Thesis (Master of Agriculture)--Cape Peninsula University of Technology, 2020 / Grain yield and its components are very important and complicated in barley (Hordeum vulgare L.) and are highly influenced by environmental factors and agronomic management practices. For 2018 growing season, a study was designed under rainfed conditions to evaluate the effects of nitrogen (N) fertilizer rate (0, 10, 20, 30 and 40 kg ha-1 of N) and planting density (120, 140, 160, and 180 to 200 seeds m-2) on the agronomic performance of three barley cultivars (Elim, Hessekwa and S16). A randomized complete block design with 3 replications was used. Combined analysis of variance showed significant (p<0.1) differences among cultivars, N rates and planting densities. The main objective of this study was to determine the effects of planting density and different fertilizer application strategies on barley grain yield and quality. The results showed that biggest increases on yield and yield components were observed at 180 seeds m-2 and 80kg ha-1 N rate. Higher N rates generally reduced kernel size. Kernel size was both increased and decreased by increasing planting density as well as N rate. Increasing planting density from 180 to 200 seeds m–2 generally provided slight reductions in grain N concentration and reduced kernel size. The three cultivars expressed a significant effect on kernel plumpness and N content of grain. The most beneficial agronomic practices for malting barley production in Western Cape were application of N fertilizer at optimum rate depending on cultivar, locality and rainfall and planting seeds at a rate of 160-180 seeds m-2 depending on cultivar. A planting density of 160-180 seeds m-2 at a rate of 80 kg N ha-1 is recommended for planting barley under dry land in the Western Cape.

The simple effects of nitrogen rates, fungicide application, and varietal responses on wheat yield and quality have been studied individually, but interactions among the inputs are less well understood. Traditionally, increased nitrogen rates have led to higher risk of lodging and disease severity (Roth and Marshall, 1987), but it has been found that fungicides can be used to delay the onset of disease (Gooding et al. 1999). Similarly, yield responses to application of a fungicide may be affected by available nitrogen (Olesen et al., 2003). Wheat quality parameters such as protein, test weight, and alveograph parameters may also be affected by different management systems. Recent Ontario research shows interactions between fungicide and wheat varieties, even in the absence of disease, but the relationships are poorly understood. Current field crop recommendations would be improved by knowledge of interactions between inputs in more intensive management systems. Field experiments were established on nine farm fields in southwestern Ontario to investigate possible interactions among nitrogen rates, fungicides, and varieties. Eight fungicide timing combinations were applied as splits on three N rate blocks (100, 135, and 170 kg ha-1), applied across variety strips (between three and seven) in a split-strip-plot design with three replicates. Measurements included leaf disease severity, fusarium head blight incidence and severity and mycotoxin concentrations, grain yield and yield components, protein, test weight, and alveograph parameters. An economic analysis was performed on the combinations of treatment variables toward the development of more comprehensive recommendations. Interaction between N application rate and fungicide application resulted in greater yield gains with increased N when fungicides were used. Grain protein concentration increased at higher N application rates. Revenue net of the variable costs examined was not significantly affected by N rate alone, while effect of fungicide application varied with site. / Agricultural Adaptation Council, Grain Farmers of Ontario

Four corn (Zea mays) hybrid types at three plant densities and two nitrogen rates were evaluated for forage yield, forage quality and ensilage quality. The four hybrid types over the first two year of the study included nutri-dense, waxy, leafy, and dualpurpose, the third year a second dual purpose hybrid was added; while the three target plant densities were 54 000, 68 000, and 81 000 plants per hectare; and the nitrogen rates were 134 and 224 kilograms per hectare. The dual-purpose hybrid consistently had high forage yields compared with the other types. When averaged over nitrogen rate and hybrid type, the two highest plant densities typically had higher yields. Across all hybrids nitrogen had no effect on forage yield when averaged across plant density. The leafy hybrid had a lower harvest index than other hybrid types indicating that leaves accounted for much of the harvested weight. Hybrids were examined both at harvest (green chop) and after ensiling for protein and digestibility. Higher nitrogen rates increased crude protein when averaged over all hybrids and plant densities. Dual purpose and waxy hybrid types typically had the lowest acid detergent fiber (ADF) and neutral detergent fiber (NDF) and the highest relative feed values (RFV); while the nutri-dense and leafy hybrids typically had the highest ADF and NDF values and lowest RFV.

Master of Science / Department of Agronomy / Johanna A. Dille / Corn yield potential is limited by water deficit stress and limited soil nitrogen. Field and greenhouse experiments were conducted near Manhattan, KS in 2005 and 2006. The field experiment evaluated the influence of nitrogen (N) rate and increasing Palmer amaranth (PA) density grown alone and in competition with corn in two moisture environments. In 2006 the dryland environment was very drought stressed, while 2005 had more intermediate conditions. Weed-free corn yields were approximately half in dryland environments compared to the irrigated environment across years. Increasing PA density increased corn yield loss similarly in both 2005 environments and in 2006 dryland environment across all N rates. In the 2006 irrigated environment corn yield loss was increased by decreasing N rate and increasing PA density. Maximum predicted yield loss at high PA densities in both 2005 environments was 20-54% while in 2006 dryland environment, maximum yield loss was 95% and in the irrigated environment was 62%. In general, soil moisture environment was more critical than N rate or PA density when determining potential corn yield. In the greenhouse study a factorial arrangement of two irrigation methods and five crop-weed combinations (corn, PA, GF, corn/PA, and corn/GF) was established with two replications and three runs conducted. Two plants were grown in 25.4 cm diameter PVC pipe cut into 91.5 cm lengths. Irrigation application method included a surface and subsurface application. Plants were harvested at the V10 corn growth stage. No differences were detected between irrigation methods with respect to above- or below ground biomass production. Corn aboveground biomass was decreased by the presence of corn or PA but not GF. Below ground biomass information was presented as column totals because species could not be separated. There was no impact on root to shoot ratio, total below ground biomass, rooting depth, or root area across the crop-weed combinations except for the GF monoculture columns which were lower than all other crop-weed combinations. Future research needs to examine the light interception of corn and PA when grown at different N rates along with examining the influence of surface and subsurface irrigation practices on crop weed interactions and weed seed germination in a field setting.

Current Virginia nitrogen (N) fertilizer recommendations do not include site-specific estimates of N supply from cover crops (CCs) or soil organic matter (SOM). Recent research successfully predicted the contribution of N from SOM and CCs to corn (Zea mays L.) in Pennsylvania. The objective of this work was to validate the biophysical model developed in Pennsylvania under Virginia conditions and to evaluate the decomposition rates of different surface-applied CC residues and the relationship between their chemical composition and decomposition rate. For the first objective, 83 N response trials were conducted in different regions of Virginia across 9 years using a randomized complete block design with four replications. The model was able to explain 47% and 15% of variability in unfertilized corn yield (RMSE = 1.6 Mg ha-1) and economical optimum N rate (EONR) (RMSE = 30 kg N ha-1) respectively. Efforts to improve the model by adding economically unresponsive sites improved the model performance to explain 45% of the variability in EONR. For the second objective, a lab incubation was performed to compare carbon (C) and N mineralization from four different CCs {Cereal Rye (CR), Hairy vetch (HV), Crimson clover (Cc) and Rapeseed (R)} on a sandy loam soil. Destructive sampling was performed at 6 different sampling dates – 3, 7, 14, 28, 56 and 112 days. ANOVA test revealed that the effects of CC species, incubation days and their interaction had a significant effect on mass decomposed, plant biochemical composition and net N mineralization. Variation in mass loss was positively related to lignin content for all the CCs while it was moderately correlated to C:N ratio for CR and R and weakly to HV and Cc. Biomass loss and N release was highest in HV followed by Cc, R and CR. Net N mineralization was highest in HV followed by R, Cc and CR amended soils. / Master of Science / Current Virginia nitrogen (N) fertilizer recommendations do not include site-specific estimates of N supply from cover crops or soil organic matter, both of which can influence crop N need. Recent research successfully predicted the contribution of N from cover crops and soil to corn (Zea mays L.) in Pennsylvania. The objectives of this work were to validate the biophysical model developed in Pennsylvania under Virginia conditions and to evaluate the decomposition rates of different surface-applied cover crop residues and the relationship between their chemical composition and decomposition rate. The Pennsylvania-developed model was able to successfully estimate the economical optimum N rate for corn and predict the yield of unfertilized corn. Corn yield did not increase with increasing N rates in some fields. When these sites were omitted, the accuracy of the model improved. For the second objective, a lab incubation study was performed comparing C and N released from Cereal Rye (CR), Hairy vetch (HV), Crimson clover (Cc) and Rapeseed (R)} on a sandy loam soil. Destructive sampling was performed at 6 different sampling dates – 3, 7, 14, 28, 56 and 112 days. Variation in mass loss was positively related to lignin content for all the cover crops while it was moderately correlated to C:N ratio for CR and R and weakly to HV and Cc. Biomass loss and N release was highest in HV followed by Cc, R and CR.

Orientador: Adalton Mazetti Fernandes / Resumo: A otimização do manejo da adubação nitrogenada com fornecimento do nitrogênio (N) no período de maior demanda pelas plantas pode ser uma estratégia para maximizar a produtividade e a qualidade de tubérculos na cultura da batata (Solanum tuberosum L.). Dessa forma, objetivou-se com este trabalho avaliar a produtividade e a qualidade físico-química e nutricional dos tubérculos das cultivares de batata Agata e Markies submetidas a diferentes formas de manejo da adubação nitrogenada tradicional combinada com a aplicação de doses de N na fase de enchimento de tubérculos. Foram conduzidos quatro experimentos, com as cultivares Agata e Markies durante a safra de inverno dos anos de 2017 e 2018. A área de 2018 não foi a mesma do ano anterior, e ambos experimentos localizavam-se em áreas comerciais de produção de batata em Botucatu-SP. O delineamento experimental adotado em todos experimentos foi em blocos ao acaso com esquema fatorial 4 x 4, com quatro repetições. As formas de manejo da adubação nitrogenada tradicional foram: M1 = 160 kg ha-1 de N no plantio; M2 = 80 kg ha-1 de N no plantio; M3 = 40 kg ha-1 de N no plantio e 120 kg ha-1 de N na amontoa; M4 = 80 kg ha-1 de N no plantio e 80 kg ha-1 de N na amontoa, combinadas com as doses de 0, 20, 40 e 80 kg ha-1 de N aplicadas na fase de enchimento dos tubérculos. As formas de manejo da adubação nitrogenada tradicional combinadas com as doses de N na fase de enchimento de tubérculos, não causaram deficiência de N nas plantas de bata... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Optimizing the management of nitrogen (N) fertilization with supply of N in the period of greatest demand for plants can be a strategy to maximize the yield and quality of tubers in the potato crop (Solanum tuberosum L.). Thus, the objective of this work was to evaluate the yield and the physico-chemical and nutritional quality of the tubers of potato cultivars Agata and Markies submitted to different forms of management of traditional N fertilization combined with N application rates at the tuber bulking stage. Four experiments were conducted with the cultivars Agata and Markies during the winter growing season of the 2017 and 2018 years. The 2018 area was not the same as the previous year, and both experiments were located in potato producer areas in Botucatu-SP. The experimental design adopted in all experiments was in randomized blocks with a 4 x 4 factorial scheme, with four replications. The forms of management of traditional N fertilization were: M1 = 160 kg N ha-1 at planting; M2 = 80 kg N ha-1 at planting; M3 = 40 kg N ha-1 at planting plus 120 kg N ha-1 at hilling; M4 = 80 kg N ha-1 at planting plus 80 kg N ha-1 at hilling, combined with rates of 0, 20, 40, and 80 kg N ha-1 applied at tuber bulking stage. The forms of traditional N fertilization management combined with the N rates at tuber bulking stage did not cause N deficiency in potato plants in both cultivars, when leaf sampling was performed at the time indicated for the crop. In the cultivar Markies, applica... (Complete abstract click electronic access below) / Doutor

付記する学位プログラム名: グローバル生存学大学院連携プログラム / 京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21465号 / 農博第2308号 / 新制||農||1064(附属図書館) / 学位論文||H31||N5160(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 舟川 晋也, 教授 間藤 徹, 教授 縄田 栄治 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Nitrogen (N) is the most commonly over-applied nutrient in urban environments because of the large visual and growth increases. This over-application has led to an increase in the loss of N gas in the forms of ammonia and nitrous oxide, as well as an increase in nitrate leaching to surface and groundwater. Furthermore, excess N results in increased maintenance costs and landfill volume due to increased shoot growth from mowed clipping removal. Polymer coated urea (PCU) has proven to be an excellent source to these losses of N to the environment, but rate and timing parameters need study. A two-year field study, on sand and sandy loam soils in Provo, UT, was initiated in April 2014. Seven fertilized treatments included: urea split applied monthly; a single application of PCU (Agrium One Ap) applied in spring, a single PCU application in fall; two evenly split applications in spring and late summer; and three evenly split applications in spring, late summer, and late fall. These were compared to an untreated control. In addition the two application of PCU also had reduced rates of half and three-quarters, in addition to the full rate. Height and verdure measurements were taken on a weekly basis, along with periodic visual and biomass readings. All fertilized treatments resulted in a significant response to N as compared to the control. The single annual application treatments had significantly greater shoot growth during the weeks immediately after application and a significant reduction in verdure months later and, therefore, were unacceptable for consumer recommendation. Two applications of PCU, either at the three-quarter or full rates, were nearly identical in all measurements as compared to the spoon feeding of urea applied monthly. The half rate of two applications showed signs of inadequate N. Three applications of PCU was identical to two and, therefore, not recommended. This study shows two applications of PCU at the three-quarter rate is equally effective as spoon feeding the N. Doing so would result in less labor for fertilization. Further work is needed to evaluate other timing approaches for a single annual application, as well as long term effects of a reduced rate of N.

Environmental concerns about winter nitrogen (N) leaching loss limit the amount of biosolids applied to winter small grains in Virginia. Ten field studies were established 2012-2014 in Virginia to determine the agronomic and environmental feasibility of fall biosolids applications to soft red winter wheat (Triticum aestivum L.). Eight studies were located in the Coastal Plain physiographic province and two in the Ridge and Valley physiographic province. The effects of eight biosolids and urea N treatments on 1) biomass production at Zadoks growth stage (GS) 25-30, 2) soil inorganic N at GS 25-30, 3) soil mineralizable N at GS 25-30,4) N use efficiency (NUE) at GS 58, 5) grain yield, 6) end-of-season soil inorganic N, and 7) estimated N recovery were studied. Anaerobically digested (AD) and lime stabilized (LS) biosolids were fall applied at estimated plant available N (PAN) rates of 100 kg N ha⁻¹ and 50 kg N ha⁻¹. The 50 kg N ha⁻¹ biosolids treatments were supplemented with 50 kg N ha⁻¹ as urea in spring. Urea N was split applied at 0, 50, 100 and 150 kg N ha⁻¹, with 1/3 applied in fall and 2/3 in spring. Biomass at GS 25-30 increased with urea N rate and biosolids always resulted in equal or greater biomass than urea. Soil mineralizable N at GS 25-30 rarely responded to fall urea or biosolids N rate, regardless of biosolids type. Biosolids and urea applied at the agronomic N rate resulted in equal grain yield and estimated N recovery in soils where N leaching loss risk was low, regardless of biosolids type or application strategy. Lime stabilized biosolids and biosolids/urea split N application increased grain yield and estimated N recovery in soils with high or moderate N leaching loss risk. Therefore, AD and LS biosolids can be fall-applied to winter wheat at the full agronomic N rate in soils with low N leaching loss risk, while LS biosolids could be applied to winter wheat at the full agronomic N rate in soils with moderate or high N leaching loss risk. / Master of Science

O nitrogênio é o nutriente absorvido em maior quantidade pelo milho e o que mais influencia na produtividade de grãos, tendo sua dinâmica no sistema solo-planta condicionada pelo manejo. O trabalho foi desenvolvido na fazenda experimental da Faculdade de Engenharia de Ilha Solteira, UNESP, Selvíria-MS, em um Latossolo Vermelho distrófico, fase cerrado. Os objetivos do trabalho foram de avaliar a melhor dose e época de aplicação do N, na forma de uréia, no milho cultivado sob semeadura direta (SD) em sucessão à crotalária (CR) (Crotalaria juncea), milheto (MI) (Pennisetum americanum) ou solo em pousio na entressafra; quantificar o aproveitamento pelo milho do N da uréia e do N mineralizado dos resíduos vegetais da parte aérea da CR e do MI; avaliar o efeito dos adubos verdes no aproveitamento do N-uréia e vice-versa, e de averiguar o aproveitamento do N remanescente da uréia e dos adubos verdes pelo milho cultivado em SD no ano agrícola subseqüente. Foram conduzidos dois ensaios em áreas distintas e anexas, nos anos agrícolas de 2001/02 e de 2002/03, com a avaliação, nas respectivas áreas e ano agrícola subseqüente, 2002/03 e 2003/04, do aproveitamento pelo milho do N residual dos adubos verdes e do N do fertilizante e seu efeito sobre a produtividade do milho. O delineamento experimental utilizado foi o de blocos casualizados com 24 tratamentos e quatro repetições, dispostos em esquema fatorial incompleto (3 x 3 x 2) + 6 tratamentos adicionais (três tratamentos controles sem a aplicação de N e três tratamentos que receberam somente 30 kg ha-1 de N na semeadura, sobre CR, MI e solo em pousio. Os demais tratamentos constituíram-se pela combinação de três doses de N: 80, 130 e 180 kg ha-1, aplicando-se 30 kg ha-1 na semeadura e o restante em cobertura; três sistemas de cobertura do solo: CR e MI cultivados no inverno/primavera e o solo em pousio na entressafra, e duas épocas de aplicação do N: estádio quatro folhas ou estádio oito folhas. O fertilizante 15N-uréia foi aplicado nos tratamentos com 30 kg ha-1 de N na semeadura ou 50, 100 e 150 kg ha-1 de N em cobertura nos estádios quatro folhas ou oito folhas. A CR ou MI marcados com 15N foram utilizados somente nos tratamentos receberam o N no estádio quatro folhas, testemunha ou apenas 30 ha-1 de N na semeadura. A produtividade de grãos foi superior no milho em sucessão à CR, nos dois anos agrícolas, em relação ao cultivo em sucessão ao MI e ao solo pousio, que diferiram entre si com menor produtividade na sucessão MI-milho no primeiro ano agrícola e quando o N foi aplicado no estádio oito folhas no segundo. As épocas de aplicação do N não influenciaram no seu aproveitamento pelo milho, mas, a aplicação no estádio quatro folhas demonstrou ser mais viável economicamente quando o milho foi cultivado em sucessão ao MI e ao solo em pousio, e indiferente para o cultivo em sucessão à CR. O incremento na dose de fertilizante nitrogenado proporcionou aumento na quantidade de N na planta proveniente do fertilizante e diminuiu o seu aproveitamento, que foi em média de 53%, 49% e 44% para o milho cultivado em sucessão à CR, pousio e MI, respectivamente. O incremento na dose de fertilizante nitrogenado proporcionou aumento linear no aproveitamento pelo milho do N da CR, e quadrático no segundo ano agrícola para o N do MI, que foi em média de 15,60% 7,60%, respectivamente. A CR promoveu maior aproveitamento pelo milho do N da uréia comparada ao MI, que acumulou proporcionalmente maior quantidade de N proveniente do solo. O aproveitamento do N remanescente da parte aérea do MI e da CR pelo milho cultivado no ano agrícola subseqüente, foi inferior a 3,5% e 3%, respectivamente, da quantidade inicial, e o do N remanescente do fertilizante uréia foi inferior a 3% do aplicado inicialmente. / Nitrogen is the most absorbed nutrient by corn crop and most affect the grains yield, and its dynamic in soil-plant system is conditioned by management. The research was carried in the Experimental Farm of Faculty of Engineering, Sao Paulo State University (UNESP), Ilha Solteira, located in Selvíria-MS, in a dystrophic Red Latosol, cerrado phase, during 2001/02 and 2002/03 growing season. The objectives were to evaluate the best rate and time of N application, as urea, and N utilization by corn crop grown under no-tillage system in succession to sunnhemp (Crotalaria juncea L) (SU), millet (Pennisetum americanum) (MI) and fallow; to quantify the utilization of N from urea and mineralized SU and MI residues by corn crop; to evaluate the effect f green manure on urea N utilization by corn crop and vice-versa; and to investigate the utilization by corn crop of N remnant from previous year applied urea and green manure by corn crop grown subsequent year under no-tillage system. Two experiments were carried out in distinct nearby areas in 2001/02 e 2002/03, with the evaluation, in the respective areas and subsequent years, 2002/03 and 2003/04, of utilization by corn by corn of green manure and fertilizer remnant N and their effects on corn yield. The experimental design was randomized complete blocks, with 24 treatments and four replications in an incomplete factorial, (3 x 3 x 2) + 6 additional treatments (three without N application and three that received 30 kg N ha-1 at seeding); three N rates: 80, 130 and 180 kg N ha-1; tree preceding cover crops SU, MI grown during winter/spring season and fallow; two N application time: four leaves or eight leaves stage. The fertilizer 15N-urea was applied in the treatments 30 kg ha-1 of N at seeding or 50, 100 and 150 kg ha-1 topdressed at four leaves or eight leaves stages. SU or MI labeled with 15N were used only in the treatments that received N in the four leaves stage, control or those which received 30 ha-1 of N at seeding. The grains yield was higher in the corn in succession to SU, in both growing seasons, in relation to the cultivation in succession to MI and the fallow soil, that differed between them, with smaller productivity in the succession MI-corn in the first year and when N was applied at the eight leaves stage in the second. The N application times did not affect its utilization by the corn, but the application in four leaves stage demonstrated to be more economically viable when the corn was grown in succession to MI and the soil in fallow, and indifferent for the cultivation in succession to SU. The amount of N derived from fertilizer (Npdff) increased with increasing N rate and reduced the N utilization efficiency (NUE), in average 53%, 49% and 44% for the corn grown in succession to SU, fallow and MI, respectively. The increasing nitrogen fertilizer rate increased linearly the utilization by corn of N from SU, and adjusted to quadratic model in the second year for N from MI, in average 15.60% 7.60%, respectively. SU promoted larger utilization of urea N compared to MI, which accumulated proportionally larger amount of N derived from the soil than SU. The utilization of N remnant from above ground part of MI and of SU by the corn grown in the subsequent year was less than 3.5% and 3%, respectively, of the initial amount, and the remaining N of the urea fertilizer was less than 3% of initially applied amount.