. qu..zl!fl.fi.Lk Adam? 3mm .. "5 .. .. g... L .l 4.; 134:... 1.! . any? .1 :1 : ‘nnfl 1i ‘ I ' “‘1“ tlx... y «.5 .:h a... J. .2. 9!... .3.qu .11 . it... .1 LP.“ .33“ ‘ O ‘ um. .52.? .k . .. .. z 1:..- :12... This is to certify that the thesis entitled Managing Nitrogen Additions and Assessing Water Quality Under the Root Zone in Field Nursery Production presented by Carmela Rios has been accepted towards fulfillment of the requirements for Masters Jegreein Horticulture 134 Owl/7 J , Major professdr/ Date May 14, 2002 0-7639 MS U is an Affirmative Action/Equal Opportunity Institution LIBRARY Michigan State University PLACE IN RETURN Box to remove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 6/01 cJCIRCIDateDuopes-p. 15 MANAGING NITROGEN ADDITIONS AND ASSESSING WATER QUALITY UNDER THE ROOT ZONE IN FIELD NURSERY PRODUCTION By Carmela M. Rios A THESIS Submitted to Michigan State University In partial fulfillment of the requirements for the degree of MASTERS OF SCIENCE Department of Horticulture 2002 ABSTRACT MANAGING NITROGEN ADDITIONS AND ASSESSING WATER QUALITY UNDER THE ROOT ZONE IN FIELD NURSERY PRODUCTION By Carmela M. Rios Michigan’s nursery industry is localized in an area of high risk for ground water contamination. This study aims to evaluate the impact of nitrogen fertilization approaches on crop growth and nitrate-N concentration of water under the root zone, and to determine the validity and logistics of applying relative addition rate principles to nursery crops. Two nurseries were used in this study. Each nursery had two fields one growing Taxus spp. and the other growing a Euonymus spp. The fertilizer treatments were: 1) control (no fertilizer); 2) operational fertilization (based on the nurseries’ current practices); and 3) relative addition rate (additions based on crop growth). Soil water below the root zone was collected after every significant rainfall event using porous cup lysimeters. Nitrate-N concentrations were found to be high when compared to other agricultural systems, reaching up to160 ppm in September. The RAR treatment reduced nitrate-N leaching in two out of the four fields. Crop growth did not differ among the treatments. Implications of the results indicate nursery management practices should be altered to improve the efficiency of fertilizer use. ACKNOWLEDGMENTS I am grateful to have studied under Bert Cregg who did everything in his power to make this the wonderful experience that it has become. Todd Herrick, Jim Oros and others at Zelenka and Northland Nursery for continuing the partnership with Michigan State, which I hope will grow. I would also like to thank my committee members James Hart, Tom Fernandez, and Brad Rowe for their guidance. Last but not least John, who was so patient and loving throughout my time here, thank you! iii TABLE OF CONTENTS LIST OF TABLES .................................................................. vi LIST OF FIGURES ................................................................ viii LITERATURE REVIEW: Introduction ................................................................. 2 1) Environmental Impacts of nitrate leaching ...................... 3 Contributions from agriculture ................................. 3 Harm to humans .................................................. 4 Effect on aquatic systems ...................................... 5 2) Maximizing the efficiency of fertilizer use ........................ 6 Studies measuring nitrate leachate concentrations ..... 7 Porous ceramic cups ............................................ 8 Soil organic nitrogen ............................................ 11 When to fertilize .................................................. 15 How much to fertilize ............................................ 17 Foliar N concentration ........................................... 18 ‘Relative Addition Rate’ ......................................... 20 3) The use of 15N for fertilizer studies ................................ 21 Fate of 15N labeled fertilizer .................................. 21 Techniques ........................................................ 24 Literature Cited ........................................................ 26 CHAPTER ONE: MANAGING NITROGEN ADDITIONS AND ASSESSING WATER QUALITY UNDER THE ROOT ZONE IN FIELD NURSERY PRODUCTION OF TAXUS AND EUONYMUS ............................ 31 Abstract ...................................................................... 32 Introduction .................................................................. 33 Materials and Methods ................................................... 36 Results ....................................................................... 40 Discussion .................................................................. 41 List of Figures .............................................................. 52 Literature Cited ............................................................ 59 CHAPTER TWO: EFFECT OF THREE FERTILIZER RATES ON FIELD-GROWN TAXUS AND EUONYMUS SPECIES IN WESTERN MICHIGAN... 62 Abstract ...................................................................... 63 Introduction ................................................................. 64 Materials and Methods ................................................... 66 Results ....................................................................... 68 iv Discussion ................................................................... 70 List of Figures ............................................................... 81 APENDIX .............................................................................. 88 TDR 2001 .................................................................... 89 ANOVA Soil Cores Taxus ................................................ 96 ANOVA Soil Cores EAC .................................................. 97 ANOVA Growth Taxus ..................................................... 98 ANOVA Growth EAC ...................................................... 99 Root/Shoot Data ............................................................ 100 LIST OF TABLES TABLE PAGE LITERATURE REVIEW Foliar nitrogen concentration of various woody species at different ages, and under various conditions 19 CHAPTER ONE Site description of year planted, plant density, plant height and site occupancy of four fields in western Michigan. Measurements represent values of April 2001. 46 Fertilizer (20-0-10) application rates and dates for two treatments (operational and RAR) applied to two Taxus nursery fields (Nursery A & B) in western Michigan during the 2001-growing season. 47 Fertilizer application rates and dates of two treatments (operational and RAR) applied to two EAC nursery fields (Nursery A 8r B) in western Michigan during the 2001-growing season. 48 Analysis of variance for nitrate-N soil water sampled with ceramic porous cups in two Taxus nursery fields (Nursery A & B) in western Michigan during the 2001-growing season. 49 Analysis of variance for nitrate-N in soil water sampled with ceramic porous cups in two EAC nursery fields (Nursery A & B) in western Michigan during the 2001-growing season. 50 Leaching studies showing nitrate-N concentrations in different agricultural and forest systems. 51 CHAPTER TWO Site description of year planted, plant density, plant height and site occupancy of four fields in western Michigan. Measurements represent values of April 2001. vi 74 Fertilizer (20-0-10) application rates and dates for two treatments (operational and RAR) applied to two Taxus nursery fields (Nursery A & B) in western Michigan during the 2001-growing season. 75 Fertilizer application rates and dates of two treatments (operational and RAR) applied to two EAC nursery fields (Nursery A & B) in western Michigan during the 2001-growing season. 76 Biomass distribution and root weight ratios for two Taxus fields in western Michigan. Twelve plants were harvested from each fertilizer treatment in Nursery A, and nine from each treatment in Nursery B, at the end of the 2001 growing season. Dry weight values are represented. 77 Biomass distribution and root weight ratios for two EAC fields in western Michigan. Twelve plants were harvested from each fertilizer treatment at the end of the 2001 growing season. Dry weight values are represented. 78 Analysis of variance for foliar nitrogen concentration from two Taxus fields (Nursery A& B) in western Michigan during the 2001-growing season. Foliage was collected from 10 random plants in each field plot. 79 Analysis of variance of foliar nitrogen concentration from two EAC fields (Nursery A&B) in western Michigan during the 2001-growing season. Foliage was collected from 10 random plants in each field. 80 vii LIST OF FIGURES FIGURE PAGE LITERATURE REVIEW Nitrogen pathways in soil. The quantity of nitrogen in each pool (kg/ha) or under each process (kg/ha/yr) is proportional to the size of the square (Powlson 1993). 14 Nitrogen pathways and transformations following land application of organic manures (Chambers et al. 1999). 15 CHAPTER ONE Simple linear function relating foliar biomass to crown volume index for 12 EAC and 12 Taxus plants grown in nursery fields in western Michigan, spring 2001. 53 Rainfall (mm) readings from a weather station in West Olive, Ml from 5/1/2001 - 10/31/2001. Sampling dates of the porous ceramic cups are indicated by *. ' 54 Nitrate-N concentrations in soil water sampled with ceramic porous cup lysimeters in two Taxus nursery fields (Nursery A & B) in western Michigan during the 2001-growing season. Nursery A had 12 sampling dates, while Nursery B had 14. 55 Nitrate-N concentrations of soil cores sampled at two Taxus nursery fields (Nursery A & B) in western Michigan during the 2001-gowing season. Vertical bars represent standard error of the mean. 56 Nitrate-N concentrations in soil water sampled with ceramic porous cup lysimeters in two EAC nursery fields (Nursery A & B) in western Michigan during the 2001-gowing season. Nursery A had 10 sampling dates, while Nursery B had 15. Vertical bars represent standard error of the mean. 57 viii Nitrate-N concentrations of soil cores sampled at two EAC nursery fields (Nursery A & B) in western Michigan during the 2001-growing season. Vertical bars represent standard error of the mean. 58 CHAPTER TWO Plant volume index measurements for two Taxus fields (Nursery A & B) in western Michigan during the 2001-growing season. Data points represent averages of 30 plant measurements per treatment. Vertical bars represent standard error of the mean. 82 Plant volume index measurements for two EAC fields (Nursery A & B) in western Michigan during the 2001-growing season. Data points represent averages of 30 plant measurements per treatment. Vertical bars represent standard error of the mean. 83 Foliar N concentrations for two Taxus fields (Nursery A & B) in western Michigan during the 2001-growing season. Each sampling date represents foliage from 10 random plants within the treatment plot. Vertical bars represent standard error of the mean. 84 Foliar N concentrations for two EAC fields (Nursery A & B) in western Michigan during the 2001-growing season. Each sampling date represents foliage from 10 random plants within the treatment plot. Vertical bars represent standard error of the mean. 85 Vector diagram showing the relative response of two Taxus fields (Nursery A & B) to different fertilizer treatments. Foliar concentration represents an average of four samples taken throughout the 2001- growing season. Relative content was derived from total growth during the season and average N concentration; the control was used as the reference value. 86 Vector diagram showing the relative response of two EAC fields (Nursery A & B) to different fertilizer treatments. Foliar concentration represents an average of three samples taken throughout the 2001- growing season. Relative content was derived from total growth during the season and average N concentrations; the control was used as the reference value. 87 ix LITERATURE REVIEW LITERATURE REVIEW Introduction Agricultural activities have been identified as major sources of surface water pollutants and environmental contaminants (Cooper 1993). For growers, nitrogen application is a very cost effective act (Goulding 2000). Presently, industry can afford to overlook inefficiencies in fertilizer application, because profits outweigh costs (Sylvester-Bradley 1993). Fertilizer however, is not free. The Haber-Bosch synthesis provides more than 99% of all inorganic nitrogen inputs to farms (Morrison and Morrison 2001). The increase cost of natural gas indicates possible future increase in the cost of synthetic fertilizer. The second larger cost of inefficient fertilizer application is the cost to our environment. Vlfith increasing governmental regulations in the US. and around the world, maximizing efficiency of fertilizer use is becoming a greater concern for the industry, and a more pressing area of research. Maximizing efficiency of fertilizer use is complex. Many factors must be taken into consideration, including, weather, time of application, the past land use and interactions among plant species, soil, nutrient source and microbial activity. In this review I will include research on the following topics: 1) Environmental impacts of nitrate leaching Contribution from agriculture Harm to humans Effect on aquatic ecosystems 2) Maximization of efficiency in use of fertilizers Measurement of nitrate concentration in leachate Porous ceramic cups Soil organic nitrogen When to fertilize How much to fertilize Foliar N concentrations Relative Addition Rate 3) Fertilizer-derived nitrogen in plants Fate of 15N-labellerl fertilizer Techniques 1. Environmental impacts of nitrate leaching Nitrate is the pollutant most commonly identified in ground water. Though nitrate (N03) is the most researched form in which nitrogen occurs in groundwater, dissolved nitrogen may also be present as ammonium (NHX), nitrite (NOz'), nitrogen (N2), nitrous oxide (N20) and as organic nitrogen (Burt et al. 1993). Contributions from agriculture Agricultural practices are responsible for a major portion of the nitrate pollutants in surface water (Cooper 1993). In the UK. 1.6 million tons of N are applied to crops as fertilizer every year, 10-60% of which is not incorporated by the crop (Sylvester-Bradley 1993). Inputs of nitrates from agricultural sources are termed non-point pollutants because they originate from a diffuse area, are generally not continuous, and can vary depending on weather and time of year. Non-point pollutants are difficult to measure, control, and regulate. Any control requires altering land management practices (Carpenter 1998). There is a lack of knowledge as to when and how much N fertilizer should be applied to crops. It has been shown that with agricultural crops it takes a large amount of fertilizer to bring a crop to its maximum yield: indeed, to increase yield from 90% of maximum to 100%, doubling the fertilizer N is required to provide the last 10% of the yield (Sylvester-Bradley 1993). Because fertilizer is inexpensive, growers are willing to over apply and be assured that the crop will grow to its maximum potential. Total N in the soil is usually underestimated. Nitrogen can derive from a combination of organic compounds already present in the soil, can be released by mineralization of applied manure, or from non- organic fertilizers. The underestimation has led to a surplus of nitrogen in the soil, and contamination of groundwater by large quantinties of N (nitrate) in leachates. (Alt 1998, Goulding 2000; Powlson et al. 1993, Shepherd 1996). In the world’s croplands, additions and removals of nutrients by humans have overwhelmed natural nutrient cycles. Worldwide, more nutrients are added as fertilizers than are removed with the crop (Carpenter 1998). Harm to humans The most susceptible group to the harmful effects of the ingestion of nitrates are infants under the age of 6 months. Adults and older children can excrete through their urine most of the ingested nitrate. Other groups at risk are pregnant women, cancer patients, and people with reduced stomach acidity (Carpenter 1998, Hallbourg 1998, Mahler et al. 1998). Infants under the age of 6 months have low levels of acid in their digestive tract, so to help with digestion they have high levels of bacteria, which convert nitrate to the toxic nitrtite (Mahler et al. 1998). In the bloodstream nitrite combines with hemoglobin and forms methemoglobin. Unlike hemoglobin, this compound is unable to carry oxygen. As more methemoglobin is produced suffocation starts to take place from the lack of oxygen. This is called “methemoglobinemia”(Mahleret al. 1998). When babies contract this it is termed “blue-baby syndrome”. To protect babies less than 6 months old, the Environmental Protection Agency has established a Maximum contaminant level for nitrate in drinking water of 10 milligrams per liter. (Carpenter 1998). Mahler et al. (1998), gives a table with “Guidelines for use of water with known nitrate content”, which includes categories such as safe for humans and livestock, short term acceptable use, high risk for adults and young livestock, and not safe for infants. Nitrate may also interact with organic compounds to form nitrosamines, which are known to cause cancer. Compounds that can interact with nitrate include some pesticides. This is important because areas contaminated with nitrates have a high probability of containing pesticides (Mahler et al. 1998). Effect on aquatic ecosystems Eutrophication is defined by Carpenter(1998) as “the fertilization of surface waters by nutrients that were previously scarce”. The nutrients that cause the most harm in this process are phosphorous and nitrogen. Eutrophication is currently the most widespread water quality problem in the US, as it is in many other nations. There are severe consequences to eutrophication which include: premature aging of lakes, proliferation of algae, increase in bacterial populations, decrease in dissolved oxygen, and fish kills. Eutrophication is part of the aging process of shallow lakes. Lakes gradually evolve to dry land, and we are accelerating this process. Vlfith the increase in plant and algae populations in a lake system there is also an increase in dead plant material, which causes the bacterial decomposer population to increase dramatically. These bacteria consume dissolved oxygen, leaving an inadequate supply for the fish, and causing fish kills (Carpenter 1998). 2. Maximizing the efficiency of fertilizer use In the UK, the government has taken steps to increase research and improve efficiency in the use of N-fertilizer. The Ministry of Agriculture, Fisheries and Food (MAFF) has established the Nitrate Program with three major goals in mind. 1) Quantify losses of N from range of crops and soils, relate these to management and weather. 2) Achieve greater understanding of N-cycle (e.g mineralization) 3) Incorporate this knowledge into better recommendations for use of fertilizer and manure. Knowledge gained from this research, will be applied to help growers improve management practices (Dampney et al. 2000; Goulding, 2000). Studies measuringnitrate leachate concentrations Plantations of hardwoods and conifers can be managed intensively. Using tension lysimeters and groundwater wells to capture soil and ground water, Williams (1999) studied whether plantation management of Loblolly pine (Pinus taeda L..) and sweeetg um (Liquidambar styraciflua L.) caused nitrate leaching, and groundwater contamination. They found a statistically significant increase in nitrate in the soil solution and groundwater throughout the plantation. .A two-year study looked at nitrate leachate and pasture yields following the application of dairy shed effluent (DSE) or ammonium fertilizer on a sandy loam. Dairy shed effluent is a mixture of feces, urine, and water. The upper limits of the recommended rates were used, or 400kg N ha'1 yr’1 of both DSE and NH4CI, split in two applications. The nitrate leached from the DSE treatments (8-25 kg NO3-N/ha) was significantly less than the amount lost from the NH4CI treatment (28-48 kg/ha) in both years. The amounts were derived because the authors used models to calculate total volume of water leached. There was only 25%-30% of mineral N in DSE, the rest being organic matter (Di et al. 1998). This study lasted only two years, mineralization of the DSE would continue long after; therefore in the long run differences in nitrate leached might not be as significant. Thomson et al. (1993) studied the effects of cropping system and addition rates of animal slurry and mineral fertilizer on nitrate leaching from a sandy loam. Treatments of either calcium ammonium nitrate (CAN) or animal manure were applied at the recommended rate 1N which averaged 19 glmz N or at 1.5N, and nitrate leaching measured with lysimeters during 4 years. During each year, there was a higher amount of leaching in the manure for both the 1N and 1.5N than for the CAN . Bauder and Schneider (1979) monitored nitrate leaching in an irrigated wheat field under two levels of urea application. They compared applying urea once at 135 kg/ha or in three applications of 45 kg/ha. Irrigation significantly increased leaching. However, the urea treatments did not affect leaching. Porous Ceramic CuLs Porous ceramic cups are used to collect soil water from porous soils. This tool is widely used due to its practicality, low cost and longevity. In contrast to lysimeters, which give a direct measurement of drainage water volume, porous cups require an independent estimation of the volume of water leached (Drainage = rainfall — evapotranspiration (Burt et al.1993)). This volume multiplied by the concentration is the amount of nitrate lost to the ground water. There is some ambiguity regarding methods of installation, sampling and general validity of porous cups. The following array of studies attempts to construct guidelines for the use of porous cups. Monolith lysimeter and soil core extracts are used to measure nitrate lost to groundwater. Webster et al. (1993) used both methods plus the porous ceramic cup to collect nitrate leachate from a loamy sand and a sandy loam soil. Results showed that the monolith lysimeter and the porous ceramic cup gave the same concentrations of mineral N in the leachates. The soil core extracts had slightly lower concentrations. In summary, the porous ceramic cup was a satisfactory technique in sandy soil. Addiscott (1990) reviewed five methods of measuring nitrate leaching that included the following: porous ceramic cups, pan/trench samplers, lysimeters, large-scale drainage collection, and soil coring. Porous ceramic cups were a reasonable choice for those with limited recourses wishing to estimate the concentration of nitrate leaving the soil, but their main problem is estimating the flux of nitrate leaving the soil. The lysimeters were stated to give a better representation of leaching, but they are more expensive and results can vary depending on where the tension is placed. Large scale drainage collection was the overall best method, but are very expensive, and work only in heavy soils where there is poor natural drainage. In shallow chalk soils, VVllliams and Lord (1997) found that porous ceramic cups were not able to collect samples reliably at depths of 60 and 90 cm, but were reliable at 30cm. Still, the measurements done at the greater depths were more accurate than samples taken with soil corers. . The lack of accuracy at greater depths seems to stem from a rockier soil type with larger pores. For more accurate results, a ceramic cup that could hold a stronger vacuum should be used. Lord and Shepherd (1993) compared various methods of porous cup instillation and sampling on “light, freely draining soils which appear best suited to the technique”. They found no difference between a sampler installed vertically, and at 30 degrees from vertical. However, steps must be taken to prevent preferential flow. These include repacking soil until about 100m below plough depth, and adding a 5-10cm layer of bentonite, which acts as a watertight sealant. The depth of installation should be below the maximum depth of nitrate extraction by roots. When sampling, they recommend that the sampler be left at atmospheric pressure until the date of sampling, so that the sample accurately reflects concentrations. The day of sampling a suction should be applied to 80 kPa and left for 10-120 minutes, and a sample of ~10-20 cm3 should be taken. From the numerous studies done by Lord and Shepherd (1993), the conclusion was that porous cups were well suited for sandy soils containing less than 10% clay. For other soil types similar studies must be done. Powlson et al. (1993) supports the reliability of porous cups on sandy soil, but not on more structured soils. A USDA bulletin (Linden (no date)) contains a protocol for installing and using porous ceramic samplers. It provides a good explanation of the relationship between at what pressure water is leaching, non-mobile, and therefore which is the correct pressure to set the sampler. Linden states that vacuum levels should be between 0.3 t00.8 atm for sample collection. If one 10 would like to collect only the most mobile water a lower level of 0.3 would be desired. Higher vacuum levels are needed in drier soils. Goulding (2000) researched different techniques to quantify losses of N by leaching, and found that porous ceramic cups are the best practical method for freely draining structure-less soil. Soil sampling was found useful, but very variable in time and space. Morrison and Lowery (1990) examined variables that could affect the time- averaged rate at which samples could be collected (Rs). Lack of knowledge on sampling rate and the sampling zone, can limit the validity of use of porous cup samplers. If this was known for various soil types, then the sampler could be better placed under the contaminant. In conclusion, they found that the variables that significantly effect Rs are sampler radius and surface area. Soil organic nitrge_n It is difficult to know how much mineral nitrogen should be applied to field horticultural crops. This is in part due to the difficulty in determining how much nitrogen is released from organic sources in the soil and manure, which is applied in large amounts to horticultural crops (Alt 1998 a). Organic nitrogen must be mineralized by soil bacteria into ammonium ions (NHI) or nitrified from ammonium into nitrate (N03) for uptake by plants. Shepherd et al. (1996) reviews methods and models to measure or predict the amount of N that could be released by mineralization. ll Powlson (1993) and Murphy (2000) reviewed the soil nitrogen cycle. Soil organic nitrogen is the largest pool in the terrestrial ecosystem (Fig.1). The nitrogen pathways and pool sizes in the soil are depicted in Fig 1. The microbial population converts to mineral N (NH4 + N03), which can then be lost by leaching and volatilization, or taken up by the crop. Mineral N can also be added to the soil by fertilizer or through the atmosphere. There is a constant flux between the organic and inorganic forms of nitrogen in the soil. These two processes are termed mineralization and immobilization. Mineralization is largely dependent on microbial activity, which in turn is dependent on temperature. It therefore causes large accumulations in late summer and early autumn. This may not coincide with crop uptake of nitrogen, and can lead to large leaching losses. Di et al,1998 measured the amount of nitrate leaching from a sandy loam fertilized with either dairy effluent, or mineral fertilizer. The dairy effluent caused a greater leaching loss than the mineral fertilizer at the same total amount of N. They indicate that the timing of nitrate release might be the cause of this. Chambers et al. (1999) describe a model to predict the plant availability of N following organic manure applications to agricultural lands. The ADAS Mme Nitrogen Evaluation Routine (MANNER) was designed to provide a quick estimate of manure N availability and losses for a range of agricultural circumstances. The model accounts for several different inputs and had good agreement (r2 60-79, P<.0001) with data from a range of independent studies. Nitrogen 12 losses and transformantions following the land application of organic manures are shown Figure 2. Input on type of manure and rate of application is required. Information is required on the total N, readily available N (NH4-N, or NHz-N+ uric acid N) and dry matter content of the manure. The model accounts for ammonia (NH3) volatilization, which is generally the first major loss pathway for manure N following land application. This loss is measured by taking into account the time between application and soil incorporation. Leaching is taken into account by selecting a soil type in the topsoil (0 30 cm) and the subsoil (30-90 cm), there are fifteen different soil types/textures to choose from. The model also requires an entry for the rainfall following the date of manure application until the date when drainage ends. Mineralization rates are taken into account with the use of the following equation: Nm = No x 0.1 (for spring applied poultry manure) Nm = No x 0.2 (for autumn applied poultry manure) No is the amount of organic N in the manure and Nm is the amount of organic N mineralized. L Livestock in the state of Michigan produced 64,000 Mg of N, and in the same year 254,000 Mg of N was applied to agricultural fields as synthetic fertilizer (von Bemuth 1999). Land application represents the most cost effective outlet for organic manures and allows their nutrient and organic matter content to be utilized to supply crop nutrient demands and maintain soil fertility (Chambers et al. 1999). Figure 2 shows the nitrogen transformations following the application of manure. 13 50 10-507 D C] 200 Soil organic __, \ ' matter 15° : 80 4000 ' , Mineral \ Loss by leaching 20100? Fig.1. Nitrogen pathways in soil. The quantity of nitrogen in each pool (kg/ha) or undergoing each process (kg/ha/yr), is proportional to the size of the square (Powlson 1993). 14 Fig. 2 Nitrogen pathways and transformations following land application of organic manures (Chambers et al. 1999). Volatilization NH3 Nitrification 1 . * NH4 N N03. N Uric acid N . . Plant Manure N Nitrate leaching available analysrs . N \ Mineralizafl’ Organic N ‘ \ immobilization IIIII l E I'l' Good and Tukey (1969) concluded that after the shoots of woody plants go dormant at lower temperatures, the roots can still grow, which gave support to late fall fertilizer application. The roots would still be able to take up the nutrients, even when the visible part of the plant has gone dormant. The nutrients taken up in the fall could stay in the roots as reserves during the winter, and then be used for the spring flush. 15 Gilliam (1978) studied the timing of fertilizer application for woody plants having multiple growing flushes during the season. He found that greater shoot growth occurred when fertilizer was applied after the shoots had stopped growing from one flush, but before the next flush began. He also found that the root growth was reduced if fertilizer was applied three or more times during the growing season. Alt (1998 b) suggests that N demand of nursery crop be calculated by measuring the amount of mineral soil N at the time of fertilizer application and subtracting the N demand from the crop. This is the Nmin method, also described in Marschner (1995). The difficulty in this method lies in calculating the contribution of mineral N from the soil. Pellet and Carter (1981) addressed the hypothesis that high level of N in the soil may delay maturity and thereby increase the plants susceptibility to winter injury. This concept had led to the perception that late fall fertilization is harmful. The review concluded that this is not the case. Rose (1999) suggests three advantages to fertilizing late during the growing season 1)soil temperatures in mid to late fall are higher than in early spring, promoting root activity and therefore uptake. 2) precipitation is usually sufficient to move nutrients into the root zone. 3) Most nursery activities, such as digging and planting, have ended. Extension bulletins usually recommend fertilizing in spring before bud break, and in late fall. From Pellet and Carter (1981) we know that fertilizing in late fall does not increase the potential for frost injury. This advice goes against 16 the work done with fruit crops, which shows that there is minimal nutrient uptake before bud break and before leaf abscission (Rose 1999). Smith and Chambers (1993) considered optimum time to apply animal slurry to cereal crops. They found that the slurry application is more efficient in spring, and should not be done between September and December. Several studies support an incremental application of fertilizer throughout the growing season, as opposed to making it available in one or two lump sums (Hansen et al. 1999; lngestad,1987; Sanchez and Doerge 1999). In the UK there has been a push for not applying fall fertilizer. Consequently, fall fertilizer applications have dropped significantly. In oilseed rape production autumn N application has gone from 90% of the area receiving autumn N in the 1980’s to about 50% In the late 1990’s. This in turn has reduced the amount of N lost to the groundwater (Dampney et al. 2000). How much to fertilize Rose (1999), proposed various recommendation rates for fertilizer application for nursery crops. These recommendations vary from 44-261 lb/acre. The fertilizer rate ought to be adjusted constantly, depending on soil mineralization, and amount of rainfall. Soil and tissue samples can be used for making adjustments (Sanchez and Doerge 1999). Recently, nurseries in western Michigan have applied 30 yd3/acre of turkey manure to fallowed farms. In field-grown nursery crops, two inorganic N applications each 140 lbs/acre are made, one in the spring and one in late 17 summer. And, ~ 100 lb/acre may be added in May or June depending on amount of rainfall or crop conditions (Zelenka Nursery Cultural, Tables 1999). Foliar N concentration Nitrogen is the fourth most abundant element in plants (Hopkins, 1995). The amount of nitrogen required for optimal growth is dependent on species, developmental stage, and plant organ. Foliar N varies between 2 and 5% (Marshcner 1995). Nitrogen is of great importance to plants because it is a constituent of many important molecules such as proteins, chlorophyll, and nucleic acids. In the leaf, up to 75% of the nitrogen is associated with the function of the chloroplast (Le Bot et al 1997). Studies with woody plants have shown that increasing nitrogen under limiting conditions increases growth, branching, and stem diameter (Will 1977). Trees have less seasonal fluctuation in nutrient concentration because of the nutrient buffering capacity of twigs and trunk (Marschner 1995). The woody tissue in perennials contains significantly less nitrogen than that in the shoots, averaging 15-20% of the amount stored in new shoots (Alt 1998 a). 18‘ Table 1. Foliar nitrogen concentration of various woody species at different ages, and under variouse conditions Species N content (% Type of study Source dry wt» Pacific yew (Taxus 1.29 Sun acclimation Mitchell (1993) brevifo/ia Nutt.) Anglojap Hybrid Yew 2-4 Terminal cuttings, Millis and (Taxus x media) container production Jones (1996) __ nursery English yew 1.98 Terminal cuttings, Millis and (Taxus baccata) container production Jones (1996 nursery English yew (Taxus 1.91 Sun acclimated Mitchell (1993) baccata L.) Douglas fir 1.58 Highest Mitchell (1993) (Pseudotsuga photosynthetic (Pn) menziesir) rate Douglas fir 1.74 Highest Pn (optimum) Brix (1981) Douglas fir 0.94 (control) Pn 78% of optimum Brix (1981) Douglas fir 2.36 P" 87% of optimum Brix (1981) Monterey Pine (Pinus 1.84 Optimal growth Will (1977) radiate) Norway Spruce (Picea 1.79 1 year old needles Marschner abies Karst) 1.76 2 yrs (1995) 1.46 3 yrs 1.22 4 yrs \Mnged Euonymus 2.37-2.62 40 mature leaves from Millis and (Euonymus alatus) new growth Jones (1996) Varigated Japanese 1.05-2.32 30 mature leaves from Millis and Euonymus new growth Jones ( 1996) (E uonymus japonicus ‘Silver King’) 19 Relative Addition Rate Since the mid 70’s Torsten lngestad and Goran I. Agren have been developing theories and models relating nutrition to plant growth. In their experiments liquid or air media was largely used. As long as N remains a limiting factor, it is shown that the plants relative growth rate (RGR) equals relative addition rate (RAR) of N, and whole plant nitrogen concentration is nearly constant (lngestad and Agren 1992). lngestad introduced the term “steady-state nutrition”. The technique “Relative Addition Rate” attempts to maintain a steady state concentration of nutrients within the plant. To maintain steady state conditions (constant nutrient concentration in the plants) relative uptake rate (Ru) and therefore relative addition rate (Ra) must be equal to relative growth rate. Ru=Ra=RGR lngestad and Agren (1992) introduced two concepts. One is that Ru and RGR are equal at constant internal nutrient conditions. The second is that if RGR linearly dependent on internal nitrogen concentration, this proportionality is valid only under N-limited conditions. The resulting slope expresses growth rate per unit of nutrient. These concepts hold true only during the exponential period of growth after which self shading comes into play and alters these relationships (lngestad 1987) There have been experiments conducted with species of conifer trees, which try to maintain steady state nutrition by repeated fertilizer treatments. This 20 method of fertilizer application resulted in substantial increase of growth (lngestad 1981). It has also been shown that fertilization must begin at low amounts and increase after a few years, when the trees root system has grown and utilize the fertilizer with minimal leakage (Clarkson, 1985; lngestad and Kahr 1985). 3) The use of 15N for fertilizer studies Research of N efficiency on horticultural crops and landscape crops is limited. There are studies on black spruce, willows and apple trees (Munson and Bernier 1993, Nielsen et al. 2001, Simon et al. 1990). To maximize fertilizer use efficiency, it would be beneficial to know the amount of nitrogen taken up by the crop per year. This is often difficult because in perennial crops nitrogen is stored in the roots and stems. With the use of the heavy isotope 15N, the source of the N taken up by the crop may be known. While there are several 15N studies on agronomic and fruit crops, the studies on landscape nursery crops are limited. Future research in the horticultural area should implement the 15N technique to further quantify fertilizer use. Fate of 15N labeled fertilizer -Agronomic crops It is important to know if the crop is taking up fertilizer-derived nitrogen (FDN) or from a non-fertilizer source. This is difficult because recovery of fertilizer is generally incomplete and can vary. Powlson et. al (1992) used 15N labeled fertilizer on winter wheat fields. In nine experiments carried out over 4 21 years, an average of 68% of the FDN was recovered in the above-ground plant material, 18% was left in the soil, and 13% was lost. In this experiment there were four microplots per plot, one for each year of the study(see plot size pg. 24). The fate of the 18% 15N left in the soil which is of environmental and economic importance was not studied. Bhogal et al. (1997) studied the fate of 15N fertilizer where there had been fertilization applications at 8 different rates since 1978. In 1992 15’N was applied at the same 8 rates, and the fate was studied for the ’92, ’93, and ’94. The aim was to understand the fate of N fertilizer in locations with sustained fertilizer regimes. By harvest on the final year an average of 69% of the 15N had been recovered in the crop + plus topsoil. Almost all losses occurred in the 1’"t and 2"‘1 growing seasons. There was no significant loss during the third year. Jokela and Randal (1997) examined the fate of 1"N in residual years after application on corn fields. The treatments were designed to determine the effect of fertilizer amount on rate of FDN uptake in the crop. Doubling the fertilizer rate from what the crop required gave the highest FDN in the crop, but logically also gave the highest FDN in the ground. The fertilizer use efficiency was lower. Asfary and Charnak (1997) results support these findings. In conclusion, N rates in excess of crop need increased the leaching of N03' - N beyond the root zone. Perennial crops Perennial crops can use N stored in their roots and branches in spring for the initial growth. It is therefore important to know when remobilization and root 22 uptake are taking place, so that the best time for fertilizer application can be determined. Quantitative relationships between the amount of fertilizer N applied and actual N usage by the tree have rarely been established in horticultural studies (Weinbaum and Kessel, 1998). Nitrogen application can affect the shoot growth in later years (Throop and Hanson 1997). Nielsen et al (2001) measured the N remobilization and uptake in apple (Ma/us domestica) tree. Less FDN was recovered with an early than a later application. This was an effect of supply and demand. In the early part of the growing season the tree is using remobilized N, while later it is taking it up from the soil. Throop and Hanson (1997) looked at nitrogen use efficiency in blueberry at different times of fertilizer application during the growing season. There were six monthly treatments from April through September. They found that bushes treated in late May, June, and July averaged about 8% FDN in the plant, while the bushes that were treated in April, August, or September, averaged 2% FDN. They concluded that uptake is determined by plant demand and not the availability in the soil. This again emphasizes the importance of knowing the growth patterns of the crop. Wienbaum and Kessel (1998) investigated the internal cycling of nitrogen in mature walnut (Jug/ans regia L. cv Hartley) for a period of 6 years using 15N- depleted fertilizer. Sixty percent of annual N demand was obtained through remobilization. The other 40% was from the soil/fertilizer source. This supported 23 their hypothesis that “about 1/2 of the total N content of perennial parts of mature walnut trees is present as non-structural N and is available for recycling’. Techniques Calculations Fertilizer derived nitrogen in the plant or in the soil is defined by Jokela and Randall (1997) as: FDN =N(s—a)/(f—a) N= amount of N in the plant or soil a=atom % 15N in soil or plant not fertilized with labeled N s and fare the atom % 15N in the sample (plant or soil) and fertilizer respectively. Asfray and Charanek (1997) list four expressions used to identify sources of N not fertilizer derived. 1) N derived from fertilizer (%Ndff) = (% 15N atom excess in plant / % "5N atom excess in fertilizer) x 100; 2) N derived from soil (%Ndfs) = 100 — (%Ndfa + % Ndff). 3) N derived from atmosphere; (%Ndfa) = 1-(%15N atom excess in fixing crop / %‘5N atom excess in non-fixing crop) x 100. 4) Soil inorganic N as units of N fertilizer (“A value”) = (% Ndfs / %Ndff) x N fertilizer rate. Li et al (1991), attempted to determine the nitrogen use efficiency between families of loblolly pine (Pinus taeda L.). They define components of nurtrient use efficiency. Nitrogen use efficiency = SDW/AN 24 Uptake efficiency = TSN/AN Utilization efficiency = SDW/T SN; SDW = above ground biomass (g), AN = applied N in the medium (mg/plant) TSN = total seedling N content (mg/plant), PM Microplots within larger plots are widely used in 15N studies to reduce amount of labeled fertilizer, and to make long-term studies possible (Bhogal et al. 1997, Karlen et al. 1996; Powlson et al. 1992). Plant and soil samples taken from within the microplot give information on the plant F DN uptake and soil recovery of FDN. Larger samples for dry matter yield can be taken from the larger plot area, where non-labeled fertilizer can be used (Jokela and Randall, 1987) Jokela and Randall (1987) describe and validate the design of a plot to allow two consecutive years of application with accurate determination of FDN uptake and retention in the soil. Additional microplots within each larger plot would allow more than two application years. This design might need to be modified for crops or soil types. 25 Addiscott, TM. 1990. Measurement of nitrate leaching: a review of methods. Nitrates, agriculture, eau. Paris. 7-8: 157-168. Alt, D. 1998 a. N-Fertilization of nursery crops in the field - A Review, Part 1. Gartenbauwissenschaft. 63: 165-1 70 Alt, D. 1998 b. N-Fertilization of nursery crops in the field — A Review, Part 2. Gartenbauwissenschaft. 63:237-242. Alt, D. 1998 c. N-Fertilization of nursery crops in the field — A Review, Part 3. Gartenbauwissenschaft. 63:278-282. Alva, K.A. and S. Paramasivam. 1998. Nitrogen management for high yield and quality of citrus in sandy soils. Soil Sci. Soc. Am. J. 62:1335-1342. Asfary, F. and A. Charanek. 1997. Nitrogen fertilizer-use efficiency studies by Syrian Atomic Energy Commission using 15N-labelled fertilizers. Atomic Energy Comission of Syria (AECS), Damascus, Syria. 64-70 Bauder, J.W. and R.P_Schneider. 1979. Nitrate-Nitrogen Leaching Following Urea Fertilization and Irrigation. Soil Sci. Soc. Am. J. 43:348-352. Bhogal, A. 8D. Young and R. Sylvester-Bradley. 1997. Fate of 15N-Iabelled fertilizer in a long-term field trial at Ropsley, UK. Journal of Agricultural Science, Cambridge. 129:49-63. ' Brix, H. 1981. Effects of nitrogen fertilizer sourve and application rates on foliar nitrogen concentration, photosynthesis, and growth of Douglas-fir. Can. J. For. Res. 11:775-780. Burt, T.P., A.L. Heathwaite and ST. Trudgill. 1993. Nitrate, Processes, Patterns, and Management. John Wiley 8: Sons. Carpenter, S. 1998. Nonpoint pollution of surface waters with phosphorous and nitrogen. Ecological Society of America. 1-12 Chambers, B.J., E.I. Lord, F.A. Nicholson and K.A.Smith. 1999. Predicting nitrogen availability and losses following application of organic manures to arable land: MANNER. Soil Use and Management. 15:137-143. Clarkson, OT. 1985. Factors affecting mineral nutrent acquisition by plants. Ann. Rev. Plant Physiol. 36277-115. Cooper, CM. 1993. Biological effects of Agriculturally derived surface water pollutants on aquatic systems — A Review. Journal of Environmental Quality. 22:402-408. 26 Dampney, P.M.R., E.l. Lord and B.J. Chambers. 2000. Development of improved advice for farmers and advisors. Soil Use and Management. 16:162- 166. Di, H.J., K.C. Cameron, S. Moore and , N.P. Smith. 1998. Nitrate leaching and pasture yields following the application of dairy shed efflueint or ammonium fertilizer under spray or flood irrigaiton: results of a lysimeter study. Soil Use and Management. 14:209-214. Gilliam, CH and RD. Wright. 1978 Timing of fertilizer application in relation to growth flushes of ‘Helleri’ Holly (Ilex crenata Thunb.).HortScience. 13(3):300-301 Will, GM. 1977. Forest Science. 23:64-68. Goulding, K. 2000. Nitrate leaching from arable and horticultural land. Soil Use and Management 16:145-151 Good, 6L. and H3. Tukey, Jr. 1969. Root Growth and Nutrient Uptake by Dormant Ligustrum ibolium and Euonymus alatus ' Compactus'. J. Amer. Soc. Hort. Sci. 94:324-326. Hansen, R.C., K.D. Cochran and RP. Fynn. 1999. Growth rate of container- grown Taxus x media ‘Hicksii’ and ‘Densiformis’ Compared at two levels of nutrition and irrigation. Special Circular 150 Ohio Agricultural Research and Development Center. 33-40. Hallbourg, RR. 1998. Nitrate in groundwater and surface water. Alachua Country Encironmental Protection Department. Jan. 12. 1-7 Hopkins, W.G. 1995. Introduction to Plant Physiology. John Wiley & Sons, Inc. lngestad, T. 1981. Nutrition and growth of birch and grey alder seedlings in low conductuvuty solutions and at varied relative rates of nutrient addition. Physiologia Plantarum. 522454-466, lngestad, T. 1987. New concepts on soil fertility and plant nutrition as illustrated by research on forest trees and stands. Geoderrna. 40:237-252. lngestad, T. and Agren G.I. 1992. Theories and methods on plant nutrition and growth. Physiologia Plantarum. 84:177-184. Iseman, T.M., D.R. Zak, W.E. Holmes and AG. 1999. Merril. Revegetation and nitrate leaching from lake states northern hardwood forests following harvest. Soil Sci. Soc. Am. J. 63:1424-1429. 27 Jokela, W.E. and G.W. Randall. 1987. A Nitrogen-15 microplot design for measurein plant and soil recovery of fertilizer nitrogen applied to corn. Agronomy Journal. 79:322-325. Jokela, W.E. and G.W. Randall. 1997. Fate of fertilizer nitrogen as affected by time and rate of application on corn. Soil Sci. Soc. Am. J. 61 :1695-1703. Karlen, D.L., P.G. Hunt and TA. Matheny. 1996. Fertilizer 15Nitrogen recovery by corn, wheat, and cotton grown with and without pre-plant tillage on Norfolk loamy sand. Crop Science. 36:975-981. Li, B., S.E. McKeand and H.L. Allen. 1991. Genetic variation in nitrogen use efficiency of loblolly pine seedlings. Foreset Science. 37(2):613-626. Linden, D.R. Design, installation, and use of porous ceramic samplers for monitoring soil-water quality. Agricultural Research Service, USDA. Technical bullitin no. 1562:1-11. Lord, El. and MA. Shepherd. 1993. Developments in the use of porous ce'ramic cups for measureing nitrate leaching. Journal of Soil Science. 44:435-449. Le Bot, J., S. Adamowicz and P. Robin. 1998. Modelling plant nutrition of horticultural crops: a review. Sceintia Horticulturae. 74:47-82. Mahler, R.L., Ernestine Porter, and. Roy Taylor. 1989. Nitrate and Groundwater. University of Idaho College of Agriculture. Series no. 872:1-5. Marschner, H. 1995. Mineral Nutrition of Hiflr Plants. Academic Press. San Diego, California. Millis, H.A., J.B. Jones. 1996. Plant Analysis Handbook. Micro Macro Publishing, Inc. Athens, Georgia. Pg. 381,209. Mitchell, AK. and TM. Hinckley. 1993. Effects of foliar nitrogen concentration on photosynthesis and water use efficiency in Douglas fir. Tree Physiology. 12:403- 410. Morrison, P., and P. Morrison. 2001. Fertile Minds.American Scientist. Scientists’ Bookshelf July-August. 1-5. Morrison, RD. and B. Lowery. 1990. Effect of cup properties, sampler geometry, and vacuum on the sampling rate of porous cup samplers. Soil Science. 149:308-316. Munson, AD, and P.Y. Bernier. 1993. Comparing natural and planted black spruce seedlings ll. Nutrient uptake and efficiency of use. Can. J. For. Res. 23:2435-2442. 28 Murphy, D.V., A.J. Macdonald, E.A. Stockdale, K.W.T. Goulding, S. Fortune, J.L. Gaunt, P.R. Poulton, J.A. Wakefield, C.P. Webster, W.S. Wilmer. Biol. Fertil Soils. 30:374-387. Neilsen, D., P. Millard, L.C. Herbert, G.H. Neilsen, E.J. Hogue, P. Parchomchuk, and B.J. Zebarth. 2001. Remobilization and uptake of N by newly planted apple (Ma/us domestica) tress in response to irrigation method and timing of N application. Tree Physiology. 21 :513-521. Pellet, M. and V.J. Carter. 1981. Effect of nutritional factors on cold hardiness of plants. Horticultural Reviews. 3:144-171. Powlson D.S., P.B.S. Hart, P.R. Poulton, A.E. Johnston and OS. Jenkinson. 1992. Influence of soil type,crop management and weather on the recovery of 15N-labelled fertilizer applied to winter wheat in spring. Journal of Agricultural Science. 128: 445-460. Powlson, OS. 1993. Understanding the soil nitrogen cycle. Soil Use and Management. 162145-151. Rose, MA. 1999. Nutrient use patterns in woody perennials: implications for increasing fertilizer efficiency in field-grown and landscape ornamentals. HorTechnology. 9(4):613-617. Sanchez, CA. and TA. Doerge. 1999. Using nutrient uptake patterns to develop efficient nitrogen management strategies for vegetables. HorTechnology. 9(4):601-606. Shepherd, M.A., EA. Stockdale, D.S. Powlson and SC. Jarvis. 1996. The influence of organic nitrogen mineralization on the management of agricultural systems in the UK. Soil Use and Management. 12:76-85 Simon, M, L. Zsuffa and D. Burgess. 1990. Variation in N, P, and K status and N efficiency in some North American willows. Can. J. For. Res. 20:1888-1893. Smith, K.A. and B.J. Chambers. 1993. Utilizing the nitrogen content of organic manures on farms — problems and practical solutions. Soil Use and Management. 9(3):105—112. Sylvester-Bradley, R. 1993. Scope for more efficient use of fertilizer nitrogen. Soil Use and Management. 92112-117. Thomsen, I.K., J.F. Hansen, V. Kjellerup and ET Christensen. 1993. Effects of cropping system and rates of nitrogen in animal slurry and mineral fertilizer on nitrate leaching from a sandy loam. Soil Use and Management. 9:53-58. 29 Throop, PA. and E.J. Hansen. 1997. Effect of application date on absorption of 15Nitrogen by highbush blueberry. J. Amer. Soc. Hort. Sci. 122(3):422-426. Von Bemuth, R.D, Salthouse, G. Manure and fertilizer nutrient balance: a methodology applied to Michigan. Applied Engineering in Agriculture. 15(6): 695- 700. Webster, C.P., M.A. Shepherd, K.W.T. Goulding and E. Lord. 1993. Comparisons of methods for measuring nitrogen from arable land. Journal of Soil Science. 44:49-62. Wienbaum, S. and CV. Kessel. 1998. Quantitative estimates of uptake and internal cycling of 14N-Iabeled fertilizer in mature walnut trees. Tree Physiology. 182795-801. Williams, JR. and E.I.Lord. 1997. The use of porous ceramic cup water samplers to measure solute leaching on chalk soils. Soil Use and Management. 13:156- 162. Williams, T.M. 1999. Nitrate leaching from intensive fiber production and abandoned agricultural land. Forest Ecology and Management. 122:141-149. Zelenka cultural tables. 1999 30 Chapter One Managing Nitrogen Additions and Assessing Water Quality Under the Root Zone in Field Nursery Production of Taxus and Euonymus 31 Managing Nitrogen Additions and Assessing Water Quality Under the Root Zone in Field Nursery Production of Taxus and Euonymus Additional index words. Nitrate leaching, fertilizer use efficiency ABSTRACT Michigan’s nursery industry is localized in an area of high risk for ground water contamination. Incidence of nitrate leaching in nursery field plantations caused by fertilizer application in this region has not been investigated. The objectives of this study are to: 1) examine patterns of nitrate-N leaching in field nursery production and 2) determine the potential of a ‘Relative Addition Rate’ approach to increase efficiency of fertilizer application and reduce nitrate-N leaching. We established the study in collaboration with two major nurseries in western Michigan. Nursery A had one field growing Taxus x media (Taxus baccata L. x T. cuspidate Sieb. & Zucc) ‘Runyan’ and the other growing Euonymus alatus Sieb. ‘Compactus’. Nursery B had one field growing Taxus cuspidate ‘Dark Green Spreader’ and the other growing Euonymus alatus ‘Compactus’. The fertilizer treatments were: 1) control (no fertilizer); 2) operational fertilization (based on the nurseries’ current practices); and 3) relative addition rate (additions based on crop growth). Soil water below the root zone was collected after every significant rainfall event using porous ceramic cup lysimeters. Mean nitrate-N concentrations were found to be high when compared to other agricultural systems, ranging from less than 7 mg L’1 prior to fertilization to over 160 mg L'1 in September. The RAR approach to fertilization reduced nitrate-N leaching in two out of the four fields. The results indicate 32 nursery management practices should be altered to improve efficiency of fertilizer use. INTRODUCTION Agricultural practices are responsible for a major portion of the nitrate pollutants in surface water (Cooper 1993, Refsgaard J.C., 1999), and they are the leading cause of regional-scale non-point source pollution in the world today (Diaz-Diaz R. 2000). Inputs of nitrates from agricultural sources are termed non- point pollutants because they originate from a diffuse area, are generally not continuous, and can vary depending on weather and time of year. Non-point pollutants are difficult to measure, control, and regulate. Any control requires altering land management practices (Carpenter, 1998). The Michigan nursery industry is the fifth largest in the United States and is one of Michigan Agriculture’s leading growth industries. In western Michigan alone, there is a total of 3,525 hectares (8,710 acres) of field grown woody ornamentals (MDA 2000). Much of the industry is concentrated in the western part of the state because of the moderating climate effect of Lake Michigan. Lower western Michigan has a hardiness zone of 6 (-17°C to - 23°C), whereas central Michigan has a hardiness zone of 5 (-23°C to -29°C) (USDA 2002). In addition to the moderate climate, the soil in this region is sandy, which is ideal for cultivation and digging field nursery crops. On the other hand, this area has a high risk of ground water contamination because it has high nitrogen (N) inputs and high aquifer vulnerability (Noland et al. 1998). 33 Field production of ornamental nursery crops may result in significant leaching of nitrate (Alt 1998 a,b,c, Goulding 2000, Rose, 1999). The amount of N applied by nursery growers often exceeds the uptake by the plants (Alt 1998 a). This leaves high amounts of residual nitrate content in the soil, which is susceptible to leaching. It is difficult to know how much mineral N should be applied to field horticultural crops. This is in part due to the difficulty in determining how much N is released from organic sources in the soil and manure, which is applied in large amounts to horticultural crops (Alt 1998 a). Uptake of nitrogen by plants occurs largely in the inorganic form. Organic nitrogen must be mineralized by soil bacteria into ammonium ions (NHI) or nitrified from ammonium into nitrate (N03). For nursery soils N mineralization may be high because of the large amounts of manure that are applied (Alt, 1998 b). Since the mid 70’s Torsten lngestad and Goran I. Agren have been developing theories and models relating nutrition to plant growth. They show that the nutrient requirement for a plant is dynamic, one related to size and growth rate of the plant. In their experiments liquid or air media was largely used, and frequent nutrient additions would be added in hourly or daily increments. In this manner full control can be achieved over nutrient status of the plant. From their studies, lngestad and Agren (1988) determined that plant growth is optimized when nutrient additions are matched with uptake rate resulting in a steady state concentration of nutrients within the plant. To maintain 34 steady state conditions relative uptake rate (R) and therefore relative addition rate (Ra) must be equal to relative growth rate: Ru = R, = RGR With this method there would be minimal loss of applied nutrients from the root zone because one would synchronize fertilization with plant uptake, thus matching nutrient additions with plant requirement at specific phases of growth. While lngestad and Agren showed this technique to improve growth of plants in short-tenn experiments using nutrient-solution cultures, later work showed validity in soil media as well. Xu and Timmer (1998) and Imo and Timmer (1992) demonstrated that exponential fertilization (increasing fertilizer rate exponentially during exponential growth) increased growth and nutrient uptake compared to conventional fertilization (either applied as a single dose, or in equal amounts throughout rotation) in container studies. This resulted in higher fertilization efficiency than standard practice, and closer synchronization of fertilizer delivery with plant growth and nutrient demand. Although the studies of lngestad Agren and Timmer have been conducted in hydroponic or container systems the ‘Relative Addition Rate’ approach may also benefit field nurseries. Alt (1998a), proposed that incorporation of RAR approach to nursery fertilization might improve efficiency of N fertilization and reduce potential leaching. The difficulty encountered in field experiments is a loss of a controlled environment. Determining the crop uptake of N in the field is an obstacle. Alt (1998a) surveyed nearly 400 samples of common nursery landscape crops and 35 established a strong linear correlation (R2=.93) between fresh matter yield of shoots and N uptake, indicating that the estimation of N uptake may be predicted from the amount of N within new shoots. More research needs to be done to match N application with the plants need as opposed to the blanket prescriptions, which are commonly used in field-nursery practices today. Study objective The objectives of the current study were to 1) examine patterns of nitrate leaching in field nursery production and 2) determine the potential of 3 RAR approach to increase efficiency of fertilizer application and reduce nitrate leaching. Materials and Methods Plot description Field plots were established in plantation fields of two large ornamental nurseries near West Olive, MI in western Michigan (42°45’ N 86°1’ W). The soils on the four fields are Granby loamy sand, which are typical of western Michigan and are characterized by an A horizon of grayish brown loamy sand followed by a B and C horizon of pure sand. These soils have rapid permeability (USDA 1972). Two fields were studied at each nursery. In Nursery A there was one field growing Taxus x media ‘Runyan’ and another Euonymus alatus ‘Compactus’ (Burning bush). In Nursery B there was a Taxus cuspidate ‘Dark Green Spreader’ and one Euonymus alatus ‘Compactus’ (Burning bush) field. The fields will be labelled Taxus Nursery A & B, and EAC Nursery A 8 B. 36 Within each field there were three replications of each treatment, totaling nine plots. The plots were laid out as a complete randomized design (CRD). Plots dimensions averaged 22 m (72 ft) in length and 2.7 m (9 ft) in width (.00061 hectare or 0.015 acre). Descriptions of plant age, planting densities and site occupancy for each of the four fields are listed in Table 1. Fertilizer treatments and application methods Treatment plots were established in the spring of 2000. Prior to the initiation of the study, EAC Nursery A received standard operational culture of 57 m3/hectare (30 yd3/acre) of turkey manure before planting. Sudangrass was planted as a cover crop and incorporated into both EAC and Taxus Nursery B prior to planting in 1997. The Sudangrass was fertilized with 112 kg N/hectare (100 lbs N/acre). Three treatments applied were: 1) Control (no fertilizer) 2) Operational fertilization, which is based on the nurseries current practices. 3) Alternative form based on the ‘RAR’ theory. The operational treatment followed the nurseries rate of 336 kg/hectare (300 lbs/acre) of 20-0-10 ammonium nitrate fertilizer, split into two applications (Table 28%. The RAR treatment was applied once per month of the same 20—0-10 fertilizer on each of the four fields (Table 2 & 3). The application rate was determined by making the addition rate of nitrogen equal to its uptake rate, measured as the rate of change of nitrogen in the biomass of the plants, or more 37 simply put the product of the internal concentration and the relative growth rate (lngestad and Agren 1988). The dependence between foliar biomass and plant volume was approximated by a linear function (Figure 1). With this relation and by taking monthly plant volume measurements from a sub sample of 10 plants within each plot we were able to estimate monthly increase in foliar biomass. The crown volume of each plant was calculated as: C.V.= flflgilz) 2 Where CV. is crown volume (cm3), h is the height of the plant (cm) and dr and d2 are two plant diameters (cm) measured at right angles. Monthly foliar nutrition samples from 10 random plants within the plot were taken along with the volume measurements. Knowing the change in both internal nutrient concentration and plant biomass that occurred each month, we calculated the N uptake since our last fertilizer application. NCtz- NCt1 = ANC, Where NCt1 = plant biomass * % N at time 1, and NCtz = plant biomass*% N at time 2. All fertilizer was applied as a banded application in order to approximate operational fertilizer application. We dug shallow trenches with a hoe, and the fertilizer was evenly distributed within. The trenches were then covered with soil to prevent volatilization. 38 Soil water sampling Vl/lthin each plot, two porous ceramic cup soil water samplers (model 1900, Soil Moisture Equip. Corp. Santa Barbara, California) were installed near the center of each plot. The samplers are 61 cm in length and they were installed at a 45° angle, 20 cm away from a plant. This method of installation assures that the porous cup is located under the root zone of the plant depth. After every significant rainfall event (Figure 2) the solution in the sampler was pumped out, and a vacuum of 3.76 bar (40 psi) was reapplied to the sampler. Thus, by only drawing in the mobile water, the concentrations and dynamics of nitrate-N leaving the soil profile are determined. If both samplers contained water they were pooled together, but if only one had water it was used independently. After samples were collected, they were stored in a cooler at 4°C for no longer than 6 weeks before analysis. Soil sampling Soil samples were collected monthly from May through August and analyzed for nitrate-N. Samples were taken from a combination of five soil cores, approximately 38 cm (15 in) in depth. Analyses Nitrate was quantitatively reduced to nitrite by passage of the sample through a copperized cadmium column. The nitrite was then determined by diazotizing with sulfanilamide followed by coupling with N-(1-naphthyl) ethylenediamine dihydrochloride. The resulting water soluble dye has a magenta color which was read at 520 nm. Nitrate-N content of the filtered soil extracts 39 was determined by using the nitrate-reduction method through the LaChat rapid flow injection unit. Each field was analyzed independently due to difference in location, age and previous fertilizer treatments. The effect of fertilizer application rate on water and soil nitrate-N concentrations was determined by repeated measures analysis of variance. Difference among treatments was established at the 5% level of probability. The treatment and day effect on nitrate-N concentrations were determined using the mixed model in SAS: Yiik = l1 + 0ti +l3i + (al3lii + eilk Where: Yiik = response of the kth replication plot of the ith fertilizer treatment on the jth sampling date. Based on BIC values from the “Fit Statistics” in the SAS output, we used a power spatial covariance structure (Wolfinger 1997). M Taxus In general, nitrate leaching under the Taxus plots was lower in early spring, increased during the summer and then declined in fall, especially at Nursery B. At Nursery A, maximum nitrate levels ranged from 30 mg NO3-N L‘1 on the control plot to 100mg NO3-N L'1 on the operational treatment. At Nursery B, Maximum levels ranged from 20 - 70 mg NO3-N L'1 for the RAR and Operational treatments, respectively. (Figure 3) Both fertilizer treatments increased soil water nitrate-N relative to the control treatment in Nursery A (Table 4, Figure 3). The operational fertilizer 40 treatment increased in mean nitrate-N when compared to the control and RAR in Nursery B (Table 4, Figure 3). The control and RAR concentrations were not significantly different from each other (Table 4, Fig. 3). Fertilizer treatments also increased soil nitrate-N concentrations relative to the control for Nursery A and B. The operational and RAR treatments were not different from each other (Table 5, Figure 4). All fertilizer treatments resulted in equal growth of Taxus plants (Rios et. al. 2002 b) EAC Nitrate leaching under the EAC plots increased from spring to the fall (Figure 5) and the rates of leaching were almost always higher than in the Taxus plots. The operational fertilizer treatment increased soil water nitrate-N when compared to the control and RAR in Nursery A (Table 5, Figure 5). Control and RAR concentrations were not significantly different from each other. There was no increase in soil water nitrate-N among any of the treatments in Nursery B. The operational treatment had higher soil nitrate-N concentrations than the control In Nursery A, the differences in soil core nitrate-N concentrations were significant (P=0.05) only between the control and the operational treatment (Figure 6). In the Nursery B field there were no significant differences among the treatments (Figure 6). The nitrate-N leaching patterns show increase later in the season on both EAC fields (Figure 5). In contrast the leaching pattern in the Taxus fields show a decrease of nitrate—N concentrations later in the season (Figure 3). 41 Discussion Pattems of nitrate-N leaching There could be two reasons for the contrasting leaching patterns that we see throughout the season in the Taxus versus EAC fields. First, the leaching patterns follow the growth characteristics of both species, Taxus being an indeterminate grower there by demanding N throughout the season, while the EAC is a determinant grower producing one early flush of growth. For this reason the fertilizer could not be taken up as readily by the EAC later in the season, causing nitrate-N levels to rise. The second potential for this pattern is that later in the season there are warmer soil temperatures, microbial activity is increasing and therefore mineralization is also increasing. This is likely because as shown in Figure 5, the controls are increasing throughout the season as well, and there was no synthetic fertilizer application, but there was organic matter from the manure and cover crop applications. The nitrate-N concentrations in current practices of field nursery production are high when compared to other agricultural systems and forests (Table 6). The concentration of nitrate-N leaching in the operational treatment of the two Taxus fields reached peak levels during late July and early August with maximum levels of 100 mg NO3-N L" in Nursery A and 70 mg NO3-N L" in Nursery B (Figure 3). The EAC operational treatments had the highest concentrations in late August through October, when the levels reached 160 mg NO3-N L" in Nursery A and 110 mg NO3-N L" in Nursery B (Figure 5). 42 Surprisingly, the control plots where we applied no fertilizer in the EAC fields reached high nitrate-N concentrations as well. During the month of September concentration of samples from the control plots in Nursery A and Nursery B were 120 mgNO3-N L" and 60 mg NOa-N L", respectively (Figure 5). Nursery A had received a manure application before planting, which along with the fact that EAC’s are a determinate growth species and may not be taking up as much N, helps explain the gradual increase of nitrate-N levels through October. Organic nitrogen in manure undergoes mineralization later in the season when temperatures in the soil have peaked and microbial activity is most active (Powlson 1993). The EAC field in Nursery B shows this same trend, the nitrate-N in this field may be from residual organic matter from the Sudangrass that had been planted in 1998, which can also contribute to mineral N in the soil. Shepherd et al. ( 1996) broke down the components of mineral N in the soil into the following equation: Nmin=SOM+R+M+F+RN Where SOM is the contribution from native soil organic matter, R that from crop residues, M that from animal manures, F from inorganic fertilizer and RN the residual nitrate remaining from the previous growing season. The multiple terms underscore the complexity of the system. As we see, many factors may be contributing to the increase in nitrate-N in the soil later in the season for Nursery B (Figure 5). The soil nitrate-N data from the EAC control plots (Figure 6) supports the idea that nitrate-N is being released from a source besides the mineral fertilizer. 43 Improving the efficiency of fertilizer use There is a lack of scientifically based information as to when and how much N fertilizer to apply to field nursery crops. Determination of N demand of nursery crops is difficult for the following reasons: there are various species with different growing patterns, ages of the crops vary, crops are pruned throughout the growing season, and planting densities vary as well (Alt 1998a). Application rate recommendations vary from 49-293 kg/hectare (44-264 lbs/acre) of N (Rose, 1999). Currently in western Michigan, nurseries are applying at least two applications each of 157 kg/hectare (140 lb/acre) of N each year (MDA 2000). From the concentrations of nitrate-N we found leaching through the root zone; therefor there is room for improving the efficiency of fertilizer use. Timing of fertilizer application is no clearer than quantity of application. Extension bulletins recommend fertilizing in spring before bud break, and in late fall (Ext. Bul. 1999). Although fertilizing in late fall does not increase the potential for frost injury (Pellet and Carter 1981), there is minimal nutrient uptake before bud break and before leaf abscission (Rose 1999). Improving advice for growers on fertilizer practices is an important step towards the protection of the ground water. In summary, high levels of nitrate-N leaching were found under the root zone of nursery field production in western Michigan when compared to other agricultural and forest systems. The RAR reduced losses of nitrate-N through leaching while maintaining crops growth in two out of the four total fields. The operational treatment in these two fields had significantly higher soil water nitrate-N concentrations than the RAR, and there were no differences between 44 the RAR treatment and the control. The soil nitrate-N concentrations did not differ between the RAR and operational treatments. Crop growth was not affected by either the RAR fertilizer treatment or the control, when compared to the operational. (Rios et al.2001 b). There appears to be an underestimation of amount of available N for plant uptake in the soil by both the growers and the extension literature. This is a step, and has led to questions and potential for further research in improving the efficiency of fertilizer use and reduction for nitrate-N leaching to ground water. 45 Table 1. Site description of year planted, plant density, plant height and site occupancy of four fields in western Michigan. Measurements represent values of April 2001. Nursery- Year Plant density Average *Site crop planted (#plantslacre) (#Plantslhectare) plant occupation height (cm) A - Taxus 1999 11771 29064 21 13.1% B - Taxus 1998 11771 29064 23 21.5% A - EAC 2001 11771 29064 22 6.7% B - EAC 1999 6272 15487 26 31.9% *Site occupation = (crown area/plot area) x 100 = % site occupation Crown area= (ave. width/2)2 x 11? 46 Table 2. Fertilizer application rates and dates for two treatments (operational and RAR) applied to two Taxus nursery fields (Nursery A 81 B) in western Michigan during the 2001-growing season. Field Treatment Nursery A Operational (lbs N/acre) (kg N/hectare) RAR (lbs N/acre) (kg N/hectare) May 9‘" m 60 67 30 34 T 14 jitter 23 23 August 3” 60 67 August 24th 11 13 Total 120 134 132 143 Nursery B May 9"T 60 67 June 14th 53 59 July 3rd 25 28 August 3'“I 60 67 August 24th 5 6 Total 120 134 113 127 (Fertilizer was applied as a blend of 20-0-10) 47 Table 3. Fertilizer application rates and dates of two treatments (operational and RAR) applied to two EAC nursery fields (Nursery A 8: B) in western Michigan during the 2001-growing season. Field Treatment Nursery A Operational RAR (lbs fertilizer/acre) (lbs fertilizer/acre) (kg fertilizer/hectare) (kg fertilizer/hectare) In _ 33.9mm 6" ‘7 33 33 July 3rd 2 2 August 3rd 60 67 August 24th 30 34 Total 120 134 64 72 Nursery B May 9‘" 60 67 30 34 June 14th ’ 7 8 July 3rd , 2 2 August 3”l 60 67 August 24tln 30 34 Total 120 134 69 48 (Fertilizer was applied as a blend 20-0-10) 48 Table 4. Analysis of variance for nitrate-N soil water sampled with ceramic porous cups in two Taxus nursery fields (Nursery A 8. B) in western Michigan during the 2001-growing season. Field Source df F P>F Nursery A TRT 2 11.49 0.0010 Day 1 1 2.37 0.0245 TRT*Day 22 1 .62 0.0901 Contrast 13.25 0.0024 20.61 0.0004 0.76 0.3988 .3 Control vs. RAR Control. vs. Operational RAR vs. Operational Ara—8 Nursery B TRT 2 3.68 0.0449 Day 14 5.58 <0.0001 TRT*Day 28 0.68 0.8623 Contrast Control vs. RAR 1 0.02 0.9018 Control. vs. Operatidnal 1 5.24 0.0336 RAR vs. Operational 1 5.91 0.0254 49 Table 5. Analysis of variance for nitrate-N in soil water sampled with ceramic porous cups in two EAC nursery fields (Nursery A 8. B) in western Michigan during the 2001-growing season. Field Source df F P>F Nurseg A TRT 2 6.34 0.0042 Day 9 6.52 <0.0001 TRT*Day 1 8 0.65 0.8388 Contrast Control vs. RAR 1 1.77 0.1926 Control. vs. Operational 1 12.53 0.001 1 RAR vs. Operational 1 4.84 0.0342 Nursem B TRT 2 3.03 0.1103 Day 14 12.66 0.0002 TRT*Day 28 2.04 0.1165 50 Table 6. Leaching studies showing nitrate-N concentrations in different agricultural and forest systems. Field system Cultural practice Leaching (mg NO3-N L") Source Plantation of Managed fields 11.4 Williams 1999 hardwoods and ”Plantation of Old fields with no 5.4 Williams 1999 hardwoods and management conifers -_.. m..- ___.. Wheat fields 135 kg N/ha/yr 7.0 Bauder and with optimum (40 cm depth) Schneider 1979 ‘ _ ., ‘- .. irrigated __ .. __.._.__._._-_________.--__.___.___.. ____. "citrus“plantation“"‘ '1'1'2kg N/riaiyr ” 4.0 ' Alva and (120 cm depth) Paramasivam - -MW- 1998 Hardwood forest Intact, preharvest 1.5 lseman et al. 1998 lntercrop period 200 kg MM 40 Martinez and wheat/maize Guiraud 1990 rotation Catch crop on 200 kg N/ha 0.25 Martinez and fallow field Guiraud 1990 Field-grown Operational 40-100 This study Taxus practices Field-grown EAC Operational 70-160 This study practices - 51 Figure LIST OF FIGURES Simple linear function relating foliar biomass to crownvolume index for 12 EAC and 12 Taxus plants grown in nursery fields in western Michigan, spring 2001. Rainfall (mm) readings from a weather station in West Olive, Ml from 5/1/2001 — 10/31/2001. Sampling dates of the porous ceramic cups are indicated by *. Nitrate-N concentrations in soil water sampled with ceramic porous cup lysimeters in two Taxus nursery fields (Nursery A & B) in western Michigan during the 2001-growing season. Nursery A had 12 sampling dates, while Nursery B had 14. Nitrate-N concentrations of soil cores sampled at two Taxus nursery fields (Nursery A & B) in western Michigan during the 2001-gowing season. Vertical bars represent standard error of the mean. Nitrate-N concentrations in soil water sampled with ceramic porous cup lysimeters in two EAC nursery fields (Nursery A & B) in western Michigan during the 2001-gowing season. Nursery A had 10 sampling dates, while Nursery B had 15. Nitrate-N concentrations of soil cores sampled at two EAC nursery fields (Nursery A & B) in western Michigan during the 2001-growing season. Vertical bars represent standard error of the mean. 52 foliar biomass (g) 160 Taxus 140- . 120 - 100 _ Taxus y = 0.006340x R2 = 0.99 EAC y = 0.000258x R2=0.90 30 _ y = biomass (g) x = crown volume (cm3) 60 - 4o - 0 O O 20 _ O O U EAC O O n 0 r r I l 0 . 20000 40000 . 60000 80000 100000 crown volume index (cm3) Figure 1 53 rainfall (mm) 70 60 50 40 30 20 1O 5/1 * = sampling dates 6/1 IUllIIi 7/1 I l I l 8/1 date Figure 2 54 9/ ill I 1 ll 10/1 v 11/1 NO3- concentration (mg N L") 100i 80 - 60 ~ 40 - 20- Nursery A —.— Control fi— Operational V\ —I- RAR / V / I 80- 60' - 40- 20- Nursery B 571 6/1 771 8/1 971 1611 1 in Figure 3 55 N03- concentration (mg N L ‘1) 50 4o- 30- 20- 10- 30- 20— 10- + Control NurseryA —{7— Operational ~I-- RAR / \ / \ \ / ‘K // \\ / // \\ \ Nursery B V \ \\ t, / \ y / / \ \ \ \ __ ._ V __ —— —— W— a 571 671 771 871 971 1671 1 171 date Figure 4 56 180 - 150I 120 - (D O O) 0 (JD 0 Nursery A —.— Control ‘V— Operational 1— RAR 120 4 100 - 80- N03- concentration (mg N L") O 60- 4o— 20- 571 671 771 871 971 10/1 1171 date Figure 5 57 NO3- concentration (mg N L") 25- 20- 15- 10- Nursery A —.— Control —{7— Operational —I—- RAR fl.” _—— ——_——- 40- 30- ZOI ioI Nursery B 5/1 6/1 7/1 8/1 9/1 10/1 11/1 date Figure 6 58 LITERATURE CITED Aldinger, H. Agricultural and Environmental Policies in the EU and their Impact on Fertilizer Consumption. European Fertilizer Manufacturers Association. May 2001. April 2002. http://wwwefmaorg Alt, D. 1998 a. N-Fertilization of nursery crops in the field — A Review, Part 1. Gartenbauwissenschaft. 63:165-170 Alt, D. 1998 b. N-Fertilization of nursery crops in the field - A Review, Part 2. Gartenbauwissenschaft. 63:237-242. Alt, D. 1998 c. N-Fertilization of nursery crops in the field - A Review, Part 3. Gartenbauwissenschaft. 63:278-282. Alva, AK. and S. Paramasivam. 1998. Nitrogen management for high yield and quality of citrus in sandy soils. Soil Sci. Soc. Am. J. 62:1335-1342. Bauder, J.W. and R.P_Schneider. 1979. Nitrate-Nitrogen Leaching Following Urea Fertilization and Irrigation. Soil Sci. Soc. Am. J. 43:348-352. Carpenter, S. 1998. Nonpoint pollution of surface waters with phosphorous and nitrogen. Ecological Society of America. 1-12 Cooper, CM. 1993. Biological effects of Agriculturally derived surface water pollutants on aquatic systems — A Review. Journal of Environmental Quality. 22:402-408. Diaz-Diaz, R., Loague, K. 2000. Comparison of two pesticide leaching indices. Jounral of the American Water Recourses Association. 36 (3):823-832. Extension Bulletin. 1999. A Fertilizer Program for Field Grown Nursery Stock. Michigan State University Exford Extension. 12-15. Extension Service (Oregon State University). 1998. Sundangrass and Sorghum- Sudangrass hybrids. Goulding, K. 2000. Nitrate leaching from arable and horticultural land. Soil Use and Management 16:145—151. Haase, UL. and R.Rose. Vector analysis and its use for interpreting plant nutrient shifts in response to silvicultural treatments. Forest Science. 41(1):54-66. 59 Helrich, K. 1990. Official Methods of Analysis. Association of Official Analytical Cmists, Inc. Arlington, Virginia. #99003. Hopkins, W.G. 1995. Introduction to Plant Physiology. John Vlfiley & Sons, Inc. New York lngestad, T. and GI. Agren. 1988. Nutrient uptake and allocation at steady-state nutrition. Physiologia Plantarum. 72:450-459. lngestad, T. and Agren G.l. 1992. Theories and methods on plant nutrition and growth. Physiologia Plantarum. 84:177-184. Imo, M. and V.R. Timmer. 1992. Nitrogen Uptake of Mesquite Seedlings at Conventional and exponential fertilization schedules. Soil Sci. Soc. Am. J. 56:927-934. Iseman, T.M., D.R. Zak, W.E. Holmes and AG. Merril.1999. Revegetation and nitrate leaching from lake states northern hardwood forests following harvest. Soil Sci. Soc. Am. J. 63:1424-1429. Kelly, WC. 1990. Minimal use of synthetic fertilizers in vegetable production. HortScience. 25(2):168-170. Kozlowksi, T.T and SC. Pallardy. 1997. Physiology of Woody Plants. Academic Press, Inc. San Diego, California. Le Bot, J., S. Adamowicz and P. Robin. 1998. Modelling plant nutrition of horticultural crops: a review. Sceintia Horticulturae. 74:47-82. Michigan Department of Agriculture. 2000. Michigan Rotational Survery. Nursery and Christmas Trees -2000. Michigan Agricuultural Statistics Service, Lansing, MI. Miller, BD and V.R. Timmer. 1994. Steady-state nutrition of Pinus resinosa seedlings: response to nutrient loading, irrigation and hardening regimes. Mills, HA. and JB Jones. 1996. Plant Analysis Handbook. MicroMacro Publishing, Inc. Athens, Georgia. Morrison, P. and P. Morrison. 2001. EnrichinLthe earth: Fritz Haber, Carl Bosch, and the transformation of world food production. The MIT Press. Cambridge, Massachusetts. 6O Noland. B.T., B.C. Ruddy, K.J. Hitt and DR. Helsel. 1998. A national look at nitrate contamination of ground water. Water Conditioning and Purification, v. 39, no. 12, pages 76-79. Pellet, M. and V.J. Carter. 1981. Effect of nutritional factors on cold hardiness of plants. Horticultural Reviews. 32144-171. Powlson, 0.8. 1993. Understanding the soil nitrogen cycle. Soil Use and Management. 162145-151. Refsgaard J.C.,.M. Thorsen, J.B. Jensen, S. Kleeschulte, S. Hansen.1999. Large scale modeling of groundwater contamination from nitrate leaching. Journal of Hydrology, 221 (3/4):1 17-140. Rios, C.M., B.M. Cregg, J.B. Hart, R.t. Fernandez, D.B. Rowe. 2001b Effect of three fertilizer rates on field-grown Taxus and Euonymus species in Western Michigan. Submitted HortScience. Rose MA. 1999. Nutrient use patterns in woody perennials: implications for increasing fertilizer efficiency in field-grown. HorTechnology. 9(4):613-617. Shepherd, M.A., E.A. Stockdale, D.S. Powlson and SC. Jarvis. 1996. The . influence of organic nitrogen mineralization on the management of agricultural systems in the UK. Soil Use and Management. 12276-85 Sylvester-Bradley, R. 1993. Scope for more efficient use of fertilizer nitrogen. Soil Use and Management. 9(3):112-117. US. Department of Agriculture. 2002. Miscellaneous Publications No. 1475. US. National Arboretum, Agriculture Research Service, USDA, Washington, DC. US. Department of Agriculture. 1972. Soil Survey of Ottawa County, Michigan. Will, G.M.1977. The influence of nitrogen supply on the growth form of Pinus radiata seedlings. Forest Science.23:64-68. Williams, TM. 1999. Nitrate leaching from intensive fiber production and abandoned agricultural land. Forest Ecology and Management. 122:141-149. Wolfinger, RD. 1997. An example of using mixed models and proc mixed for longitudinal data. Journal of Biopharmaceutical Statistics. 7(4):481-500 Xu, X. and V.R. Timmer. 1998. Biomass and nutrent dynamics of Chinese fir seedlings under concentional and exponential fertilization regimes. Plant and Soil. 203:313-322. 61 Chapter Two Growth and Nitrogen Content of Field-grown Taxus and Euonymus in Response to Different Fertilizer Regimes. 62 Growth and Nitrogen Content of Field-grown Taxus and Euonymus in Response to Different Fertilizer Regimes. Additional index words. fertilizer use efficiency, biomass allocation ABSTRACT To increase the efficiency of fertilizer use we incorporated the ‘Relative Addition Rate’ theory of plant nutrition into field production. We compared plant growth, biomass partitioning and foliar nitrogen concentration in response to three treatments; 1) control (no fertilizer); 2) operational fertilization (based on the nurseries’ current practices); and 3) relative addition rate (additions based on crop growth). We established the study in collaboration with two major nurseries in western Michigan. Nursery A had one field growing Taxus x media (Taxus baccata L. x T. cuspidate Sieb. & Zucc) ‘Runyan’ and the other growing Euonymus alatus Sieb. ‘Compactus’. Nursery B had one field growing Taxus cuspidate ‘Dark Green Spreader’ and the other growing Euonymus alatus ‘Compactus’. There was no difference in growth among the three treatment plots in any of the four fields. Foliar N concentrations were not found to be deficient in any of the treatments, and more specifically vector analysis indicated the occurrence of luxury consumption. Implications of these results indicate that continuing the refinement of nutrient management can protect the environment while improving grower efficiency and profitability. 63 INTRODUCTION Nitrogen is of great importance to plants because it is a constituent of many important molecules such as proteins, chlorophyll and nucleic acids. In the leaf, up to 75% of the nitrogen is associated with the function of the chloroplast (Le Bot et al. 1997). Nitrogen is the fourth most abundant element in plants, but arguably the most important in terms of soil derived elements (Hopkins 1995). Woody plant studies have shown that increasing nitrogen under limiting conditions increases growth, branching, and stem diameter (VVlII 1977). The amount of nitrogen required for optimal growth is dependent on species, developmental stage, and plant organ. For woody horticultural crops it can be difficult to know how much and when the plant demands external source of N because plants can use N stored in their roots and branches in the spring for the initial growth (Kozlowksi and Pallardy. 1997). One of Michigan’s largest growing industries is landscape nursery production. There are 3,525 hectares (8,710 acres) of fields growing nursery crops in the western part of the state where the industry is concentrated (MDA 2000). Nitrogen is critical for crop growth and development, however recommendations for N application in nursery systems vary from 20-120 kg (44-264 lbs) per year, and the recommendations for timing of application are very broad as well (Ext. Bul. 1999, Rose 1999). Presently, growers may afford to overlook inefficiencies in fertilizer application, because profits outweigh costs (Kelly 1990, Sylvester-Bradly 1993). Fertilizer however is not 64 free, and neither is the equipment or the labor used for application. For example, large nursery growers in western Michigan may spend $25/acre a year on fertilizer. In addition, the Haber-Bosch synthesis provides more than 99% of all inorganic N inputs to farms, and with the increasing cost of natural gas there will be a potential increase in synthetic fertilizer cost (Morrison and Morrison 2001). The larger cost of inefficient fertilizer use however, is the cost to the environment. Vlfith increasing governmental regulations in the US. and around the world (Aldinger 2001), maximizing efficiency of fertilizer use is becoming a greater concern for industry and a more pressing area of research. There is a need to improve the advice we provide to nursery growers for fertilizer use. Based on theory, the relative addition rate (Ra) required to replace nutrients taken up by the crop plants should equal relative uptake rate (R) under limiting conditions (Rios et al. 2002a). The technique termed ‘Relative Addition Rate’ tries to maintain steady state conditions of nutrients within the plant to produce optimal growth (lngestad and Agren 1988). The amount of nutrients added is dynamic, relating to size and growth rate of the plant. Alt (1998a) proposes the incorporation of this ‘RAR’ technique to horticultural crops, and stated that the uptake rate (R) may be estimated by the growth rate. Since the largest concentration of N in woody plants is stored in new shoots; the amount of N uptake may be estimated from the amount of N stored within new shoots. Alt (1998a) showed a strong correlation between fresh matter yield of shoots and N uptake with many 65 different horticultural crops. In this manner Ru may be estimated as the rate of change of nitrogen in the biomass of the plants (Rios et al 2002a). Contrary to prescription fertilizer applications that are commonly used in field horticultural practices, the ‘RAR’ technique is one based on the physiological requirement for nutrients by a plant. If ‘RAR’ could be incorporated to operational practices, there would be several potential benefits. For instance, leaching losses of nitrate would be minimized by only applying the amount of nitrogen that the crop requires, growers could save money, and plant growth could be optimized. Study objective To increase the efficiency of fertilizer use we incorporated the ‘Relative Addition Rate’ theory of plant nutrition into field production. We compared results of plant growth, biomass partitioning, and foliar nitrogen concentration during three different treatments. 1) Relative Addition Rate treatment 2) Operational treatment, which is based on nurseries current application rates 3) Control (no mineral fertilizer applied) Materials and Methods Plot description This study was done with the collaboration of two major nurseries in western Michigan (42°45’ N 86°1’W), using two fields at each nursery. Nursery A had one field growing Taxus x media ‘Runyan’ and another 66 growing Euonymus alatus ‘Compactus’ (Burning bush). Nursery B had a Taxus cuspidate ‘Dark Green Spreader” field and a Euonymus alatus ‘Compactus’ (Burning bush) field. These two taxa were selected because they represent two of the most important taxa in nursery production in Michigan and they also represent contrasting growth habits (evergreen conifer vs. deciduous broad-leaved). The fields will be identified as Taxus Nursery A & B and EAC Nursery A & B. The age of the fields, and size of the plots vary (Table 1). Within each field there were three replications of each treatment, for a total of nine plots. The plots were laid out as a complete randomized design (CRD). Fertilizer treatments Treatment plots were established in spring of 2000. Fertilizer blend (20-0-10) was donated by the nurseries, and was applied in a banding form on various dates throughout the season (Table 2 & 3). Prior to the initiation of the study, EAC Nursery A received standard operational culture of 57 m3/hectare (30 yd/acre) of turkey manure the year before planting. Sudangrass was planted as a cover crop and incorporated into both EAC and Taxus fields in Nursery B prior to planting in 1997. The Sudangrass was fertilized with 112 kg N/hectare (100lbs/acre). For further description of soil type, plot information, and fertilizer application method refer to Rios et al. 2002a. Growth measurements 67 Height and crown diameter were taken on 10-tagged plants from the center row of each plot and the average was used to plot a growth trend. The crown diameter was measured in two perpendicular directions. The crown volume of each plant was calculated as a volume index: c.v.= rr*h ital?) 2 Where C.V.l. is crown volume index (cm3), h is the height of the plant (cm) and d1 and d2 are two plant diameters (cm) measured at right angles. The volume was measured five times throughout the growing season. Foliar samples Samples of mature, current year foliage were collected from 10 random plants 3-4 times throughout the growing season, depending on foliar availability. Total foliar nitrogen was quantified by the combustion method approved by the Association of Official Analytical Chemists reference # 99003 (AOAC 1990). Whole plant harvest Three plants were selected at random from each replicated treatment plot in each field totaling nine plants per treatment per field (in Nursery B, Taxus we only harvested a total of six plants per treatment). The nine harvested plants were washed, and separated into root, shoot, and leaf component parts. The separate components were dried and weighed. Statistical analysis for growth and biomass was done by analysis of variance. The foliar samples were analyzed by analysis of variance repeated 68 measures (Rios et al. 2002a). Differences among treatments were established at the 5% level of probability. 39% Growth Neither fertilizer treatment increased crown volume growth relative to the control (Figures 1 8r 2) on either the Taxus or the EAC. Taxus grew steadily throughout the season at both nurseries among all of the treatments. Dark green spreader (Nursery B) appeared to have a larger initial growth flush in May than the Runyan (Nursery A), which grew more in June. In contrast to the indetenninent growth pattern of the Taxus, the EAC grew into July and then set bud. Biomass Biomass allocation to roots, stems, and leaves was relatively unaffected by fertilizer treatment. The root weight ratio varied by field, which relates to the age of the plants. A root weight ratio of ~0.5 was found for the EAC Nursery A that was planted in 2001, while the older EAC Nursery B field planted in 1999 had a root weight ratio of ~0.36. (Tables 4 & 5) Foliar concentration Taxus Fertilization increased foliar N of the Taxus, though the difference was statistically significant only at Nursery B (Figures 3). Overall, foliar N levels were high in the spring, decreased in mid summer and increased again in the fall. The substantial decrease in foliar concentration during late July that 69 occurred in the Runyan (Nursery A, Figure 3) field is likely due to the corresponding growth flush (Nursery A, Figure 1). The control was significantly lower than the RAR and operational treatment (Figure 3 and Table 6) only in Nursery B. EAC In the EAC fields there were not significantly different foliar N concentration among any of the treatments (Figure 4 and Table 7). The foliar trend of the EAC differed from the Taxus in that they were low in the spring, increased at mid summer, and returned back down in the fall (Figure 4). Discussion The seasonal trends in both crop growth and in foliar N concentration provide valuable information. The growth patterns of the Taxus plants indicate that this is an inderterminant grower. Therefore, applying fertilizer more frequently and in lower amounts would be recommended over the current practice of two large applications. In contrast, the growth of the EAC plants show that this is a determinate grower, releasing one large flush of growth in the spring. From our data it appears that for this crop fertilizer does not need to be applied throughout the season. The foliar N concentrations show a seasonal trend as well, which is important to note. From the Taxus fields we see that in mid summer (August) foliar levels of N are at a low, this trend is evident across all treatments. If a grower is using foliar samples to diagnose nutrient deficiencies, it is important to know the natural fluctuations that occur throughout the season. In contrast, 70 foliar N concentration of the EAC peaked at mid summer and then declined towards the fall. This is likely due to retranslocation that is occurring in the plant. The N might be being stored in the woody tissue and roots for the next springs flush (Kozlowski and Pallardy 1997). Ideally, the RAR theory applied to field practices would have the grower apply only the amount of fertilizer to the fields that would be taken up by the crop, leaving no residual nitrate susceptible to leaching. Complexity increases when a theory that has been established with liquid or air media (lngestad and Agren 1988) is used in field practices. The R, = Ru equality sought after in a controlled environment is without leaks, and limiting nutrient conditions may be met. In the field however, there are other sources releasing nitrates besides what is added as a synthetic N fertilizer. There can be contributions of nitrate from native soil organic matter, animal manures, crop residues and residual nitrate from the previous growing season (Shepherd et al. 1996), which all need to be taken into consideration and make it difficult to attain limiting conditions. For instance, once incorporated, Sudangrass is estimated to add an additional 150 kg/hectare (133 lbs/acre) of organic N (Michigan State University 1999). Along with growth measurements, the health of the crop may be assessed by foliar nutrition. Foliar N varies between 2 and 5% for woody plants (Marshcner 1995). Mills and Jones (1996) found that for Winged Euonymus (Euonymus alatus) the optimal N concentration lies between 2.37- 2.62%, and for Anglojap Hybrid Yew (Taxus x media) is between 2 and 4%. 71 The N concentrations from the samples of each of the three treatments in this study were within optimal range (Figures 3 8r 4). The lack of deficiency helps explain why there were no differences in the growth among the treatments, and supports the notion that the plants were obtaining N from other sources in the field. The N concentrations in our study show that luxury consumption was taking place. In Figure 3 we see that there was a difference in N concentration between the control in Nursery B, yet there was no difference in growth, this tells us that during the month of August 2% N is a sufficient level. Vector analysis allows for simultaneous comparison of plant growth, nutrient concentration, and nutrient content, in response to fertilizer regimes (Haase and Rose 1995). When examining vector diagrams, the longest vector expresses the most responsive treatment. Plotting our data in this format can add to our understanding of treatment effect. More specifically, the major vectors occur in both Taxus fields, and follow the 1:1 line further indicating that luxury consumption is taking place (plant N content increase due to increase in foliar concentration not growth). The vectors in the EAC fields are not long (Figure 6) indicating less of a treatment effect (Figure 5). The direction of the vector however, indicates the start of toxicity or possibly an antagonistic effect (fertilizer addition decreases growth). The vector diagrams indicate the importance of accounting for past cultural treatments when deciding how much synthetic fertilizer to apply. The Dark green spreader (Nursery B) was the oldest of the four fields, possibly containing less soil organic matter due to the longer duration since the last 72 fallow or manure application, and therefore showed the most response to synthetic fertilizer application (Figure 5). The Runyan (Nursery A) field had no record of recent fallow planting or manure application, and also showed a treatment response. There was a masking of synthetic fertilizer effect due to the more recent application of manure and cover crop planting in the EAC fields (Figure 6). In the process of trying to apply the ‘RAR’ theory to field practices we found that there are large inefficiencies occurring in fertilizer application in the nursery industry. The same plant growth, and for the most part biomass distribution, occurred with no application of fertilizer than with operational levels, indicating that there are releases of plant available N in the nursery fields that are not accounted for. There were no nutrient deficiencies present among any of the treatment plots, and luxury consumption may have occurred. Seasonal trends were apparent in the growth and foliar N data, which can help future fertilizer recommendations. For example, this data can assist in estimating removal rates required for determining management guidelines. There must be more specific recommendations given to our nursery growers, which is based on scientific knowledge. Continued refinement of nutrient management can protect the environment while improving grower efficiency and profitability. 73 Table 1. Site description of year planted, plant density, plant height and site occupancy of four fields in western Michigan. Measurements represent values of April 2001. Nursery- Year Plant density Average *Site crop planted (#plants/acre) plant occupation (#plants/hectare) height (cm) A - Taxus 1999 11771 29064 21 13.1 % B - Taxus 1998 11771 29064 23 21.5% A - EAC 2001 11771 29064 22 6.7% B - EAC 1999 6272 15487 26 31.9% *Site occupation = (crown area/plot area) x 100 = % site occupation Crown area= (ave. width/2)2 x it 74 Table 2. Fertilizer application rates and dates for two treatments (operational and RAR) applied to two Taxus nursery fields (Nursery A 8. B) in western Michigan during the 2001-growing season. Field Treatment Nursery A Operational RAR (lbs Nlacre) (lbs Nlacre) (kg N/hectare) (kg N/hectare) May 9m 60 67 30 34 June 14th 39 43 July 3rd 52 58 August 3rd 60 67 August 24th 11 13 Total 120 134 132 148 Nursery B May 9‘" 60 67 June 14th 53 59 July 3rd 25 28 August 3ml 60 67 August 24th 5 6 Total 120 134 113 127 (Fertilizer was applied as a blend of 20-0-10) 75 Table 3. Fertilizer application rates and dates of two treatments (operational and RAR) applied to two EAC nursery fields (Nursery A 8. B) in western Michigan during the 2001-growing season. Field Treatment Nursery A Operational RAR (lbs fertilizer/acre) (lbs fertilizer/acre) (kg fertilizer/hectare) (kg fertilizer/hectare) tl'l k _ 313.2918 5" ‘5’ 33 3‘2‘ July 3'“I 2 2 August 3'“ 60 67 August 24th 30 34 Total 120 134 64 72 Nursery B May 9m 60 67 30 34 June 14th 7 8 July 3“ 2 2 August 3'“I 60 67 Aigust 24th 30 34 Total 120 134 69 48 (Fertilizer was applied as a blend 20-0-10) 76 Table 4. Biomass distribution and root weight ratios for two Taxus fields in western Michigan. Twelve plants were harvested from each fertilizer treatment in Nursery A, and nine from each treatment in Nursery B, at the end of the 2001 growing season. Dry weight values are represented. Field Treat. Total Root Shoot F oliar Root weight biomass biomas biomass biomas ratio (root (9) s (g) (g) s (g) biomss/total biomass) Nursery A. Control 164 40 50 75 0.249 Oper. 209 53 62 94 0.261 RAR 258 ** 66 79 1 13 0.260 Nursery _B_ Control 301 1 12 88 101 0.368 Oper. 310 s 82 73 155 0.278* RAR 286 105 93 89 0.365 * = Operational treatment significantly different than control and RAR p 5 .05 ** = RAR significantly different than control p 5 .01 77 Table 5. Biomass distribution and root weight ratios for two EAC fields in western Michigan. Twelve plants were harvested from each fertilizer treatment at the end of the 2001 growing season. Dry weight values are represented. Field Treat. Total Root Shoot F oliar Root biomass biomass biomass biomass weight (9) (9) (9) (9) ratio Nursegr A Control 35 19 12 4 0.529 Oper. 45 25 14 7 0.536 RAR 17 1 1 4 32 0.507 Nursery B Control 20 25 10 55 0.359 Oper. 23 28 13 65 0.320 RAR 28 32 9 68 0.402 *= Differences among treatments pg .05 **= Differences among treatments p_<_ .01 78 Table 6. Analysis of variance for foliar nitrogen concentration from two Taxus fields (Nursery A& B) in western Michigan during the 2001- growing season. Foliage was collected from 10 random plants in each field plot. Field Source df F P>F Nursery A TRT 2 4.98 0.0600 Day 3 24.46 <0.0001 TRT*Day 6 1 .00 0.4686 Nursery B TRT 2 39.97 <0.0001 Day 3 40.14 <0.0001 TRT*Day 6 1.05 0.4191 Contrast Control vs. RAR 1 54.91 <0.0001 64.64 <0.0001 0.40 0.5331 a Control vs. Operational RAR vs. Operational a—k *= Differences among treatments pg .05 **= Differences among treatments pg .01 79 Table 7. Analysis of variance of foliar nitrogen concentration from two EAC fields (Nursery A&B) in western Michigan during the 2001-growing season. Foliage was collected from 10 random plants in each field. Field Source df F P>F Nursery A TRT 2 0.24 0.7856 Day 2 7.61 0.0048 TRT*Day 4 2.37 0.0961 Nygery B TRT 2 0.28 0.7715 Day 2 43.9 0.0019 TRT*Day 4 0.33 0.8456 *= Differences among treatments pg .05 **= Differences among treatments pg .01 80 Figure LIST OF FIGURES Plant volume index measurements for two Taxus fields (Nursery A & B) in western Michigan during the 2001-growing season. Data points represent averages of 30 plant measurements per treatment. Verticle lines represent standard error of the mean. Plant volume index measurements for two EAC fields (Nursery A & B) in western Michigan during the 2001-growing season. Data points represent averages of 30 plant measurements per treatment. Verticle lines represent standard error of the mean. Foliar N concentrations for two Taxus fields (Nursery A & B) in western Michigan during the 2001-growing season. Each sampling date represents foliage from 10 random plants within the treatment plot. Vertical lines represent standard error of the mean. Foliar N concentrations for two EAC fields (Nursery A & B) in western Michigan during the 2001-growing season. Each sampling date represents foliage from 10 random plants within the treatment plot. Vertical lines represent standard error of the mean. Vector diagram showing the relative response of two Taxus fields (Nursery A & B) to different fertilizer treatments. Foliar concentration represents an average of four samples taken throughout the 2001-growing season. Relative content was derived from total growth during the season and average N concentration; the control was used as the reference value. Vector diagram showing the relative response of two EAC fields (Nursery A & B) to different fertilizer treatments. Foliar concentration represents an average of three samples taken throughout the 2001-growing season. Relative content was derived from total growth during the season and average N concentrations; the control was used as the reference value. 81 crown volume index (cm3) NurseryA 35000 - 25000 - —.— Control 15000 - —V— Operational —l— RAR 5000 - Nursery B /// 30000 . 20000 . 10000 4 4/1 5/1 6/1 7/1 8/1 9/1 10/1 date Figure 1 82 14000 12000 - 10000 - Nursery A 8000 - 6000 - .5 O O O 2000 - .i— =— ——- -——-——- :4 —.— Control —-v— Operational —I—- RAR 0 50000 4 crown volume index (cm3) 40000 J 30000 — 20000 - 10000 - 4/1 5/1 6/1 7/1 8/1 9/1 1 0/1 date Figure 2 83 foliar nitrogen (%) 3.3 - 3.1 - 2.9 - 2.7 - 2.5 2.3 - 2.1 1.9 - 3.3 ~ 3.1 - 2.9 - 2.7 - 2.5 - 2.3 - 2.1 - 1.9 - Nursery A —Q— Control 49— Operational —I— RAR Nursery B 571 6/1 7/1 871 9/1 1071 1 171 date Figure 3 84 foliar nitrogen (%) 3.8 3.6 - 3.4 - 3.2 - 3.0 . 2.8 - 2.6 - 2.4 - 3.6 - 3.4 . 3.2 . 3.0 - 2.8 - 2.6 - 2.4 2.2 —.— Control I —\7— Operational Nursery A -I-- RAR #/ Nursery B 5/1 6/1 7/1 8/1 9/1 10/1 11/1 date Figure 4 85 relative concentration 140 13o _ Nursery A I. / / 120 - I 110 ‘ _._ 1:1 —v— Control 100 4 —I— Oper —<>— RAR 90 - 80 130 - Nursery 13 O / / 120 4 .C’ I /<> / 110 - / 100 - /U/ / 90 - ./ 80 T r f T l 80 90 100 110 120 130 relative content Figure 5 86 140 relative concentration 140 13o _ NurseryA /. / // 120 4 .0 / / / 110 - /O' —Q— 1:1 I / —V- Control \ / O 100 — <> e—v -l- Per // —<>— RAR / 90 i 0’ 80 130 - Nursery B O / / 120 - 3’ / / 110 - /. / 100 - 0%. / 90 - ./ 80 , . . l . 80 90 100 110 120 130 relative content Figure 6 87 140 Appendix 88 Field Plot Date Depth Moisture (%) Ka ZT 1 5/18/01 17 12.5 6.9 ZT 2 5/18/01 17 14.8 7.8 ZT 3 5I18/01 17 12 6.7 ZT 4 5/18/01 17 12.5 6.9 ZT 5 5/18/01 17 12 6.8 ZT 6 5/18/01 17 17.4 8.9 ZT 7 5/18/01 17 16.3 8.4 ZT 8 5/18/01 17 19.4 9.8 ZT 9 5/18/01 17 15.4 8 ZT 1 5/22/01 17 12.1 6.8 ZT 2 5/22/01 17 8.4 5.3 ZT 3 5/22/01 17 13.7 7.3 ZT 4 5/22/01 17 10.1 6.1 ZT 5 5/22/01 17 11.3 6.5 ZT 6 5/22/01 17 10.5 6.2 ZT 7 5/22/01 17 15.9 8.2 ZT 8 5/22/01 17 17.2 8.8 ZT 9 5/22/01 17 14 7.5 ZT 1 6/5/01 17 26.2 13.9 ZT 2 6/5/01 17 22 11.1 ZT 3 6/5/01 17 28.1 15.7 ZT 4 6/5/01 17 26 13.8 ZT 5 6/5/01 17 26 13.8 ZT 6 6/5/01 17 25.4 13.2 ZT 7 6/5/01 17 30 17.5 ZT 8 6/5/01 17 33.3 19.9 ZT 9 6/5/01 17 29.3 16.8 ZT 1 6/13/01 17 13.4 7.2 .2T 2 6/13/01 17 9.2 5.7 ZT 3 6/13/01 17 15.8 8.2 ZT 4 6/13/01 17 13.7 7.3 ZT 5 6/13/01 17 13.1 7.1 ZT 6 6/13/01 17 12.7 7 ZT 7 6/13/01 17 17.8 9 ZT 8 6/13/01 17 19.6 9.8 ZT 9 6/13/01 17 16.6 8.5 ZT 1 6/20/01 17 8.9 5.5 ZT 2 6/20/01 17 7.1 4.7 ZT 3 6/20/01 17 11.2 6.4 ZT 4 6/20/01 17 9.2 5.7 ZT 5 6/20/01 17 9.8 5.9 ZT 6 6/20/01 17 8.9 5.5 ZT 7 6/20/01 17 14.2 7.5 89 ZT 8 6/20/01 17 14.6 7.7 ZT 9 6/20/01 17 11.3 6.5 ZT 6 6/26/01 17 8 5.2 ZT 7 6/26/01 17 13.4 7.3 ZT 8 6/26/01 17 13 7.1 ZT 9 6/26/01 17 9.8 5.9 ZT 1 7/19/01 17 5.3 4 ZT 2 7/19/01 17 4.5 3.6 ZT 3 7/19l01 17 6 4.2 ZT 4 7/19/01 17 5.5 4 ZT 5 7/19/01 17 6.6 4.5 ZT 6 7/19/01 17 4.9 3.8 ZT 8 7/19/01 17 8.4 5.3 ZT 9 7/19/01 17 6.4 4.4 ZT 1 7/21/01 17 9.3 5.7 ZT 2 7/21/01 17 8.5 5.4 2T 3 7/21/01 17 8.2 5.2 ZT 4 7/21/01 17 7.2 4.8 ZT 5 7/21/01 17 8.7 5.4 ZT 6 7/21/01 17 6.9 4.7 ZT 7 7/21/01 17 9.4 5.8 ZT 8 7/21/01 17 9.8 5.9 ZT 9 7/21/01 17 7.2 4.8 ZT 1 8/21/01 17 11.6 6.6 ZT 2 8/21/01 17 8.3 5.3 ZT 3 8/21/01 17 13.5 7.3 ZT 4 8/21/01 17 11.7 6.6 ZT 5 8/21/01 17 11.3 6.5 ZT 6 8/21/01 17 11 6.4 ZT 7 8/21/01 17 15.8 8.2 ZT 8 8/21/01 17 17.5 8.9 ZT 9 8/21/01 17 14.9 7.8 ZE 1 5/10/01 17 10.1 6 ZE 2 5/10/01 17 10 6 ZE 3 5/10/01 17 10.5 6.2 ZE 4 5/10/01 17 12.2 6.8 ZE 5 5/10/01 17 10.4 6.2 ZE 6 5/10/01 17 9.4 5.8 ZE 7 5/10/01 17 10.7 6.3 ZE 8 5/10/01 17 11.1 6.4 ZE 9 5/10/01 17 9.7 5.9 ZE 1 5/18/01 17 12.4 6.9 ZE 2 5/18/01 17 11.2 6.5 ZE 3 5/18/01 17 13 7.1 90 ZE 4 5/18/01 17 17.4 8.9 ZE 5 5/18/01 17 12.8 7 ZE 6 5/18/01 17 12.1 6.8 ZE 7 5/18/01 17 14 7.4 ZE 8 5/18/01 17 14.1 7.5 ZE 9 5/18/01 17 13.4 7.3 ZE 1 5/22/01 17 12.7 7 ZE 2 5/22/01 17 11.9 6.7 ZE 3 5/22l01 17 14 7.4 ZE 4 5/22/01 17 17.4 8.9 ZE 5 5/22/01 17 12.5 6.9 ZE 6 5/22/01 17 12 6.7 ZE 7 5/22/01 17 13.5 7.3 ZE 8 5/22/01 17 14.5 7.6 ZE 9 5/22/01 17 13.3 7.2 ZE 1 6/5/01 12 26.2 13.9 ZE 2 6/5/01/ 12 26.1 13.8 ZE 3 6/5/01 12 28.2 15.8 ZE 4 6/5/01 12 30.8 18.1 ZE 5 6/5/01 12 26.3 14 ZE 6 6/5/01 12 26.2 14 ZE 8 6/5/01 12 27.8 15.5 ZE 8 6/5/01 12 28.3 15.9 ZE 9 6/5/01 12 26.6 14.3 ZE 1 6/13/01 17 12.5 6.9 ZE 2 6/13/01 17 12.1 6.8 ZE 3 6/13/01 17 15.3 8 ZE 4 6/13/01 17 18.7 9.4 ZE 5 6/13/01 17 13.3 7.2 ZE 6 6/13/01 17 12.4 6.9 ZE 8 6/13/01 17 15.4 8 ZE 8 6/13/01 17 15.1 7.8 ZE 9 6/13/01 17 14.7 7.7 ZE 1 6/20/01 17 10.3 6.1 ZE 2 6/20/01 17 9.5 5.8 ZE 3 6/20/01 17 11.7 6.6 ZE 4 6/20/01 17 16 8.3 ZE 5 6/20/01 17 10.8 6.3 ZE 6 6/20/01 17 10.2 6.1 ZE 7 6/20/01 17 12.8 7 ZE 8 6/20/01 17 11.9 6.7 ZE 9 6/20/01 17 11.5 6.5 ZE 1 6/26/01 17 9.1 5.6 ZE 2 6/26/01 17 9 5.6 ZE 3 6/26/01 17 10.7 6.3 91 ZE 4 6/26/01 17 14.9 7.8 ZE 5 6/26/01 17 10 6 ZE 6 6/26/01 17 9.8 5.9 ZE 7 6/26/01 17 10.8 6.3 ZE 8 6/26/01 17 10.8 6.3 ZE 9 6/26/01 17 10.7 6.3 ZE 1 7/19/01 17 8.6 5.4 ZE 2 7l19/01 17 7.8 5.1 ZE 3 7/19/01 17 9.7 5.9 ZE 4 7/19/01 17 13.9 7.4 ZE 5 7l19/01 17 8.2 5.2 ZE 6 7/19/01 17 8.6 5.4 ZE 7 7/19/01 17 10.4 6.2 ZE 8 7/19/01 17 9.5 5.8 ZE 9 7/19/01 17 10.5 6.2 ZE 1 8/21/01 17 7.1 4.7 ZE 2 8/21/01 17 7.6 5 ZE 3 8/21/01 17 9.9 6 ZE 4 8/21/01 17 13.4 7.2 ZE 5 8/21/01 17 6.8 4.6 ZE 6 8/21/01 17 7.7 5 ZE 7 8/21/01 17 10 6 ZE 9 8/21/01 17 8.8 5.5 NT 1 5/18/01 17 13.7 7.4 NT 2 5/18l01 17 15.3 8 NT 3 5/18/01 17 14.9 7.8 NT 4 5/18/01 17 16.6 8.5 NT 5 5/18/01 17 11.6 6.6 NT 6 5/18/01 17 18.3 9.3 NT 7 5/18/01 17 15.8 8.2 NT 9 5/18/01 17 17.2 8.8 NT 1 5/22/01 17 10.4 6.2 NT 2 5/22/01 17 12.3 6.8 NT 3 5/22/01 17 11.7 6.6 NT 4 5/22/01 17 11.4 6.5 NT 5 5/22/01 17 9.2 5.7 NT 6 5/22/01 17 15.1 7.9 NT 7 5/22/01 17 13.1 7.1 NT 8 5/22/01 17 14.3 7.6 NT 9 5/22/01 17 13.2 7.2 NT 1 6/5/01 12 28 15.6 NT 2 6/5/01 12 28.9 16.4 NT 3 6/5/01 12 28.2 15.8 NT 4 6/5/01 12 29.5 17 92 NT 5 6/5/01 12 25.8 13.6 NT 6 6/5/01 12 32.6 19.4 NT 7 6/5/01 12 29.1 16.6 NT 8 6/5/01 12 31.2 18.3 NT 9 6/5/01 12 30.3 17.7 NT 1 6/13/01 17 16.7 8.6 NT 2 6/13/01 17 17.2 8.8 NT 3 6/13/01 17 16.2 8.3 NT 4 6/13/01 17 17.7 9 NT 5 6/13/01 17 13.5 7.3 NT 6 6/13/01 17 18.7 9.5 NT 7 6/13/01 17 16.5 8.5 NT 8 6/13/01 17 18.7 9.5 NT 9 6/13/01 17 16.4 8.4 NT 1 6/20/01 17 8.5 5.4 NT 2 6/20/01 17 10.2 6.1 NT 3 6/20/01 17 8.6 5.4 NT 4 6/20/01 17 9.1 5.6 NT 5 6/20/01 17 7.1 4.7 NT 6 6/20/01 17 9.8 6 NT 7 6/20/01 17 8.7 5.5 NT 8 6/20/01 17 10.3 6.1 NT 9 6/20/01 17 9.8 6 NT 1 6I26/01 17 7.3 4.8 NT 2 6/26/01 17 8.5 5.4 NT 3 6/26/01 17 7.8 5.1 NT 4 6/26/01 17 8.1 5.2 NT 5 6/26/01 17 6.4 4.4 NT 6 6/26/01 17 7.9 5.1 NT 7 6/26/01 17 7 4.7 NT 8 6/26/01 17 8.5 5.3 NT 9 6/26/01 17 8.5 5.4 NT 1 7/19/01 17 4.2 3.5 NT 2 7/19/01 17 5.2 3.9 NT 3 7/19/01 17 5.1 3.9 NT 4 7/19/01 17 5.6 4.1 NT 5 7/19/01 17 4.3 3.5 NT 6 7/19/01 17 5.4 4 NT 7 7/19/01 17 4.8 3.7 NT 8 7/19/01 17 5.6 4.1 NT 9 7/19/01 17 5.5 4.1 NT 1 8/21/01 17 12.3 6.8 NT 2 8/21/01 17 13.2 7.2 NT 3 8/21/01 17 12.3 6.8 NT 4 8/21/01 17 15.3 7.9 93 NT 5 8/21/01 17 10.6 6.2 NT 6 8/21/01 17 12.1 6.8 NT 7 8/21/01 17 11.3 6.5 NT 8 8/21/01 17 15.7 8.1 NT 9 8l21/01 17 14.3 7.6 NE 1 5/18/01 17 12.3 6.9 NE 2 5/18/01 17 11.7 6.6 NE 3 5/18/01 17 10.7 6.3 NE 4 5/18/01 17 14.5 7.6 NE 5 5/18/01 17 11.8 6.7 NE 6 5/18/01 17 15.8 8.2 NE 7. 5/18/01 17 13 7.1 NE 8 5/18/01 17 13.4 7.2 NE 9 5/18/01 17 15.2 7.9 NE 1 5/22/01 17 13.1 7.1 NE 2 5/22/01 17 12.6 7 NE 3 5/22/01 17 11.4 6.5 NE 4 5/22/01 17 13.4 7.2 NE 5 5/22/01 17 11.5 6.6 NE 6 5/22/01 17 15 7.8 NE 7 5/22/01 17 14 7.5 NE 8 5/22/01 17 14.1 7.5 NE 9 5/22/01 17 13.3 7.2 NE 1 6/5/01 12 28.7 16.3 NE 2 6/5/01 12 28.6 16.2 NE 3 6/5/01 12 26.9 14.6 NE 4 6/5/01 12 29.4 16.9 NE 5 6/5/01 12 27.4 15.1 NE 6 6/5/01 12 29.9 17.3 NE 7 6/5/01 12 26.6 14.4 NE 8 6/5/01 12 29.2 16.7 NE 9 6/5/01 12 28.6 16.2 NE 1 6/13/01 17 16.3 8.4 NE 2 6/13/01 17 15 7.8 NE 3 6/13/01 17 15.9 8.2 NE 4 6/13/01 17 16.7 8.6 NE 5 6/13/01 17 14 7.5 NE 6 6/13/01 17 16.4 8.4 NE 7 6/13/01 17 12.7 7 NE 8 6/13/01 17 15.3 7.9 NE 9 6/13/01 17 14.9 7.8 NE 1 6/20/01 17 11.2 6.4 NE 2 6/20/01 17 10.5 6.2 NE 3 6/20/01 17 10.1 6.1 94 NE 4 6/20/01 17 11 6.4 NE 5 6/20/01 17 11 6.4 NE 6 6/20/01 17 12.3 6.8 NE 7 6/20/01 17 12 6.7 NE 8 6/20/01 17 11.6 6.6 NE 9 6/20/01 17 12.1 6.8 NE 1 6/26/01 17 10 6 NE 2 6/26/01 17 8.4 5.3 NE 3 6/26/01 17 9.3 5.7 NE 4 6/26/01 17 10 6 NE 5 6/26/01 17 10.3 6.1 NE 6 6/26/01 17 11.8 6.7 NE 7 6/26/01 17 10.9 6.3 NE 8 6/26/01 17 9.9 6 NE 9 6/26/01 17 11 6.4 NE 1 7/19/01 17 7.2 4.8 NE 2 7/19/01 17 5.3 3.9 NE 3 7/19/01 17 5.5 4.1 NE 4 7/19/01 17 6.4 4.5 NE 5 7/19/01 17 8 5.1 NE 6 7/19/01 17 7.5 4.9 NE 8 7/19/01 17 5.7 4.1 NE 9 7/19/01 17 8.5 5.4 NE 1 8/21/01 17 11.4 6.5 NE 3 8/21/01 17 9.5 5.8 NE 4 8/21/01 17 11.8 6.7 NE 5 8/21/01 17 10.7 6.3 NE 6 8/21/01 17 12.3 6.8 NE 7 8/21/01 17 10.7 6.3 NE 8 8/21/01 17 11.3 6.5 NE 9 8/21/01 17 12.4 6.9 95 Analysis of variance table of Nitrate-N concentrations of soil cores sampled in four Taxus nursery fields in during the 2001 growing-season Field Source df F P>F Nursery A TRT 2 55.14 <.0001 Day 3 11.33 <.0001 TRT*Day 6 1.97 0.1 104 Contrast Control vs. RAR 1 92.93 <.0001 Control. vs. Operational 1 71.06 <.0001 RAR vs. Operational 1 1.46 0.2389 Nursery B TRT 2 24.47 0.0003 Day 3 6.13 0.0057 TRT*Day 6 2.08 0.1 134 Contrast Control vs. RAR 1 37.58 0.0002 Control. vs. Operational 1 37.76 0.0003 RAR vs. Operational 1 0.023 0.8876 96 Analysis of variance table of Nitrate-N concentrations of soil cores sampled in four EAC nursery fields in during the 2001 growing-season Field Source df F P>F Nursery A TRT 2 3.76 0.0432 Day 2 31.67 <.0001 TRT*Day 4 0.36 0.8320 Contrast Control vs. RAR 1 3.39 0.0822 Control. vs. Operational 1 7.18 0.0153 RAR vs. Operational 1 0.71 0.4117 Nursery B TRT 2 1.57 0.2811 Day 3 26.65 <.0001 TRT*Day 6 6.53 0.0038 97 Analysis of variance table of volume growth in four Taxus nursery fields in during the 2001 growing-season Field Souce df F P>F Nursery A TRT 2 0.58 0.56 Nursery B TRT 2 0.19 0.83 98 Analysis of variance table of volume growth in four EAC nursery fields in during the 2001 growing-season Field Souce df F P>F Nursery A TRT 2 0.88 0.42 Nursery B TRT 2 0.58 0.56 99 Nursery Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka‘s Zelenka's Zelenka’s Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zemmkas Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's Zelenka's SPP Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus Taxus EA£> EA£: EAK: EA£§ EA£> EA£> EA£> EAE: EA£§ EA£> EA£§ EA£> EBAC EA£> EA£> EA£2 EA£3 EA£2 Plot O’JCDGU'IU'IOTb-h#waNNN-bé-Fmfiommmm‘lflflmmmulU'l01h-b-hwwwNNN—t-i-t plant dewN—lwN—in—in-FOON-fiWN-in—fiwN—le-lwNAwNéwN-‘wN—IwN-fi Roots 100 83 27 49 17 46 74 75 97 42 53 51 76 55 51 70 39 50 21 29 41 50 47 60 77 62 24 20 27 17 45 24 35 17 25 45 11 19 28 14 23 13 17 1 1 Shoot 91 28 39 19 62 79 1 12 90 70 47 59 87 73 65 95 31 81 47 56 30 42 70 40 61 90 82 77 18 1 1 13 14 19 15 20 1 1 14 17 12 15 11 15 11 13 Leaves 140 28 47 17 82 99 169 120 50 164 135 108 97 120 63 128 85 92 33 72 88 104 1 14 63 1 17 1 14 V0 #AGOOJOIUIUICDU'IODUICDCDOJ—t Zelenka's EAC Zelenka's EAC Zelenka's EAC Zelenka’s EAC Zelenka's EAC Zelenka's EAC Zelenka's EAC Zelenka's EAC Zelenka's EAC Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland Taxus Northland EAC Northland EAC Northland EAC Northland EAC Northland EAC Northland EAC Northland EAC Northland EAC wwNNNA—S-‘(DCDCOCDCDCDVVNODGODQOQOTUTCflbub-hwwwNNN—F—t—‘(DQDOGJWQNNN NAQNAwNéwN-fiwN—FQN—immbQN-fiwN-AwNAWNAwN—thdwN—FQN-AOJN—i 101 19 15 10 21 17 10 17 13 142 106 75 116 87 45 101 72 178 71 165 38 55 83 70 62 142 108 11 1 1 11 55 121 70 84 35 87 41 12 28 41 24 13 15 11 10 12 12 1 0 14 108 109 57 93 73 60 83 57 1 13 72 68 169 35 79 103 69 78 86 91 79 77 70 82 58 88 42 61 48 23 28 24 27 39 1 3 1 7 (”aw-54.50001 Ae—i 71386» 162 94 72 81 93 120 89 85 1 16 44 89 121 131 86 108 99 45 97 1 04 404 92 103 44 72 \l-h 28 01-50 Northland Northland Northland Northland Northland Northland Northland Northland Northland Northland Northland Northland Northland Northland Northland Northland Northland Northland Northland EAC EAC EAC EAC EAC EAC EAC EAC EAC EAC EAC EAC EAC EAC EAC EAC EAC EAC EAC oomcoooooxixlxlmmcnoiotoihbtsw wN-le—in—le—IOJN-KQN-lw 102 21 57 29 47 37 27 47 N 24 39 15 18 20 19 32 10 23 45 23 52 60 21 45 13 10 31 53 24 14 17 20 22 47 14 10 13 27 12 11 14 13 14 20 17 10 14 ii Ill 31 Ill Illl IIIIII 3 IIIIII 821