AN ABSTRACT OF THE THESIS OF BRENT C. SUNDERLAGE, for the Master of Science degree in Plant, Soil, and Agricultural Systems, presented on March 8, 2017, at Southern Illinois University Carbondale. TITLE: LATE APPLICATION NITROGEN ON CORN IN SOUTHERN ILLINOIS AND SOIL PROPERTIES AFFECTING AMMONIA VOLATILIZATION FROM UREA FERTILIZER MAJOR PROFESSOR: Dr. Rachel L. Cook In corn (Zea mays L.) production systems, typical nitrogen fertilization occurs either before planting or after crop emergence, as late as the V6 stage. Since the majority of nitrogen uptake does not occur until V10 through R1, delaying nitrogen fertilization until V10 may reduce potential for early season soil N transformations and losses, while sustaining crop yields. A two-year study, conducted across three southern Illinois locations, evaluated the effects of various late sidedress nitrogen applications and enhanced efficiency fertilizers on corn yield and residual mineral soil N. The various nitrogen treatments compared: rates from 0-224 kg N ha-1; sources of urea and 32% UAN, with and without urease inhibitors 0.09% N-(n-butyl) thiophosphoric triamide (NBPT) as Agrotain® Ultra (AT) and 0.06% NBPT + 0.02% N-(n-propyl) thiophosphoric triamide (NPPT) as Limus® (L), and polymer-coated urea (ESN®); application timings at planting, V6, V10, and VT; placement either dribble applied, broadcasted, or injected. Across sites and years, late (V10) nitrogen split applications generally resulted in corn yields greater than or equal to the same total nitrogen rate applied at planting. Most late N treatment differences varied between sites and years, but 56 kg N ha-1 as broadcasted UAN at planting with 112 kg N ha-1 as broadcasted urea, either with or without AT or L at V10 were on average highest yielding treatments among sites in both years, with 16% greater yield than 168 kg N ha-1 as broadcasted UAN at planting. Urease inhibitors did not enhance yield in most instances, likely due to sufficient incorporating rainfall shortly after application. The effects of urease inhibitors used with late-application nitrogen on corn yield and actual ammonia volatilization remained ambiguous. Residual soil mineral nitrogen concentrations between 0-30 cm after harvest in the late nitrogen treatments did not elicit water quality concerns. Furthermore, ammonia volatilization from surface applied urea is controlled by many interrelated soil properties as well as environmental conditions. However, conclusions about the influence of soil properties on ammonia volatilization differ according to geographies and are not well established across a wide range of soil types. A laboratory soil incubation experiment measured the effects of soil properties on ammonia volatilization over 7 days from surface-applied urea and the efficacy of three urease inhibitors: Agrotain® Ultra (AT) as 0.09% NBPT, Limus® (L) as 0.06% NBPT + 0.02% NPPT, and NutriSphere-N® (NS) 30% calcium salt of maleic-itaconic copolymer among 83 soil surface samples from across the United States with a wide range of soil properties. The soil properties evaluated were: total exchange capacity, 1:1 CaCl2 pH, organic matter, buffering capacity, clay content, and urease activity. In Urea (R2 = 0.69) and Urea + NS (R2 = 0.62) models, total exchange capacity, clay, and buffering capacity significantly reduced ammonia volatilization, and organic matter significantly increased ammonia volatilization, while 1:1 CaCl2 pH and urease activity were non-significant. Clay, organic matter, and buffering capacity were correlated to total exchange capacity. Total exchange capacity was the strongest predictor and best consolidated variable to predict N loss of urea. In Urea + AT (R2 = 0.54) and Urea + L (R2 = 0.67) models, ammonia volatilization was significantly reduced at lower 1:1 CaCl2 pH and total exchange capacity, and all other soil properties were non-significant. The NBPT in Urea + AT and Urea + L likely decayed more rapidly under acidic soil conditions, resulting reduced NBPT efficacy and greater N loss at lower pH. Urea + AT and Urea + L reduced volatilization significantly by 18.2 percentage points compared to Urea or Urea + NS, and there were no significant differences between Urea + AT and Urea + L (α = 0.05). On average, NutriSphere-N® did not reduce volatilization.

Selection of optimum nitrogen (N) fertilizer timing, rate, and placement strategies by corn (Zea mays L.) producers are among their most important annual management decisions. Much research has been conducted on pre-plant, at-plant, and one or more sidedress timings for N application to corn, but few public-sector studies employ modern technological approaches for N placement in their experimental designs. Research gaps on optimum placements for at-plant N systems are especially acute when N banding quantity exceeds 20% of the intended season-long N rate. Previous sidedress research has rarely utilized modern N placement tools with high clearance delivery devices for early and late in-season sidedress timings when >50% of the season-long N rate was already applied at planting. Therefore, this 2017 and 2018 Indiana-based field research addressed three questions i) are corn planters that deliver 50% to 100% of a full-season N rate at traditional or alternate band placements capable of matching or exceeding grain yields achieved by lower starter fertilizer N rates, ii) what is the impact of split N management on grain yield and/or N fertilizer recovery efficiency (NRE) when ≥50% of the total N rate is supplied at-plant, and iii) do alternate sidedress N placements (i.e. soil-surface streaming versus injection versus broadcast at multiple timings) in split-N sidedress applications influence grain yield and aboveground plant recovery of N fertilizer?<p></p> <p>To evaluate the consequences of moderate to high N rates banded at planting, urea-ammonium nitrate (UAN) was coulter-banded with a prototype Deere DB20 row-crop planter as close as 5cm x 5cm (5x5) (distance from soil surface x distance from seed row) to as far as 10x20 at planter applied N rates of 34, 101, and/or 202 kg ha-1. These at-plant applications were followed by a V5 to V6 stage mid-row sidedress application (if required) to achieve a uniform total N rate of 202 kg N ha-1. Analyses were primarily focused on 5x5 and 10x5 starter band positions as these were the only placements represented at the 34 kg N ha-1 rate. In these placement comparisons, 5x5 banding yielded similarly to 10x5 banding in 2017, but increased yield 6.6% (averaged across 34, 101, and 202 kg N ha-1 rates) in 2018. Corn grown in 2018 with at-plant rates of 101 and 202 kg N ha-1 produced grain yields statistically similar to or greater than that obtained with the 34 kg N ha-1 rate (averaged across 5x5 and 10x5 placements). In 2018, the 101 kg N ha-1 rate increased yields by 14.8% and NRE by 18.5 g g-1 compared to banding of 34 kg N ha-1. A secondary analysis included 6 placements (5x5, 5x13, 5x20, 10x5, 10x13, and 10x20) at just the 101 and 202 kg N ha-1 rates. Among these additional placement treatment combinations (averaged across 101 and 202 kg N ha-1 rates), both 5x13 and 10x20 banding reduced grain yield in 2018 by 12.5% and 10.1%, respectively, when compared to 5x5 banding. No yield differences among these 6 at-plant placements were found in 2017. Therefore, moderate to high N rates can be banded safely at-planting with the typically close starter fertilizer placements, but higher NRE and optimum yields can be achieved when a 50:50 split N fertilizer management approach is used.</p> <p>The optimal sidedress experiment targeted placement and/or timing impacts on corn yields and NRE when at-plant N was ≥50% and sidedress N was ≤50% of the total N rate. Single at-plant (AP) applications at total N rates of 26 (Zero), 112 (AP_112) and 224 (AP_224) kg N ha-1 were compared to split applications of 202 kg N ha-1 (with ~55% of total N applied at-plant plus the balance at sidedress). Sidedress N was applied at V5 or V12 timings with surface streamed versus subsurface injection of UAN, or via high-clearance broadcasting of urea at the V8-stage. In nearly every split sidedress approach, apart from the V12 injection treatment in 2017, grain yields and NRE with split-N sidedress responded similarly to AP_224 each year despite the reduced total N rate at 202 kg N ha-1. Both V12 streaming and AP_224 yielded 6.7% more than the V12 injection approach in 2017. The reduced yield in 2017 from late-season injection contributed to the 4.6% grain yield gain for surface-streaming applications (averaged across timings) with no apparent NRE advantage.</p> <p>These responses confirmed that in-season sidedress N placement influenced yield and, in our case, the surface-streaming advantage over injection was most evident at V12 where late vegetative to flowering rainfall was plentiful. Similarly, planter N placement was not influenced by N band depth as much as by N band distance from the seed row where 13 and 20cm distances occasionally decreased yield in 2018. This research provided evidence of modern placement technology impacts at planting and sidedress times where UAN placed near corn seeds in the seed-furrow and/or plants in the row never reduced, and occasionally increased, grain yield and/or N recovery in corn cropping systems.</p> <p> </p>

Feed grain consumption in Virginia and the mid-Atlantic region is more than double the total production. Producing more feed grains in this region could generate more profit for grain growers and lower costs for end-users. Increased feed grain production in this region will necessitate improved corn (Zea mays L.) management techniques and adoption of alternative feed grains such as grain sorghum (Sorghum bicolor L.). In order to achieve our overall objective of increased corn and grain sorghum production in the region, experiments were conducted to assess tools with the ability to increase the efficiency of sidedress nitrogen (N) application for corn and to test the performance of grain sorghum in both full season and double-crop rotations in this region. For the corn studies, seven field experiments were established in 2012-2014 with four replications in a randomized complete block design. Treatments included a complete factorial of four different preplant N rate (0, 45, 90, 134 kg ha-1) with three different approach simulation model-prescribed rates (Virginia Corn Algorithm, Maize-N, Nutrient Expert-Maize) and the standard Virginia yield-goal based approach. No differences in corn yield were found between the different simulation model and preplant N rate, however the prescribed sidedress N rate varied significantly due to the simulation model, preplant N rate and the interaction between them. The nitrogen use efficiency (NUE) was estimated based on partial factor productivity (PFP) of nitrogen. The greatest PFP resulted from use of the Virginia Corn Algorithm (VCA), which produced 68 kg grain kg N-1 compared with 49 kg grain kg N-1 for the yield-goal based approach. While the VCA shows promise as a tool for improving NUE of sidedress applications in corn, more research is needed to validate performance. Soybean (Glycine max L.) is often double-cropped after small grain in the mid-Atlantic region. Growing grain sorghum in this niche in the cropping system instead could result in greater overall feed grain production. In order to assess the performance of grain sorghum as an alternative in common cropping systems, four field experiments were established at the Southern Piedmont Agriculture Research and Extension Center (SPAREC) and Tidewater Agriculture Research and Extension Center (TAREC), near Blackstone and Holland, Virginia, respectively. The experiments were conducted using a split plot design with four replications and fourteen treatments. Main plot was winter small grain crop; either barley (Hordeum vulgare L.), triticale (x Triticosecale.), wheat (Triticum aetivum L.) or winter-fallow and the subplot either soybean or sorghum. In three of four instances, full season sorghum yields were greater than double-cropped sorghum after small grain. At two locations, sorghum yields following triticale were lower than when following barley, possibly indicating an antagonistic or allelopathic effect of triticale. The most profitable cropping system was wheat-soybean based on the price assumptions and measure yields in this experiment. Among the sorghum cropping system, the most profitable system was also wheat-sorghum. Sorghum can be successfully grown in both full-season and double-crop systems and offers good potential to increase feed grain production in this region. / Ph. D.

A necessidade da adubação nitrogenada no milho e as perdas significativas de N que podem ocorrer, tanto do solo, como pela folhagem das plantas, são fatores que elevam os custos de produção. Contudo, com a possibilidade de aplicação do N em cobertura em diferentes estádios fenológicos da cultura do milho e, como o N pode ser perdido na forma de amônia e as plantas apresentam a capacidade de absorver NH3 da atmosfera pela folhagem, torna-se interessante a quantificação dessa via de ganho de N nos agrossistemas em diferentes estádios de desenvolvimento das culturas, com a finalidade de proporcionar maior aproveitamento do nutriente pelas plantas. Nesse contexto, objetivou-se: i) avaliar a época de aplicação da ureia em cobertura no milho que proporcione maior aproveitamento do N do fertilizante e produtividade de grãos; ii) mensurar a absorção foliar de NH3 oriunda da ureia aplicada na superfície do solo em diversos estádios fenológicos do milho, e verificar a correlação entre a quantidade de NH3 absorvida e a área foliar da cultura. O estudo foi desenvolvido no bairro rural de Tanquinho, município de Piracicaba, SP, nas safras 2011/12 e 2012/13. Foram desenvolvidos dois experimentos em campo, em delineamento experimental de blocos ao acaso, com quatro repetições. O solo da área experimental é classificado como Latossolo Vermelho Distrófico, manejado em sistema convencional de preparo do solo. No primeiro experimento foi quantificado o aproveitamento do N do fertilizante pela cultura, a produção de fitomassa seca da parte aérea em diversos estádios fenológicos, bem como a produtividade de grãos, em função dos tratamentos testados, a saber: cinco épocas de aplicação de ureia (140 kg ha-1 de N) em cobertura nos estádios fenológicos V4, V6, V8, V10 e V12, e um controle sem adubação de cobertura. No segundo experimento, foi quantificada a área foliar e a absorção da amônia volatilizada da ureia aplicada em bandejas contendo o mesmo solo da área experimental, para que não fosse exposto ao sistema radicular de plantas de milho, em função de cinco tratamentos (épocas de aplicação - idem ao primeiro experimento). Os resultados foram submetidos à análise de variância (p<=0,05) e à comparação das médias pelo teste de Tukey. Não houve diferença entre os tratamentos quanto ao acúmulo de fitomassa seca da parte aérea em todos os estádios fenológicos avaliados. Do mesmo modo, não houve incremento na produtividade de grãos com a aplicação de N em cobertura em diferentes estádios fenológicos. Por outro lado, a aplicação de N em cobertura nos estádios mais precoces (V4 ou V6) proporcionou maior recuperação do N do fertilizante, chegando a valores de 53 %. Na média das duas safras, o nitrogênio volatilizado da ureia que foi absorvido pelas plantas apresentou valores de 3,4, 5,5, 6,2, 9,0 e 14,8 %, respectivamente, nos estádios V4, V6, V8, V10 e V12; aproximadamente 90 % do N absorvido pela folhagem foram acumulados nas folhas e apenas 10 % nos colmos. Houve alta correlação entre a área foliar e a porcentagem de amônia absorvida pelas folhas (r = 0,93, p<=0,05). Isto ocorreu porque a área foliar representa a superfície de contato da planta com a amônia da atmosfera, confirmando a hipótese de que a maior área foliar reflete em maior absorção foliar percentual de amônia / The need for nitrogen fertilization of corn crop and the significant losses of N that can occur both from soil and plants foliage are factors that increase production costs. However, with the possibility of sidedress application of N at different corn growth stages and considering that N can be lost as ammonia, and that plants have the capacity to uptake NH3 from the atmosphere by the foliage, it is interesting to measure this pathway of N uptake in agricultural systems in different stages of crop development, in order to provide greater N fertilizer recovery by plants. In this context, this study aimed to: i) evaluate the urea sidedress timing in corn that provides the greater N fertilizer recovery and grain yield; ii) measure the foliar uptake of NH3 volatilized from urea applied on the surface at different corn growth stages, and to evaluate the correlation between the amount of NH3 absorbed and corn leaf area. The study was performed in Piracicaba, State of São Paulo, during the growth seasons of 2011/12 and 2012/13. Two field experiments were performed in experimental design of randomized blocks with four replications. The soil of experimental area is classified as Rhodic Haplustox, cultivated under conventional tillage system. In the first experiment, N fertilizer recovery by crop, dry matter yield in different growth stages and grain yield were evaluated as a function of five urea sidedress timing (140 kg ha-1 N), represented by growth stages V4, V6, V8, V10 and V12, and a control without N application. In the second, leaf area was measured and the absorption of volatilized ammonia from urea applied in trays containing the same soil of the experimental area, to avoid that N was exposed to the corn roots, according to five treatments (application times - same as the first experiment). The data were submitted to analysis of variance (p<=0.05) and comparison of means by Tukey test. There was no difference among treatments for dry matter accumulation of shoots in all growth stages. Similarly, there was no increase in grain yield with the N application at different growth stages. However, the N application in the early stages (V4 or V6) provided greater N fertilizer recovery, reaching values of 53 %. In average, the nitrogen volatilized recovered by plants presented values of 3.4, 5.5, 6.2, 9.0 and 14.8 %, respectively, in V4, V6, V8, V10 and V12; approximately 90 % of N absorbed by foliage were retained in the leaves and only 10 % in the stalks. There was a high correlation between leaf area and the percentage of ammonia absorbed by the leaves (r = 0.93, p<=0.05). This occurred because the leaf area is the contact surface of the plant with atmospheric ammonia, confirming the hypothesis that the greater leaf area reflects in greater percentage of leaf ammonia absorption

A necessidade da adubação nitrogenada no milho e as perdas significativas de N que podem ocorrer, tanto do solo, como pela folhagem das plantas, são fatores que elevam os custos de produção. Contudo, com a possibilidade de aplicação do N em cobertura em diferentes estádios fenológicos da cultura do milho e, como o N pode ser perdido na forma de amônia e as plantas apresentam a capacidade de absorver NH3 da atmosfera pela folhagem, torna-se interessante a quantificação dessa via de ganho de N nos agrossistemas em diferentes estádios de desenvolvimento das culturas, com a finalidade de proporcionar maior aproveitamento do nutriente pelas plantas. Nesse contexto, objetivou-se: i) avaliar a época de aplicação da ureia em cobertura no milho que proporcione maior aproveitamento do N do fertilizante e produtividade de grãos; ii) mensurar a absorção foliar de NH3 oriunda da ureia aplicada na superfície do solo em diversos estádios fenológicos do milho, e verificar a correlação entre a quantidade de NH3 absorvida e a área foliar da cultura. O estudo foi desenvolvido no bairro rural de Tanquinho, município de Piracicaba, SP, nas safras 2011/12 e 2012/13. Foram desenvolvidos dois experimentos em campo, em delineamento experimental de blocos ao acaso, com quatro repetições. O solo da área experimental é classificado como Latossolo Vermelho Distrófico, manejado em sistema convencional de preparo do solo. No primeiro experimento foi quantificado o aproveitamento do N do fertilizante pela cultura, a produção de fitomassa seca da parte aérea em diversos estádios fenológicos, bem como a produtividade de grãos, em função dos tratamentos testados, a saber: cinco épocas de aplicação de ureia (140 kg ha-1 de N) em cobertura nos estádios fenológicos V4, V6, V8, V10 e V12, e um controle sem adubação de cobertura. No segundo experimento, foi quantificada a área foliar e a absorção da amônia volatilizada da ureia aplicada em bandejas contendo o mesmo solo da área experimental, para que não fosse exposto ao sistema radicular de plantas de milho, em função de cinco tratamentos (épocas de aplicação - idem ao primeiro experimento). Os resultados foram submetidos à análise de variância (p<=0,05) e à comparação das médias pelo teste de Tukey. Não houve diferença entre os tratamentos quanto ao acúmulo de fitomassa seca da parte aérea em todos os estádios fenológicos avaliados. Do mesmo modo, não houve incremento na produtividade de grãos com a aplicação de N em cobertura em diferentes estádios fenológicos. Por outro lado, a aplicação de N em cobertura nos estádios mais precoces (V4 ou V6) proporcionou maior recuperação do N do fertilizante, chegando a valores de 53 %. Na média das duas safras, o nitrogênio volatilizado da ureia que foi absorvido pelas plantas apresentou valores de 3,4, 5,5, 6,2, 9,0 e 14,8 %, respectivamente, nos estádios V4, V6, V8, V10 e V12; aproximadamente 90 % do N absorvido pela folhagem foram acumulados nas folhas e apenas 10 % nos colmos. Houve alta correlação entre a área foliar e a porcentagem de amônia absorvida pelas folhas (r = 0,93, p<=0,05). Isto ocorreu porque a área foliar representa a superfície de contato da planta com a amônia da atmosfera, confirmando a hipótese de que a maior área foliar reflete em maior absorção foliar percentual de amônia / The need for nitrogen fertilization of corn crop and the significant losses of N that can occur both from soil and plants foliage are factors that increase production costs. However, with the possibility of sidedress application of N at different corn growth stages and considering that N can be lost as ammonia, and that plants have the capacity to uptake NH3 from the atmosphere by the foliage, it is interesting to measure this pathway of N uptake in agricultural systems in different stages of crop development, in order to provide greater N fertilizer recovery by plants. In this context, this study aimed to: i) evaluate the urea sidedress timing in corn that provides the greater N fertilizer recovery and grain yield; ii) measure the foliar uptake of NH3 volatilized from urea applied on the surface at different corn growth stages, and to evaluate the correlation between the amount of NH3 absorbed and corn leaf area. The study was performed in Piracicaba, State of São Paulo, during the growth seasons of 2011/12 and 2012/13. Two field experiments were performed in experimental design of randomized blocks with four replications. The soil of experimental area is classified as Rhodic Haplustox, cultivated under conventional tillage system. In the first experiment, N fertilizer recovery by crop, dry matter yield in different growth stages and grain yield were evaluated as a function of five urea sidedress timing (140 kg ha-1 N), represented by growth stages V4, V6, V8, V10 and V12, and a control without N application. In the second, leaf area was measured and the absorption of volatilized ammonia from urea applied in trays containing the same soil of the experimental area, to avoid that N was exposed to the corn roots, according to five treatments (application times - same as the first experiment). The data were submitted to analysis of variance (p<=0.05) and comparison of means by Tukey test. There was no difference among treatments for dry matter accumulation of shoots in all growth stages. Similarly, there was no increase in grain yield with the N application at different growth stages. However, the N application in the early stages (V4 or V6) provided greater N fertilizer recovery, reaching values of 53 %. In average, the nitrogen volatilized recovered by plants presented values of 3.4, 5.5, 6.2, 9.0 and 14.8 %, respectively, in V4, V6, V8, V10 and V12; approximately 90 % of N absorbed by foliage were retained in the leaves and only 10 % in the stalks. There was a high correlation between leaf area and the percentage of ammonia absorbed by the leaves (r = 0.93, p<=0.05). This occurred because the leaf area is the contact surface of the plant with atmospheric ammonia, confirming the hypothesis that the greater leaf area reflects in greater percentage of leaf ammonia absorption

Cereal rye (CR), the most common and effective nitrogen (N) scavenging cover crop option in the Midwest, is often utilized in cropping systems to reduce nitrate loss for environmental benefits. To increase environmental efficiency in Midwest corn cropping systems, we must increase the overall adoption of CR. However, due to the yield reduction potential (6%) for corn planted after CR termination, CR is primarily recommended before soybean. To increase CR adoption, we must develop adaptive fertilizer management practices that achieve competitive grain yields relative to cropping systems where CR is not adopted. Therefore, the objectives of this study are to determine (1) the effect of CR and starter nitrogen rate on corn growth and nitrogen content. (2) the optimum starter nitrogen rate to achieve agronomic optimum corn yield following CR. (3) the impact of phosphorus (P) at starter on plant growth, nitrogen content, and yield with the inclusion of CR. For our study, five starter N rates were applied in a 5x5 cm band to both CR and non-CR plots, concentrations ranged from 0-84 kg N ha^-1in 28 kg N ha^-1 intervals. Total N applied was the same for each treatment, relative to its location, and was split between starter N at planting and sidedress applied at growth stage V6 relatively. Although CR termination took place at least two weeks before planting, CR decreased corn grain yield at one of three locations by an average of 8%, nitrogen recovery efficiency (NRE) by 27%, and R6 total N content by 23%, relative to the conventional control (non-CR 0N), when no starter N was applied. At one of three locations, starter N rates of 56 kg N ha^-1, 56 kg N ha^-1plus 17 kg P ha^-1, and 84 kg N ha^-1 increased corn grain yield, in CR plots, and 56 kg N ha^-1 plus 17 kg P ha^-1 increased corn grain yield in non-CR plots. Phosphorus increased corn grain N content at growth stage R6 in one of three locations and did not impact corn grain yield at all locations. We conclude that the inclusion of starter N at planting has the potential to increase agronomic productivity in CR corn cropping systems in soil environments with a high capacity to mineralize soil N. However, further research is required to refine our starter N results to find an optimum starter N rate to apply before planting corn following CR.