WI WIMUINWINININlNl\\\|W|(|\|\U|Hl\\\l( I_.\_‘ (hm—l '—+_._‘ LIBRARY “‘fl Michigan State U' .q MM“\\L|\9\Ll\\\\|\l\\wj\\Hllllfllfllll 31 47 This is to certify that the thesis entitled The Accumulation and Distribution of Nitrogen in Four Winter Wheat Cultivars l presented by Geoffrey M. Heinrich has been accepted towards fulfillment of the requirements for 1 Master Crop Science r degree in ,/ 7/ 36445/ Orétfl’nq / l l Major professor Date ’f’ ALI-I/l? 0-7639 v‘. flank; ." "E (“livym ilt_-" I ~ -. . '11“ ., .9 « .7. EU» I 31994 OVERDUE FINES: 25¢ per day per ital RETURNING LIBRARY MATERIALS: Place in book return to remove charge from circulation records ACCUMULATION AND DISTRIBUTION OF NITROGEN IN FOUR WINTER WHEAT CULTIVARS By Geoffrey M. Heinrich A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTERS OF SCIENCE Department of Crop and Soil Sciences ABSTRACT ACCUMULATION AND DISTRIBUTION OF NITROGEN IN FOUR WINTER WHEAT CULTIVARS By Geoffrey M. Heinrich Different rates and sources of nitrogen were applied at different dates to two wheat cultivars. Nitrogen topdressings were split and applied to four cultivars. The cultivars studied varied in their ni- trogen response patterns. The concentration of reduced nitrogen was determined in the above ground plant parts of the four cultivars over four growth stages and two nitrogen treatments to determine whether as- similation and/or partitioning systems for nitrogen were related to the response patterns. The yield response patterns of cultivars to nitrogen varied con- siderably with location. There were no major effects due to date of application and no gains resulted from splitting the application over two dates. Internal plant nitrogen levels showed no major differences in con- centration or distribution of reduced nitrogen in plant parts, on a per culm basis. Nitrogen fertilizer increased the reduced nitrogen concen- tration in all plant parts, of all cultivars, at all growth stages. ACKNOWLEDGEMENTS I would like to express my appreciation to Dr. S. K. Ries for the use of his laboratory and equipment and for his advice in the analysis of plant nitrogen, and also to Dr. Violet Wert for her assistance. I would like to thank Dr. E. H. Everson as my major professor for his guidance and Dr. D. D. Warnke, Dr. S. K. Ries and Dr. C. Harrison for their assistance with the thesis. Lester Morrison, Larry Fitzpatrick and Dr. Everson's current grad- uate students deserve a special thanks for their assistance with the field work. And lastly, I would like to thank my parents. ii TABLE OF CONTENTS List of Figures . . . . . . . . . . . Introduction . . . . . . . . . . . . Literature Review Importance of nitrogen to yields . Varietal differences in response to nitrogen Merphological response characters The balance of morphological characters with accumulation . . . . . . . . . . Internal plant nitrogen and its relationship Nitrogen uptake and partitioning in relationship to yield The nitrogen uptake patterns . . . Nitrogen partitioning . . . . . . Date of N application . . . . . . Losses of applied fertilizer . . . . . . . Splitting N applications to reduce losses Materials and Methods Fertilizer experiments (general) . carbohydrate to yield Nitrogen source, rate and date of application on wheat cultivars O O O O O O O O O O 0 0 Split application of nitrogen on wheat . . Partitioning of organic nitrogen by the wheat plant Results and Discussion Nitrogen source, rate and date of application on wheat cultivars O O O O O O O O O I O 0 Split application of nitrogen on wheat cultivars . sumry O O O O O O O O O O O O O Partitioning of organic nitrogen by the wheat plant The concentration of reduced nitrogen in plant parts at different growth stages . . . . . Weight of plant parts per shoot Total accumulation of RN per plant part Total RN accumulation within culms . Discussion . . . . . . . . . . . . Notes on protein content per head, on a per culm basis . iii Page NN OOQWCDNU‘ID H . 13 . 14 . 15 . 15 . 19 21 25 . 26 . 26 27 29 29 . 31 34 Summary and Conclusions . Appendix 1 Appendix 2a . Appendix 2b . Appendix 3a . Appendix 3b . . . . . . Appendix 4 Appendix 5 . . . References . . . . . iv Page . 35 . 37 . 38 . 39 . 4O 41 . 42 43 . 44 LIST OF FIGURES The yield responses of two wheat cultivars to nitrogen applied on four different dates in E. Lansing . . . . . . . . The mean yields of Ionia in response to two sources of nitrogen at E. Lansing and Saranac . . . . . . . . . . . . . The mean yields of Tecumseh in response to two sources of nitrogen at E. Lansing and Saranac . . . . . . . . . . . The mean yields of four wheat cultivars in response to three rates of applied nitrogen at E. Lansing and Saranac . . Total dry weight per culm of four wheat cultivars at four growth 8 tages I O 0 I O O O O O O O O I O I O O O O O O O O The reduced nitrogen content per culm of four wheat cultivars at four growth stages . . . . . . . . . . . . . . . . . . . . The Z of total plant RN contained in various plant parts . . Page . 20 22 23 24 28 3O 32 INTRODUCTION The increasing cost of nitrogen fertilizer and the possible harm- ful effects of excess nitrogen in ground water are making efficient use of nitrogen by crOps a high priority. Three winter wheat cultivars, Ionia, Yorkstar, and Tecumseh were found to have different yield response patterns to nitrogen fertilizer (17). Through understanding the genetic nature of these differences the characters of high responsiveness and efficient nitrogen utiliza- tion might be more effectively included in wheat breeding programs. This study was initiated to: A) further examine the response pat- terns of wheat to nitrogen fertilization and the factors that affect them, and B) to determine whether restricted nitrogen assimilation or different nitrogen partitioning systems within the cultivars might be related to responsiveness. LITERATURE REVIEW The Importance of Nitroggn to Yields G. W. Cooke in his book "The Control of Soil Fertility" (11), stated that in most agriculture, the nitrogen (N) supply controls the yield of crops that have enough water. F. E. Allison, in "Advances in Agronomy" (2), attributed the large increases in the acre yields of crops, that have occurred in the U.S.A. in the last thirty years, mainly to the increase in application of com- mercial N. He stated that crOps require greater amounts of N than other nutrients, and soils generally supply smaller quantities. Varietal Differences in Response to Nitroggg Varietal differences in yield response patterns under increasing increments of N have been well documented in small grains. Yamada (37) demonstrated responses in rice cultivars ranging from zero to 70% yield increases. Vose (35) in a review article in 1963 stated it was common- place that differential responses to nutrition levels between cultivars occur and cites Lamb and Salter who concluded that wheat cultivars may respond differently to a given fertility level. Mbrphological Response Characters. Investigations at the International Rice Research Institute (IRRI) in the Philippines showed that straw length was important because long strawed cultivars lodged at high nitrogen rates (7). Decard £2.11. (14) 2 3 in a study using paired, near-isogenic lines of durum wheat found that the semi-dwarf gene had no effect on yield. Apparently straw length affected yield only in relation to lodging. The main morphological characters that govern yield increases in small grains are: 1) the number of heads per unit area; 2) the number of seeds per head, and ;3) the weight per seed (7, 25). Yamada (37) described five different yield responses to N in rice, in terms of yield components. One cultivar increased yields under high N rates solely through increasing panicle number per unit area, a second primarily through increases in the seed number per panicle and a third increased both panicle number and seed number per panicle, but to a lesser degree, and achieved yield levels between the first two cultivars. The fourth cultivar increased both panicle number and seeds per panicle as much as the first two cultivars and thus out-yielded both. The last cultivar showed no increase in panicle number or the number of seeds per panicle and achieved no yield increase through added N. This last cultivar had the greatest total and per-day dry matter accumulation rate. In Yamada's study, increasing panicle number caused the greatest yield increase. A good example of the range that exists in tiller number between genotypes is work done by S. Yoshida (7) where rice cul- tivars ranged from thirty to one hundred and twenty-six tillers when the plants were widely spaced and heavily fertilized with N. F. H. McNeal and D. J. Davis (25) showed differences in tillering between nine spring wheat cultivars. "Ceres" increased tiller number 7.5% and 31% between 0, 56 and 135 kg N/ha, while "Lee" showed the greatest increases of 46% and 105%. While increased culm number ac- counted for much of the yield increase in seven cultivars, more than 4 half of the yield increase in "Ceres" and N2211 were due to a greater number of seeds per head. They found little variation in test weight. Seed weight has not been shown to be a major factor but F. H. McNeal £5 31. (23), found that kernel weight and the grain/straw ratio decreased with added N. The Balance of Morphological Characters with Carbohydrate Accumulation Khalifa (20) found that early applications of N on wheat increased the leaf area index (LAI) near the time of ear emergence, and that this increased the leaf area duration (LAD) during grain development. This did not oCcur with applications made at ear emergence. He concluded that the response to early N applications was due to greater amounts of photosynthate produced during grain filling as a result of greater LAD. Baba (4) found that the decrease in the starch content of the leaf sheath and stem, at high N levels, was greater in lowbresponse rice cul- tivars than in high response types. From this, and the facts that (a) there were fewer infertile spikelets per head in high response culti— vars, and; (b) the grain to straw ratio was reduced less in high re- sponse cultivars at high N levels, he concluded that starch accumula- tion and transport to the grain was reduced less in high response cul- tivars. He postulated that either: 1) higher N levels caused greater uptake of N during early growth and resulted in a rapid growth rate which consumed photosynthate and thus depleted carbohydrate reserves in low response cultivars; or 2) there was a greater LAI at high N levels. Low response cultivars, because of their leaf angle, had a greater mu- tual shading of leaves and therefore, less photosynthesis per unit leaf area. There was no reduction of the respiration rate per unit leaf area and therefore, the net accumulation of photosynthate was reduced, 5 lowering the relative yield response. Work at IRRI (7) has shown smaller, more upright leaves to be an important factor in the respon- siveness of rice cultivars. Furthermore, it has been found that roots obtained carbohydrates from the lower leaves of the plant (15). In cultivars where the light extinction coefficient was high there was re- duced photosynthesis with unchanged respiration. The carbohydrate supply to the root was depleted, reducing the plant's nutrient uptake. Thus, responsiveness to N has been found to be dependent upon the rate of N uptake, the LAI, LAD, leaf size and angle, and their inter- active effects upon photosynthesis and respiration. Internal Plant Nitrogen and Its Relationship to Yield Plant nitrogenous constituents, apart from nitrate, contain N al- most exclusively in the reduced form (22). The majority of plant N is contained in proteins to an extent such that multiplication of the plant RN content by the average nitrogen content of protein (100 g protein/ 16 g N) results in a fairly accurate measure of plant protein (5). Other important N containing compounds within the green plant material include free amino acids, nucleic acids, chlorophyll, ATP and NADP (5, 22). Nitrogen in the seed is almost exclusively in proteins (5). There is considerable discussion in the literature about the role of plant nitrate levels, nitrate reductase (NR), nitrate reductase ac- tivity (NRA), the amount of reduced nitrogen (RN) in the plant and the relationship of these with grain yield and grain protein levels. Nitrate reductase is the rate limiting enzyme in the assimilation of nitrate into usable organic form within the plant. It is induced by nitrate. However, Decard 2E.él° (14), found all correlations between leaf nitrate and leaf NR to be near zero, thus showing that there were 6 factors besides the levels of nitrate controlling the amount of NR in the plant. Deckard (l4) concluded that the total plant RN was largely depen- dent upon NRA and a number of researchers have found positive correla- tions between the NRA (prior to or at anthesis) and grain yield (1, 13, 16). However, this also is not consistent; Rao gt 2A- (29), in a study of two cultivars, found that while one cultivar had a 70% higher in ‘yiggg NRA, there was little in ziyg difference in their capacities to reduce nitrate. Researchers in rice have shown a high correlation between N in the top growth in the thirty days prior to flowering and grain yield. This effect seemed to be caused by increased photosynthetic activity (7). Abrol and Nair (1) stated that there is a linear relationship be- tween N content or supply with; a) leaf expansion rate; b) total leaf area development; c) tiller numbers; d) the number of spikelets ini- tiated per head, and; e) photosynthetic activity. These factors are important to crop yield and so available RN in the plant must be related to yield. However, all of these qualities can vary between cultivars. They can be affected by conditions such as soil moisture, light inten- sity and the level of other nutrients in the soil. Factors such as leaf size, leaf angle and LAI can alter the photosynthesis/respiration ratio, increasing or reducing the net accumulation rate. Thus it is clear that crop yield cannot be simply and directly correlated with the total RN content of the plant. 7 Nitrogen Uptake and Partitioning in Relationship to Yield Ashley gt 31. (3) found that nitrate was reduced in both the roots and shoots of wheat seedlings and that the shoots had lower nitrate/RN ratios at all times. McNeal gt 31. (23) found that the levels of N in wheat roots were low throughout the plant's life. He concluded that there was rapid translocation of N from root to shoot. Huffaker and Rains (27) stated that nitrate uptake in wheat showed saturation kinet- ics, was closely coupled to metabolism with ATP or other high energy in- termediates and a permease may have been involved in the transport system. Using two wheat cultivars, Daigger g; 31. (12), found that while yield response to N varied between locations and years, plant N content was influenced only by the amount of applied N and the time of sampling. Yamada (37) reported that low response cultivars of rice tended to take up more nutrients at low soil fertility levels than high response cultivars. He found that the Optimum.concentration of N in nutrient solution for Japonic cultivars caused "striking retardation" of root growth in Indica cultivars, which required a much lower concentration of N for optimum growth. Chevalier and Schrader (8) showed that even among genotypes of maize with similar dry weight there were significant differences in ni- trate uptake and suggested this was possibly related to differences in root dry weight. They showed that there were significant differences between inbred lines in the amount of dry matter produced per gram of nitrate absorbed. N assimilation may be influenced by temperature. Peterson and Shrader (28) showed that RN in oat leaves was maximized by different day/night temperature regimes in different cultivars. They found that 8 high day temperatures depressed RN accumulation in all cultivars, but this effect was more pronounced in some cultivars. The cultivar least affected had the greatest yield. Thus, there are differences in N uptake and assimilation between cultivars. However, Rao_g£.§l. (29), concluded that cultivars differing in various production parameters do not necessarily absorb different amounts of soil N. The Nitrogen Uptake Patterns It has been postulated that different N uptake patterns affect a plant's growth habit (4) and thus, yield and grain protein. McNeal 32 £1. (23), found that leaf N in five wheat cultivars was maximized at flowering but the total N in top growth increased to matur- ity. Abrol and Nair (1) concluded from literature that wheat cultivars may or may not absorb N after anthesis depending on their genetic make- up. Daigger ggngl. (12), noted that the rate of uptake of N was not a steady system. They found that accumulation of N and dry matter was rapid in the month prior to anthesis and that maximum plant N content occurred at anthesis. They reported net plant N losses, post anthesis, of 25 to 80 kg/ha, depending on the amount of N applied. With possible losses of this magnitude, it would be difficult to determine how much N was taken up after anthesis. Nitrggen Partitioning There are different partitioning systems and translocation patterns between grain genotypes (8, 26). However, there have been no reports to date of a specific partitioning pattern correlated to yield responsive- ness 0 9 The grain protein percent seems to be more related to the grain/ straw ratio than with: 1) N in grain (kg/ha); 2) N in top growth or; 3) differences between cultivars in translocation of N. Date of N Application There is considerable disagreement in the literature over the best time to apply top dressings of N on winter wheat. Some farmers in Michigan apply top dressings in late fall when the ground is frozen, to ensure that N is available as soon as growth starts in the spring. Stanford and Hunter (32) in Pennsylvania, Hunter g£.§l. (l9), and Clapp (10) in North Carolina, have all conducted experiments that showed no difference between fall and spring topdressings, or a slight yield advantage for fall applications. Clapp found that this did not hold true on sandy soils. On the other hand, Welch gg_§l. (36), in a three year study, found that spring topdressings increased yields over fall applications in most cases. Cooke (11) stated that almost all of the experiments done in Britain showed that for winter cereals, N given in the autumn was gen- erally less effective than the same amount in spring. Vitosh and Warncke (34) stated that: 1) spring applications of N in Michigan were usually more efficient than fall applications, espec- ially on sandy soils and on poorly drained fine textured soils; 2) it was best to avoid topdressings on frozen soils with slopes greater than 3%, and; 3) March and April were the best months for N applications. Losses of Applied Fertilizer Nitrate, nitrite and ammonium constitute no more than 2% of the total soil N, but can be regarded agronomically as an important fraction 10 since they are the major forms of N that are taken up by plants and from which soil N losses occur (9). Allison (2) concluded that real losses of applied N were in the range of 5 to 25% of the fertilizer applied. He further stated that the largest losses of N were due to leaching of nitrate and nitrite in the fall and spring. As regards the quantification of leaching, he cited Wallace and Smith (1954) who found that when N03 was added to the surface of a 2 foot column of loam soil at field capacity, approximately 10 inches of water were needed to leach 50% of the added N from the soil, and 16 inches to remove 98%. He stated that the major form of gaseous loss of N was the denitrification of nitrate and nitrite. These conclusions as to the major sources of soil N loss were gen- erally supported by Cooke (11) but he described larger losses of applied N, ranging from 25 to 60%. He also described losses of applied N due to volatilization as high as 15%. He bases these conclusions on lysim- eter studies which Allison questioned because they could not account for immobilized N. When corn was grown on irrigated sandy soils, nitrate loss was cor- related with water loss (r = .95) (31). Twenty five to 80 kg N/ha may be lost from the crop between anthe- sis and maturity and that this may be affecting computation of crop re- covery rates based on the N content of the crop at maturity (12). Vol- italization losses of N from senescing leaves have been reported (18, 33). Soybeans were shown to lose 45 kg N/ha during a growing season in this manner (33). Denitrification may occur rapidly under conditions of high soil moisture in the presence of rapidly decomposing organic matter. On acid ll soils (pH < 6.5) gaseous losses through the chemical dismutation of nitrite accounted for losses of up to two-thirds of the N in fertili- zers releasing ammonium or ammonia. Volatilization losses of ammonium from surface applied ammonium salts were only likely on alkaline soils (9). Splitting N Applications to Reduce Losses Because losses of applied N can occur so rapidly, splitting the applications of N fertilizer should reduce the amount of N susceptible to loss at any one time. G. W. Cooke (11) cited work done in Britain which showed that when nitrogen was applied at rates below 78 kg N/ha, in years when there was heavy winter precipitation, single applications in spring gave the best results. However, in years of normal or dry winters, when applied rates of N exceeded 112 kg N/ha equally split topdressings applied in fall and March or March and May, were superior to any single applica- tion. He also cited work by Devine and Holmes where split applications (betweel fall and spring) did not increase yields over spring applica- tions, and may actually have increased the loss of applied N. Work done by Boswell gtwgl. (6), showed that split applications of ammonium sulfate on wheat were superior to fall applications, even when a nitrification inhibitor ("N-serve") was applied with the fall treat- ments. On a Cecil sandy loam, split applications were superior to fall applications without the nitrification inhibitor and equal in yield re- sponse when the N.I. was applied with the fall treatments. In general, splitting the N application reduced loss of N from the soil and split applications were superior or equal to a well timed 12 single application. However, spreading the applications out over a longer period of time increased the risk of N loss. MATERIALS AND METHODS The Fertilizer Experiments The experiment on source, rate, date and cultivar and the split application experiment were conducted in the field at two locations, the Michigan State University farm at E. Lansing and the Carl Stuart farm near Saranac, Michigan. The study of the organic N content of different cultivars was conducted at E. Lansing. All experiments at East Lansing were planted on October 4, 1977. The soil was primarily a Selfridge sand with a 2—6% slope. There was also a small area of Capac loam of 0-3% slope. The dates of the fer- tilizer applications and growth stages at the time of application were as follows: December 1977, winter dormant; April 10, 1978, growth ini- tiation; May 5, 1978, growth initiation plus three weeks; May 27, 1978, fully tillered. All experiments at Saranac were planted on October 6, 1977. The soil was predominantly a Matherton loam of 2-6% slope, the remainder being an Ionia loam of 2-6% slope. The dates of the fertilizer appli- cations and growth stages at the time of application were as follows: December 1977, winter dormant; April 16, 1978, growth initiation; May 7, 1978, growth initiation plus three weeks; May 28, 1978, fully til- lered. At both locations, the wheat was planted after soybeans which were plowed down in the last week of July, 1977. The seed was planted with 13 14 a 4-row drill, at the rate of 60 g/plot (100 kg/ha). The soil was fer- tilized with 560 kg/ha 0-25-25, broadcast at time of planting. All plots were 1.22 x 5.49 m and cut back to 1.22 x 3.66 m for harvest. Each plot contained 4 rows of plants and received one treatment. All fertilizer treatments were made by hand, except for the 0-25-25 at planting. At the time of the December applications,there was no snow cover at either location, but the ground was frozen and remained so until the spring thaw. Weeds were controlled with l pt/a (1.45 l/ha) of 2, 4-D, applied at the fully tillered stage, before stem elongation. This treatment was very successful on the East Lansing field, but resulted in poor control at the Saranac location. Nitrogen Source, Rate and Date Application on Wheat Cultivars The effects of source, rate and date of application of N on two cultivars of wheat were examined in a split-split plot randomized block design at East Lansing and Saranac. Dates and cultivars were the first and second main plot factors respectively. A factorial arrangement of treatments was used with three blocks at each location. Two cultivars of Michigan soft white winter wheat (Ionia and Tecumseh) were used because of their differing responses to nitrogen fertilizer. Two types of fertilizer were used; ammonium nitrate (34—0-0) as a nitrogen source, and 19-19-19 as a complete fertilizer. The fertilizers were applied at four different rates (0, 45, 90 and 135 kg N/ha) and the applications were made at four separate growth stages (winter dor— _mant, growth initiation, growth initiation plus three weeks, and fully tillered before stem elongation). 15 When all plots had reached full maturity the border rows of each plot were removed and the two center rows of plants were harvested with a "Hegge" combine. The grain from each plot was dried, recleaned, weighed, and test weight determined. Split Application of Nitrogen on Wheat The effect of applying N in two separate increments was studied in a split-application experiment using four cultivars of soft white winter wheat: Ionia, Yorkstar, Tecumseh and Frankenmuth. The experi- ment was conducted at East Lansing and Saranac as a split-split plot in a randomized complete block design. A factorial arrangement of treat- ments with three blocks was used. Four rates of fertilizer were applied (0, 45, 90, 135 kg N/ha as NH4N03) and there were three "time of application" treatments. These were: 1) Half the fertilizer at spring growth initiation and half at spring growth initiation plus three weeks. 2) Half at spring growth initiation and half at fully tillered. 3) Half at spring growth initiation plus three weeks and half at fully tillered. Harvest and the post harvest treatment of the grain followed the same procedure as previously described. Partitioning of Organic Nitrogen by the Wheat Plant N uptake and distribution through the life cycle of the wheat plant was studied to determine whether there were differences in RN as- similation and partitioning between different response types. 16 The experiment was conducted in East Lansing as a split plot in a randomized complete block design with a factorial arrangement of treat- ments and three blocks. The whole plot factor (A) was the fertilizer and cultivar treatments and the split factor (B) was the plant parts within a plot. Four rates of N were applied to the four cultivars (Ionia, Yorkstar, Tecumseh and Frankenmuth), but because of the generally low response to N (in 1978), only plants that received the two extremes (0 kg N/ha and 135 kg N/ha) were analyzed for organic nitrogen. The nitrogen applica- tion was split over two dates (67.5 kg N/ha at spring growth initiation and 67.5 kg N/ha at growth initiation plus three weeks). This was done to ensure high soil N levels during the early stages of growth as well as after the major portion of the spring run-off had occurred. Whole-plant samples were harvested at growth initiation in the spring, at the fully tillered stage before stem elongation, at anthe- sis and maturity. The respective harvest dates were 4-14-78, 5-20-78, 6-13-78*, 7-22-78. Whole-plant samples were taken only from the center two rows of each plot, to avoid edge effects. The person harvesting the plants selected a uniform foot long section in one of the two center rows, more than 2' from either end. After measuring the section the plants were up-rooted and the soil on the roots removed. Each sample was placed in a pre-labelled paper bag and taken to a cold-storage room (42°F). These samples comprised the "bulk samples". Ten fairly uni- form culms were selected out of each bulk sample, cut up with scissors into their major parts and the crowns washed free of soil. This was *Tecumseh reached anthesis one week before the other cultivars and was harvested on 6-8-78. 17 all done on the day the samples were collected. The entire sample taken at growth initiation was partitioned, because the amount of plant mater- ial was so small. At the growth initiation and fully tillered stages,the plants were partitioned into crowns, "stems" and leaves only. On the last two col- lection dates the plants were partitioned into crowns, stems, lower leaves, flag leaves and heads. The leaves were removed at the base of the blade, the leaf sheaths remaining on the stem. The grain was not separated from the rachis. The plant parts for each plot were placed separately in pre-labelled paper bags and dried at 70°C for four to five days. They were then stored. After all the material had been harvested, cut into sections and dried, each plant part was weighed separately and ground in a Wiley-mill with a 40-mesh screen. This ground material was stored in labelled coin envelopes. Two determinations were made of the organic N content of each plant part from each plot. The ground material was stirred for homogeneity and two identical samples were weighed out to one ten-thousandth of a gram. These weighed samples were put in test tubes, labelled, corked and stored until the analysis was done. The sample sizes taken in the above process were as follows: 1) 20 mg samples were used in testing green leaf tissue because of its expected high protein content. 2) 30 mg samples were used in testing crown and dry leaf tissues. 3) 40 mg samples were used for stemetissue analysis because of its low expected protein content. 18 The analysis for organic N was done using an automated micro- kjeldahl procedure performed on a Technicon Auto-analyserll. The weighed samples were pre-digested by adding 4 ml of the standard diges- tion mixture and then boiling until clear. The samples were allowed to cool, diluted with 6 ml of distilled H20 and stirred on an automatic stirrer. An aliquot of this liquid sample was then poured into an an- alyser cup. Forty such cups were prepared and placed on the analyser at one time. The machine measured only the RN content (Appendix 1). It gave the results as light adsorption peaks on a graph. The RN con- tent was calculated from these peaks by the standard procedure. When all the organic nitrogen concentrations had been calculated, the values for the two determinations on each plant part were averaged to give one means value. 1/ -Description of procedure available from: Technicon Corporation, Tarrytown, NY. RESULTS AND DISCUSSION I. Nitrogen Source, Rate and Date of Application on Wheat Cultivarsi/ Regardless of all other factors, nitrogen increased average yields. There was a strong response to N at Saranac, while at E. Lansing there were no yield increases from applied N above 45 kg/ha. Yields were higher in E. Lansing, but responses to N were lower. This might have been partially due to the higher disease and insect infestations and lower native N fertility at Saranac. In general, this year, yields of both cultivars were five to ten bu/a (350 to 650 kg/ha) lower than av- erage (17). The mean yield of Tecumseh was lower than Ionia at both locations, but both cultivars showed similar response patterns. It ap- peared that there was a difference in the cultivars responses to date of N application. However, this was due to Tecumseh's low base yield in the blocks receiving fertilizer treatments in December (Fig. 1). Both cultivars showed small, similar responses to N applications at all dates at both locations ranging from 45 kg/ha to 370 kg/ha in East Lansing and from 30 to 810 kg/ha at Saranac. In general, the data supported the current recommendations for Michigan on N applications and suggests that there can be benefit from applying N even at the fully tillered stage if the soil was too wet for earlier applications. 1/ -Mean yields for each treatment at both locationsznxagiven in Appendix 2. l9 4400 3900 3800 3700 3600I 3500 34005 3300 3200 3I 00 3000 2900I 2300 ‘HELD (Kg/ha) Figure l. 20 I . mm 0- 2ER0 FERTILIZER Cl . TECUMSEH + . FERTILIZER APPLIED 0+0+ 0+0+ 0+0+ 0+0?’ DECEMBER APRIL I0 MAY 5 MAY 27 The mean yield response of two wheat culti- vars (Ionia and Tecumseh) to nitrogen applied on four different dates in East Lansing. Columns designated with a + represent mean yields averaged over 45, 90 and 135 kg/ha and over two sources (34-0-0 and 19-19-19) L.S.D. .05 for the date x cultivar inter- action = 331 kg/ha. 21 There was a difference in yield in relation to source of N at Saranac. The consistently higher yields of plots that received N from the complete fertilizer (19-19-19) over plots that received the same amount of N from NH4NO3 indicated this was not due to chance. Ionia showed it's usual low response pattern when topdressed with N alone, but had a high response pattern under complete fertilizer topdressings (Figure 2a. and 2b.). At Saranac, the yield of Tecumseh was also higher under complete fertilizer (Figure 3a. and 3b.). Soil tests at Saranac showed 83 kg/ha of phosphorous and 165 kg/ha of potassium and at E. Lansing 83 kg/ha of phosphorous and 340 kg/ha of potassium. With 560 kg/ha of 0-25-25 plowed down at planting, P and K should not have been limiting factors. This data suggests that higher P and K levels could be of benefit to Ionia. Moreover, the increased yields with 19-19-19 in both cultivars, indicate that with the new varieties in use today, and the higher levels of N being used on wheat, higher levels of P and K may be of benefit, or banding of fertilizer may be necessary. Split-Application of Nitrogen on Wheat Cultivarsl/ In this experiment each N application was split over 2 dates. Three combinations of such splits were compared. The different date treatments had no effect on response so only the effects of the total rate of N (45, 90, 135 kg/ha) applied in this fashion are considered in Figures 4a. and 4b. All cultivars showed a significant response to applied N at Saranac (Figure 4b.). In E. Lansing, (Figure 4a.) increasing rates of applied N caused yield increases in Ionia and Frankenmuth only. 1/ -Mean yields for both locations are shown in Appendix 3. ELIJANSHQG 4200 4I00 YIELD 4000 (”3"“)3900 3800 3700 3600 Figure 2a 0 games 4I00 4000 3900 YIELD 380° (Kg/ho) 3700 3600 3300 3400 3!!) Figure 2b Figures 2a 0 22 I = NITROGEN APPLIED As I9-l9-I9 CI . NITROGEN APPLIED As NH4NO3 45 90 I35 RATE OF N APPLIEDIKq/ha) and 2b. The mean yields of the wheat cultivar Ionia in response to rates_of nitrogen applied as NH4N03 and 19-19-19 at two locations. Results are averaged over dates of application. The difference between sources at Saranac is significant at the .05 level. 23 E.LANSING I-N APPLIED As I9-I9-I9 El . N APPLIED As NH4NO3ONLY 3600 (Kg/hol34oo 33 3200 0 45 90 I35 Figure 3a RATE OF N APPLIED (Kg/ho) SARANAC 330 3400 3300 3200 YIELD (qu ho ) 3' 00 3000 2900 2000 2700 2600 2300 0 45 90 I35 Figure 3b RATE OF N APPLIED ‘Kfl/ ho) Figures 3a and 3b. The mean yields of the wheat cultivar Tecumseh in response to rates of nitrogen applied as NH4N03 and 19-19-19 at two loca- tions. Results are averaged over dates of application. The differences between sources at Saranac is significant at the .05 level 24 4200 E. LANSING 4°00 FRANKENMUTH 3800 5 Y0RIzqzmmzw 4. 04 4042. ner: 4883 2 .444 .444 .444 .444 .444 600 490 255.44 11... 0\0 Ofi GO. 4643.. oer: an amoeomo z «o .90 .444 .44m .444 .444 .444 99424 442.... Sim... E43 4:6 :26 4.524 4.54 rm>4uaao mam oouoom «wuma «mung one .4 3uaso no 04mm 2 mo mama Hzmszmme ZOHBwua=o mo mama 2 mo Mama unamHMm u< Am 42 Appendix 4 The RN concentration in Plant Parts of four Winter Wheat Cultivars at four growth Stagesj over two levels of N fertility. Growth Stage Fertilizer Rate and 0 kg N/ha 135 kg N/ha Plant Part Cultivar* Cultivar* I Y T F I Y T F Z RN Z RN Growth Initiation: crown 3.95 4.06 4.25 4.04 4.02 4.06 4.44 3.84 "stem" 4.04 4.42 4.13 4.38 4.00 4.34 4.15 4.33 leaves 4.30 4.34 4.42 4.65 4.32 4.62 4.63 4.54 Fertilizer applied here Fully Tillered: crown 2.41 2.12 2.16 2.33 3.04 3.03 2.61 2.92 "stem" 3.36 2.96 2.73 3.29 3.75 4.01 3.69 3.80 leaves 4.60 5.06 4.66 5.27 5.31 5.54 5.50 5.56 Anthesis: crown 1.30 1.00 1.00 1.00 1.73 1.60 1.40 1.60 lower leaves 3.59 3.24 3.30 3.26 3.77 3.63 3.54 3.84 flag leaves 4.79 4.52 4.69 4.47 4.97 4.89 5.25 5.20 head 2.01 1.77 1.78 1.86 1.94 1.87 1.91 2.00 stems 0.98 0.95 1.04 0.88 1.13 1.22 1.41 1.20 Maturitx: crown 0.47 0.40 0.48 0.39 0.50 0.53 0.45 0.51 lower leaves 0.83 1.38 1.05 1.07 1.62 1.90 1.68 1.96 flag leaves 0.95 1.35 1.08 1.13 1.32 1.80 1.67 1.65 head 1.62 1.74 2.09 1.76 2.24 2.08 2.47 1.93 stems 0.26 0.33 0.31 0.29 0.35 0.43 0.41 0.37 * I = Ionia Y a Yorkstar T = Tecumseh F = Frankenmuth Appendix 5 Dry Weight of Plant Parts of four Winter Wheat Cultivars at four growth Stages and two levels of N fertilitx. Growth Stage Fertilizer Rate and 0 kg N/ha 0 kg N/ha Plant Part Cultivar* Cultivar* I Y T F I Y T F Dry Wt. (3) Dry Wt. (g) Growth Initiation**: crown 0.039 0.033 0.029 0.025 0.034 0.026 0.029 0.038 stems 0.040 0.038 0.046 0.032 0.049 0.038 0.041 0.041 leaves 0.150 0.127 0.089 0.105 0.147 0.079 0.150 0.124 Fertilizer applied here Fullx Tillered: crown 0.021 0.023 0.019 0.032 0.030 0.377 0.176 0.026 stems 0.129 0.138 0.136 0.141 0.144 0.140 0.126 0.147 leaves 0.188 0.184 0.143 0.202 0.194 0.224 0.135 0.217 Anthesis: crown 0.065 0.063 0.053 0.056 0.054 0.063 0.048 0.055 lower leaves 0.262 0.265 0.143 0.225 0.307 0.339 0.151 0.296 flag leaf 0.142 0.131 0.076 0.106 0.159 0.172 0.098 0.155 head 0.354 0.282 0.233 0.345 0.368 0.403 0.231 0.367 stems 1.371 1.201 0.754 1.304 1.416 1.263 0.758 1.233 Maturitz: crown 0.142 0.161 0.086 0.096 0.079 0.082 0.121 0.131 lower leaves 0.137 0.154 0.089 0.159 0.138 0.176 0.096 0.144 flag leaves 0.067 0.085 0.052 0.071 0.082 0.093 0.077 0.069 head 1.748 1.711 1.240 1.899 1.711 1.842 1.291 1.839 stems 1.106 0.888 0.803 0.853 1.082 0.937 0.737 0.884 * I = Ionia Y = Yorkstar T = Tecumseh F = Frankenmuth ** The weights for growth initiation are representative of the propor- tional weights of the plant parts but cannot be used for comparisons with other growth stages. 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International Rice Comm. News letter FvoOo 8:14-19. MICHIGAN STATE UNIV. LIBRaRIEs WWI"U".“IHIIIIWWIWIW[HII‘IHIWHI 31293100647837