderately sensitive to Zn application and consistent grain yield increases to Zn application have only been observed in corn (Havlin et al., 2014; Kaiser et al., 2016). Soils with pH < 6.5 may supply adequate Zn for grain crop production in Michigan (Warncke et al., 2009). Lack of grain yield response to foliar Zn application in deficient Michigan soils suggested current critical levels may be too high for soybean (Quinn, 2018). Mallarino et al. (2017) observed no yield increases in 99 field trials across the North Central U.S. from foliar Zn application despite 24 trials with low soil Zn levels and an expected yield increase. Among 42 sites across Iowa, Enderson et al. (2015) did not observe a single yield increase from foliar Zn applications and suggested soil test values were a poor indicator of micronutrient sufficiency. Previous studies commonly utilized foliar applications of Zn at late vegetative and early reproductive stages which coincide with periods of accelerated nutrient uptake (Bender et al., 2015; Enderson et al., 2015; Mallarino et al., 2017; Quinn, 2018). However, soil Zn uptake 14 during grain-fill may supply up to 53% of grain Zn (Gaspar et al., 2018). Soil nutrient uptake during grain-fill may be associated with increased yields due to direct partitioning of nutrients to developing grain tissues (Gaspar et al., 2018). Global and Domestic Corn Production Corn Corn is a primary component of animal feed, alcohol, high-fructose corn syrup, and ethanol fuel (USDA-ERS, 2017). In 2017, 29% of arable land in the United States (U.S.) was used for corn production and produced an average yield of 11.1 Mg ha-1 (USDA-NASS, 2017b,c). The U.S. was the largest producer and exporter of corn in 2017, and resulted in 85% of total world exports when combined with Ukraine, Brazil, and Argentina (USDA-FAS, 2017a). Major corn importers in 2017 included the European Union, Japan, South Korea, and Mexico (USDA-FAS, 2017a). In 2017, over 2 million acres of corn were planted in Michigan and produced an average grain yield of 9.6 Mg ha-1 (USDA-NASS, 2017b,c). The Census of Agriculture estimated Michigan’s agricultural industry contributed $8.7 billion to 2012’s national economy and employed 80,000 farm operators (USDA-NASS, 2017a). Nitrogen Uptake and Removal Nitrogen (N) is used in excess of any other essential nutrient and can be responsible for up to 41% of grain yield (Smith et al., 1990). Bender et al. (2013) reported a corn grain yield of 12.0 Mg ha-1 removed 286 kg N ha-1 with an additional 120 kg N ha-1 accumulated in stover. Ciampitti and Vyn (2014) found the long-term (i.e., 1880 to 2012) average corn N uptake in the U.S. was 217 kg N ha-1. Peak N accumulation rates can occur between V10 and V14 at a rate of 8.9 kg N ha-1 d-1 but may be dependent on N availability (Russelle et al., 1983; Bender et al., 15 2013). Corn N uptake prior to V6 may be < 15% of total N accumulation and suggests N loss potential may be greater with N applications made prior to rapid N uptake periods (i.e., V8) (Bender et al., 2013). Nitrogen Timing Nitrogen applications synchronized with peak uptake periods (V10 to V14) may reduce N loss potential and maximize nutrient use efficiency (Dinnes et al., 2002; Bender et al., 2013). Binder et al. (2000) reported positive grain yield responses when N applications were delayed until R3 but full yield potential was not achieved. In Minnesota and Missouri, grain yield was unaffected when sidedress N applications were delayed until V16 and V11, respectively (Randall et al., 1997; Scharf et al., 2002). However, Walsh et al. (2012) observed unrecoverable yield reductions when N applications were delayed until V10. Producers may be hesitant in delaying N applications beyond V6 due to increased yield loss potential (Binder et al., 2000; Scharf et al., 2002). Split-applications are considered a Best Management Practice (BMP) in Michigan due to synchrony of N availability with corn N uptake (Warncke et al., 2009). Compared to single pre- plant N application, Rubin et al. (2016) found split applications increased grain yield up to 5.4%. Howard and Tyler (1989) reported reduced grain yield when applying 100% of N at planting rather than applying 50% of N at planting and V8 sidedress. In contrast, Ruiz Diaz et al. (2008) found 100% of N application at planting increased yield compared to a split N application. Nitrogen application in season may not increase grain yield when previous N application satisfied corn N demands (Mueller et al., 2017). Nitrogen timing strategy may depend on environmental factors influencing N availability, mobility, and loss conditions (Stecker et al., 1993). 16 Nitrogen Placement Improved N management and placement may optimize agronomic and economic potential while reducing environmental impacts (Randall and Hoeft, 1988). The majority of corn N accumulation may occur within a 40-cm radius of the base of the plant (Hodgen et al., 2009). Nitrogen application placed outside of corn’s primary root radius may be subject to N loss. Grain yield response to N placement may be contingent on climatic and soil conditions promoting or hindering N loss (Stecker et al., 1993; Rehm and Lamb, 2009). Spring surface applied: Pre-emerge (PRE) surface applied N fertilizer without incorporation may increase volatilization potential but can provide benefit to growers by combining nutrient application and weed control into a single-pass system (Fox and Piekielek, 1993; Nelson et al., 2011). Havlin et al. (2014) suggested optimal application conditions for surface application of urea-containing fertilizers consisted of cool, dry soils with at least 6.4-mm precipitation occurring within three days of N application. Spring surface broadcast N applications in Michigan can be delayed or prevented by excessive precipitation (Dinnes et al., 2002; Scharf et al., 2006). Additionally, broadcast N applications may reduce early-season corn growth compared to subsurface N application at planting (Bates, 1971). The moisture requirement for N movement into the root zone suggested N uptake with PRE applications may be reduced during dry soil conditions (Chaudhary and Prihar, 1974; Khosla et al., 2000; Rutan and Steinke, 2018). Subsurface band: Compared to surface N application, subsurface placement can reduce volatile N loss potential while encouraging early-season nutrient and biomass accumulation (Niehues et al., 2004; Kaiser et al., 2005; Warncke et al., 2009). Increased early-season root growth may give 17 plants greater access to moisture and N during mid- and late-season drought conditions (Mullock, 2014). Niehues et al. (2004) reported placing 34 kg N ha-1 5-cm below and 5-cm to the side of the seed (5x5) at planting optimized early-season (i.e., V6) plant growth and grain yield. In a no-till corn production system, grain yield increased 0.82 Mg ha-1 with a 5x5 N placement strategy (Scharf, 1999). In sorghum (Sorghum bicolor), Khosla et al. (2000) reported no positive grain yield response to 5x5 N placement due to high soil nitrate levels (i.e., > 95 kg N ha-1). Total corn N requirements may exceed the capacity of 5x5 N placement and require supplemental in-season N applications (Kaiser et al., 2005; Rutan and Steinke, 2018). Coulter-inject: In-season sidedress N placement may increase synchrony of N availability with peak corn N uptake periods (Bender et al., 2013). Fox et al. (1986) reported increased nitrogen use efficiency (NUE) with V5-6 coulter-inject N applications. Fox and Piekielek (1993) reported increased NUE with sidedress coulter-inject N application compared to sidedress surface banded N and broadcast N at planting. Compared to surface banded N, coulter-inject N applications reduced volatile N loss and increased grain yield 15 to 20% (Stecker et al., 1993; Sweeney, 2016). Relative to broadcast UAN, Shapiro et al. (2016) reported increased R2 SPAD measurements and stalk nitrate levels with coulter-inject N application but no yield differences were observed. Excessive precipitation following coulter-inject N application may increase N leaching potential (Stecker et al., 1993). Additionally, dry mid-season soil conditions can limit N movement into the root zone and reduce corn yield potential (Stecker et al., 1993). Surface band: Compared to surface broadcast, N placement in a surface band may reduce volatile N loss and leaf burn potential (Mengel et al., 1982; Nelson et al., 2011). Nelson et al. 18 (2011) reported reduced crop injury and increased grain yield (2.0 Mg ha-1) when surface banding N between corn rows compared to broadcast N placement. At 9 of 19 sites, surface dribbling UAN during late vegetative stages increase grain yield in Iowa (Ruiz Diaz et al., 2008). In a ridge-till system, Randall et al. (1997) reported increased N recovery with surface-banded N applications relative to pre-plant broadcast N applications. Several authors reported similar or reduced grain yield with surface banded N compared to coulter-inject (Fox et al., 1986; Howard and Tyler, 1989; Stecker et al., 1993). Few data exist evaluating surface N placement directly adjacent to the base of the plant at the same time or growth stage as traditional coulter-inject sidedress N placement. Corn Root Growth Corn root growth can be influenced by genotype, environment, planting date, and water table depth (Hilfiker and Lowery 1988; Peng et al., 2012; Ordóñez et al., 2018). Averaged between 10 experimental sites in Iowa, Ordóñez et al. (2018) reported maximum root depth in 105 to 111-day maturity corn hybrids was approximately 139-cm. Roots can reach the center of 76-cm rows at 480 growing degree days (GDD) C or approximately the V6 growth stage (Ordóñez et al., 2018). Corn root densities may be concentrated directly below the base of the plant at a 60-cm depth and decrease with distance from the plant (Mengel and Barber, 1974; Anderson, 1987; Hilfiker and Lowery, 1988; Kaspar et al., 1991; Sharratt and McWilliams, 2005; Peng et al., 2012). Nitrogen fertilizer can influence corn root growth distribution (Anderson, 1987). Maizlish et al. (1980) reported N application increased root branching, lateral root number, and root length. Duncan and Ohlrogge (1958) found similar results in a greenhouse experiment and suggested increased root surface area may increase water and nutrient uptake potential. However, 19 Peng et al. (2012) reported reduced root length with N application and indicated N placement may affect root growth and nutrient uptake efficiency. Nitrogen Volatilization and Urease Inhibitors In Michigan, surface N applications typically include urea-containing fertilizer and are subject to volatilization when not incorporated into the soil (Keller and Mengel, 1986; Warncke et al., 2009). Urea (CO2[NH]2) must be hydrolyzed into a plant available form of N (i.e., NH4 +) for plant uptake (Warncke et al., 2009; Franzen, 2017). Volatilization may occur if urea hydrolysis occurs near or at the soil surface (Fox et al., 1986; Halvorson and Bartolo, 2014; Franzen, 2017). Mid-season surface N applications may increase volatilization potential due to warmer air and soil temperatures (Warncke et al., 2009). Previous research suggested a minimum of 6 to 10-mm of precipitation was needed within 2 days of surface N application to reduce volatilization potential (Fox et al., 1986; Schwab and Murdock, 2010). Urea-containing fertilizer incorporation is a university recommended practice to mitigate volatile N loss potential (Warncke et al., 2009). Pan et al. (2016) estimated global volatile N loss averaged 18% and equated to an economic loss of US$15 billion in 2014. Cropping systems with large amounts of plant residues and soil pH > 7.0 may increase volatilization potential (Schwab and Murdock, 2010; Havlin et al., 2014; Adotey et al., 2017). In a global synthesis on ammonia volatilization, Pan et al. (2016) suggested the use of non-urea containing fertilizers, subsurface N placement, and use of a urease inhibitor can reduce volatile N loss by 75, 55, and 54%, respectively. Franzen (2017) suggested urease inhibitors can reduce volatilization for up to 10 days through delayed urea hydrolysis. Adotey et al. (2017) reported volatilization was reduced 6 to 11% when a urease inhibitor was 20 used with N application. However, urea is an uncharged molecule and may be prone to leaching when applied with a urease inhibitor (Dawar et al., 2011). Nitrogen Use Efficiency Moll et al. (1982) described NUE as a plant’s ability to utilize N for grain production. Estimated global NUEs of 33 to 47% indicate a significant amount of N is lost to the environment (Raun and Johnson, 1999; Lassaletta et al., 2014; Walsh et al., 2012; Rubin et al., 2016). Low NUEs can be caused by leaching, volatilization, surface runoff, denitrification and gaseous plant emissions (Raun and Johnson, 1999; Franzen, 2017). Nitrogen use efficiency may also be influenced by crop management (e.g., nutrient application timing, pest damage, crop rotation, and plant genetics) which can be altered to reduce the risk for N loss and improve NUE (Fixen and West, 2002; Attia et al., 2015; Woli et al., 2016). Compared to applying 100% of N at planting or during mid-season, Walsh et al. (2012) observed greater NUE with split applications. Mueller et al. (2017) reported increased N recovery with late-season (V12) supplemental N applications but no differences in grain yield were observed. Rutto et al. (2013) suggested N placement within 30-cm of the plant may not affect NUE. Urease and nitrification inhibitors increased grain yield and NUE up to 7.5 and 12.9%, respectively (Abalos et al., 2014). Environmental conditions significantly impact N loss potential therefore management practices to increase NUE should consider predicted weather conditions and environmental trends (Bock, 1984). 21 LITERATURE CITED 22 LITERATURE CITED effect of urease and nitrification inhibitors on crop productivity and nitrogen use efficiency. Agriculture, Ecosystems and Environment 189:136-144. Abalos, D., S. Jeffery, A. Sanz-Cobena, G. Guardia, and A. Vallejo. 2014. Meta-analysis of the Ablett, G.R., W.D. Beversdorf, and V.A. Dirks. 1991. Row width and seeding rate performance of indeterminate, semideterminate, and determinate soybean. J. Prod. Agric. 4:391-395. Adotey, N., M. Kongchum, J. Li, G.B. Whitehurst, E. Sucre, and D.L. Harrell. 2017. Ammonia Afza, R., G. Hardarson, F. Zapata, and S.K.A. Danso. 1987. Effects of delayed soil and foliar N volatilization of zinc sulfate-coated and NBPT-treated urea fertilizers. Agron. J. 109:1-9. fertilization on yield and N2 fixation of soybean. Plant Soil 97: 361-368. Alessi, J., and J.F. Power. 1982. Effects of plant and row spacing on dryland soybean yield and water-use efficiency. Agron. J. 74:851-854. Anderson, E.L. 1987. Corn Root growth and distribution as influenced by tillage and nitrogen Assefa, Y., P.V. Vara Prasad, P. Carter, M. Hinds, G. Bhalla, R. Schon, M. Jeschke, S. fertilization. Agron. J. 79:544-549. Paszkiewicz, and I.A. Ciampitti. 2016. Yield responses to planting density for US modern corn hybrids: A synthesis-analysis. Crop Sci. 56:2802-2817. Attia, A., C. Shapiro, W. Kranz, M. Mamo, and M. Mainz. 2015. Improved yield and nitrogen Balboa, G.R., V.O. Sadras, and I.A. Ciampitti. 2018. Shifts in soybean yield, nutrient uptake, and use efficiency of corn following soybean in irrigated sandy loams. Soil Sci. Soc. Am. J. 79:1693-1703. nutrient stoichiometry: A historical synthesis-analysis. Crop Sci. 58:43-54. Barker, D.W. and J.E. Sawyer. 2005. Nitrogen application to soybean at early reproductive development. Agron. J. 97:615-619. Summary of 22 field trials. Agron. J. 63:369-371. Bates, T.E. 1971. Response of corn to small amounts of fertilizer placed with the seed: II. Bender, R.R., J.W. Haegele, M.L. Ruffo, and F.E. Below. 2013. Nutrient uptake, partitioning, Bender, R.R., J.W. Haegele, and F.E. Below. 2015. Nutrient uptake, partitioning, and and remobilization in modern, transgenic insect-protected maize hybrids. Agron. J. 105:161-170. remobilization in modern soybean varieties. Agron. J. 107:563-573. 23 Binder, D.L., D.H. Sander, and D.T. Walters. 2000. Maize response to time of nitrogen application as affected by level of nitrogen deficiency. Agron. J. 92:1228-1236. Board, J. 2000. Light interception efficiency and light quality affect yield compensation of soybean at low plant populations. Crop Sci. 40:1285-1294. Bock, B.R. 1984. Efficient use of nitrogen in cropping systems. In: R.D. Hauck, editor, Nitrogen Boem, F.H.G., P. Prystupa, and G. Ferraris. 2007. Seed number and yield determination in sulfur in crop production. ASA, CSSA, and SSSA, Madison, WI. p. 273-294. deficient soybean crops. J. Plant Nut. 30:93-104. Borges, R., and A.P. Mallarino. 2000. Grain yield, early growth, and nutrient uptake of no-till soybean as affected by phosphorus and potassium placement. Agron. J. 92:380-388. Borst, H.L., and L.E. Thatcher. 1931. Life history and composition of the soybean plant. Bull. 494. Ohio Agricultural Experiment Station, p. 1-96. Brooker, A.P., L.E. Lindsey, S.W. Culman, S.K. Subburayalu, and P.R. Thomison. 2017. Low soil phosphorus and potassium limit soybean grain yield in Ohio. Crop, Forage & Turfgrass Management 3:2016-12-0081. Bundy, L.G., H. Tunney, and A.D. Halvorson. 2005. Agronomic aspects of phosphorus management. In: J.T. Sims, A.N. Sharpley, editors, Phosphorus: Agriculture and the environment, Agron. Monogr. 46. ASA, CSSA, and SSSA, Madison, WI. p. 685-727. Cafaro La Menza, N., J.P. Monzon, J.E. Specht, and P. Grassini. 2017. Is soybean yield limited by nitrogen supply? Field Crops Research 213:204-212. Carpenter, A.C., and J.E. Board. 1997a. Branch yield components controlling soybean yield stability across plant populations. Crop Sci. 37:885-891. Carpenter, A.C., and J.E. Board. 1997b. Growth dynamic factors controlling soybean yield stability across plant populations. Crop Sci. 37:1520-1526. Ceccotti, S.P. 1996. Plant nutrient sulphur – a review of nutrient balance, environmental impact and fertilizers. Fert. Res. 43:117-125. Chaudhary, M.R., and S.S. Prihar. 1974. Comparison of banded and broadcast fertilizer Chen, G., and P. Wiatrak. 2011. Seeding rate effects on soybean height, yield, and economic applications in relation to compaction and irrigation in maize and wheat. Agron. J. 66:560-564. return. Agron. J. 103:1301-1307. 24 Chien, S.H., L.A. Teixeira, H. Cantarella, G.W. Rehm, C.A. Grant, and M.M. Gearhart. 2016. Agronomic effectiveness of granular nitrogen/phosphorus fertilizers containing elemental sulfur with and without ammonium sulfate: A review. Agron. J. 108:1203-1213. Ciampitti, I.A., and T.J. Vyn. 2014. Understanding global and historical nutrient use Cigelske, B.D. 2016. Soybean response to nitrogen and sulfur fertilization. M.S. thesis. ProQuest efficiencies for closing maize yield gaps. Agron. J. 106:2107-2117. Diss. Publ. UMI 10267419. North Dakota State Univ. Clover, M.W., and A.P. Mallarino. 2013. Corn and soybean tissue potassium content responses to potassium fertilization and relationships with grain yield. Soil Sci. Soc. Am. J. 77:630- 642. Coleman, R. 1966. The importance of sulfur as a plant nutrient in world crop production. Soil Sci. 101:230-239. Cox, W.J., J.H. Cherney, and E. Shields. 2010. Soybeans compensate at low seeding rates but not at high thinning rates. Agron. J. 102:1238-1243. Dawar, K., M. Zaman, J.S. Rowarth, J. Blennerhassett, and M.H. Turnbull. 2011. Urea De Bruin, J.L., and P. Pedersen. 2008a. Effect of row spacing and seeding rate on soybean yield. hydrolysis and lateral and vertical movement in the soil: Effects of urease inhibitor and irrigation. Biol. Fertil. Soils 47:139-146. Agron. J. 100:704-710. De Bruin, J.L., and P. Pedersen. 2008b. Soybean seed yield response to planting date and seeding rate in the Upper Midwest. Agron. J. 100:696-703. Devlin, D.L., D.L. Fjell, J.P. Shroyer, W.B. Gordon, B.H. Marsh, L.D. Maddux, V.L. Martin, and S.R. Duncan. 1995. Row spacing and seeding rates for soybean in low and high yielding environments. J. Prod. Agric. 8:215-222. Dibb D.W., and W.R. Thompson Jr. 1985. Interaction of potassium with other nutrients. In: R.D. Munson, editor, Potassium in agriculture. ASA, CSSA, SSSA, Madison, WI. p. 515-533. Cambardella. 2002. Nitrogen management strategies to reduce nitrate leaching in tile- drained Midwestern soils. Agron. J. 94:153-171. Dinnes, D.L., D.L. Karlen, D.B. Jaynes, T.C. Kaspar, J.L. Hatfield, T.S. Colvin, and C.A. Duncan, W.G., and A.J. Ohlrogge. 1958. Principles of nutrient uptake from fertilizer bands. Egli, D.B. 1988. Alterations in plant growth and dry matter distribution in soybean. Agron. J. II. Root development in the band. Agron. J. 50:605-608. 80:86-90. 25 AMBIO 31:169-176. time of application effects on no-till corn yields and nitrogen uptakes. Agron. J. 78:741-746. Fixen, P.E., and F.B. West. 2002. Nitrogen fertilizers: Meeting contemporary challenges. Fox, R.H., J.M. Kern, and W.P. Piekielek. 1986. Nitrogen fertilizer source, and method and Fox, R.H., and W.P. Piekielek. 1993. Management and urease inhibitor effects on nitrogen Franzen, D.W. 2017. Nitrogen extenders and additives for field crops. Bull. SF1581, North Gaspar, A.P., C.A.M. Laboski, S.L. Naeve, and S.P. Conley. 2017a. Dry matter and nitrogen use efficiency in no-till corn. J. Prod. Agric. 6:195-200. Enderson, J.T., A.P. Mallarino, and M.U. Haq. 2015. Soybean yield response to foliar-applied micronutrients and relationships among soil and tissue tests. Agron. J. 107:2143-2161. Dakota State University, Fargo, ND. uptake, partitioning, and removal across a wide range of soybean seed yield levels. Crop Sci. 57:2170-2182. Gaspar, A.P., C.A.M. Laboski, S.L. Naeve, and S.P. Conley. 2017b. Phosphorus and potassium uptake, partitioning, and removal across a wide range of soybean seed yield levels. Crop Sci. 57:2193-2204. Gaspar, A.P., C.A.M. Laboski, S.L. Naeve, and S.P. Conley. 2018. Secondary and micronutrient uptake, partitioning, and removal across a wide range of soybean seed yield levels. Agron. J. 110:1328-1338. Halvorson, A.D., and M.E. Bartolo. 2014. Nitrogen source and rate effects on irrigated corn Ham, G.E., I.E. Liener, S.D. Evans, R.D. Frazier, and W.W. Nelson. 1975. Yield and yields and nitrogen-use efficiency. Agron. J. 106:681-693. composition of soybean seed as affected by N and S fertilization. Agron. J. 67:293-297. Hammond, L.C., C.A. Black, and A.G. Norman. 1951. Nutrient uptake by soybeans on two Iowa soils. Res. Bull. 384. Hankinson, M.W., L.E. Lindsey, and S.W. Culman. 2015. Effect of planting date and starter fertilizer on soybean grain yield. Crop, Forage & Turfgrass Management 1:2015-0178. Hanway, J.J., and J.W. Johnson. 1985. Potassium nutrition of soybeans. In: R.D. Munson, editor, Potassium in agriculture. ASA, CSSA, and ASSA, Madison, p. 753–764. Hanway, J.J., and C.R. Weber. 1971a. Accumulation of N, P, and K by soybean (Glycine max (L.) Merrill) Plants. Agron. J. 63:406-408. 26 Hanway, J.J., and C.R. Weber. 1971b. Dry matter accumulation in eight soybean (Glycine max (L.) Merrill) varieties. Agron. J. 63:227-230. Hanway, J.J., and C.R. Weber. 1971c. Dry matter accumulation in soybean (Glycine max (L) Merrill) plants as influenced by N, P, and K fertilization. Agron. J. 63:263-266. Hanway, J.J., and C.R. Weber. 1971d. N, P, and K percentages in soybean (Glycine max (L.) Merrill) plant parts. Agron. J. 63:286-290. Harder, D.B., C.L. Sprague, and K.A. Renner. 2007. Effect of soybean row width and population on weeds, crop yield, and economic return. Weed Technol. 21:744-752. Harper, J.E., and R.H. Hageman. 1972. Canopy and seasonal profiles of nitrate reductase in soybeans (Glycine max L. Merr.). 49:146-154 Havelka, U.D., M.G. Boyle, and R.W.F. Hardy. 1982. Biological nitrogen fixation. In: F.J. Stevenson, editor, Nitrogen in agricultural soils, Agron. Monogr. 22. ASA, CSSA, SSSA, Madison, WI. p. 365-422. Havlin, J.L., S.L. Tisdale, J.D. Beaton, and W.L. Nelson. 2014. Soil fertility and fertilizers: An introduction to nutrient management 8th ed. Upper Saddle River, New Jersey, USA: Pearson Prentice Hall. Hilfiker, R.E., and B. Lowery. 1988. Effect of conservation tillage systems on corn root growth. Soil & Tillage Research 12:269-283. Hitsuda, K., K. Toriyama, G.V. Subbarao, and O. Ito. 2008. Sulfur management for soybean production. In: J. Jez, editor, Sulfur: A missing link between soils, crops, and nutrition, Agron. Monogr. 50. ASA, CSSA, SSSA, Madison, WI. p. 117-142. Hitsuda, K., M. Yamada, and D. Klepker. 2005. Sulfur requirement of eight crops at early stages of growth. Agron. J. 97:155-159. Hodgen, P.J., R.B. Ferguson, J.F. Shanahan, and J.S. Schepers. 2009. Uptake of point source depleted 15N fertilizer by neighboring corn plants. Agron. J. 101:99-105. Howard, D.D., and D.D. Tyler. 1989. Nitrogen source, rate, and application method for no- tillage corn. Soil Sci. Soc. Am. J. 53:1573-1577. Hymowitz, T., and W.R. Shurtleff. 2005. Debunking soybean myths and legends in the historical and popular literature. Crop Sci. 45:473-476. Hungria, M., J.C. Franchini, R.J. Campo, C.C. Crispino, J.Z. Moraes, R.N.R. Sibaldelli, I.C. Mendes, and L. Arihara. 2006. Nitrogen nutrition of soybean in Brazil: Contributions of biological N2 fixation and N fertilizer to grain yield. Can. J. Plant. Sci. 86:927-939. 27 Isidro-Sánchez, J., B. Perry, A.K. Singh, H. Wang, R.M. DePauw, C.J. Pozniak, B.L. Beres, E.N. Johnson, and R.D. Cuthbert. 2017. Effects of seeding rate on durum crop production and physiological responses. Agron. J. 109:1981-1990. Kaiser, D.E., A.P. Mallarino, and M. Bermudez. 2005. Corn grain yield, early growth, and Kaiser, D.E., F.G Fernandez, J.A. Lamb, J.A. Coulter, and B. Barber. 2016. Fertilizing corn in early nutrient uptake as affected by broadcast and in-furrow starter fertilization. Agron. J. 97:620-626. Minnesota. Ext. Publ. AG-FO-3790-D. Univ. of Minnesota Extension. St Paul, MN. Kaiser, D.E., and K. Kim. 2013. Soybean response to sulfur fertilizer applied as a broadcast or starter using replicated strip trials. Agron. J. 105:1189-1198. applied to no-till corn. Soil Sci. Soc. Am. J. 50:1060-1063. sorghum production: I. Rate and time of application. Agron. J. 92:321-328. tillage, wheel traffic, and fertilizer placement. Soil Sci. Soc. Am. J. 55:1390-1394. Kaspar, T.C., H.J. Brown, and E.M. Kassmeyer. 1991. Corn root distribution as affected by Keller, G.D., and D.B. Mengel. 1986. Ammonia volatilization from nitrogen fertilizers surface Khosla, R., M.M. Alley, and P.H. Davis. 2000. Nitrogen management in no-tillage grain Lassaletta, L., G. Billen, B. Grizzetti, J. Anglade, and J. Garnier. 2014. 50 year trends in nitrogen Lee, C.D., D.B. Egli, and D.M. TeKrony. 2008. Soybean response to plant population at early use efficiency of world cropping systems: The relationship between yield and nitrogen input to cropland. Environ. Res. Lett. 9:1-9. and late planting dates in the Mid-South. Agron. J. 100:971-976. Lueschen, W.E., and D.R. Hicks. 1977. Influence of plant population on field performance of three soybean cultivars. Agron. J. 69:390-393. Lusas, E.W. 2004. Soybean processing and utilization. In: H.R. Boerma, J.E. Specht, editors, Soybeans: Improvement, production, and uses, Agron. Monogr. 16. ASA, CSSA, and SSSA, Madison, WI. p. 949-1045. Mallarino, A.P., J.D. Kaiser, D.A. Ruiz-Diaz, C.A.M. Laboski, J.J. Camberato, and T.J. Vyn. 2017. Micronutrients for soybean production in the north central region. Bull. 3145. Iowa State Univ. Ext., Amez, IA. Mallarino, A.P., J.R. Webb, and A.M. Blackmer. 1991. Soil test values and grain yields during 14 years of potassium fertilization of corn and soybean. J. Prod. Agric. 4:560-567. Maizlish, N.A., D.D. Fritton, and W.A. Kendall. 1980. Root morphology and early development of maize at varying levels of nitrogen. Agron. J. 72:25-31. 28 under field conditions. Agron. J. 66:341-344. till and conventional till corn. Agron. J. 74:515-518. Mengel, D.B, and S.A Barber. 1974. Development and distribution of the corn root system Mengel, D.B., D.W. Nelson, and D.M. Huber. 1982. Placement of nitrogen fertilizers for no- Moll, R.H., E.J. Kamprath, and W.A. Jackson. 1982. Analysis and interpretation of factors Morse, W., J. Cartter, and E. Hartwig. 1950. Soybean production for hay and beans. USDA which contribute to efficiency of nitrogen utilization. Agron. J. 74:562-564. Farmers’ Bulletin 2024:1-15. Mourtzinis, S., D. Marburger, J. Gaska, T. Diallo, J.G. Lauer, and S. Conley. 2017. Corn, soybean, and wheat yield response to crop rotation, nitrogen rates, and foliar fungicide application. Crop Sci. 57:983-992. Mueller, S.M., J.J. Camberato, C. Messina, J. Shanahan, H. Zhang, and T.J. Vyn. 2017. Late- split nitrogen applications increased maize plant nitrogen recovery but not yield under moderate to high nitrogen rates. Agron. J. 109:2689-2699. Mullock, J.L. 2014. I. Effect of preplant nitrogen distance from corn rows on grain yield and Naeve, S.L., and R.M. Shibles. 2005. Distribution and mobilization of sulfur during soybean nitrogen uptake II. Development of a winter wheat sensor-based nitrogen rate algorithm for Kansas and Oklahoma. Ph.D. dissertation. ProQuest Diss. Publ. UMI 3728094. Oklahoma State Univ. reproduction. Crop Sci. 45:2540-2551. applications for corn. Soil Sci. Soc. Am. J. 75:143-151. Nelson, K.A., P.C. Scharf, W.E. Stevens, and B.A. Burdick. 2011. Rescue nitrogen Niehues, B.J., R.E. Lamond, C.B. Godsey, and C.J. Olsen. 2004. Starter nitrogen fertilizer Norsworthy, J.K., and L.R. Oliver. 2001. Effect of seeding rate of drilled glyphosate-resistant soybean (Glycine max) on seed yield and gross profit margin. Weed Technol. 15:284- 292. management for continuous no-till corn production. Agron. J. 96:1412-1418. Ordóñez, R.A., M.J. Castellano, J.L. Hatfield, M.J. Helmers, M.A. Licht, M. Liebman, R. Dietzel, R. Martinez-Feria, J. Iqbal, L.A. Puntel, S.C. Córdova, K. Togliatti, E.E. Wright, and S.V. Archontoulis. 2018. Maize and soybean root front velocity and maximum depth in Iowa, USA. Field Crops Res. 215:122-131. Orlowski, J.M., B.J. Haverkamp, R.G. Laurenz, D.A. Marburger, E.W. Wilson, S.N. Casteel, S.P. Conley, S.L. Naeve, E.D. Nafziger, K.L. Roozeboom, W.J. Ross, K.D. Thelen, and 29 C.D. Lee. 2016. High-input management systems effect on soybean seed yield, yield components, and economic break-even probabilities. Crop Sci. 56:1988-2004. Osborne, S.L., and W.E. Riedell. 2006. Starter nitrogen fertilizer impact on soybean yield and quality in the Northern Great Plains. Agron. J. 98:1569-1574. Pan, B., S.K. Lam, A. Mosier, Y. Luo, and D. Chen. 2016. Ammonia volatilization from synthetic fertilizers and its mitigation strategies: A global synthesis. Agriculture, Ecosystems and Environment 232:283-289. Parvej, M.R., N.A. Slaton, L.C. Purcell, and T.L. Roberts. 2016. Soybean yield components and seed potassium concentration responses among nodes to potassium fertility. Agron. J. 108:854-863. Peng, Y., X. Li, and C. Li. 2012. Temporal and spatial profiling of root growth revealed novel Pettigrew, W.T. 2008. Potassium influences on yield and quality production for maize, what, response of maize roots under various nitrogen supplies in the field. PLoS One. 7:1-11. soybean, and cotton. Physiologia Plantarum 113:670-681. Quinn, D. 2018. Influence of input-intensive management on soft winter wheat and soybean grain yield and profitability. M.S. thesis. ProQuest Diss. Publ. UMI 10790844. Michigan State Univ. Randall, G.W., and R.G. Hoeft. 1988. Placement methods for improved efficiency of P and K fertilizers: A Review. J. Prod. Agric. 1:70-79. Randall, G.W., T.K. Iragavarapu, and B.R. Bock. 1997. Nitrogen application methods and timing for corn after soybean in a ridge-tillage system. J. Prod. Agric. 10:300-307. Raun, W.R., and G.V. Johnson. 1999. Improving nitrogen use efficiency for cereal Rehm, G.W., and J.A. Lamb. 2009. Corn response to fluid fertilizers placed near the seed at Rigsby, B., and J.E. Board. 2003. Identification of soybean cultivars that yield well at low plant planting. Soil Sci. Soc. Am. J. 73:1427-1434. production. Agron. J. 91:357-363. populations. Crop Sci. 43:234-239. use efficiency in Upper Midwest irrigated sandy soils. Agron. J. 108:1681-1691. Rubin, J.C., A.M. Struffert, F.G. Fernández, and J.A. Lamb. 2016. Maize yield and nitrogen Ruiz Diaz, D.A., J.A. Hawkins, J.E. Sawyer, and J.P. Lundvall. 2008. Evaluation of in-season nitrogen management strategies for corn production. Agron. J. 100:1711-1719. 30 maize. Agron. J. 75:593-598. Northern Corn Belt. Agron. J. 110:2059-2069. Russelle, M.P., R.D. Hauck, and R.A. Olson. 1983. Nitrogen accumulation rates of irrigated Rutan, J., and K. Steinke. 2018. Pre-Plant and in-season nitrogen combinations for the Rutto, E., J.P. Vossenkemper, J. Kelly, B.K. Chim, and W.R. Raun. 2013. Maize grain yield response to the distance nitrogen is placed away from the row. Expl. Agric. 49:3-18. Sale, P.W.G., and L.C. Campbell. 1980. Patterns of mineral accumulation in soybean seed. Field Crops Research 3:157-163. Salvagiotti, F., K.G. Cassman, J.E. Specht, D.T. Walters, A. Weiss, and A. Dobermann. 2008. Nitrogen uptake, fixation and response to fertilizer N in soybeans: A review. Field Crops Res. 108:1-13. Schlegel, A.J., and C.A. Grant 2006. Soil Fertility. In: G.A. Peterson, P.W. Unger, W.A. Payne, editors, Dryland agriculture, Agron. Monogr. 23. ASA, CSSA, SSSA, Madison, WI. p. 141-194. 695. nitrogen need and yield response of corn in the North-Central USA. Agron. J. 98:655-665. Scharf, P. C. 1999. On-farm starter fertilizer response in no-till corn. J. Prod. Agric. 12:692- Scharf, P.C., S.M. Brouder, and R.G. Hoeft. 2006. Chlorophyll meter readings can predict Scharf, P.C., W.J. Wiebold, and J.A. Lory. 2002. Corn yield response to nitrogen fertilizer Schwab, G.J., and L.W. Murdock. 2010. Nitrogen transformation: Inhibitors and controlled release urea. Publ. AGR-185. Univ. of Kentucky Coop. Ext. Serv., Lexington, KY. Schmitt, M.A., J.A. Lamb, G.W. Randall, J.H. Orf, and G.W. Rehm. 2001. In-season fertilizer timing and deficiency level. Agron. J. 94:435-441. nitrogen applications for soybean in Minnesota. Agron. J. 93:983-988. Sexton, P.J., N.C. Paek, and R. Shibles. 1998. Soybean sulfur and nitrogen balance under varying levels of available sulfur. Crop Sci. 38:975-982. systems for improved nitrogen management of irrigated corn. Soil Sci. Soc. Am. J. 80:1663-1674. Shapiro, C., A. Attia, S. Ulloa, and M. Mainz. 2016. Use of five nitrogen source and placement Sharratt, B.S., and D.A. McWilliams. 2005. Microclimatic and rooting characteristics of narrow-row versus conventional-row corn. Agron. J. 97:1129-1135. 31 Shibles, R.M., and C.R. Weber. 1966. Interception of solar radiation and dry matter production by various soybean planting patterns. Crop Sci. 6:55-59. Smith, E.G., R.D. Knutson, C.R. Taylor, and J.B. Penson. 1990. Impact of chemical use Specht, J.E., D.J. Hume, and S.V. Kumudini. 1999. Soybean yield potential - a genetic and reduction on crop yields and costs. Texas A&M Univ., Dep. of Agric. Econ., Agric. and Food Policy Cent., College Station. physiological perspective. Crop Sci. 39:1560-1570. Starling, M.E., C.W. Wood, and D.B. Weaver. 1998. Starter nitrogen and growth habit effects on late-planted soybean. Agron. J. 90:658-662. Stecker, J.A., D.D. Buchholz, R.G. Hanson, N.C. Wollenhaupt, and K.A. McVay. 1993. Application placement and timing of nitrogen solution for no-till corn. Agron. J. 85:645-650. Steinke, K., J. Rutan, and L. Thurgood. 2015. Corn response to nitrogen at multiple sulfur rates. Stone, L.R., D.A. Whitney, and C.K. Anderson. 1985. Soybean yield response to residual NO3-N Agron. J. 107:1347-1354. and applied N. Plant Soil 84:259-265. Suhre, J.J., N.H. Weidenbenner, S.C. Rowntree, E.W. Wilson, S.L. Naeve, S.P. Conley, S.N. Casteel, B.W. Diers, P.D. Esker, J.E. Specht, and V.M. Davis. 2014. Soybean yield partitioning changes revealed by genetic gain and seeding rate interactions. Agron. J. 106:1631-1642. Sunarpi, and J.W. Anderson. 1997. Inhibition of sulphur redistribution into new leaves of vegetative soybean by excision of the maturing leaf. Plant Physiol. 99:538-545. Sutradhar, A.K., D.E. Kaiser, and L.M. Behnken. 2017. Soybean response to broadcast application of boron, chlorine, manganese, and zinc. Agron. J. 109:1048-1059. Sweeney, D.W. 2016. Tillage, seeding rate, and fertilizer placement for corn grown in Tamagno, S., G.R. Balboa, Y. Assefa, P. Kovács, S.N. Casteel, F. Salvagiotti, F.O. Garciá, W.M. claypan soil under low-yielding conditions. Crop, Forage & Turfgrass Management 2:2015-0217. Stewart, and I.A. Ciampitti. 2017. Nutrient partitioning and stoichiometry in soybean: A synthesis-analysis. Field Crops Res. 200:18-27. Taylor, R.S., D.B. Weaver, C.W. Wood, and E. van Santen. 2005. Nitrogen application increases yield and early dry matter accumulation in late-planted soybean. Crop Sci. 45:854-858. 32 Research Service. https://www.ers.usda.gov/data-products/us-bioenergy-statistics (accessed 20 March 2017). USDA-ERS. 2017. U.S. bioenergy statistics, Table 5. Statistics by subject. USDA Economic USDA-FAS. 2017a. Grain: World markets and trade. USDA Foreign Agricultural Service. USDA-FAS. 2017b. Soybeans: World supply and distribution. USDA Foreign Agricultural https://apps.fas.usda.gov/psdonline/circulars/grain.pdf (accessed 17 March 2017). Service. https://apps.fas.usda.gov/psdonline/reporthandler.ashx?reportId=706& templateId=8&format=html&fileName=Table%2007:%20Soybeans:%20World%20Supp ly%20and%20Distribution (accessed 31 October 2017). Agriculture Statistics Service. http://www.agcensus.usda.gov/Publications/2012/ (accessed 17 March 2018). USDA-NASS. 2017a. 2012 Census of agriculture publications: Full report. USDA National USDA-NASS. 2017b. National statistics for corn: Corn, area planted, acres planted. Statistics by USDA-NASS. 2017c. National statistics for corn: Corn, yield, measured in bu/acre. Statistics by USDA-NASS. 2017d. National statistics for soybeans: Soybeans, production, measured in $. subject. USDA National Agriculture Statistics Service. http://www.nass.usda.gov/Statistics_by_Subject/index.php (accessed 17 March 2018). subject. USDA National Agriculture Statistics Service. http://www.nass.usda.gov/Statistics_by_Subject/index.php (accessed 17 March 2018). Statistics by subject. USDA National Agriculture Statistics Service. http://www.nass.usda.gov/Statistics_by_Subject/index.php (accessed 27 February 2017). USDA-NASS. 2017e. National statistics for soybeans: Soybeans, yield, measured in bu/acre. Statistics by subject. USDA National Agriculture Statistics Service. http://www.nass.usda.gov/ Statistics_by_Subject/index.php (accessed 31 October 2017). USDA-NASS. 2017f. 2016 State agriculture overview. Statistics by state. USDA National Agriculture Statistics Service. https://www.nass.usda.gov/Quick_Stats/Ag_Overview/ stateOverview.php?state=MICHIGAN (accessed 1 September 2017). Walker, E.R., A. Mengistu, N. Bellaloui, C.H. Koger, R.K. Roberts, and J.A. Larson. 2010. Plant population and row-spacing effects on maturity group III soybean. Agron. J. 102:821- 826. maize (Zea Mays L.) grain yields and nitrogen use efficiency. Journal of Plant Nutrition 35:538-555. Walsh, O., W. Raun, A. Klatt, and J. Solie. 2012. Effect of delayed nitrogen fertilization on Warncke, D., J. Dahl, and L. Jacobs. 2009. Nutrient recommendations for field crops in Michigan. Bull. E2904, Michigan State University Extension, East Lansing, MI. 33 Wells, R. 1993. Dynamics of soybean growth in variable planting patterns. Agron. J. 85:44-48. Wesley, T.L., R.E. Lamond, V.L. Martin, and S.R. Duncan. 1998. Effects of late-season nitrogen fertilizer on irrigated soybean yield and composition. J. Prod. Agric. 11:331-336. Wilson, R.F. 2004. Seed composition. In: H.R. Boerma, J.E. Specht, editors, Soybeans: Improvement, production, and uses, Agron. Monogr. 16. ASA, CSSA, and SSSA, Madison, WI. p. 621-677. Woli, K.P., M.J. Boyer, R.W. Elmore, J.E. Sawyer, L.J. Abendroth, and D.W. Barker. 2016. Corn era hybrid response to nitrogen fertilization. Agron. J. 108:473-486. Zapata, F., S.K.A. Danso, G. Hardarson, and M. Fried. 1987. Time course of nitrogen fixation in field-grown soybean using nitrogen-15 methodology. Agron. J. 79:172-176. Zhao, F.J., M.J. Hawkesford, A.G.S. Warrilow, S.P. McGrath, and D.T. Clarkson. 1996. Responses of two wheat varieties to sulphur addition and diagnosis of sulphur deficiency. Plant Soil 181:317-327. 34 CHAPTER 2 SOYBEAN SEEDING RATE AND FERTILIZER APPLICATION INTERACTIONS ON PLANT GROWTH AND GRAIN YIELD Abstract Inconsistent soybean (Glycine max L. Merr.) grain yield response to fertilizer applications necessitate the need for improved fertilizer investment strategies. Greater dry matter (DM) may support nutrient uptake and grain yield potential but it is not clear whether increased plant DM and reduced interplant competition found in decreased seeding rates may maximize grain yield response to fertilizer applications. A three-site-year trial was conducted to evaluate the interaction between soybean seeding rates and fertilizer applications on plant growth, nutrient accumulation, grain yield, and net economic return. Seeding rates included: 123,500, 222,400, 321,200, and 420,100 seeds ha-1. Fertilizer applications consisted of: unfertilized; 90 kg MOP (0- 0-62 N-P-K) ha-1 pre-plant incorporated (PPI); 168 kg MESZ (12-40-0-10-1 N-P-K-S-Zn) ha-1 applied 5-cm below and to the side of the seed at planting (5x5); and 90 kg MOP ha-1 PPI and 168 kg MESZ ha-1 applied 5x5. Dry matter at V4 increased 37.7 to 116.6% and 73.3 to 137.5% with seeding rates ≥ 222,400 seeds ha-1 and MESZ application, respectively, and greater early- season DM supported increased nutrient uptake and grain yield potential. Increasing seeding rate from 123,500 to 222,400 seeds ha-1 increased grain yield 9% but no differences were observed above 222,400 seeds ha-1. The MESZ and MOP+MESZ application increased grain yield 7.4 and 6.9%, respectively, while MOP did not affect grain yield across all site-years. Results suggest focusing fertilizer application at seeding rates ≥ 222,400 seeds ha-1 may reduce early-season 35 nutrient loss potential through greater dry matter accumulation, although grain yield response may be predominately influenced by environmental conditions and soil nutrient concentrations. Introduction Michigan 2018 soybean yield (3228 kg ha-1) and crop price (US$0.32 kg-1) were +807 kg ha-1 and +US$0.15 kg-1 than in 2000, respectively (USDA-NASS, 2018a,b). Soybean prices in 2013 reached US$47 kg-1 but have since declined US$0.15 kg-1 (USDA-NASS, 2018a,b). Inconsistent yield responses to fertilizer applications at current Michigan production levels coupled with stagnant or decreasing soybean commodity prices have prompted interest in focusing fertilizer applications. In 1931, total dry matter (TDM) at soybean maturity and grain yield were 4,700 and 1,200 kg ha-1, respectively, but in high yield environments both have since increased to 10,700 and 5,500 kg ha-1, respectively (Borst and Thatcher, 1931; Gaspar et al., 2017a). Increased grain yields and nutrient uptake from 1930 to 2017 may be due to increased TDM (0.025 Mg ha-1 yr-1) rather than grain production per unit of TDM (i.e., harvest index [HI]; 0.0008 yr-1) (Balboa et al., 2018). Biological nitrogen fixation (BNF) and soil nitrogen (N) may fulfill soybean grain N requirements in grain yields ≤ 4500 kg ha-1 and grain yield may be 95 to 97% of maximum when soil phosphorus (P), potassium (K), and micronutrient supply exceeds critical concentrations (i.e., potential for < 5% grain yield increase to fertilizer applications when soil nutrient concentrations are sufficient) (Salvagiotti et al., 2008; Warncke et al., 2009). Grain yield response to fertilizer application may further be limited in plant densities between 1.5 to 6.0 plants m-2 due to interplant competition (Duncan, 1986; Egli, 1988b; Havlin et al., 2014) and may create additional difficulty in developing widespread plant-responsive fertilizer management strategies. Greater TDM in modern soybean varieties and reduced interplant 36 competition from decreased seeding rates (i.e., < 300,000 seeds ha-1) may provide potential for both increased nutrient accumulation and grain yield response to fertilizer application (Board, 2000; Bender et al., 2015; Balboa et al., 2018). Greater soybean planting densities (i.e., ≥ 300,000 seeds ha-1) tend to increase competitiveness with weeds, improve light interception, and increase grain yield potential but the additional interplant competition may contribute to grain yield plateaus (Holliday, 1960; Ball et al., 2000; Norsworthy and Oliver, 2001; Harder et al., 2007). Compared to increased seeding rates, decreased seeding rates (i.e., < 300,000 seeds ha-1) reduce production costs, plant lodging, and disease severity (Ball et al., 2000; de Souza Jaccoud-Filho et al., 2016; Lee et al., 2008). In weed-free environments, Harder et al. (2007) reported similar grain yields between plant densities of 185,000 to 445,000 plants ha-1. Decreased plant densities produced similar grain yields as increased plant densities through increased crop growth rate, TDM, and plant branch and pod production (Egli, 1988a; Wells, 1993; Carpenter and Board, 1997b; Suhre et al., 2014). De Bruin and Pedersen (2008a) reported grain yield was maximized at 462,200 plants ha-1 while 95% of maximum yield was achieved with plant densities between 118,800 and 213,800 seeds ha-1. Modern soybean germplasm offers increased compensation ability at reduced planting populations and improved tolerance to interplant competition at increased planting populations (De Bruin and Pedersen, 2009; Suhre et al., 2014). Limited data exist examining opportunities to maximize grain yield in response to combinations of seeding rates and fertilizer applications. Positive correlations between TDM and grain yield exist (Parvez et al., 1989; Ball et al., 2000; Gaspar et al., 2017a) but TDM has also been a poor predictor of grain yield (Shibles and Weber, 1966; Weber et al., 1966). At increased seeding rates, interplant competition for sunlight and other resources (e.g., water and nutrients) may limit DM accumulation and crop growth 37 (Carpenter and Board, 1997b, Board, 2000). In a determinate cultivar, Carpenter and Board (1997a) reported DM plant-1 was 63.6 and 19.3 g plant-1 at 70,000 and 234,000 plants ha-1, respectively. Due to greater DM plant-1, Board (2000) reported no differences in TDM between plant densities of 80,000 and 390,000 plants ha-1. Similarly, Norsworthy and Frederick (2002) reported similar TDM and grain yield among seeding rates between 370,000 and 620,000 seeds ha-1. Chen and Wiatrak (2011) suggested greater early-season DM may be achieved with increased seeding rates but TDM plateaued above 272,000 seeds ha-1. Maximum DM provides potential for increased nutrient uptake, nutrient remobilization, and grain yield potential while simultaneously reducing the risk for nutrient loss (Bender et al., 2015). In 2012, 44, 43, and 69% of Michigan soybean hectares were fertilized with N, P, and K, respectively (USDA-NASS, 2018c). Biological N fixation and soil N supply may satisfy soybean N requirements for grain yields ≤ 4500 kg ha-1 (Salvagiotti et al., 2008) but grower interest in soybean N applications continues to increase due to higher-yielding cultivars. Starter P applications are common in Michigan due to slow root growth during cool, wet springs (Warncke et al., 2009). In Ohio, Hankinson et al. (2014) reported no grain yield increase to starter P application when soil P concentrations exceeded 33 mg kg-1. Similarly, grain yield response to K applications were unlikely in soils above 173 mg K kg-1 (Clover and Mallarino, 2013) but current Michigan K recommendations also consider cation exchange capacity due to large production hectares on coarse-textured soils (Warncke et al., 2009). Recent awareness of greater soybean yields, decreased incidental fertilizer sulfur (S), decreased atmospheric S deposition in the North Central U.S., and perceived increases in micronutrient deficiencies have prompted interest in both S and zinc (Zn) application (Hitsuda et al., 2008; Chien et al., 2016; Sutradhar et al., 2017). Subsurface fertilizer applications at planting may increase both early and 38 late season nutrient availability and help mitigate inconsistent grain yield responses to foliar fertilizer applications as grain N, P, S, and Zn requirements rely more on soil uptake after R5.5 rather than vegetative remobilization (Orlowski et al., 2016; Gaspar et al., 2017a,b; 2018). Volatile spring environmental conditions, variable soil texture, and minimal BNF N contributions until V2-4 may contribute to spatial and temporal soil N inconsistency and provide opportunities for increased early-season DM and nutrient accumulation with starter N application (Osborne and Riedell, 2006; Havlin et al., 2014; Tamagno et al., 2018). Additionally, P applications may promote early-season growth during cool spring temperatures with a greater and consistent DM increase in P deficient soils (Borges and Mallarino, 2000; Warncke et al., 2009). Results of Kaiser and Kim (2013) suggested N, P, K, and S were synergistic nutrients that promoted early-season (i.e., V4-7) nutrient uptake and DM accumulation. Calcareous (pH >6.5) or high P (i.e., > 40 mg kg-1) soils may provide opportunity to increase DM accumulation with Zn application due to potential Zn deficiency (Vitosh et al., 1995). Gaspar et al. (2017b) reported grain K requirements relied on vegetative remobilization past R5.5 emphasizing the importance K tissue concentrations to support soybean DM and K accumulation prior to grain-fill. Dry matter partitioning previously was thought to be distributed into leaves, stems, pods, and grain at 25, 27, 19, and 29%, respectively (Borst and Thatcher, 1931). However in modern soybean varieties, Bender et al (2015) reported 16, 33, 14, and 37% of TDM partitioning into leaves, stems, pods, and grain, respectively, and greater stem distribution in current cultivars may support greater yield on lateral branches as compared to the main stem (Hanway and Weber, 1971; Suhre et al., 2014). Egli et al. (1985) reported soybean partitioning ratios were not affected by seeding rates. However, Wilcox (1974) and Spaeth et al. (1984) suggested increased grain removal relative to TDM (i.e., HI) at decreased seeding rates. Additionally, Gaspar et al. (2017a) 39 suggested HI may vary by yield level. Seeding rate and fertilizer application affecting grain yield and DM distribution may in tandem influence nutrient uptake, partitioning, and removal (Bender et al., 2015; Gaspar et al., 2017a). The objective of this study was to evaluate the effects of seeding rate and fertilizer application on DM accumulation and partitioning, nutrient uptake, grain yield, and net economic return. Materials and Methods Field trials were conducted in Richville, MI (4323’57.3”N, 8341’49.7”W) at the Saginaw Valley Research and Extension Center on a non-irrigated Tappan-Londo loam soil (fine-loamy, mixed, active, calcareous, mesic Typic Epiaquolls) in 2017 and in Lansing, MI (4242’37.0”N, 8428’14.6”W) at the South Campus Research Farm on a non-irrigated Capac loam soil (fine-loamy, mixed, active, mesic Aquic Glossudalf) in 2017 and 2018. All sites were previously cropped to corn (Zea mays L.) with autumn chisel plow (20-cm depth) and spring field cultivation (10-cm depth). Pre-plant soil samples (20-cm depth) were collected prior to nutrient application, ground to pass through a 2-mm sieve, and analyzed for soil chemical properties (Table 2.01). Weed control consisted of an application of S-metolachlor (2-chloro-N- (2-ethyl-6-methylphenyl)-N-[(1S)-2-methoxy-1-methylethyl]acetamide) and glyphosate (N- (phosphonomethyl) glycine) followed by a second application of glyphosate across site-years. In Lansing 2017, lambda-syhalothrin (1a(S*),3a(Z)]-cyano(3-phenoxyphenyl)methyl-3-(2-chloro- 3,3,3-trifluoro-1-propenyl)-2,2- dimethylcyclopropanecarboxylate) was applied on 19 July for Japanese beetle (Popillia japonica) leaf feeding damage. Environmental data were collected using the Michigan State University Enviro-weather (https://enviroweather.msu.edu, Michigan 40 State University, East Lansing, MI). Temperature and precipitation 30-yr means were obtained from the National Oceanic and Atmosphere Administration (NOAA, 2018). Trials were arranged as a randomized complete-block split-plot design with four replications. Main plots consisted of seeding rate while subplots were fertilizer application. The four seeding rates were 123,500, 222,400, 321,200, and 420,100 seeds ha-1. The targeted seeding rate of 123,500 seeds ha-1 resulted in a seeding rate of 135,900 seeds ha-1 therefore plots were thinned to 123,500 seeds ha-1 at V1 while all other plant populations were within 10% of the targeted seeding rate as evidenced by stand counts (Fehr and Caviness, 1977; Hicks et al., 1990). Four fertilizer treatments included: i) an unfertilized control, ii) 90 kg MOP ha-1 PPI, iii) 168 kg MicroEssentials® SZ® (MESZ) (Mosaic CO., Plymouth, MN) ha-1 5x5, and iv) a combination of MOP PPI and MESZ 5x5 (MOP+MESZ). Plots measured 12.2 m in length and 4.6 m in width and were planted with a Monosem planter (Monosem Inc., Kansas City, KS) in 76-cm rows using variety ‘AG2535’ (Monsanto Co., St. Louis, MO). Planting dates were 27 April 2017 in Richville and 10 May 2017 and 9 May 2018 in Lansing. Aboveground biomass samples were collected at V4, R2, R5, and R8 growth stages when approximately 50% of plants reached the respective growth stage (Fehr and Caviness, 1977). Dry matter sampling areas were selected from the second row within each plot and consisted of 10 consecutive whole plants that were partitioned into leaves, stems and petioles, flowers and pods, and grain (Bender et al., 2015). Prior to the onset of leaf senescence, 1-cm by 1-cm netting was assembled around sampling areas to retain senesced DM. To determine dry weight, plant tissues were dried at 66C (0% moisture) and total DM accumulation reported as the dry weight sum of all plant components. Whole-plant V4 and R8 grain samples were analyzed for N (AOAC, 1995a), P (AOAC, 1995b), K (AOAC, 1995b), S (AOAC, 1995b), and Zn (AOAC, 1995b). 41 Nutrient accumulation (kg ha-1) was calculated from nutrient concentration, dry matter accumulation, and plant density. A research plot combine (Almcao, Nevada, IA) harvested the center two rows for grain yield, moisture, and test weight with yield adjusted to 135 g kg-1 moisture. Net economic return was calculated using a partial budget by subtracting input cost from gross revenue (i.e., grain price multiplied by yield). Input costs included seed, fertilizer, and application costs obtained from local grain elevators and retailers. Soybean grain prices were US$351.27 Mg-1 in 2017 and US$318.57 Mg-1 in 2018. Fertilizer costs were US$0.33 and $0.54 kg-1 and US$0.39 and $0.65 kg-1 for MOP and MESZ during 2017 and 2018, respectively. Seed cost estimates for 2017 and 2018 were US$82.50 140,000 seeds-1. Application costs were estimated from the Michigan State University Extension Custom Machine and Work Rate Estimates and included US$4.65, $16.16, and $33.63 ha-1 for subsurface 5x5 nutrient application, MOP broadcast application, and MOP incorporation, respectively (Stein, 2016). Data were analyzed in SAS 9.4 (SAS Institute, 2012) using the GLIMMIX procedure. Site-year, seeding rate, and nutrient application were considered fixed effects and replication as random. Normality of residuals were examined using the UNIVARIATE procedure (P ≤ 0.05). Squared and absolute values of residuals were examined with Levene’s Test to confirm homogeneity of variances (P ≤ 0.05). Least square means were separated using the LINES option of the slice statement when ANOVA indicated a significant interaction (P ≤ 0.10). A quadratic plateau model was developed to investigate the response of grain yield and economic return to seeding rate using the NLIN procedure. Pearson product-moment correlations were derived using the REG procedure of SAS to investigate the relationship between DM accumulation and net economic return with grain yield and final DM accumulation with R8 grain nutrient accumulation. 42 Environmental Conditions Results and Discussion Total 2017 growing season (Apr. – Sept.) precipitation was 8 and 15% below the 30-year mean in Richville and Lansing, respectively, but 49 and 44% below the 30-year mean at these locations during the critical July through September pod development and grain fill periods (Table 2.02). In 2018, total growing season precipitation and July through September rainfall volumes in Lansing were within 5% and 2% of the 30-year mean, respectively. Dry soil conditions from deficit precipitation (i.e., greater than 10% below the 30-year mean) during July – September 2017 at both locations and July 2018 may have limited nutrient movement and grain yield potential across site-years. Mean May 2017 air temperatures were within 0.4 and 0.6˚C of the 30-year mean in Richville and Lansing, respectively, and 3.3˚C above the 30-year mean for Lansing May 2018. June through September mean monthly air temperatures were within 1.6˚C of the 30-year mean across site-years. Dry Matter Production and Nutrient Accumulation An interaction between seeding rate and fertilizer treatment (P < 0.01) influenced individual soybean V4 DM production per plant (g plant-1). Treatment interaction means were presented across locations and years (Table 2.03). Maximum V4 DM production per plant occurred at 123,500 seeds ha-1 (1.12 to 2.50 g plant-1) and progressively decreased at each sequentially greater seeding rate interval. Increased leaf area in response to decreased seeding rate is considered important for aboveground soybean plasticity and required to support greater branch and pod production (Carpenter and Board, 1997a; Board, 2000). Regardless of fertilizer treatment, reductions of 0.17 to 0.67 g plant-1 and 0.16 to 0.38 g plant-1 in individual plant DM going from the 123,500 to 222,400 seeds ha-1 and the 222,400 and 321,200 seeds ha-1 seeding 43 rates, respectively, indicated interplant competition prior to the V4 growth stage (Carpenter and Board, 1997a). Reduced planting densities (e.g., 70,000 plants ha-1) may experience decreased overall growth rates (g m-2 d-1) for up to 30 days after soybean emergence compared to greater plant populations (e.g., 164,000 to 234,000 plant ha-1) and may not produce similar growth rates until R1 (Carpenter and Board, 1997b). Current trial results however agree with Board (2000) who found 80,000 plants ha-1 increased plant growth rate 21 days after soybean emergence compared to 145,000 to 390,000 plants ha-1. Results suggest interplant competition may limit early-season plant growth rate solely associated with greater seeding rates (i.e., ≥ 222,400 seeds ha-1). Across fertilizer treatments, MESZ application produced more DM plant-1 across all seeding rates (0.57 to 1.38 g plant-1) and in several instances the additional DM produced was sufficient to offset any reductions in DM due to greater seeding rates. When the mean of treatments not receiving MESZ were subtracted from the mean of treatments with MESZ application (i.e., response to MESZ), MESZ applications increased individual plant DM 76 to 120% (0.54 to 1.34 g plant-1) across all seeding rates. Results indicated that reduced population densities provided a larger per plant DM response to MESZ application, but growers should be cognizant that accelerated crop growth rates during V4 – R1 may reduce vegetative responses observed prior to V4 and often may not translate into grain yield increases (Bender et al., 2015; Gaspar et al., 2017a). Total V4 aboveground DM accumulation (V4DM) (kg ha-1) was influenced by the interaction between site-year and seeding rate (P < 0.01) (Table 2.04). Within each site-year, increasing seeding rate from 123,500 to ≥ 222,400 seeds ha-1 increased V4DM and indicated interplant competition did not limit V4DM. In 2017, V4DM did not increase above 321,200 and 222,400 seeds ha-1 in Richville and Lansing, respectively. Alessi and Power (1982) suggested 44 increased seeding rates limited crop growth under moisture-limiting conditions by depleting early-season water reserves. In 2017, both locations received deficit May precipitation (42 and 22% below the 30-year mean in Richville and Lansing, respectively) which likely limited V4DM accumulation at greater seeding rates. Total 2017 precipitation between planting to V4 was 8.9 and 5.3-cm in Richville and Lansing, respectively, and V4DM may have been limited at lower seeding rates in Lansing (i.e., 222,400 seeds ha-1) compared to Richville (i.e., 321,200 seeds ha-1) due to reduced precipitation. In contrast to 2017, V4DM in 2018 was maximized at 421,100 seeds ha-1 in Lansing. Excessive May 2018 precipitation (i.e., 48% above the 30-year mean) and 13.4-cm precipitation occurring between planting and V4 at this location suggested early-season crop growth was not limiting to increased seeding rates despite the greater interplant competition. Soybean growth and development are affected by environmental conditions (i.e., temperature and precipitation) and current data suggest increased seeding rates limited soybean growth during dry environmental conditions (i.e., Richville and Lansing 2017) but supported additional growth and interplant competition when soil moisture was not limiting (i.e., 2018). Dry matter at V4 (kg ha-1) was influenced by the interaction between site-year and fertilizer treatment (P < 0.01) (Table 2.04). At no point did MOP applications influence V4DM indicating that plant K requirements prior to V4 were sufficiently supplied by the soil (Warncke et al., 2009). Relative to the unfertilized treatment, subsurface MESZ application increased mean V4DM 85, 135, and 79% in Richville and Lansing 2017 and Lansing 2018, respectively. The MESZ fertilizer is a co-granulated product containing N, P, S, and Zn. Biological N fixation may not occur until V2-4 suggesting V4 plant N requirements may heavily rely on residual soil N and soil organic matter (SOM) mineralization (Tamagno et al., 2018). Trial SOM concentrations (21 to 28 g kg-1) across locations and cool soil temperatures at planting (13.1 to 18.8˚C) indicated 45 minimal SOM mineralization and may have provided potential for increased early-season (i.e., V4) DM in response to N in the MESZ application (Taylor et al., 2005; Cigelske, 2016). Sufficient soil P concentrations (23 to 49 mg kg-1) and lack of environmental conditions hindering soybean root growth (i.e., cool, wet soils) across locations suggest P contributions to increased V4DM were unlikely (Warncke et al., 2009). Minimal S accumulation prior to V4 (< 10%) coupled with lack of previous increased DM response to S application until R2 suggest the S component in MESZ also may not have influenced V4DM (Boem et al., 2007; Gaspar et al., 2018). However, soil Zn concentrations (2-6 mg kg-1) and soil pH (6.6 to 8.2) across locations indicated potential Zn deficiency (critical level = ([(5.0 x pH) – (0.4 x soil nutrient concentration)] – 32) and suggest Zn in MESZ may have partially contributed to increased V4DM (Warncke et al., 2009). Benefits to increased plant size may include greater plant photosynthetic capacity and a larger root system able to support or initiate BNF earlier and soil nutrient uptake, but yield-limiting factors including plant lodging and disease severity (e.g., white mold [Sclerotinia sclerotiorum]) may both simultaneously increase with plant size (Ball et al., 2000; Salvagiotti et al., 2008; de Souza Jaccoud-Filho et al., 2016; Tamagno et al., 2018). Subsurface banded fertilizer applications have been previously used in cool, wet soils to increase early-season DM and nutrient accumulation in corn (Niehues et al., 2004; Rutan and Steinke, 2018). As soybean growers respond to a changing climate and perhaps plant earlier in the season in response to warmer air and soil temperatures, similar benefits may exist in soybean production (Hankinson et al., 2015). Due to similar nutrient accumulation patterns in leaves and stems, early-season (V4) nutrient accumulation data were presented by whole-plant as affected by the interaction between site-year and treatment (Table 2.05). Greater nutrient accumulation generally occurred with 46 increased seeding rates (i.e., ≥ 222,400 seeds ha-1) and MESZ applications. Correlation analysis indicated a positive relationship between V4DM and N, P, K, S, and Zn nutrient uptake (r = 0.90 to 0.99; P < 0.01) suggesting increased DM production may have enabled greater nutrient uptake (Bender et al., 2015). Greater TDM in current soybean varieties emphasizes maintaining soil nutrient critical levels to support early-season DM and nutrient accumulation. Previous research reported slow early-season nutrient accumulation until approximately R1 (Bender et al., 2015). Gaspar et al. (2017a, 2017b, 2018) found high yield levels (i.e., 5500 kg ha-1) decreased the time of minimal early-season nutrient accumulation and termed it the “lag- phase”. Increased DM through increased seeding rates (i.e., ≥ 222,400 seeds A-1) and subsurface MESZ applications likely reduced the “lag-phase” of soybean nutrient uptake and maintained grain yield potential. Previous research indicated DM and nutrient uptake at V4 were less than 20% of total accumulation and that the majority of grain nutrient requirements were supplied from the soil during grain-fill rather than vegetative nutrient remobilization (Bender et al., 2015; Gaspar et al., 2017a, 2017b, 2018). However, when soil nutrient availability is insufficient to meet plant demands, vegetative nutrient remobilization may fulfill grain nutrient requirements but reduces the photosynthetic capacity and grain yield potential (Salvagiotti et al., 2008, 2009). Total R5 and R8 dry matter accumulation (R5DM and R8TDM, respectively) ranged between 5000 and 6126 kg ha-1 and 8229 and 9192 kg ha-1, respectively (data not shown) and were not influenced by seeding rate, fertilizer treatment, or any interaction likely due to accelerated crop growth rates post-R1 and peaking by R4 (Bender et al., 2015). Environmental and agronomic conditions promoting (e.g., adequate precipitation and nutrient availability) or hindering plant development (e.g., deficit or excessive precipitation, compaction, nutrient deficiency, or increased pest pressure) may simultaneously influence TDM accumulation (Wells, 47 1993; Kaiser and Kim, 2013). Increased R8TDM may provide a nutrient source for subsequent crops through residue mineralization but can also harbor pathogen inoculum and increase potential disease development (e.g., brown spot [Septoria glycines], downey mildew [Peronospora manshurica], or cercospora leaf blight [Cercospora kikuchii]) (Mueller et al., 2016). Implementation of soybean seeding rate or fertilizer application programs to enhance DM production may be more successful on marginally productive soils or in those areas where yield- limiting factors may already be known to exist (e.g., deficient soil nutrient concentrations, sudden death syndrome (Fusarium virguliforme), and soybean cyst nematode [Heterodera glycines]). Grain nutrient accumulation data at maturity (R8) were presented across locations and years. At a grain yield level of 3400 to 3800 kg ha-1, grain nutrient accumulation ranged from 216 to 243 kg N ha-1, 19 to 22 kg P ha-1, 72 to 83 kg K ha-1, 11 to 13 kg S ha-1, and 144 to 167 g Zn kg-1 (Table 2.06). Similar DM and HI among seeding rates and adequate soil nutrient levels indicated no differences in grain nutrient accumulation would be expected. Macronutrient removal in grain was previously reported to remain unaffected by soybean grain yield level or variety when soil nutrient levels were sufficient (Gaspar et al., 2017a, 2017b). Grain nutrient concentrations within seeding rate and fertilizer treatment ranged from 59 to 60 g N kg-1, 5.09 to 5.34 g P kg-1, 19.8 to 20.1 g K kg-1, 3.03 to 3.29 g S kg-1, and 39.8 to 40.8 mg Zn kg-1 (data not shown) and were in agreement with current removal values (Warncke et al., 2009; Bender et al., 2015). However, increased DM in current soybean varieties simultaneously increased nutrient accumulation and grain yield and therefore total nutrient requirements (Bender et al., 2015). Lack of differences in grain nutrient accumulation across seeding rates suggest producers utilizing both increased and decreased seeding rates should follow university fertilizer 48 recommendation guidelines (i.e., soil test value and yield potential) to maintain soil nutrient levels. Within fertilizer treatment, R8 grain S accumulation increased from 12 to 13 kg ha-1 with MESZ application while N, P, K, and Zn accumulation was not affected (Table 2.06). Due to the lack of reliability with soil S testing, Hitsuda et al. (2004) previously quantified seed concentrations below 2.3 g S kg-1 as deficient. Grain S concentrations in the current study (3.03 to 3.29 g kg-1) suggested adequate S supply regardless of fertilizer treatment. Delayed S availability with elemental S, grain S requirements that rely on continuous soil uptake past grain- fill, direct partitioning of nutrients accumulated past R5.5 to grain, and a large S HI (70%) may have increased grain S accumulation with MESZ applications (Chien et al., 2016; Gaspar et al., 2018). However, grain S accumulation may also be dependent on early-season nutrient uptake and remobilization efficiency from vegetative and other reproductive tissues (Sunarpi and Anderson, 1997; Naeve and Shibles, 2005). Dynamics of nutrient remobilization continue to emphasize the importance of maintaining sufficient soil nutrient concentrations. Soybeans grown on low organic matter soils i.e., (< 20 g kg-1), non-manured, or with no immediate history of S application may benefit from soil applied S to satisfy grain S requirements. Dry Matter Partitioning Physiological maturity (R8) TDM partitioning data were combined across locations and years due to few differences between treatments and ranges for individual plant components (Table 2.07). Total DM was partitioned into leaves, stems and petioles, flowers and pods, and grain and consisted of 12 to 14, 26 to 29, 14 to 17, and 44 to 45%, respectively, closely resembling the results from Bender et al. (2015). Total DM partitioning was reported to remain similar across fertilizer treatments (Bender et al., 2015) and seeding rates (Egli et al., 1985). 49 However in high yield environments (i.e., 5500 kg ha-1), Gaspar et al. (2017a) reported greater TDM and grain harvest index (HI) which can affect stem and leaf allocation. Compared to pre- 2000 released soybean cultivars, current soybean germplasm increased TDM and stem DM partitioning to support increased grain yield on plant branches (Hanway and Weber, 1971; Suhre et al., 2014). Dry matter allocation may vary with factors affecting plant growth and development (i.e., environmental conditions, soil nutrient availability, and precipitation frequency) (Egli et al., 1983; Chen and Wiatrak, 2010). Minimal TDM production partitioning differences suggest soybean DM management for greater nutrient uptake, residue content, or grain yield potential should focus on other agronomic management factors (e.g., pest and disease control, moisture availability) rather than seeding rate or fertilizer application when soil nutrient concentrations are above critical levels. Harvest index was not affected by seeding rate, fertilizer treatment, or any interaction and ranged between 44 to 45% (Table 2.07). Similar R8TDM and HI in seeding rates between 123,500 and 420,100 seeds ha-1 suggested no differences in grain yield should be expected (Table 2.07). Comparison of machine-harvested HI with hand-harvested grain R8TDM indicated approximately 1247 kg ha-1 (24%) of grain was not collected at 123,500 seeds ha-1 (data not shown) and would equate to an additional 79 kg N ha-1, 16 kg P2O5 ha-1, and 29 kg K2O ha-1 returned to the soil. Stover nutrient content and uncollected grain may increase nutrient availability to the following crop (Warncke et al., 2009). Grower management options that result in flat ground harvest conditions (e.g., less aggressive row cleaners, rolling after planting, or reduced surface crop residue) may address challenges of branches and pods produced close to the soil surface at reduced seeding rates (i.e., 123,500 seeds ha-1) (Quick and Buchele, 1974; Berglund and Helms, 2003). Despite increased potential for grain loss at reduced seeding rates 50 (i.e., 123,500 seeds ha-1) due to branching closer to the soil surface (Lueschen and Hicks, 1977), growers should fertilize for full yield potential. Grain Yield Grain yield indicated significant seeding rate (P < 0.01) and fertilizer treatment (P < 0.01) main effects but no interaction between site-year and treatment (P = 0.34) therefore data were combined across locations and years (Table 2.08). Mean grain yields ranged from 3.39 to 3.81 Mg ha-1 with no statistical differences beyond 222,400 seeds ha-1. Increasing seeding rate from 123,500 to 222,400 seeds ha-1 improved grain yield by 304 kg ha-1. At the two lowest seeding rates in the current study, increasing the seeding rate 80% only resulted in 9% increased yield indicating interplant competition for light, water, and nutrients may have occurred and contributed to the lack of proportioned grain yield increases at greater seeding rates (i.e., > 222,400 seeds ha-1) (Duncan, 1986; Egli, 1988b; Walker et al., 2010). At lower than recommended seeding rates (i.e., < 321,200 seeds ha-1), soybean may compensate for reduced plant densities by increasing individual plant DM production including branching, pods, and seed production (Cox et al., 2010; Suhre et al., 2014). In the current study, similar pods m-2 (P = 0.46, data not shown) between seeding rates indicated soybean plants were able to compensate for a reduced seeding rate (i.e., 123,500 seeds ha-1) by producing greater numbers of pods and branches plant per plant. Decreased seeding rates (e.g., 123,500 seeds ha-1) can produce greater lateral branching and pods closer to the soil surface (Lueschen and Hicks, 1977; Carpenter and Board, 1997a; Suhre et al., 2014), which may help explain the 24% grain loss at 123,500 seeds ha-1 due to machine harvest difficulties and the 9% yield difference between the 123,500 and 222,400 seeds ha-1 seeding rates. Additionally, greater sinks (e.g., pods) plant-1 competing for available water and nutrients under normal to deficit precipitation during July – September may 51 also have contributed to the yield reduction observed at 123,500 seeds ha-1 (Egli et al., 1985). Decreased seeding rates (i.e., < 222,400 seeds ha-1) may be supported under adequate moisture but crop stress during pod formation and grain-fill likely impacted grain yield potential in this study (Egli et al., 1983; Prasad et al., 2008). Growers deliberating seeding rate management practices may want to consider weather forecasts and site-specific factors that can influence emergence and level of interplant competition (i.e., tillage practice, nutrient availability, surface crusting, or compaction). When averaged across locations and years, grain yield was affected by fertilizer treatment (P < 0.01). Compared to the unfertilized treatment, MESZ and MOP+MESZ applications increased grain yield 261 and 241 kg ha-1, respectively. Current trial (< 3800 kg ha-1) and Michigan (3228 kg ha-1) average soybean grain yields below the suggested threshold for high- yield levels (i.e., 4500 kg ha-1) indicate grain yield response to N applications would be inconsistent (Salvagiotti et al., 2008; USDA-NASS, 2018a). However, correlation analysis indicated a positive relationship between V4DM and grain yield (r = 0.41, P < 0.01), and suggested the N component in MESZ may have increased both V4DM and grain production. Sufficient soil P concentrations (23 to 49 mg kg-1) indicated a positive grain yield response to P application was not likely (Warncke et al., 2009). Results of Kaiser and Kim (2013) suggested SOM > 20 g kg-1 was sufficient for soybean growth. However, the elemental S component within MESZ may delay S availability until later in the season and increased grain S accumulation as 58% of grain S may be contributed through soil S sources after the R5.5 growth stage (Sutradhar et al., 2017; Gaspar et al., 2018). Additionally, pre-plant soil nutrient analysis indicated soil Zn concentrations were below critical levels and an additional 0.1 to 7.4 kg Zn ha-1 were needed to support soybean growth (Warncke et al., 2009). Therefore grain yield increases with MESZ 52 application may have been due to N, S, Zn, or some combination or synergism. Grain yield response to MOP applications were not observed presumably due to sufficient soil K concentrations at all locations. Significant reliance of grain K on vegetative remobilization as opposed to continued soil uptake during grain-fill continues to emphasize the importance of maintaining pre-plant and mid-season soil K levels for soybean production (Mallarino et al., 1991; Clover and Mallarino, 2013; Gaspar et al., 2017b). While grain yield is often limited by environmental conditions (i.e., precipitation and temperature), maintaining sufficient soil nutrient concentrations may allow growers to capitalize on favorable growing conditions for optimal grain yield potential. However, growers should continue to justify fertilizer applications with soil and plant analysis, diagnostic tools, and principles of integrated pest management rather than rely upon a preventative management approach (Quinn, 2018). Correlation analysis indicated a positive relationship between V4DM and grain yield (r = 0.41, P < 0.01) and suggested increased early-season DM may maintain grain yield potential when limited by precipitation. During cool spring soil and air temperatures in the Northern soybean production region, early-planted soybeans (i.e., planted prior to May 8) may benefit from increased early-season DM through increased seeding rates (i.e., ≥ 222,400 seeds ha-1) and subsurface MESZ applications (Hankinson et al., 2015). However, crop growth acceleration at R1 coupled with environmental factors that hamper plant development (i.e., deficit precipitation) may negate benefits of increased early-season DM. In the current study, correlation analysis indicated a weak relationship between grain yield and overall R8TDM (r = 0.32, P < 0.01), and suggested DM accumulation rate and timing of accelerated growth may influence grain yield greater than TDM at maturity. Previous research has indicated both positive and negative relationships between grain yield and R8TDM. Shibles and Weber (1966) found grain yield and 53 TDM to be independent due to environmental factors (e.g., temperature and precipitation) which influence vegetative DM much earlier than grain formation. However, Gaspar et al. (2017a) suggested TDM accumulation and grain yield were positively correlated due to grain being a primary factor of TDM. In a short-season production system (e.g., July planting or double- cropped systems), Ball et al. (2000) reported seed number determination occurred prior to R5. Therefore, conditions affecting DM accumulation also affected grain yield and resulted in a positive relationship (Ball et al., 2000). Trial results support previous research that suggest environmental conditions encountered during soybean reproductive stages may greater influence grain yield than those during vegetative DM accumulation (Prasad et al., 2008). Gaspar et al. (2017a) reported DM accumulation post-R5 was 32 and 22% in high (i.e., 5500 kg ha-1) and low yield levels (i.e., 3600 kg ha-1), respectively, and suggested increased grain yields were associated with greater late-season DM accumulation. In the current study, treatments associated with greater yield (i.e., ≥ 222,400 seeds ha-1 and MESZ applications) obtained 25-31% of DM production after R5. However, 32 to 40% of DM was obtained after R5 with treatments where no yield increases were observed (i.e., 123,500 seeds ha-1 and unfertilized and MOP application) (data not shown) suggesting that despite no differences in overall R8TDM across treatments, more DM production early rather than later in the season may have allowed the plant to partition greater photosynthate to grain yield. Greater and continued DM accumulation between R5 and R8 increased canopy greenness 5 to 7 days (visual observation) which may increase the photosynthetic capacity (i.e., “stay-green” potential) and duration grain- fill. A greater grain-fill period may increase grain yield potential but can delay soybean maturity and subsequent planting of fall-seeded small grain crops (e.g., winter wheat [Triticum aestivum]) (Egli, 2004). As forecasts for more intense rainfall periods followed by extended periods of 54 drought, unpredictable drought frequencies, and deficit July and August precipitation trends continue across the North Central U.S, the importance of increasing early-season DM to maintain soybean grain yield potential may increase (Ham et al., 1975; Karl et al., 2009). Economic Analysis Net economic return at current soybean prices (US$351.27 and $318.57 Mg-1 in 2017 and 2018, respectively) was not influenced by location or year (P = 0.25) and data were presented by seeding rate and fertilizer treatments (Table 2.08). Net economic return was maximized at 222,400 seeds ha-1 and decreased both above and below this seeding rate. Below 222,400 seeds ha-1 profitability decreased US$78 ha-1 while greater seeding rates decreased return between US$67 and US$77 ha-1. A quadratic model describing yield and net return to seeding rate was fit to the data and suggested maximum grain yield was achieved at 364,300 seeds ha-1 while net economic return was maximized at 265,300 seeds ha-1. Growers often identify grain yield potential as a greater risk factor in lieu of profitability (Rutan and Steinke, 2018). In light of forecasted stagnant commodity prices, results from this study suggest growers may want to consider incrementally decreasing seeding rates to < 321,200 seed ha-1 for increased profitability instead of maximizing yield. Net economic return (P = 0.08) was affected by fertilizer treatment (Table 2.08). Compared to the unfertilized control, the addition of MOP did not affect net return but reduced profit US$56 ha-1 when combined with MESZ (i.e., MOP+MESZ) and emphasized the risk of profit loss when nutrient (e.g., K) application occurs to soils with nutrients above critical concentrations. No differences were observed between the unfertilized treatment and MESZ application indicating the grain yield increase from the MESZ application was not large enough to offset the costs of the product and application. No visual plant nutrient deficiencies were 55 observed, and sufficient soil test values indicated an economic response to fertilizer application was unlikely (Warncke et al., 2009; Sutradhar et al., 2017). To achieve greater economic return, soil test concentrations, nutrient recommendations, and crop-specific nutrient responsiveness should all be considered in addition to yield improvements when considering fertilizer strategies. Conclusions Soybean seeding rates ≥ 222,400 seeds ha-1 and MESZ fertilizer applications were effective at increasing early-season DM, plant nutrient accumulation, and grain yield. Seeding rate and fertilizer application are two factors that increased early-season DM accumulation, which provided opportunities to increase nutrient uptake and grain yield. However, environmental conditions and soil nutrient concentrations may supersede plant growth and grain yield response to seeding rate and fertilizer application. A positive relationship between V4DM and grain yield suggests growers focusing on soybean grain production should consider management practices that enhance early-season plant growth. However, a positive plant response may not translate into increased grain yield when soil nutrient concentrations are at or above critical levels. Trial results demonstrated grain yield response to fertilizer applications were similar across seeding rates. To promote a durable and resilient soybean agroecosystem that reduces the risk for nutrient loss, nutrient applications should be focused at seeding rates that maximize DM accumulation (i.e., ≥ 222,400 seeds ha-1). Both positive and negative effects exist when managing for enhanced soybean DM. However, greater DM may not be sufficient justification for a nutrient application. Economic analysis emphasized seeding rates and fertilizer applications that optimize profit rather than yield, but long-term fertilizer investments (i.e., maintenance fertilizer applications) should be considered to maintain soil nutrient concentrations 56 and support plant growth. Fertilizer applications and seeding rate selection may be used to adapt to weather volatility and global soybean markets, but site-specific factors that influence plant growth and grain yield (e.g., soil nutrient concentrations, precipitation, and pest pressure) must be considered. Future research which includes additional fertilizer applications, row spacings, and planting dates under a variety of environmental conditions will provide additional data for enhanced soybean management. Acknowledgements The authors would like to thank the USDA National Institute of Food and Agriculture, the Michigan Soybean Promotion Committee, Michigan State AgBioResearch, and the Michigan State University College of Agriculture and Natural Resources for partial funding and support of this research. In addition, the authors would like to thank Andrew Chomas, research farm staff, and undergraduate research assistants for their technical assistance in the field. 57 APPENDICES 58 APPENDIX A: CHAPTER 2 TABLES Table 2.01. Soil chemical properties and mean nutrient concentrations (0 to 20-cm depth), Richville and Lansing, MI, 2017 to 2018. pH CEC P K 23 30 49 cmolc kg-1 155 134 106 16.2 7.6 11.9 Soil test values† SOM S Zn g kg-1 mg kg-1 6 2 3 Location Year Richville 2017 8.2 2017 6.6 Lansing 2018 7.1 †pH (1:1, soil/water) (Peter et al., 2015); SOM soil organic matter (loss-on-ignition) (Combs and Nathan, 2015); P Phosphorus (Bray-P1) (Frank et al., 2015), K potassium (ammonium acetate method) (Warncke and Brown, 2015), S sulfur (monocalcium phosphate extraction) (Combs et al., 2015), Zn Zinc (0.1 M HCl extraction) (Whitney, 2015). 26 21 28 7 8 8 59 5.7 8.4 3.5 11.7 8.2 4.0 9.7 3.3 10.3 8.9 Total cm Aug. Sep. Jun. Jul. 2.8 6.6 6.7 2.7 7.2 Table 2.02. Monthly† and 30-yr mean‡ temperature and precipitation data for the soybean growing season, Richville and Lansing, MI, 2017 to 2018. Location Year Apr. May Richville 2017 30-yr. 2017 Lansing 2018 30-yr. Richville 2017 Lansing †Monthly precipitation and air temperatures collected from MSU Enviro-weather (https://enviroweather.msu.edu). ‡30-year means collected from the National Oceanic and Atmosphere Administration (https://www.ncdc.noaa.gov/cdo-web/datatools/normals). §Cumulative precipitation Jul.-Sep. considered normal if within 10% of 30-yr. mean, deficit if ≥ 10% below 30-yr. mean, and excessive if ≥ 10% above 30-yr. mean. 14.7 7.3 13.3 6.0 7.7 ˚C 10.3 30-yr. 7.8 11.1 2017 4.1 2018 30-yr. 8.6 44.5 Deficit§ 48.2 41.8 Deficit 47.0 Normal 49.3 21.2 21.7 21.7 21.9 21.9 17.9 16.3 17.9 18.0 16.6 13.7 14.1 13.7 17.6 14.3 19.3 20.4 19.3 21.8 21.0 12.3 7.6 8.4 3.7 8.8 20.4 19.6 19.9 20.0 19.8 ̶ ̶ ̶ ̶ ̶ ̶ ̶ 5.0 8.6 6.6 12.6 8.5 Jul.-Sep. ̶ ̶ ̶ ̶ ̶ 60 Table 2.03. Interaction between soybean seeding rate and fertilizer application (P < 0.01) on V4 individual plant dry matter (DM) production, across locations and years, Richville and Lansing, MI, 2017 to 2018. All values reported on a dry weight (0% moisture) basis. Fertilizer 123,500 Seeding rate (seeds ha-1) 222,400 321,200 420,100 P > F g plant-1 0.95 bB 0.89 bB 1.83 aB 1.85 aB 1.12 b†A‡ 1.18 bA 2.43 aA 2.50 aA <0.01 1.34 A Unfertilized MOP§ MESZ¶ MOP + MESZ P > F Response to MESZ# †Values followed by the same lowercase letter within each column are not significantly different at α = 0.10. ‡Values followed by the same uppercase within each row are not significantly different at α = 0.10. §MOP: muriate of potash (0-0-62 N-P-K). ¶MESZ: MicroEssentials® SZ® (12-40-0-10-1 N-P-K-S-Zn). #Response to MESZ multiple degree of freedom contrasts was the mean plant DM from treatments receiving MESZ application minus plant DM from treatments receiving no nutrient application within each respective seeding rate. 0.71 bC 0.70 bC 1.21 aD 1.28 aC <0.01 <0.01 <0.01 <0.01 ̶ <0.01 0.79 bC 0.82 bB 1.55 aC 1.47 aC <0.01 0.72 B <0.01 0.85 B <0.01 0.54 C 61 Table 2.04. Soybean seeding rate and fertilizer application effects on V4 aboveground dry matter accumulation across years, Richville and Lansing, MI, 2017 to 2018. All values reported on a dry weight (0% moisture) basis. Location Richville, 2017 Lansing, 2017 Lansing, 2018 kg ha-1 276 b† 311 b 399 a 380 a <0.01 166 b 284 a 313 a 311 a <0.01 Treatment Seeding rate (seeds ha-1) 123,500 222,400 321,200 420,100 P > F Fertilizer Unfertilized MOP‡ MESZ§ MOP + MESZ P > F †Values followed by the same letter are not significantly different at α = 0.10. ‡MOP: muriate of potash (0-0-62 N-P-K). §MESZ: MicroEssentials® SZ® (12-40-0-10-1 N-P-K-S-Zn). 160 b 160 b 373 a 380 a <0.01 237 b 251 b 443 a 435 a <0.01 211 d 325 c 394 b 457 a <0.01 249 b 243 b 441 a 454 a <0.01 62 Table 2.05. Soybean seeding rate and fertilizer application effects on V4 total nutrient accumulation, Richville and Lansing, MI, 2017 and 2018. Site-year Main effect Aboveground plant nutrient accumulation† Zn K S P N kg ha-1 g ha-1 Seeding rate (seeds ha-1) 123,500 222,400 321,200 420,100 P > F Nutrient application Unfertilized MOP§ MESZ¶ MOP + MESZ P > F Seeding rate 123,500 222,400 321,200 420,100 P > F Nutrient application Unfertilized MOP MESZ MOP + MESZ P > F Seeding rate 123,500 222,400 321,200 420,100 P > F Nutrient application Unfertilized MOP MESZ MOP + MESZ P > F Richville, 2017 Lansing, 2017 Lansing, 2018 †Total nutrient accumulation calculated as the sum of leaf and stem (nutrient concentration x dry matter accumulation). ‡Values followed by the same letter are not significantly different at α = 0.10. §MOP: muriate of potash (0-0-62 N-P-K). ¶MESZ: MicroEssentials® SZ® (12-40-0-10-1 N-P-K-S-Zn). 1.1 b 1.2 b 1.5 a 1.4 a <0.01 0.9 b 0.9 b 1.6 a 1.6 a <0.01 0.7 b 1.1 a 1.2 a 1.1 a <0.01 0.6 b 0.6 b 1.5 a 1.5 a <0.01 0.9 d 1.4 c 1.7 b 1.9 a <0.01 1.0 b 1.0 b 1.9 a 1.9 a <0.01 8 c 9 bc 11 ab 10 a <0.01 7 b 7 b 11 a 11 a <0.01 5 b 8 a 8 a 8 a <0.01 5 b 5 b 10 a 10 a <0.01 4 c 6 b 7 b 9 a <0.01 5 b 5 b 8 a 8 a <0.01 0.7 b 0.8 b 0.9 a 0.9 a <0.01 0.6 b 0.6 b 1.1 a 1.0 a <0.01 0.5 b 0.8 a 0.8 a 0.8 a <0.01 0.4 b 0.4 b 1.0 a 1.0 a <0.01 0.6 d 0.9 c 1.1 b 1.3 a <0.01 0.7 b 0.7 b 1.3 a 1.3 a <0.01 11 b‡ 11 b 14 a 13 a <0.01 9 b 9 b 16 a 16 a <0.01 7 b 12 a 12 a 12 a <0.01 6 b 7 b 15 a 15 a <0.01 8 c 12 b 14 a 15 a <0.01 9 b 9 b 15 a 15 a <0.01 12 b 13 b 16 a 15 a <0.01 11 b 12 b 17 a 17 a <0.01 9 b 15 a 15 a 14 a <0.01 7 b 8 b 20 a 19 a <0.01 8 c 14 b 15 b 19 a <0.01 10 b 10 b 19 a 18 a <0.01 63 Table 2.06. Soybean grain nutrient accumulation at physiological maturity (R8) as affected by seeding rate and fertilizer application presented across locations and years, Richville and Lansing, MI, 2017 to 2018. Grain nutrient accumulation† P K S N Zn kg ha-1 g ha-1 Treatment Seeding rate (seeds ha-1) 123,500 222,400 321,200 420,100 P > F Fertilizer Unfertilized MOP§ MESZ¶ MOP + MESZ P > F †Grain nutrient accumulation calculated as nutrient concentration x grain dry matter accumulation. ‡Values followed by the same letter are not significantly different at α = 0.10. §MOP: muriate of potash (0-0-62 N-P-K). ¶MESZ: MicroEssentials® SZ® (12-40-0-10-1 N-P-K-S-Zn). 243 a‡ 225 a 216 a 229 a 0.28 229 a 216 a 237 a 230 a 0.27 13 a 12 a 11 a 12 a 0.12 12 bc 11 c 13 a 13 ab <0.01 167 a 150 a 144 a 154 a 0.12 153 a 148 a 159 a 156 a 0.46 83 a 75 a 72 a 77 a 0.16 76 a 74 a 79 a 77 a 0.56 22 a 20 a 19 a 20 a 0.13 20 a 20 a 21 a 21 a 0.27 64 Table 2.07. Influence of soybean seeding rate and fertilizer application on R8 total dry matter partitioning presented across locations and years, Richville and Lansing, MI, 2017 to 2018. Leaves Avg. Range† Avg. Range Avg. Range Percent (%) of aboveground dry matter Stems/Petioles Flowers/Pods Avg. Range Grain Treatment Seeding rate (seeds ha-1) 123,500 222,400 321,200 420,100 P > F Fertilizer Unfertilized MOP§ MESZ¶ MOP + MESZ P > F †Range represents the least and greatest values observed across all site-years. ‡Values followed by the same letter are not significantly different at α = 0.10. §MOP: muriate of potash (0-0-62 N-P-K). ¶MESZ: MicroEssentials® SZ® (12-40-0-10-1 N-P-K-S-Zn). 26 b 24-28 27 b 25-29 27 b 25-29 29 a 26-32 0.03 26 c 25-29 27 b 25-29 28 a 26-31 28 a 26-29 0.02 12 b‡ 11-13 13 b 12-13 14 a 13-14 12 b 12-13 0.02 13 a 13-14 13 a 12-14 12 a 12-14 13 a 12-14 0.88 17 a 16-18 16 b 15-18 15 c 14-17 14 d 12-16 <0.01 17 a 15-18 16 ab 15-17 15 c 14-17 15 bc 14-17 <0.01 45 a 43-47 44 a 43-46 44 a 43-45 45 a 44-46 0.52 44 a 43-47 44 a 44-45 45 a 43-46 44 a 43-45 0.98 65 Grain yield Economic return kg ha-1 US$ ha-1 Table 2.08. Seeding rate and fertilizer application effects on soybean grain yield† and economic return‡, across locations and years, Richville and Lansing, MI, 2017 to 2018. Treatment Seeding rate (seeds ha-1) 123,500 3394 b§ 222,400 3698 a 321,200 3695 a 420,100 3808 a P > F <0.01 Fertilizer Unfertilized 3510 b MOP¶ 3563 b MESZ# 3771 a MOP + MESZ 3751 a P > F <0.01 †Grain yield adjusted to 135 g kg-1 moisture. ‡Economic return calculated as (soybean price x yield) minus partial budget costs. §Values followed by the same letter are not significantly different at α = 0.10. ¶MOP: muriate of potash (0-0-62 N-P-K). #MESZ: MicroEssentials® SZ® (12-40-0-10-1 N-P-K-S-Zn). 959 b 1037 a 980 b 970 b 0.04 1008 ab 969 bc 1017 a 952 c 0.08 66 CHAPTER 2 DATA COLLECTED BUT NOT INCLUDED IN PUBLICATION APPENDIX B: Table 2.09. Influence of soybean seeding rate and fertilizer application on V4 dry matter partitioning, across locations and years, Richville and Lansing, MI, 2017 to 2018. Leaves Stems/Petioles Avg. Range Percent (%) of aboveground dry matter Avg. Range† Treatment Seeding rate (seeds ha-1) 123,500 222,400 321,200 420,100 P > F Fertilizer Unfertilized MOP§ MESZ¶ MOP + MESZ P > F †Range represents the least and greatest values observed across all site-years. ‡Values followed by the same letter are not significantly different at α = 0.10. §MOP: muriate of potash (0-0-62 N-P-K). ¶MESZ: MicroEssentials® SZ® (12-40-0-10-1 N-P-K-S-Zn). 67.6-72.9 64.5-70.1 64.4-69.2 62.5-68.2 68.0-71.2 67.0-73.7 61.6-68.7 62.4-66.8 70.0 a‡ 67.3 b 66.5 bc 65.4 c <0.01 69.7 a 69.9 a 65.0 b 64.6 b <0.01 30.0 c 32.7 b 33.5 ab 34.6 a <0.01 30.3 b 30.1 b 35.0 a 35.4 a <0.01 27.1-32.4 29.9-35.5 30.8-35.6 31.8-37.6 28.8-32.1 26.3-33.0 31.3-38.4 33.2-37.6 67 Table 2.10. Soybean seeding rate and fertilizer application effect on R2 dry matter partitioning, across locations and years, Richville and Lansing, MI, 2017 to 2018. Stems/Petioles Range Avg. Flowers Range† Leaves Avg. Avg. Range Percent (%) of aboveground dry matter 56.8 a‡ 52.8-63.3 53.4 b 50.2-57.8 49.8-55.6 52.1 c 49.4-55.0 51.9 c <0.01 52.1-60.0 55.4 a 52.4-60.5 55.4 a 51.6 b 48.8-55.4 49.0-55.7 51.8 b <0.01 Treatment Seeding rate (seeds ha-1) 123,500 222,400 321,200 420,100 P > F Fertilizer Unfertilized MOP§ MESZ¶ MOP + MESZ P > F †Range represents the least and greatest values observed across all site-years. ‡Values followed by the same letter are not significantly different at α = 0.10. §MOP: muriate of potash (0-0-62 N-P-K). ¶MESZ: MicroEssentials® SZ® (12-40-0-10-1 N-P-K-S-Zn). 41.8 c 35.4-45.9 44.8 b 40.4-48.4 46.2 a 42.6-48.9 46.5 a 43.3-49.5 <0.01 42.9 b 38.1-46.6 42.9 b 37.8-46.3 46.9 a 43.1-50.0 46.7 a 42.7-49.7 <0.01 1.4 b 1.7 a 1.7 a 1.7 a 0.03 1.7 a 1.7 a 1.5 b 1.5 b <0.01 1.3-1.6 1.4-2.0 1.3-1.9 1.1-2.1 1.4-1.9 1.3-2.0 1.3-1.9 1.2-1.7 68 Table 2.11. Impact of seeding rate and fertilizer application on soybean dry matter partitioning, across locations and years, Richville and Lansing, MI, 2017 to 2018. Stems/Petioles Range Flowers/Pods Range Avg. Avg. Range† Leaves Avg. Percent (%) of aboveground dry matter Treatment Seeding rate (seeds ha-1) 123,500 222,400 321,200 420,100 P > F Fertilizer Unfertilized MOP§ MESZ¶ MOP + MESZ P > F †Range represents the least and greatest values observed across all site-years. ‡Values followed by the same letter are not significantly different at α = 0.10. §MOP: muriate of potash (0-0-62 N-P-K). ¶MESZ: MicroEssentials® SZ® (12-40-0-10-1 N-P-K-S-Zn). 32.3-40.5 31.1-39.5 31.5-38.5 31.3-38.3 32.5-39.9 31.9-40.0 30.8-38.5 31.4-38.5 35.2 a‡ 34.4 b 33.9 bc 33.8 c <0.01 35.0 a 34.8 a 33.5 c 34.0 b <0.01 50.6 a 49.5 b 49.6 b 49.3 b <0.01 49.9 a 49.9 a 49.6 a 49.6 a 0.66 49.0-53.1 48.2-51.2 49.0-50.9 47.3-51.5 48.2-51.8 49.0-51.4 48.2-51.6 48.1-51.8 14.2 c 6.5-18.8 16.2 b 9.3-20.1 16.5 ab 10.6-19.6 16.9 a 10.2-21.0 <0.01 15.1 b 15.4 b 16.9 a 16.4 a <0.01 8.3-19.3 8.6-19.2 9.9-21.1 9.7-20.5 69 Table 2.12. Seeding rate and fertilizer application effects on soybean grain yield† and machine- harvest loss‡, across locations and years, Richville and Lansing, MI, 2017 to 2018. Grain yield Hand-harvest 3394 b§ 3698 a 3695 a 3808 a <0.01 Machine-harvest kg ha-1 % Treatment Seeding rate (seeds ha-1) 123,500 222,400 321,200 420,100 P > F Fertilizer Unfertilized MOP¶ MESZ# MOP + MESZ P > F †Grain yield adjusted to 135 g kg-1 moisture. ‡Calculated as the percent change from hand-harvest grain to machine-harvest grain. Positive numbers indicate a decrease in grain yield with machine-harvest mechanism. §Values followed by the same letter are not significantly different at α = 0.10. ¶MOP: muriate of potash (0-0-62 N-P-K). #MESZ: MicroEssentials® SZ® (12-40-0-10-1 N-P-K-S-Zn). 4643 a 4270 a 4114 a 4346 a 0.56 4372 a 4150 a 4494 a 4356 a 0.59 3510 b 3563 b 3771 a 3751 a <0.01 Loss 24 b 7 a 6 a 9 a 0.02 15 a 10 a 10 a 11 a 0.60 70 Table 2.13. Impact of soybean seeding rate and fertilizer application on R1 uppermost trifoliate nutrient concentrations, Richville and Lansing, MI, 2017 to 2018. Site-year Treatment P K S Zn g kg-1 mg kg-1 43 a 42 a 40 b 38 b <0.01 40 a 41 a 41 a 42 a 0.48 36 a 33 b 33 b 33 b 0.01 30 b 30 b 38 a 38 a <0.01 41 a 38 b 39 b 35 c <0.01 39 a 38 a 39 a 8 a 37 a 0.14 3.8 b 3.8 b 4.2 a 4.1 a <0.01 3.0 a 3.1 a 3.0 a 3.0 a 0.51 3.1 a 3.2 a 3.3 a 3.3 a 0.61 4.0 a† 4.0 a 4.0 a 3.9 a 0.79 24 a 24 a 24 a 23 a 0.51 25 a 2.9 b 25 a 2.9 b 23 b 3.2 a 23 b 3.1 a <0.01 <0.01 Seeding rate (seeds ha-1) 123,500 222,400 321,200 420,100 P > F Fertilizer Unfertilized MOP‡ MESZ§ MOP + MESZ P > F Seeding rate 123,500 222,400 321,200 420,100 P > F Fertilizer Unfertilized MOP MESZ MOP + MESZ P > F Seeding rate 123,500 222,400 321,200 420,100 P > F Fertilizer Unfertilized MOP MESZ MOP + MESZ P > F Richville, 2017 Lansing, 2017 Lansing, 2018 2.7 b 2.7 b 2.8 a 2.8 a <0.01 †Values followed by the same letter are not significantly different at α = 0.10. ‡MOP: muriate of potash (0-0-62 N-P-K). §MESZ: MicroEssentials® SZ® (12-40-0-10-1 N-P-K-S-Zn). 20 a 19 a 20 a 17 b <0.01 20 a 19 a 19 a 19 a 0.17 2.9 a 2.9 a 3.0 a 3.0 a 0.24 24 a 25 a 25 a 25 a 0.46 2.8 b 26 a 2.8 b 25 a 3.0 a 24 b 24 b 3.1 a <0.01 <0.01 2.8 b 2.8 b 3.7 a 3.7 a <0.01 5.1 a 4.7 b 5.2 a 4.3 c <0.01 2.8 a 2.7 a 2.7 a 2.8 a 0.41 4.7 a 4.9 a 5.0 a 4.8 a 0.15 71 Table 2.14. Influence of soybean seeding rate and fertilizer application on R8 grain secondary and micronutrient accumulation, across locations and years, Richville and Lansing, MI 2017 to 2018. Grain nutrient accumulation† Treatment Ca Mg B Mn Fe Cu kg ha-1 g ha-1 Seeding rate (seeds ha-1) 123,500 222,400 321,200 420,100 P > F Fertilizer Unfertilized MOP§ MESZ¶ MOP + MESZ P > F †Grain nutrient accumulation calculated as nutrient concentration x grain dry matter accumulation. ‡Values followed by the same letter are not significantly different at α = 0.10. §MOP: muriate of potash (0-0-62 N-P-K). ¶MESZ: MicroEssentials® SZ® (12-40-0-10-1 N-P-K-S-Zn). 284 a 254 b 240 b 262 ab 0.08 263 a 248 a 265 a 263 a 0.56 104 a 92 b 87 b 97 a 0.08 95 a 91 a 99 a 96 a 0.39 13 a‡ 11 b 11 b 12 ab 0.09 12 a 11 a 12 a 11 a 0.59 129 a 116 a 113 a 121 a 0.12 121 a 117 a 125 a 117 a 0.75 11 a 10 a 10 a 11 a 0.13 11 a 10 a 11 a 11 a 0.54 62 a 55 ab 52 b 56 ab 0.09 56 a 54 a 57 a 57 a 0.67 72 LITERATURE CITED 73 LITERATURE CITED analysis. 15th ed. Association of Official Agricultural Chemists, Washington, DC. AOAC. 1995a. Protein (crude) in animal feed. Dumas method (968.06). Official methods of AOAC. 1995b. Metals and other elements in plants and pet foods. Inductively coupled plasma Alessi, J., and J.F. Power. 1982. Effects of plant and row spacing on dryland soybean yield and spectroscopic method (985.01). Official methods of analysis. 15th ed. Association of Official Agricultural Chemists, Washington, DC. water-use efficiency. Agron. J. 74:851-854. Balboa, G.R., V.O. Sadras, and I.A. Ciampitti. 2018. Shifts in soybean yield, nutrient uptake, and nutrient stoichiometry: A historical synthesis-analysis. Crop Sci. 58:43-54. Ball, R.A., L.C. Purcell, and E.D. Vories. 2000. Optimizing soybean plant population for a short- season production system in the Southern USA. Crop Sci. 40:757-764. Barber, S.A. 1978. Growth and nutrient uptake of soybean roots under field conditions. Agron. J. Bender, R.R., J.W. Haegele, and F.E. Below. 2015. Nutrient uptake, partitioning, and 70:457-461. remobilization in modern soybean varieties. Agron. J. 107:563-573. Berglund, D.R., and T.C. Helms. 2003. Soybean Production. Bull. A-250, North Dakota State University, Fargo, ND. Board, J. 2000. Light interception efficiency and light quality affect yield compensation of soybean at low plant populations. Crop Sci. 40:1285-1294. Boem, F.H.G., P. Prystupa, and G. Ferraris. 2007. Seed number and yield determination in sulfur deficient soybean crops. J. Plant Nut. 30:93-104. till soybean as affected by phosphorus and potassium placement. Agron. J. 92:380-388. Borges, R., and A.P. Mallarino. 2000. Grain yield, early growth, and nutrient uptake of no- Borst, H.L., and L.E. Thatcher. 1931. Life history and composition of the soybean plant. Bull. Carpenter, A.C., and J.E. Board. 1997a. Branch yield components controlling soybean yield 494. Ohio Agricultural Experiment Station, p. 1-96. stability across plant populations. Crop Sci. 37:885-891. Carpenter, A.C., and J.E. Board. 1997b. Growth dynamic factors controlling soybean yield stability across plant populations. Crop Sci. 37:1520-1526. 74 Chen, G., and P. Wiatrak. 2010. Soybean development and yield are influenced by planting date and environmental conditions in the Southeastern Coastal Plain, United States. Agron. J. 102:1731-1737. Chen, G., and P. Wiatrak. 2011. Seeding rate effects on soybean maturity group IV-VIII for the southeastern production system: I. Vegetation indices. Agron. J. 103:32-37. Chien, S.H., L.A. Teixeira, H. Cantarella, G.W. Rehm, C.A. Grant, and M.M. Gearhart. 2016. Agronomic effectiveness of granular nitrogen/phosphorus fertilizers containing elemental sulfur with and without ammonium sulfate: A review. Agron. J. 108:1203-1213. Cigelske, B.D. 2016. Soybean response to nitrogen and sulfur fertilization. M.S. thesis. ProQuest Diss. Publ. UMI 10267419. North Dakota State Univ. Clover, M.W., and A.P. Mallarino. 2013. Corn and soybean tissue potassium content responses to potassium fertilization and relationships with grain yield. Soil Sci. Soc. Am. J. 77:630- 642. Combs, S.M., and M.V. Nathan. 2015. Soil organic matter. In: M.V. Nathan and R. Gelderman, editors, Recommended chemical soil test procedures for the North Central Region. North Central Region Res. Publ. 221 (rev.). SB 1001. Missouri Agric. Exp. Stn, Columbia. p. 12.1-12.6. Combs, S.M., J.L. Denning, and K. D. Frank. 2015. Sulfate-sulfur. In: M.V. Nathan and R. Cox, W.J., J.H. Cherney, and E. Shields. 2010. Soybeans compensate at low seeding rates but Gelderman, editors, Recommended chemical soil test procedures for the North Central Region. North Central Region Res. Publ. 221 (rev.). SB 1001. Missouri Agric. Exp. Stn, Columbia. p. 8.1-8.6. not at high thinning rates. Agron. J. 102:1238-1243. De Bruin, J.L., and P. Pedersen. 2008. Effect of row spacing and seeding rate on soybean yield. Agron. J. 100:704-710. De Bruin, J.L., and P. Pedersen. 2009. New and old soybean cultivar responses to plant density de Souza Jaccoud-Filho, D., F.F. Sartori, M. Manosso-Neto, C.M Vrisman, M.L. da Cunha and intercepted light. Crop Sci. 49:2225-2232. Pierre, A. Berger-Neto, H.E. Tullio, A. Justino, A.F. da Fonseca, and S. Zanon. 2016. Influence of row spacing and plant population density on management of “white mould” in soybean in southern Brazil. Australian Journal of Crop Science 10:161-168. Duncan, W.G. 1986. Planting patterns and soybean yields. Crop Sci. 26:584-588. Egli, D.B. 1988a. Alterations in plant growth and dry matter distribution in soybean. Agron. J. 80:86-90. 75 Egli, D.B. 1988b. Plant density and soybean yield. Crop Sci. 28:977-981. Egli, D.B. 2004. Seed-fill duration and yield of grain crops. Adv. Agron. 83:243-279. Egli, D.B., R.D. Guffy, and J.E. Leggett. 1985. Partitioning of assimilate between vegetative and reproductive growth in soybean. Agron. J. 77:917-922. Egli, D.B., L. Meckel, R.E. Phillips, D. Radcliffe, and J.E. Leggett. 1983. Moisture stress and N redistribution in soybean. Agron. J. 75:1027-1031. editors, Recommended chemical soil test procedures for the North Central Region. North Central Region Res. Publ. 221 (rev.). SB 1001. Missouri Agric. Exp. Stn, Columbia. p. 6.1-6.6. Frank, K., D. Beegle, and J. Denning. 2015. Phosphorus. In: M.V. Nathan and R. Gelderman, Fehr, W.R., and C.E. Caviness. 1977. Stages of soybean development. Spec. Rep. 80. Iowa Gaspar, A.P., C.A.M. Laboski, S.L. Naeve, and S.P. Conley. 2017a. Dry matter and nitrogen Agric. Home Econ. Exp. Stn., Iowa State Univ., Ames. uptake, partitioning, and removal across a wide range of soybean seed yield levels. Crop Sci. 57:2170-2182. Gaspar, A.P., C.A.M. Laboski, S.L. Naeve, and S.P. Conley. 2017b. Phosphorus and potassium uptake, partitioning, and removal across a wide range of soybean seed yield levels. Crop Sci. 57:2193-2204. Gaspar, A.P., C.A.M. Laboski, S.L. Naeve, and S.P. Conley. 2018. Secondary and micronutrient uptake, partitioning, and removal across a wide range of soybean seed yield levels. Agron. J. 110:1328-1338. Ham, G.E., I.E. Liener, S.D. Evans, R.D. Frazier, and W.W. Nelson. 1975. Yield and composition of soybean seed as affected by N and S fertilization. Agron. J. 67:293-297. Hankinson, M.W., L.E. Lindsey, and S.W. Culman. 2015. Effect of planting date and starter fertilizer on soybean grain yield. Crop, Forage, and Turfgrass Management doi:10.2134/cftm2015.0178 Hanway, J.J., and C.R. Weber. 1971. Dry matter accumulation in eight soybean (Glycine max (L.) Merrill) varieties. Agron. J. 63:227-230. population on weeds, crop yield, and economic return. Weed Technol. 21:744-752. Harder, D.B., C.L. Sprague, and K.A. Renner. 2007. Effect of soybean row width and Hicks, D.R., W.E. Lueschen, and J.H. Ford. 1990. Effect of stand density and thinning on soybean. J. Prod. Agric. 3:587-590. 76 Hitsuda, K., G.J. Sfredo, and D. Klepker. 2004. Diagnosis of sulfur deficiency in soybean using seeds. Soil Sci. Soc. Am. J. 68:1445-1451. Hitsuda, K., K. Toriyama, G.V. Subbarao, and O. Ito. 2008. Sulfur management for soybean production. In: J. Jez, editor, Sulfur: A missing link between soils, crops, and nutrition, Agron. Monogr. 50. ASA, CSSA, SSSA, Madison, WI. p. 117-142. Holliday, R. 1960. Plant population and crop yield. Nature. 186:22-24. Kaiser, D.E., and K. Kim. 2013. Soybean response to sulfur fertilizer applied as a broadcast or starter using replicated strip trials. Agron. J. 105:1189-1198. United States. Cambridge Univ. Press, New York. Karl, T.R., J.M. Melillo, and T.C. Peterson, editors, 2009. Global climate change impacts in the Lee, C.D., D.B. Egli, and D.M. TeKrony. 2008. Soybean response to plant population at early Lueschen, W.E., and D.R. Hicks. 1977. Influence of plant population on field performance of and late planting dates in the Mid-South. Agron. J. 100:971-976. three soybean cultivars. Agron. J. 69:390-393. Mallarino, A.P., J.R. Webb, and A.M. Blackmer. 1991. Soil test values and grain yields during 14 years of potassium fertilization of corn and soybean. J. Prod. Agric. 4:560-567. Mueller, D., K. Wise, A. Sisson, D. Smith, E. Sikora, C. Bradley, and A. Robertson. A farmer’s guide to soybean diseases. St. Paul, Minnesota, USA: The American Phytopathological Society. Naeve, S.L., and R.M. Shibles. 2005. Distribution and mobilization of sulfur during soybean reproduction. Crop Sci. 45:2540-2551. http://www.ncdc.noaa.gov/ (accessed 18 October 2018). National Oceanic and Atmospheric Administration. 2017. National climatic data center. NOAA. Niehues, B.J., R.E. Lamond, C.B. Godsey, and C.J. Olsen. 2004. Starter nitrogen fertilizer Norsworthy, J.K., and J.R. Frederick. 2002. Reduced seeding rate for glyphosate-resistant, management for continuous no-till corn production. Agron. J. 96:1412-1418. drilled soybean on the Southeastern Coastal Plain. Agron. J. 94:1282-1288. Norsworthy, J.K., and L.R. Oliver. 2001. Effect of seeding rate of drilled glyphosate-resistant soybean (Glycine max) on seed yield and gross profit margin. Weed Technol. 15:284- 292. Orlowski, J.M., B.J. Haverkamp, R.G. Laurenz, D.A. Marburger, E.W. Wilson, S.N. Casteel, S.P. Conley, S.L. Naeve, E.D. Nafziger, K.L. Roozeboom, W.J. Ross, K.D. Thelen, and 77 C.D. Lee. 2016. High-input management systems effect on soybean seed yield, yield components, and economic break-even probabilities. Crop Sci. 56:1988-2004. quality in the Northern Great Plains. Agron. J. 98:1569-1574. Osborne, S.L., and W.E. Riedell. 2006. Starter nitrogen fertilizer impact on soybean yield and Parvez, A.Q., F.P. Gardner, and K.J. Boote. 1989. Determinate- and indeterminate-type Prasad, P.V.V., S.A. Staggenborg, and Z. Ristic. 2008. Impacts of drought and/or heat stress on soybean cultivar responses to pattern, density, and planting date. Crop Sci. 29:150- 157. physiological, developmental, growth, and yield processes of crop plants. In: L.R. Ahuja, V.R. Reddy, S.A. Saseendran, Q. Yu, editors, Response of crops to limited water: Understanding and modeling water stress effects on plant growth processes, Adv. Agric. Syst. Model. 1. ASA, CSSA, SSSA, Madison, WI. p. 301-355. Quick, G.R., and W.F. Buchele. 1974. Reducing combine gathering losses in soybean. TRANSACTIONS of the ASAE 17:1123-1129. Quinn, D. 2018. Influence of input-intensive management on soft winter wheat and soybean grain yield and profitability. M.S. thesis. ProQuest Diss. Publ. UMI 10790844. Michigan State Univ. Northern Corn Belt. Agron. J. 110:2059-2069. Rutan, J., and K. Steinke. 2018. Pre-plant and in-season nitrogen combinations for the Salvagiotti, F., J.E. Specht, K.G. Cassman, D.T. Walters, A. Weiss, and A. Dobermann. 2009. Growth and nitrogen fixation in high-yielding soybean: Impact of nitrogen fertilization. Agron. J. 101:958-970. Salvagiotti, F., K.G. Cassman, J.E. Specht, D.T. Walters, A. Weiss, and A. Dobermann. 2008. Nitrogen uptake, fixation and response to fertilizer N in soybeans: A review. Field Crops Res. 108:1-13. SAS Institute. 2012. The SAS System for windows. Version 9.4. SAS Inst., Cary, NC. Shibles, R.M., and C.R. Weber. 1966. Interception of solar radiation and dry matter production by various soybean planting patterns. Crop Sci. 6:55-59. index. Agron. J. 76:482-486. Spaeth, S.C., H.C. Randall, T.R. Sinclair, and J.S. Vendeland. 1984. Stability of soybean harvest Stein, D. 2016. 2017 Custom machine and work rate estimates. Michigan State University Extension. https://msu.edu/~steind/cp17%20MASTER%20Cust_MachineWrk% 20NOV% 2009%202016.pdf (accessed 29 November 2018). 78 Agron. J. 107:1347-1354. Steinke, K, J. Rutan, and L. Thurgood. 2018. Corn response to nitrogen at multiple sulfur rates. Suhre, J.J., N.H. Weidenbenner, S.C. Rowntree, E.W. Wilson, S.L. Naeve, S.P. Conley, S.N. Sunarpi, and J.W. Anderson. 1997. Allocation of S in generative growth of soybean. Plant Casteel, B.W. Diers, P.D. Esker, J.E. Specht, and V.M. Davis. 2014. Soybean yield partitioning changes revealed by genetic gain and seeding rate interactions. Agron. J. 106:1631-1642. Physiol. 114:786-693. Sutradhar, A.K., D.E. Kaiser, and L.M. Behnken. 2017. Soybean response to broadcast application of boron, chlorine, manganese, and zinc. Agron. J. 109:1048-1059. Tamagno, S., G.R. Balboa, Y. Assefa, P. Kovács, S.N. Casteel, F. Salvagiotti, F.O. Garciá, W.M. Stewart, and I.A. Ciampitti. 2017. Nutrient partitioning and stoichiometry in soybean: A synthesis-analysis. Field Crops Res. 200:18-27. Tamagno, S., V.O. Sadras, J.W. Haegele, P.R. Armstrong, and I.A. Ciampitti. 2018. Interplay Taylor, R.S., D.B. Weaver, C.W. Wood, and E. van Santen. 2005. Nitrogen application increases between nitrogen and biological nitrogen fixation in soybean: Implications on seed yield and biomass allocation. Scientific Reports. 8:17502. yield and early dry matter accumulation in late-planted soybean. Crop Sci. 45:854-858. USDA-NASS. 2018a. USDA-NASS. 2018b. National statistics for soybeans: Soybeans, yield, measured in bu/acre. Statistics by state. USDA National Agriculture Statistics Service. https://www.nass.usda.gov/Statistics_by_State/index.php (accessed 5 November 2018). USDA-NASS. 2018b. National statistics for soybeans: Soybeans, price received, measured in USDA-NASS. 2018c. 2012 Census of agriculture publications: Full report. USDA National Vitosh, M.L., J.W. Johnson, and D.B. Mengel. 1995. Tri-state fertilizer recommendations for Walker, E.R., A. Mengistu, N. Bellaloui, C.H. Koger, R.K. Roberts, and J.A. Larson. 2010. Plant corn, soybeans, wheat, and alfalfa. Bull. E2567. Michigan State Univ. Ext., East Lansing, MI. $/acre. Statistics by subject. USDA National Agriculture Statistics Service. http://www.nass.usda.gov/Statistics_by_Subject/index.php (accessed 4 September 2018). Agriculture Statistics Service. http://www.agcensus.usda.gov/Publications/2012/ (accessed 2 August 2018). population and row-spacing effects on maturity group III soybean. Agron. J. 102:821- 826. 79 Gelderman, editors, Recommended chemical soil test procedures for the North Central Region. North Central Region Res. Publ. 221 (rev.). SB 1001. Missouri Agric. Exp. Stn, Columbia. p. 7.1-7.3. Warncke, D., and J.R. Brown. 2015. Potassium and other basic cations. In: M.V. Nathan and R. Warncke, D., J. Dahl, and L. Jacobs. 2009. Nutrient recommendations for field crops in Michigan. Bull. E2904, Michigan State University Extension, East Lansing, MI. on soybean development and production. Agron. J. 58:99-102. Weber, C.R., R.M. Shibles, and D.E. Byth. 1966. Effect of plant population and row spacing Wells, R. 1993. Dynamics of soybean growth in variable planting patterns. Agron. J. 85:44-48. Whitney, D.A. 2015. Micronutrients: Zinc, iron, manganese and copper. In: M.V. Nathan and R. Wilcox, J.R. 1974. Response of three soybean strains to equidistant spacings. Agron. J. 66:409- Gelderman, editors, Recommended chemical soil test procedures for the North Central Region. North Central Region Res. Publ. 221 (rev.). SB 1001. Missouri Agric. Exp. Stn, Columbia. p. 9.1-9.4. 412. 80 CORN NITROGEN TIMING AND SIDEDRESS PLACEMENT STRATEGIES CHAPTER 3 Abstract Volatile spring and summer weather patterns coupled with poor global nitrogen (N) recovery emphasize the importance of improved corn (Zea mays L.) N management strategies. Synchrony of N application with peak uptake periods and flexible in-season sidedress (SD) placement may improve N use efficiency while reducing N loss potential. A four site-year field study was conducted during 2017 and 2018 at Richville and Lansing, Michigan to evaluate four N timing strategies including: broadcast after planting (PRE); V4-6 SD (0/100), a 50:50 split (pre-plant incorporated:V4-6 SD) (50/50); and 45 kg N ha-1 applied 5-cm below and to the side of the seed at planting followed by V4-6 SD (5x5) and two SD placement methods including: coulter-inject (CI) and Y-drop surface application (YD). The PRE N timing strategy and YD SD placement was applied with and without a urease inhibitor (UI). During dry environmental conditions following application, N timing strategy, SD placement, or their combinations did not affect grain yield. Agronomic efficiency (AE) of applied N increased 11.2 to 13.5% with 5x5 and 0/100 N timing strategies compared to 50/50 and PRE and 7.8% with CI compared to YD suggesting greater application efficiency with delayed (V4-6 SD) N application and CI SD placement. Grain yield, net economic return, or AE were not affected by UI. Mid-season N applications allow greater flexibility in rate and placement but uptake may be restricted by dry soil conditions. Benefit of YD surface application may be realized with adequate moisture or when used as a late-season rescue N application method. 81 Introduction Concern for both ground and surface water quality has driven the continued interest in improving corn N management strategies (Schepers et al., 1991; Smil, 1997). Since 2008, mean United States (U.S.) corn grain yields have increased 1567 kg ha-1 yet nitrogen use efficiencies (NUE) of 33 to 47% indicate applied N is not captured by the plant (Raun and Johnson, 1999; Lassaletta et al., 2014; Rubin et al., 2016; USDA-NASS, 2018). Climatic variability including more frequent and longer periods of drought followed by intense rainfall combined with N applications applied outside of peak N uptake periods may increase the potential for N loss (Schepers et al., 1991; Smil, 1997; Cassman et al., 2002; Karl et al., 2009; Venterea and Coulter, 2015). Nitrogen availability and mobility within the soil is influenced by environmental variables (i.e. precipitation and soil moisture) thus emphasis has been placed on decreasing N loss through placement and timing strategies (Bock, 1984; Bruulsema et al., 2009; Gardinier et al., 2013). Broadcast N applications after planting but prior to crop emergence (PRE) have been used to reduce time and resources required for multiple applications by combining weed control and fertilization into a single-pass application (Fox and Piekielek, 1993). Although PRE N strategies may be as effective as other N application methods, the potential for N loss may increase due to volatility of surface applied urea N sources. (Stecker et al., 1993; Randall et al., 1997; Lehrsch et al., 2000; Nelson et al., 2011). Incorporating surface-applied N is a recommended Michigan practice and may reduce the risk of N loss and protect economic investments related to weather volatility (Warncke et al., 2009). However, N mobility and availability from pre-plant incorporation (PPI) application may be limited under dry soil conditions and reduce early-season growth relative to starter fertilizer placed 5-cm below and 5- cm to the side of the seed (5x5) (i.e. subsurface N placement) (Chaidhary and Prihar, 1974; 82 Khosla et al., 2000; Rutan and Steinke, 2018). In Michigan, Rutan and Steinke (2018) reported PPI application reduced yield relative to subsurface N placement when cumulative April – June rainfall was deficit but resulted in similar yields when cumulative May – June precipitation was above normal. Despite flexibility in N rate with 5x5 applications compared to in-furrow starter N, 22 to 45 kg N ha-1 are recommended in the North Central U.S. followed by SD applications to improve N recovery and reduce risks for N loss (Vitosh et al., 1995; Niehues et al., 2004; Warncke et al., 2009). Sidedressing N during corn growth is one method growers can utilize to improve synchrony of N application with corn uptake (Rutan and Steinke, 2018). Timing of SD applications may depend on the ability of early-N management to maintain corn yield potential until preferred SD time (Rutan and Steinke, 2018). Delaying N applications until late-season (V10) may reduce corn yield potential while N applications made prior to peak uptake periods are exposed to a greater risk for N loss (Walsh et al., 2012; Scharf et al., 2002). In Nebraska, Russelle et al. (1983) reported no yield reductions when N applications were delayed until V8 and V16. Similar results were reported in Missouri where no yield reductions were observed when delaying SD N applications until V11 (Scharf et al., 2002). However, a recent study reported little to no benefit in delaying SD N applications from V4 to V11 under dry conditions or when applying less than 45 kg N ha-1 at planting as a starter N application (Rutan and Steinke, 2018). Supplying the majority of N application near the beginning of rapid uptake (V6-V8) may reduce the risk for N loss while simultaneously maintaining corn yield potential (Scharf et al., 2002; Bender et al., 2013). Warm, moist soil conditions during June and July increase the risk for volatile N loss (Warncke et al., 2009). Coulter-injection of SD N 10 to 13-cm deep halfway between corn rows 83 may reduce volatile N losses (Fox et al., 1986; Warncke et al., 2009). Woodley et al. (2018) reported an average yield decrease of 11% when surface streaming UAN compared to coulter- inject UAN in Ontario. Similar results were reported by Stecker et al. (1993) where coulter-inject UAN increased corn yield 5 to 40% relative to broadcast UAN and 4 to 20% relative to surface band UAN between rows. Root density is greater near the base of a corn plant and decreases with distance from the plant (Anderson, 1987; Ordóñez et al., 2018). A study in Oklahoma evaluating surface N placement 0 to 30-cm from the row found no differences in grain yield or NUE across placement distances (Rutto et al., 2013). Mueller et al. (2017) reported increased N recovery and efficiency with V12 surface band N application adjacent to the base of the plant relative to V3 coulter-inject applied N although no differences in grain yield occurred. Studies evaluating surface N placement adjacent to the plant relative to coulter-inject at the same growth stage individually and as a component within other N timing strategies are minimal and warrants further investigation. Volatile N losses increase with increasing soil pH, surface residue, air and soil temperature, and precipitation-free periods (Fox et al., 1986; Stecker et al., 1993; Schwab and Murdock, 2010; Franzen, 2017). The addition of UI to urea-containing N sources have been used to reduce NH3 volatilization (Pan et al., 2016). Urease inhibitors reduce the rate at which urea is hydrolyzed by the urease enzyme for up to 10 days (Franzen, 2017). In a global synthesis on ammonia volatilization, Pan et al. (2016) suggested UIs reduced volatilization up to 54%. In Pennsylvania, fertilizer use efficiency, N uptake, and corn grain yield were improved when combining PRE applications with a UI (N-(n-butyl) thiophosphoric triamide [NBPT]) and ammonia losses reduced up to 29% (Fox and Piekielek, 1993). When using NBPT coated urea in Missouri, Nelson et al. (2011) observed a corn grain yield increase of 260 kg ha-1 across multiple 84 N application timings. However, the uncharged urea molecule may be prone to leaching when treated with a UI (Dawar et al., 2011). Environmental conditions promoting NH3 volatilization need to be present to observe a positive yield response from a UI (Woodley et al., 2018). The use of a UI may be considered a risk management tool which growers may not always realize a benefit (Quinn and Steinke, 2019). The objective of this study was to evaluate the effects of multiple N timing and sidedress placement strategies on corn growth, grain yield, agronomic efficiency (AE) of applied N, and net economic return. Materials and Methods Field trials were conducted from 2017 to 2018 at the Saginaw Valley Research and Extension Center in Richville, MI (4323’57.3”N, 8341’49.7”W) on a non-irrigated Tappan- Londo loam soil (fine-loamy, mixed, active, calcareous, mesic Typic Epiaquolls) and at the South Campus Research Farm in Lansing, MI (4242’37.0”N, 8428’14.6”W) on a non-irrigated Capac loam soil (fine-loamy, mixed, active, mesic Aquic Glossudalf). The Richville locations were previously cropped to winter wheat (Triticum aestivum L.), while the Lansing locations were previously cropped to soybean (Glycine max L. Merr.). Tillage included autumn chisel plow to a depth of 20-cm and spring field cultivation to a 10-cm depth. Pre-plant soil characteristics at Richville measured 7.2 to 7.8 pH (1:1, soil/water) (Peters et al., 2015), 23 to 28 g kg-1 SOM (loss-on-ignition) (Combs and Nathan, 2015), 23 to 27 mg kg-1 P (Bray-P1) (Frank et al., 2015), and 108 to 173 mg kg-1 K (ammonium acetate method) (Warncke and Brown, 2015). Soil characteristics at Lansing measured 7.1 to 7.9 pH, 28 to 31 g kg-1 SOM, 13 to 14 mg kg-1 P, and 82 to 196 mg kg-1 K. Broadcast P and K fertilizer were applied as triple- superphosphate (0-45-0 N-P-K) and muriate of potash (0-0-62 N-P-K) based on soil tests. Prior 85 to planting soil nitrate-N (NO3 -) samples were collected to a 30-cm depth, air-dried, and ground to pass through a 2 mm sieve resulting in concentrations between 3.5 to 5.7 mg kg-1 NO3 - (nitrate electrode method) across years and locations (Gelderman and Beegle, 1998). Weed control consisted of S-metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1S)-2-methoxy-1- methylethyl]acetamide) and glyphosate (N-(phosphonomethyl) glycine) followed by a second application of glyphosate at both locations across years. Cumulative growing season weather data were collected using the Michigan State University Enviro-weather (https://enviroweather.msu.edu, Michigan State University, East Lansing, MI). Monthly air temperature and cumulative precipitation 30-year means were obtained from the National Oceanic and Atmosphere Administration (NOAA, 2018). Trials consisted of 12 treatments arranged in a randomized complete block design with four replications. Treatments included eleven N strategies and a zero-N control (Table 3.01). Four N timing strategies were utilized and included: i) N applied immediately after planting (PRE), ii) 50% of N pre-plant incorporated (PPI) with 50% of N SD (50/50), iii) all N applied SD (0/100), and iv) 45 kg N ha-1 applied 5-cm below and to the side of the seed with remaining N SD (5x5). Treatments within the PRE strategy included with and without a UI (Agrotain Advanced, N-(n-butyl)-thiophosphoric triamide (NBPT) [2.09 ml kg-1 urea]; Koch Agronomic Services LLC, Wichita, KS). Treatment combinations within the 50/50, 0/100, and 5x5 strategies included evaluation of the following SD methods i) coulter-inject (CI) 10-cm deep 38-cm from the plant, ii) Y-drop (YD) (360 Yield Center, Morton, IL) surface applied on both sides at the base of the plant, and iii) YD with a UI (Agrotain Advanced, N-(n-butyl)-thiophosphoric triamide (NBPT) [1.04 ml kg-1 urea ammonium nitrate (UAN)]; Koch Agronomic Services LLC, Wichita, KS). Sidedress applications occurred at V4-6 on 6 June 2017 and 31 May 2018 in 86 Richville and on 9 June 2017 and 7 June 2018 in Lansing. Nitrogen source for PRE and PPI applications consisted of urea while 5x5 and SD applications were applied using UAN. Nitrogen rates were equalized to a total N rate based on the site-specific maximum return to nitrogen rate resulting in 191 kg N ha-1 in Richville and 163 kg N ha-1 in Lansing (Sawyer et al., 2006). Plots measured 4.6 m in width and 12.2 m in length. All site-years utilized Dekalb DKC51-38 (Monsanto Co., St. Louis, MO) seeded in 76-cm rows at 84,014 seeds ha-1 using a Monosem planter (Monosem Inc., Kansas City, KS) and seeded on 28 April 2017 and 1 May 2018 in Richville and 12 May 2017 and 8 May 2018 in Lansing. At V6 and V10, canopy normalized difference vegetation index (NDVI) was collected using a GreenSeeker Model 505 handheld red-band optical sensor (Trimble Agriculture Div., Westminister, CO). Corn ear leaf N status at R1 and R4 were assessed using a Minolta SPAD 502 chlorophyll meter (CM) (Konica Minolta, Tokyo, Japan). Ten plants were randomly selected in each plot with one measurement plant-1 recorded from halfway between the leaf collar and leaf tip (Peterson et al., 1993). The center two rows (1.5 m width) of each plot were harvested with a Massey Ferguson 8XP research combine (Kincaid Equipment Manufacturing, Haven, KS) to determine grain yield, moisture, and test weight. Yield data were reported at 155 g kg-1 moisture. Agronomic efficiency was calculated as the difference between yield of treatments with N and yield of unfertilized control, divided by N rate (Sawyer et al., 2017). Net economic return was calculated as the product of grain price and yield minus total input cost for each treatment. The sum of fertilizer, chemical, and application costs equaled total input costs. Average grain prices from three local grain elevators consisted of US$137.04 Mg-1 in 2017 and US$144.48 Mg-1 in 2018. Fertilizer and UI prices from three local retailers were averaged to estimate product costs and included US$0.20 and $0.34 kg-1 in 2017 and US$0.25 and $0.40 kg-1 in 2018 for UAN and 87 urea, respectively. Urease inhibitor cost estimates for 2017 and 2018 were US$34.34 L-1. Michigan State University Extension Custom Machine and Work Rate Estimates were used for application costs and consisted of US$4.65, $16.16, $33.63, $27.47, and $29.65 ha-1 for 5x5 starter application, urea broadcast application, urea incorporation, coulter-inject sidedress application, and Y-drop sidedress application, respectively, in 2017 and 2018 (Stein, 2016). Data were subject to analysis of variance using PROC GLIMMIX in SAS 9.4 (SAS Institute, 2012) at α = 0.10. Treatment, year, and location were considered fixed effects and replication as random. Residuals were assessed for normality using the UNIVARIATE procedure (P ≤ 0.05). Homogeneity of variances were examined by Levene’s test using squared and absolute values of residuals (P ≤ 0.05). Dunnett’s test was used to compare each treatment with the non-fertilized control to confirm a significant response to N fertilizer occurred (P ≤ 0.01). Multiple degree of freedom (df) contrasts were constructed as the mean of treatments within each management strategy to compare data across N timing strategies, SD methods, and the effects of UI. Pearson product-moment correlations were generated using the REG procedure of SAS to investigate the relationship between SPAD indices and AE with grain yield. Environmental Conditions Results and Discussion Cumulative 2017 and 2018 growing season (April – September) precipitation was deficient across site-years with shortages of 37 and 20 mm at Richville and 75 and 23 mm at Lansing from the respective 30-year means (Table 3.02). Cumulative April and May precipitation differed by +23 and -21% and +23 and +15% from the 30-year mean at Richville and Lansing during 2017 and 2018, respectively. Deficit June – August precipitation (i.e., >10% 88 below the 30-year mean) in Lansing during 2017 and 2018 likely limited response to sidedress N applications while increasing volatile N loss potential with surface applications (Stecker et al., 1993; Maharjan et al., 2016). April 2017 mean daily air temperatures were 2.5C above the 30- year mean in both Richville and Lansing while May air temperatures deviated by -0.6C. April and May 2018 air temperatures in Richville and Lansing differed by -4.2 and +3.5C and -4.5 and +3.3C from the 30-year mean, respectively. June through September mean air temperatures were within 10% of 30-year means across all site-years. Grain Yield Grain yield was not influenced by N treatment, year, location, nor any interaction (P > 0.10). With N application, grain yield averaged across site-years ranged from 10.4 to 11.5 Mg ha- 1 (Table 3.03). Environmental conditions have affected nutrient loss potential and corn yield response to N applications (Stecker et al., 1993) and may explain a lack of treatment effects on grain yield. Soil moisture was greater in Richville (0.303 to 0.402 cm3 cm-3) than Lansing (0.101 to 0.219 cm3 cm-3) across both years during the 21 d following N applications (Table 3.04). However dry soil conditions within 21 d following N application combined with below-average cumulative growing season precipitation suggest grain yield response to N application was limited by rainfall frequencies rather than soil moisture (Venterea and Coulter, 2015). Dry soil conditions may limit vertical N movement within the soil profile reducing root N uptake and inhibiting urea transformation into plant-available N (Gardinier et al., 2013; Venterea and Coulter, 2015; Maharjan et al., 2016). Multiple df contrasts indicated grain yield was not affected by N timing strategy (P = 0.40). Grain yield from the PRE, 50/50, 0/100, and 5x5 N timing strategies ranged from 10.7 to 11.2 Mg ha-1 across site years. Due to reduced rainfall in June following SD application, dry 89 soils may have resulted in decreased SD N uptake providing little benefit to split N applications. Split N applications are a suggested practice to improve N recovery and nutrient use efficiency due to greater synchronization of application timing with peak uptake periods (Cassman et al., 2002; Mueller et al., 2017; Rutan and Steinke, 2018). However, results agree with Stecker et al. (1993) who suggested single N applications at planting may be as effective as split applications when deficit rainfall limited sidedress N movement into the root zone. Despite non-significant data, delaying N applications until mid-season (V4-6) may allow producers the advantage of adjusting management practices according to environmental trends. However, single N applications at planting warrant consideration as limited June and July soil moisture may limit N uptake and corn yield potential (Stecker et al., 1993). Nitrogen SD placement did not influence grain yield (P = 0.31) as CI and YD surface applications resulted in mean grain yields of 11.3 and 10.9 Mg ha-1, respectively. Limited (< 8 mm) precipitation within seven days following SD applications across all site-years may have limited N movement in the soil and reduced N uptake (Table 3.04). Moisture, plant-available nutrients, oxygen, and roots must simultaneously be in the same place for root nutrient uptake (Havlin et al., 2014). Corn root densities are generally greater directly beneath the plant (Mengel and Barber, 1974) but precipitation soon after application would still be required with YD surface applications. Previous research comparing N placement at the same application time or growth stage concluded similar or reduced grain yield and nitrogen use efficiency with surface N application relative to CI (Fox et al., 1986; Fox and Piekielek, 1993; Woodley et al., 2018). Results from the current study suggest YD surface N application at the base of the corn plant at V4-6 may be as effective as CI during drier conditions. However, greater risk may exist with mid-season YD surface application due to increased volatilization potential and reduced N 90 positional availability during limited precipitation (Gardinier et al., 2013; Woodley et al., 2018). Greater benefits from YD surface placement may exist with late-season rescue N applications due to reduced leaf injury and greater canopy shading (Nelson et al., 2011). Addition of a UI did not improve grain yield suggesting volatile N loss conditions may not have been present for a long enough period to observe a positive response to UI applications (Table 3.03). Precipitation events of 9 and 5 mm and 26 and 8 mm occurred on 9 and 1 d and 8 and 2 d after SD application in Richville and Lansing during 2017 and 2018, respectively, which can be sufficient to move urea into the root zone and reduce the likelihood of a grain yield response to urease inhibitors (Table 3.04) (Franzen, 2017). Nitrogen loss conditions must be present to observe a positive response from a UI (Quinn and Steinke, 2019). Economic Analysis Net economic return was influenced by N strategy (P = 0.08) and presented as an average of site-years due to no interacting effects of treatment, year, and location (Table 3.03). Within each N timing strategy, SD placement or addition of a UI did not influence net economic return suggesting producers may want to first consider application timing to maximize profitability. Pearson product-moment correlations suggested a positive relationship between grain yield and net return (r = 0.98, P < 0.01) indicating strategies that increased grain yield increased net economic returns. However, lack of significant grain yield differences emphasize the importance of accounting for treatment costs when considering N strategies. Multiple df contrasts indicated the 0/100 and 5x5 N timing strategies increased net return US$113 and US$107 ha-1, respectively compared to the 50/50 N timing strategy. Relative to split applying N (i.e. 50/50 N timing strategy), delaying N applications until V4-6 (i.e. 0/100 and 5x5 91 N timing strategies) likely reduced N loss potential. In the current study, greater agronomic and economic benefits existed by delaying SD applications until V4-6 due to dry soil conditions. Coulter-inject SD placement increased net economic return US$64 ha-1 compared to YD surface placement despite lack of significant grain yield differences. Soil moisture is greater beneath the soil surface as compared to on the soil surface. Subsurface N placement (i.e., CI) may protect the economic investment in N fertilizer through increased potential for root N uptake and reduced potential for volatile N loss (Havlin et al., 2014; Woodley et al., 2018). Addition of a UI to the PRE timing strategy or with YD surface application did not affect net return and required greater input costs. Producers often perceive yield loss as a greater risk than profitability but rather may need to justify agronomic inputs (i.e., integrated pest management) and balance both grain production and economic return by considering cost of inputs and nutrient placement in addition to potential yield benefits (Rutan and Steinke, 2018). Agronomic Efficiency Treatment, year, location, and interactions between N timing and placement did not influence AE (P > 0.10) (Table 3.05). Dry soil conditions were previously reported to reduce AE due to limited N uptake and mobility within the soil profile (Steinke et al., 2015). When averaged across all site-years and placement strategies, the 0/100 and 5x5 N timing strategies increased AE indicating greater efficiency of applied N fertilizer per unit of grain yield. Results agree with Rubin et al. (2016) who reported a 6% increase in AE with split applications of urea compared to a single application at planting. Across site-years, AE decreased from 30.4 kg grain kg N-1 with CI SD placement to 28.2 kg grain kg N-1 with YD surface application. Reduced AE with YD surface application emphasizes the difficulty of N recovery when limited precipitation (< 8 mm) follows N application preventing N mobility within the root zone. Addition of a UI did 92 not significantly influence AE. Despite no grain yield differences, improved AE with 0/100 and 5x5 N strategies and CI SD placement reduced the potential for environmental N loss (Rubin et al., 2016). Normalized Difference Vegetation Index Mean V6 NDVI measurements were influenced by N timing and year (P = 0.02, Table 3.06). Due to NDVI measurements occurring within six days of SD N application and limited precipitation following application, data were averaged across SD placement methods and addition of a UI. No differences in V6 NDVI were observed in 2017 suggesting limited plant response to N applications. Bender et al. (2013) reported season-long N accumulation prior to V6 was less than 15%. Corn yield potential determination occurs up until the V8 growth stage and earlier NDVI measurements can give inaccurate indications of yield (Teal et al., 2006). In 2018, the 0/100 N timing strategy reduced V6 NDVI compared to the PRE, 50/50, and 5x5 N timing strategies. Tucker et al. (1979) reported red NDVI was an indicator of green biomass and plant growth. Delaying 100% of N until SD (i.e., 0/100 N timing strategy) reduced early season plant growth in 2018 during more consistent rainfall periods emphasizing the importance of satisfying N requirements prior to SD application (Rutan and Steinke, 2018). Pearson product-moment correlation suggested no relationship (P > 0.10) between grain yield and V6 NDVI in either year indicating increased green dry matter at V6 did not result in greater yield. Mean V10 NDVI measurements were unaffected by year or location (P = 0.43) and data presented as a mean across site-years (Table 3.06). Multiple df contrasts indicated NDVI was reduced 3.0 and 4.2% with the 0/100 N timing strategy compared to PRE and 5x5, respectively. Poor relationships between V10 NDVI and grain yield (r = 0.20, P < 0.01) suggested late- vegetative (V10) plant response to N timing may not influence grain production. Accelerated dry 93 matter production and N accumulation occurs between V10-14 (Bender et al., 2013) and likely diminishes plant response to early-season N applications if sufficient N is present. Results of active canopy sensing at V10 suggest the 5x5 N timing strategy may allow growers to utilize reduced N rates at planting and reduce risk of N loss while still satisfying early corn N requirements for optimal growth. Chlorophyll Meter Chlorophyll meter measurements were used to indicate N status. A treatment by year interaction occurred at R1 (P = 0.03) and CM values were combined across locations within each year (Table 3.07). Within the 50/50 timing strategy and compared to CI, YD surface application reduced R1 CM values in 2017 but increased values in 2018. Minimal precipitation (< 5 mm) 7 d following SD N application in 2017 may have limited N uptake and R1 chlorophyll production with YD surface application (Table 3.04). During 2018, one and two precipitation events totaling 7 and 8 mm occurring within 4 d of SD application in Richville and Lansing, respectively, suggested wetting fronts may have moved N into the root zone for N uptake and chlorophyll production with YD surface application. Treatment differences in both years were mostly due to time of application as SD placement and addition of a UI did not affect R1 CM values within the PRE, 0/100, and 5x5 N timing strategies. Multiple df contrasts indicated N timing strategies influenced R1 CM values during 2017 (P = 0.03) and 2018 (P < 0.01). Similar trends in the data were observed both years where the 50/50 N timing strategy reduced R1 CM values 3.3 to 4.8% relative to PRE, 0/100, and 5x5 N timing strategies and indicated some degree of N loss prior to SD application. The PRE N timing strategy may have increased N concentration in the root zone and accounted for N loss resulting in greater R1 CM compared to the 50/50 N timing strategy. However, increasing N availability (e.g., 0/100 and 5x5 N timing strategies) during peak uptake 94 periods may sustain chlorophyll production. Multiple df contrasts indicated CI SD placement increased R1 CM values during 2017 but decreased chlorophyll production relative to YD surface placement during 2018. Data suggest CI SD placement may increase plant N status at R1 during minimal precipitation following SD application, but YD surface application was more effective when moisture was adequate for nutrient uptake. Addition of a UI did not affect R1 CM values in either year. At R4 corn, CM values were influenced by N strategy (P = 0.04) but year and location did not impact results thus data were presented as means across site-years (Table 3.07). The effect of N timing strategy on R4 CM values closely follow that at R1 where delaying N applications until V4-6 (i.e., 0/100 and 5x5) increased chlorophyll content. Increased potential for N loss with PRE and 50/50 N timing strategies may decrease late-season chlorophyll production and reduce N availability needed for grain production. Delaying N applications until V4-6 may maintain N status in the plant and increase chlorophyll production and photosynthetic capacity. No differences were observed in R4 CM values with SD placement strategies. Addition of a UI increased R4 CM values despite no differences in grain yield suggesting delayed urea hydrolysis may have increased N available for mid-season chlorophyll production (Warncke et al., 2009). A positive relationship between grain yield and R4 CM values (r = 0.84, P < 0.01) indicated greater plant N status and chlorophyll production translated into increased grain yield. Conclusions Trial results demonstrated little evidence in improving N management strategies during drier soil conditions. Minimal precipitation following application and during peak N uptake produced negligible grain yield differences from N application timing, SD placement, or addition 95 of a UI. Precipitation frequency affects corn grain yield response to N timing and placement methods and forecast of weather patterns should be considered when deliberating N management strategies. Adequate moisture may provide opportunity for corn N response to timing and sidedress placement strategies, but excessive precipitation can exposure applied fertilizer to N loss conditions and delay or prevent application equipment. Greater AE and net economic return with 5x5 and 0/100 N timing strategies suggest increased N utilization and grower profit with V4-6 N applications. Greater concern for economic profitability and water quality place emphasis on N management strategies that both increase profitability while reducing environmental impacts. Delayed N applications that synchronize N availability with corn N uptake may be a greater agronomic and economic investment that reduces N loss potential. Additionally, delayed N applications may offer the possibility of N management strategy adjustment (i.e., N rate, SD placement, addition of a UI) according to previously encountered and predicted environmental conditions, but pre-plant N strategies may be an effective alternative when dry mid-season conditions restrict N uptake. Greater moisture beneath the soil surface than at the soil surface emphasizes the potential for positional unavailability of YD surface application for plant uptake during dry conditions. Benefit of YD surface application may be exist during late-season rescue N applications that restrict CI application or when precipitation immediately follows N application. Additional corn research involving similar treatments across multiple production management systems and soil classifications under a variety of environmental conditions will further develop improved N management. 96 Acknowledgements The authors would like to thank the USDA National Institute of Food and Agriculture, the Corn Marketing Program of Michigan, Michigan State AgBioResearch, and the Michigan State University College of Agriculture and Natural Resources for partial funding and support of this research. In addition, the authors would like to thank Andrew Chomas, research farm staff, and undergraduate research assistants for their technical assistance in the field. . 97 APPENDICES 98 APPENDIX A: CHAPTER 3 TABLES Nitrogen timing and sidedress placement Table 3.01. Overview of corn nitrogen (N) timing and sidedress placement treatments, Richville and Lansing, MI, 2017 to 2018. Treatment N rate† (lbs N ha-1) 1 2 3 4 5 6 7 8 9 10 11 12 †Maximum return to nitrogen rate used in Richville and Lansing were 190 and 162 kg N ha-1, respectively. ‡Urease inhibitor (N-[n-butyl]-thiophosphoric triamide) applied at a rate of 2.09 ml kg-1 urea. §Urease inhibitor (N-[n-butyl]-thiophosphoric triamide) applied at a rate of 2.09 ml kg-1 urea ammonium nitrate. Untreated control Pre-emerge (PRE) PRE + urease inhibitor‡ (UI) 50/50, PPI:SD Coulter-inject (CI) 50/50, PPI:SD Y-drop surface application (YD) 50/50, PPI:SD YD+UI§ 0/100, PPI:SD CI 0/100, PPI:SD YD 0/100, PPI:SD YD+UI§ 5x5, 45 kg N ha-1 5x5:remainder of N SD CI 5x5, 45 kg N ha-1 5x5:remainder of N SD YD 5x5, 45 kg N ha-1 5x5:remainder of N SD YD+UI§ 0 190/162 190/162 190/162 190/162 190/162 190/162 190/162 190/162 190/162 190/162 190/162 99 Apr. May Jun. Jul. Year Aug. Sep. Total mm 147 72 73 133 60 77 123 37 76 84 37 88 40 49 97 33 103 89 50 54 86 66 126 85 28 50 66 67 27 72 445 462 482 418 470 493 Table 3.02. Mean monthly precipitation and temperature† for the corn growing season, Richville and Lansing, MI, 2017 to 2018. Site Richville 2017 2018 30-yr.‡ avg. Lansing 2017 2018 30-yr. avg. Richville 2017 2018 30-yr. avg. Lansing 2017 2018 30-yr. avg. 17.9 17.8 16.3 17.9 18.0 16.6 †Monthly precipitation and air temperature data collected from Michigan State University Enviro-weather (https://enviroweather.msu.edu) ‡30-yr means were collected from the National Oceanic and Atmosphere Administration (https://www.ncdc.noaa.gov/cdo-web/datatools/normals). 20.4 19.8 19.6 19.9 20.0 19.8 10.3 3.6 7.8 11.1 4.1 8.6 57 200 84 35 117 82 19.3 21.8 20.4 19.3 21.8 21.0 13.7 17.6 14.1 13.7 17.6 14.3 ˚C 21.2 22.1 21.7 21.7 21.9 21.9 ̶ ̶ ̶ ̶ ̶ ̶ 100 Grain yield Net economic return Mg ha-1 US$ ha-1 Table 3.03. Corn grain yield† and net economic return‡ as affected by pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed V4-6 (SD), 0/100 PPI and SD, and 5x5 N strategies in combination with SD placements of coulter-inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI), across locations and years in Richville and Lansing, MI, 2017 to 2018. N strategy§ PRE PRE + UI 50/50: PPI/CI 50/50: PPI/YD 50/50: PPI/YD + UI 0/100: PPI/CI 0/100: PPI/YD 0/100: PPI/YD + UI 5x5 + CI 5x5 + YD 5x5 + YD + UI P > F Untreated# 1328 cd 1344 bcd 1339 bcd 1295 cd 1260 d 1436 ab 1397 abc 1398 abc 1466 a 1383 abc 1364 abcd 0.08 772 10.7 a¶ 10.8 a 11.0 a 10.6 a 10.4 a 11.5 a 11.1 a 11.3 a 11.5 a 11.1 a 11.1 a 0.60 6.0 Multiple df contrasts 10.7 a 10.7 a 11.3 a 11.2 a 0.40 11.3 a 10.9 a 0.31 10.8 a 10.9 a 0.92 1336 bc 1298 c 1411 a 1405 ab <0.01 1414 a 1350 b 0.05 1351 a 1342 a 0.78 Nitrogen timing†† PRE 50/50 0/100 5x5 P > F Sidedress placement‡‡ CI YD P > F Urease inhibitor§§ -UI +UI P > F †Grain yield at 155 g kg-1 moisture. ‡Net economic return calculated as (yield x corn price) minus partial budget costs. §Maximum return to nitrogen rate used in Richville and Lansing were 190 and 162 kg N ha-1, respectively. ¶Values within each column followed by the same lowercase letter are not significantly different at α = 0.10. #Untreated control not included in statistical analysis. ††Contrasts consisted of two treatment means for the PRE N timing and three treatment means for the 0/100, 50/50, and 5x5 N timing strategies. ‡‡Coulter-inject multiple degree of freedom contrast was the mean of all coulter-inject treatments. Y-drop surface application was the mean of all treatments utilizing Y-drop surface application sidedress method. §§‘+UI’ multiple degree of freedom contrast was the mean of all treatments containing a UI. ‘-UI’ was a mean of all treatments not containing an UI. 101 Table 3.04. Mean soil moisture (cm3 cm-3) and cumulative precipitation† (mm) three weeks following corn nitrogen (N) applications, Richville and Lansing, MI, 2017 to 2018. N applications initiated at planting‡ Sidedress N applications§ 2017 2018 2017 2018 2017 2018 2017 2018 0-7 d 8-14 d 0-7 d 8-14 d 15-21 d 0.303 0.356 0.153 0.219 0.304 0.358 0.172 0.206 0.316 0.348 0.143 0.187 0.315 0.376 0.101 0.207 0.395 0.374 0.131 0.189 mm 15-21 d cm3 cm-3 0.402 0.372 0.159 0.186 Location Year Richville Lansing 52 Richville 5 7 Lansing 9 †Mean soil moisture (0 to 30-cm), and cumulative precipitation data collected from Michigan State University Enviro-weather (https://enviroweather.msu.edu). ‡Applications include pre-emerge (PRE), PRE with a urease inhibitor, and pre-plant incorporated. Applications were made in Richville on 28 April 2017 and 1 May 2018, and in Lansing on 12 May 2017 and 8 May 2018. §Applications include coulter-inject, Y-drop surface application, and Y-drop surface application with a urease inhibitor. Applications were made in Richville on 6 May 2017 and 31 May 2018, and in Lansing on 9 June 2017 and 7 June 2018. 38 16 1 68 1 20 40 23 6 11 0 0 0 7 5 8 55 3 70 9 102 Agronomic Efficiency kg grain kg N-1 Table 3.05. Agronomic efficiency† (AE) of applied corn nitrogen (N) fertilizer‡ compared across main effects of N timing strategy including pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed V4-6 (SD), 0/100 PPI and SD, and 5x5 N strategies, SD placement including coulter-inject (CI) and Y-drop surface application (YD), and addition of a urease inhibitor (UI) using multiple degree of freedom contrasts, across locations and years in Richville and Lansing, MI, 2017 to 2018. N timing§ PRE 50/50 0/100 5x5 P > F Sidedress placement# CI YD P > F Urease inhibitor†† -UI +UI P > F †Agronomic efficiency calculated by subtracting yield of unfertilized control from mean yield of treatments with N and dividing by N rate. ‡Maximum return to nitrogen rate used in Richville and Lansing were 190 and 162 kg N ha-1, respectively. §Contrasts consisted of two treatment means for the PRE N timing and three treatment means for the 0/100, 50/50, and 5x5 N timing strategies. ¶Values within each column followed by the same lowercase letter are not significantly different at α = 0.10. #Coulter-inject multiple degree of freedom contrast was the mean of all coulter-inject treatments. Y-drop surface application was the mean of all treatments utilizing Y-drop surface application sidedress method. ††‘+UI’ multiple degree of freedom contrast was the mean of all treatments containing a UI. ‘-UI’ was a mean of all treatments not containing an UI. 26.9 b¶ 26.6 b 30.2 a 29.9 a 0.03 30.4 a 28.2 b 0.09 27.7 a 28.0 a 0.86 103 Table 3.06. Multiple degree of freedom contrasts comparing pre-emergence (PRE), 50/50 pre- plant incorporated (PPI) and sidedressed V4-6 (SD), 0/100 PPI and SD, and 5x5 N strategies on mean canopy normalized difference vegetation index (NDVI) measurements at V6 across locations in 2017 and 2018 and at V10 across years and locations in Richville and Lansing, MI, 2017 to 2018. V6 NDVI‡ V10 NDVI 2017-2018 NDVI 2018 2017 0.3105 a§ 0.3061 a 0.3123 a 0.3246 a 0.13 0.2805 N timing† PRE 50/50 0/100 5x5 P > F Untreated¶ †Contrasts consisted of two treatment means for the PRE N timing and three treatment means for the 0/100, 50/50, and 5x5 N timing strategies. ‡Measurements were taken within two to six days of sidedress application at each site-year. §Values within each column followed by the same lowercase letter are not significantly different at α = 0.10. ¶Untreated control not included in statistical analysis. 0.7770 a 0.7730 ab 0.7546 b 0.7866 a 0.04 0.7145 0.4408 a 0.4346 a 0.3862 b 0.4307 a <0.01 0.3978 104 Table 3.07. Corn SPAD chlorophyll† as affected by pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed V4-6 (SD), 0/100 PPI and SD, and 5x5 N strategies in combination with SD placements of coulter-inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI) at R1 across locations in 2017 and 2018 and at R4 across years and locations in Richville and Lansing, MI, 2017 to 2018. N combination PRE PRE + UI 50/50: PPI/CI 50/50: PPI/YD 50/50: PPI/YD + UI 0/100: PPI/CI 0/100: PPI/YD 0/100: PPI/YD + UI 5x5 + CI 5x5 + YD 5x5 + YD + UI P > F Untreated§ R1 chlorophyll 2017 56.9 a‡ 55.0 abc 55.5 ab 53.3 c 54.0 bc 56.9 a 56.3 a 55.3 abc 56.2 a 55.6 ab 56.5 a 0.07 39.5 2018 49.6 b 50.7 ab 48.3 c 50.4 b 50.5 b 50.9 ab 51.2 ab 53.1 a 51.2 ab 53.0 a 51.8 ab <0.01 40.9 Multiple df contrasts R4 Chlorophyll 2017-2018 46.8 cd 49.1 ab 47.2 cd 46.7 d 48.6 bcd 50.2 ab 48.6 bcd 51.0 a 49.2 ab 50.8 a 50.2 ab <0.01 27.4 48.0 b 47.5 b 49.9 a 50.1 a <0.01 48.9 a 49.3 a 0.42 48.3 b 49.7 a <0.01 56.0 a 54.3 b 56.1 a 56.1 a 0.03 56.2 a 55.1 b 0.09 55.5 a 55.2 a 0.57 50.1 bc 49.6 c 51.7 ab 52.0 a <0.01 50.1 b 51.6 a 0.04 51.0 a 51.4 a 0.60 Nitrogen timing¶ PRE 50/50 0/100 5x5 P > F Sidedress placement# CI YD P > F Urease inhibitor†† -UI +UI P > F †Average of 10 plant measurements taken halfway between the leaf collar and leaf tip. ‡Values within each column followed by the same lowercase letter are not significantly different at α = 0.10. §Untreated control not included in statistical analysis. ¶Contrasts consisted of two treatment means for the PRE N timing and three treatment means for the 0/100, 50/50, and 5x5 N timing strategies. #Coulter-inject multiple degree of freedom contrast was the mean of all coulter-inject treatments. Y-drop surface application was the mean of all treatments utilizing Y-drop surface application sidedress method. ††‘+UI’ multiple degree of freedom contrast was the mean of all treatments containing a UI. ‘-UI’ was a mean of all treatments not containing an UI. 105 CHAPTER 3 DATA COLLECTED BUT NOT INCLUDED IN PUBLICATION APPENDIX B: Table 3.08. Corn V4 normalized difference vegetation index (NDVI) measurements as affected by pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed (SD), 0/100 PPI and SD, and 5x5 N strategies in combination with SD placements of coulter-inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI), across locations and years in Richville and Lansing, MI, 2017 to 2018. N combination† V4 NDVI 0.3218 a‡ PRE 0.3224 a PRE + UI 50/50: PPI/CI 0.2978 a 0.3173 a 50/50: PPI/YD 0.3216 a 50/50: PPI/YD + UI 0.2946 a 0/100: PPI/CI 0/100: PPI/YD 0.3009 a 0.2900 a 0/100: PPI/YD + UI 0.3106 a 5x5 + CI 0.3153 a 5x5 + YD 5x5 + YD + UI 0.3001 a P > F 0.35 Untreated§ 0.2871 †Not all treatments received total N rate. ‡Values within each column followed by the same lowercase letter are not significantly different at α = 0.10. §Untreated control not included in statistical analysis. 106 V6 chlorophyll† Table 3.09. Corn V6 SPAD chlorophyll as affected by pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed (SD), 0/100 PPI and SD, and 5x5 N strategies in combination with SD placements of coulter-inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI), across years and locations in Richville and Lansing, MI, 2017 to 2018. N combination PRE PRE + UI 50/50: PPI/CI 50/50: PPI/YD 50/50: PPI/YD + UI 0/100: PPI/CI 0/100: PPI/YD 0/100: PPI/YD + UI 5x5 + CI 5x5 + YD 5x5 + YD + UI P > F Untreated§ 42.5 c‡ 42.0 c 43.0 bc 42.6 c 44.9 ab 40.0 d 41.0 cd 42.0 c 44.6 ab 44.9 a 43.0 bc <0.01 40.0 Multiple df contrasts 42.3 bc 43.5 ab 41.0 c 44.2 a <0.01 42.5 a 43.1 a 0.38 42.8 a 43.0 a 0.75 Nitrogen timing¶ PRE 50/50 0/100 5x5 P > F Sidedress placement# CI YD P > F Urease inhibitor†† -UI +UI P > F †Measurements were taken within two to six days of SD application. ‡Values within each column followed by the same lowercase letter are not significantly different at α = 0.10. §Untreated control not included in statistical analysis. ¶Contrasts consisted of two treatment means for the PRE N timing and three treatment means for the 0/100, 50/50, and 5x5 N timing strategies. #Coulter-inject multiple degree of freedom contrast was the mean of all coulter-inject treatments. Y-drop surface application was the mean of all treatments utilizing Y-drop surface application sidedress method. ††‘+UI’ multiple degree of freedom contrast was the mean of all treatments containing a UI. ‘-UI’ was a mean of all treatments not containing an UI. 107 Table 3.10. Impact of pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed (SD), 0/100 PPI and SD, and 5x5 N strategies in combination with SD placements of coulter- inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI) on V6 corn plant height presented by year and location, Richville and Lansing, MI, 2017 to 2018. Lansing Richville N combination PRE PRE + UI 50/50: PPI/CI 50/50: PPI/YD 50/50: PPI/YD + UI 0/100: PPI/CI 0/100: PPI/YD 0/100: PPI/YD + UI 5x5 + CI 5x5 + YD 5x5 + YD + UI P > F Untreated‡ 2017 2018 2017 2018 m 0.2477 bcd† 0.3082 abcd 0.3382 ab 0.2540 abc 0.3220 abc 0.2604 ab 0.3567 a 0.2413 bcd 0.2477 bcd 0.2990 bcd 0.2965 bcd 0.2286 d 0.2632 d 0.2350 dc 0.2286 d 0.2773 cd 0.3345 ab 0.2731 a 0.3460 ab 0.2731 a 0.3250 abc 0.2350 dc 0.01 0.08 0.2810 0.2286 0.3250 abc 0.3328 ab 0.3400 a 0.3153 abcd 0.3138 abcd 0.2890 de 0.3038 cde 0.2758 e 0.3093 bcd 0.3175 abcd 0.3013 cde 0.03 0.3060 0.2870 a 0.2991 a 0.2845 a 0.2927 a 0.3111 a 0.2991 a 0.3023 a 0.2908 a 0.2883 a 0.2896 a 0.2762 a 0.59 0.2737 Multiple df contrasts 0.2931 a 0.2961 a 0.2974 a 0.2847 a 0.45 0.2906 a 0.2938 a 0.67 0.2929 a 0.2943 a 0.85 0.2508 a 0.2498 a 0.2307 b 0.2603 a <0.01 0.2540 a 0.2434 a 0.12 0.2492 a 0.2413 a 0.24 0.3289 a 0.3230 ab 0.2895 c 0.3093 b <0.01 0.3127 a 0.3045 a 0.34 0.3154 a 0.3059 a 0.27 Nitrogen timing§ PRE 50/50 0/100 5x5 P > F Sidedress placement¶ CI YD P > F Urease inhibitor# -UI +UI P > F †Values within each column followed by the same lowercase letter are not significantly different at α = 0.10. ‡Untreated control not included in statistical analysis. §Contrasts consisted of two treatment means for the PRE N timing and three treatment means for the 0/100, 50/50, and 5x5 N timing strategies. ¶Coulter-inject multiple degree of freedom contrast was the mean of all coulter-inject treatments. Y-drop surface application was the mean of all treatments utilizing Y-drop surface application sidedress method. #‘+UI’ multiple degree of freedom contrast was the mean of all treatments containing a UI. ‘-UI’ was a mean of all treatments not containing an UI. 0.3232 a 0.3259 a 0.2790 b 0.3352 a 0.01 0.3177 a 0.3112 a 0.67 0.3186 a 0.3099 a 0.56 108 Table 3.11. Impact of pre-emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed (SD), 0/100 PPI and SD, and 5x5 N strategies in combination with SD placements of coulter- inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI) on R1 corn plant height across years and locations, Richville and Lansing, MI, 2017 to 2018. N combination R1 height m PRE PRE + UI 50/50: PPI/CI 50/50: PPI/YD 50/50: PPI/YD + UI 0/100: PPI/CI 0/100: PPI/YD 0/100: PPI/YD + UI 5x5 + CI 5x5 + YD 5x5 + YD + UI P > F Untreated‡ 2.2668 a† 2.2370 a 2.2490 a 2.2617 a 2.2406 a 2.2489 a 2.2319 a 2.2298 a 2.2962 a 2.2895 a 2.2877 a 0.58 2.0088 Multiple df contrasts 2.2699 ab 2.2504 b 2.2368 b 2.2911 a 0.06 2.2647 a 2.2569 a 0.66 2.2620 a 2.2582 a 0.83 Nitrogen timing§ PRE 50/50 0/100 5x5 P > F Sidedress placement¶ CI YD P > F Urease inhibitor# -UI +UI P > F †Values within each column followed by the same lowercase letter are not significantly different at α = 0.10. ‡Untreated control not included in statistical analysis. §Contrasts consisted of two treatment means for the PRE N timing and three treatment means for the 0/100, 50/50, and 5x5 N timing strategies. ¶Coulter-inject multiple degree of freedom contrast was the mean of all coulter-inject treatments. Y-drop surface application was the mean of all treatments utilizing Y-drop surface application sidedress method. #‘+UI’ multiple degree of freedom contrast was the mean of all treatments containing a UI. ‘-UI’ was a mean of all treatments not containing an UI. 109 NO3-N mg kg-1 Table 3.12. Post-harvest soil residual nitrate† (NO3-N) concentration as affected by pre- emergence (PRE), 50/50 pre-plant incorporated (PPI) and sidedressed (SD), 0/100 PPI and SD, and 5x5 N strategies in combination with SD placements of coulter-inject (CI), Y-drop surface application (YD), and addition of a urease inhibitor (UI) across locations and years, Richville and Lansing, MI, 2017 to 2018. N combination PRE PRE + UI 50/50: PPI/CI 50/50: PPI/YD 50/50: PPI/YD + UI 0/100: PPI/CI 0/100: PPI/YD 0/100: PPI/YD + UI 5x5 + CI 5x5 + YD 5x5 + YD + UI P > F Untreated§ 5.19 a‡ 5.05 a 5.52 a 3.64 a 4.23 a 5.66 a 4.75 a 5.99 a 5.02 a 3.67 a 5.22 a 0.71 2.62 Multiple df contrasts 5.12 a 4.46 a 5.47 a 4.63 a 0.53 5.40 a 4.58 a 0.16 4.31 a 5.12 a 0.53 Nitrogen timing¶ PRE 50/50 0/100 5x5 P > F Sidedress placement# CI YD P > F Urease inhibitor†† -UI +UI P > F †Samples taken at 0 to 30-cm depth. ‡Values within each column followed by the same lowercase letter are not significantly different at α = 0.10. §Untreated control not included in statistical analysis. ¶Contrasts consisted of two treatment means for the PRE N timing and three treatment means for the 0/100, 50/50, and 5x5 N timing strategies. #Coulter-inject multiple degree of freedom contrast was the mean of all coulter-inject treatments. Y-drop surface application was the mean of all treatments utilizing Y-drop surface application sidedress method. ††‘+UI’ multiple degree of freedom contrast was the mean of all treatments containing a UI. ‘-UI’ was a mean of all treatments not containing an UI. 110 LITERATURE CITED 111 LITERATURE CITED fertilization. Agron. J. 79:544-549. and remobilization in modern, transgenic insect-protected maize hybrids. Agron. J. 105:161-170. in crop production. ASA, CSSA, and SSSA, Madison, WI. p. 273-294. efficiency, and nitrogen management. AMBIO. 31:132-140. applications in relation to compaction and irrigation in maize and wheat. Agron. J. 66:560-564. Anderson, E.L. 1987. Corn root growth and distribution as influenced by tillage and nitrogen Bender, R.R., J.W. Haegele, M.L. Ruffo, and F.E. Below. 2013. Nutrient uptake, partitioning, Bock, B.R. 1984. Efficient use of nitrogen in cropping systems. In: R.D. Hauck, editor, Nitrogen Bruulsema, T., J. Lemunyon, and B. Herz. 2009. Know your fertilizer rights. Crop Soil 42:13-18. Cassman, K.G., A. Dobermann, and D.T. Walters. 2002. Agroecosystems, nitrogen-use Chaudhary, M.R., and S.S. Prihar. 1974. Comparison of banded and broadcast fertilizer Combs, S.M., and M.V. Nathan. 2015. Soil organic matter. In: M.V. Nathan and R. Gelderman, editors, Recommended chemical soil test procedures for the North Central Region. North Central Region Res. Publ. 221 (rev.). SB 1001. Missouri Agric. Exp. Stn, Columbia. p. 12.1-12.6. Dawar, K., M. Zaman, J.S. Rowarth, J. Blennerhassett, and M.H. Turnbull. 2011. Urea Fox, R.H., J.M. Kern, and W.P. Piekielek. 1986. Nitrogen fertilizer source, and method and Fox, R.H., and W.P. Piekielek. 1993. Management and urease inhibitor effects on nitrogen Frank, K., D. Beegle, and J. Denning. 2015. Phosphorus. In: M.V. Nathan and R. Gelderman, Franzen, D.W. 2017. Nitrogen extenders and additives for field crops. Bull. SF1581, North editors, Recommended chemical soil test procedures for the North Central Region. North Central Region Res. Publ. 221 (rev.). SB 1001. Missouri Agric. Exp. Stn, Columbia. p. 6.1-6.6. hydrolysis and lateral and vertical movement in the soil: Effects of urease inhibitor and irrigation. Biol. Fertil. Soils 47:139-146. time of application effects on no-till corn yields and nitrogen uptakes. Agron. J. 78:741-746. use efficiency in no-till corn. J. Prod. Agric. 6:195-200. Dakota State University, Fargo, ND. 112 Agronomy Fact Sheet Series. Cornell Univ. Coop. Extension. http://nmsp.cals.cornell.edu/publications/fact-sheets/factsheet80.pdf. Gardinier, A., Q. Ketterings, B. Verbeten, and M. Hunter. 2013. Urea fertilizer. Fact Sheet 80. Gelderman, R.H., and D. Beegle. 2015. Nitrate-nitrogen. In: M.V. Nathan and R. Gelderman, Havlin, J.L., S.L. Tisdale, J.D. Beaton, and W.L. Nelson. 2014. Soil fertility and fertilizers: An editors, Recommended chemical soil test procedures for the North Central Region. North Central Region Res. Publ. 221 (rev.). SB 1001. Missouri Agric. Exp. Stn, Columbia. p. 5.1-7.4. introduction to nutrient management 8th ed. Upper Saddle River, New Jersey, USA: Pearson Prentice Hall. United States. Cambridge Univ. Press, New York. sorghum production: I. Rate and time of application. Agron. J. 92:321-328. management under fully-irrigated vs. water-stressed conditions. Agron. J. 108:2089- 2098. use efficiency of world cropping systems: The relationship between yield and nitrogen input to cropland. Environ. Res. Lett. 9:1-9. Karl, T.R., J.M. Melillo, and T.C. Peterson, editors, 2009. Global climate change impacts in the Khosla, R., M.M. Alley, and P.H. Davis. 2000. Nitrogen management in no-tillage grain Lassaletta, L., G. Billen, B. Grizzetti, J. Anglade, and J. Garnier. 2014. 50 year trends in nitrogen Lehrsch, G.A., R.E. Sojka, and D.T. Westermann. 2000. Nitrogen placement, row spacing, Maharjan, B., C.J. Rosen, J.A. Lamb, and R.T. Venterea. 2016. Corn response to nitrogen Mengel, D.B, and S.A Barber. 1974. Development and distribution of the corn root system Mueller, S.M., J.J. Camberato, C. Messina, J. Shanahan, H. Zhang, and T.J. Vyn. 2017. Late- split nitrogen applications increased maize plant nitrogen recovery but not yield under moderate to high nitrogen rates. Agron. J. 109:2689-2699. National Oceanic and Atmospheric Administration. 2017. National climatic data center. NOAA. Nelson, K.A., P.C. Scharf, W.E. Stevens, and B.A. Burdick. 2011. Rescue nitrogen Niehues, B.J., R.E. Lamond, C.B. Godsey, and C.J. Olsen. 2004. Starter nitrogen fertilizer management for continuous no-till corn production. Agron. J. 96:1412-1418. http://www.ncdc.noaa.gov/ (accessed 18 October 2018). applications for corn. Soil Sci. Soc. Am. J. 75:143-151. and furrow irrigation water positioning effects on corn yield. Agron. J. 92:1266-1275. under field conditions. Agron. J. 66:341-344. 113 Ordóñez, R.A., M.J. Castellano, J.L. Hatfield, M.J. Helmers, M.A. Licht, M. Liebman, R. Dietzel, R. Martinez-Feria, J. Iqbal, L.A. Puntel, S.C. Córdova, K. Togliatti, E.E. Wright, and S.V. Archontoulis. 2018. Maize and soybean root front velocity and maximum depth in Iowa, USA. Field Crops Res. 215:122-131. Pan, B., S.K. Lam, A. Mosier, Y. Luo, and D. Chen. 2016. Ammonia volatilization from synthetic fertilizers and its mitigation strategies: A global synthesis. Agriculture, Ecosystems and Environment 232:283-289. Peters, J.B., M.V. Nathan, and C.A.M. Laboski. 2015. pH and lime requirement. In: M.V. Peterson, T.A., T.M. Blackmer, D.D. Francis, and J.S. Schepers. 1993. Using a chlorophyll Quinn, D., and K. Steinke. 2019. Soft red and white winter wheat response to input-intensive Nathan and R. Gelderman, editors, Recommended chemical soil test procedures for the North Central Region. North Central Region Res. Publ. 221 (rev.). SB 1001. Missouri Agric. Exp. Stn., Columbia. p. 4.1-4.7. meter to improve N management. NebGuide G93-1171-A. Univ. of Nebraska Extension, Lincoln. management. Agron. J. 111:428-439. production. Agron. J. 91:357-363. Northern Corn Belt. Agron. J. 110:2059-2069. maize. Agron. J. 75:593-598. use efficiency in Upper Midwest irrigated sandy soils. Agron. J. 108:1681-1691. Randall, G.W., T.K. Iragavarapu, and B.R. Bock. 1997. Nitrogen application methods and timing for corn after soybean in a ridge-tillage system. J. Prod. Agric. 10:300-307. Raun, W.R., and G.V. Johnson. 1999. Improving nitrogen use efficiency for cereal Rubin, J.C., A.M. Struffert, F.G. Fernández, and J.A. Lamb. 2016. Maize yield and nitrogen Rutan, J., and K. Steinke. 2018. Pre-Plant and in-season nitrogen combinations for the Russelle, M.P., R.D. Hauck, and R.A. Olson. 1983. Nitrogen accumulation rates of irrigated Rutto, E., J.P. Vossenkemper, J. Kelly, B.K. Chim, and W.R. Raun. 2013. Maize grain yield response to the distance nitrogen is placed away from the row. Expl. Agric. 49:3-18. SAS Institute. 2012. The SAS System for windows. Version 9.4. SAS Inst., Cary, NC. Sawyer, J., E. Nafziger, G. Randall, L. Bundy, G. Rehm, and B. Joern. 2006. Concepts and rationale for regional nitrogen rate guidelines for corn. Publ. PM2015, Iowa State Univ. Ext., Ames, IA. 114 plant biomass, nitrogen, and use efficiency. Agron. J. 109:802-810. timing and deficiency level. Agron. J. 94:435-441. on groundwater quality. J. Environ. Qual. 20:12-16. Extension. https://msu.edu/~steind/cp17%20MASTER%20Cust_MachineWrk% 20NOV% 2009%202016.pdf (accessed 29 November 2018). Sawyer, J.E., K.P. Woli, D.W. Barker, and J.L. Pantoja. 2017. Stover removal impact on corn Scharf, P.C., W.J. Wiebold, and J.A. Lory. 2002. Corn yield response to nitrogen fertilizer Schepers, J.S., M.G. Moravek, E.E. Alberts, and K.D. Frank. 1991. Maize production impacts Schwab, G.J., and L.W. Murdock. 2010. Nitrogen transformation: inhibitors and controlled release urea. Publ. AGR-185. Univ. of Kentucky Coop. Ext. Serv., Lexington, KY. Smil, V. 1997. Global population and the nitrogen cycle. Sci. Am. 277:76-813. Stecker, J.A., D.D. Buchholz, R.G. Hanson, N.C. Wollenhaupt, and K.A. McVay. 1993. Application placement and timing of nitrogen solution for no-till corn. Agron. J. 85:645-650. Stein, D. 2016. 2017 Custom machine and work rate estimates. Michigan State University Steinke, K., J. Rutan, and L. Thurgood. 2015. Corn response to nitrogen at multiple sulfur rates. Teal, R.K., B. Tubana, K. Girma, K.W. Freeman, D.B. Arnall, O. Walsh, and W.R. Raun. Tucker, C.J. 1979. Red and photographic infrared linear combinations for monitoring vegetation. USDA-NASS. 2018. National statistics for corn: Yield, measured in bu/acre. Statistics by subject. USDA National Agriculture Statistics Service http://www.nass.usda.gov/ Statistics_by_ Subject/index.php (accessed 19 September 2018). Venterea, R.T., and J.A. Coulter. 2015. Split application of urea does not decrease and may Vitosh, M.L., J.W. Johnson, and D.B. Mengel. 1995. Tri-state fertilizer recommendations for Walsh, O., W. Raun, A. Klatt, and J. Solie. 2012. Effect of delayed nitrogen fertilization on corn, soybeans, wheat, and alfalfa. Bull. E2567. Michigan State Univ. Ext., East Lansing, MI. 2006. In-season prediction of corn grain yield potential using normalized difference vegetation index. Agron. J. 98:1488-1494. maize (Zea Mays L.) grain yields and nitrogen use efficiency. Journal of Plant Nutrition 35:538-555. increase nitrous oxide emissions in rainfed corn. Agron. J. 107:337-348. Agron. J. 107:1347-1354. Remote Sens. Environ. 8:127-150. 115 Gelderman, editors, Recommended chemical soil test procedures for the North Central Region. North Central Region Res. Publ. 221 (rev.). SB 1001. Missouri Agric. Exp. Stn, Columbia. p. 7.1-7.3. Warncke, D., and J.R. Brown. 2015. Potassium and other basic cations. In: M.V. Nathan and R. Warncke, D., J. Dahl, and L. Jacobs. 2009. Nutrient recommendations for field crops in Michigan. Bull. E2904, Michigan State University Extension, East Lansing, MI Woodley, A.L., C.F. Drury, X.M. Yang, W D. Reynolds, W. Calder, and T.O. Oloya. 2018. Streaming urea ammonium nitrate with or without enhanced efficiency products impacted corn yields, ammonia, and nitrous oxide emissions. Agron. J. 110:444-454. 116