Cover crops play a part in improving sustainability by reducing negative environmental impacts such as soil erosion and nutrient runoff. Energycane could benefit from cover crops due to its row spacing. This study was conducted at the Bearden Dairy Research Center to determine differences in nitrogen accumulation, weed suppression, and energycane yield among treatments. Four cool-season species (planted in the fall of 2020 and 2021) [balansa clover (Trifolium michelianum), hairy vetch (Vicia villosa), white clover (T. repens) and winter pea (Pisum sativum subsp. arvense)], and four warm-season species (planted in the spring of 2021 and 2022 [alfalfa (Medicago sativa), alyceclover (Alysicarpus vaginalis), soybean (Glycine max), and sunnhemp (Crotalaria juncea)] plus negative and positive controls (0 and 168 kg N ha-1) were used. Regarding cool-season cover crops, significant differences were seen in all previously mentioned metrics. Warm-season cover crops only showed differences regarding nitrogen accumulation and weed suppression abilities.

Made available in DSpace on 2014-06-11T19:33:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-05-28Bitstream added on 2014-06-13T20:25:27Z : No. of bitstreams: 1 rodrigues_hca_dr_jabo.pdf: 400724 bytes, checksum: 82cd2243d4fe3775e52d061e2d9d9e59 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O estudo de aspectos químicos e bioquímicos associados ao desenvolvimento das diferentes partes das plantas permite o entendimento das reações que refletem na produção de grãos. O presente trabalho buscou avaliar dois híbridos de milho com potencial produtivo distintos, a fim de determinar as diferenças na biomassa de raízes, colmo, folhas e grãos e suas respostas bioquímico-fisiológicas. Para isso, foram montados três experimentos: O primeiro foi realizado em casa de vegetação, por 20 dias, em solução nutritiva, com quatro doses de nitrogênio e três repetições, com o intuito de estudar a diferença nas raízes e parte aérea; Um ensaio em campo, com o plantio dos mesmos híbridos, submetidos a quatro doses de N; O terceiro experimento consistiu do cultivo de grãos in vitro, submetidos a quatro doses de N e cinco repetições, a fim de avaliar a diferença de eficiência de absorção de N pelos grãos. No experimento I, a parte aérea das plantas apresentou as maiores diferenças entre os genótipos, comparados com a raiz. Na raiz, a atividade da redutase do nitrato foi a que proporcionou as maiores diferenças entre os híbridos; na parte aérea, houve maior acúmulo de biomassa seca para o genótipo AS1596. No experimento II, o genótipo AS1596 foi superior ao AS1522 para a atividade da redutase do nitrato, acúmulo de N nos grãos e biomassa seca do caule e grãos; houve acúmulo no teor de aminoácidos livres totais no híbrido AS1596. No experimento III, observou-se que o híbrido AS1596 possui maior capacidade de absorção de N pelos grãos, sendo mais responsivo às doses de N que o AS1522 / The study of chemical and biochemical aspects associated with the development of different plant parts allows the understanding of reactions that reflect on kernels production. This study evaluated two corn hybrids with different yield potential in order to determine the differences in root biomass, stem, leaves and grains and their associated biochemical and physiological responses. Three experiments were carried out: The first was conducted in a greenhouse for 20 days with nutritive solution, with four nitrogen levels, in order to study the difference in the roots and shoots; The second essay was conducted in the field subject on four N levels; and the third experiment consisted of growing kernels in vitro subject to four N levels, in order to evaluate the difference in efficiency N uptake by kernels. In the first experiment, the shoots showed the greatest differences between genotypes. In the root, the activity of nitrate reductase activity provided the greatest differences among the hybrids; in the shoot, there was a greater accumulation of dry biomass for genotype AS1596. In experiment II, the genotype AS1596 was higher than AS1522 for nitrate reductase activity, N accumulation in the grain, and stem or grain dry biomass, the total free amino acid content was greatest in hybrid AS1596. In experiment III, the hybrid AS1596 has a greater capacity for N uptake being more responsive to N levels than AS1522

Cover crops (CC) are planted in between cash crops to improve soil quality and to supply nitrogen (N) to cash crops through biological N fixation or soil N scavenging. Most producers use single species CC, in part because potential benefits of using mixtures of three or more CC species are poorly understood. A three-year study was initiated at Painter, Virginia to observe effects of CC mixtures on a no-till (NT) corn (Zea mays), wheat (Triticum aestivum L.), and soybean (Glycine max) rotation to measure CC performance, N cycling, cash crop yield, and soil quality in a sandy, low organic matter soil. Twelve treatments were created with conventional tillage (CT), NT, no CC control, and monoculture or CC mixtures of 3 to 9 species. Corn was grown in year 3 in all 12 treatments and four N rates were applied (0, 56, 112 and 156 kg N ha-1). Cover crop biomass, N accumulation, CC C:N ratio, and corn and soybean yield were measured annually. Soil bulk density, compaction, infiltration rate, pH, electrical conductivity, soil respiration, earthworm counts, soil microbial respiration, and soil microbial biomass carbon (C) after three years of CC. Cover crop biomass production varied significantly each year (5633 kg ha-1 in year 1, 755 kg ha-1 in year 2, 5370 kg ha-1 in year 3) due to climate and agronomic parameters, but a CC mixture always produced the highest biomass at termination. Nitrogen accumulation was strongly correlated with biomass production (R2= 0.94) and followed the same trend due to all CC having C:N < 30:1. Corn and soybean yields in years 1 and 2 were not significantly different, but corn yield was significantly affected by treatment and N fertilizer rate in year 3. After 3 years, soil respiration, earthworm populations and soil microbial biomass C increased in CC compared to CT without CC. However, infiltration rate, bulk density, microbial respiration, pH did not improve or declined compared to CT. In conclusion, adding CC mixtures to crop rotations shows promise for producing high CC biomass, accumulating N, and increasing crop yields, while improving some soil quality parameters on sandy low organic matter soils. / Doctor of Philosophy / Cover crop (CC) are planted in between cash crops to protect the soil from erosion, improve soil quality, and supply N to next cash crop through biological N fixation or soil N scavenging. Traditionally, CC were single species, but new CC methodologies utilize mixtures of three or more species planted together to protect soils as well as produce high biomass to suppress weeds, conserve soil moisture, and improve soil quality. A long-term study was initiated in fall 2014 in Painter, VA to observe CC mixture effects on no-till (NT) corn (Zea mays), wheat (Triticum aestivum L.), and soybean (Glycine max) rotations on CC performance, N cycling, cash crop yield, and soil quality of a sandy, low organic matter soil. Twelve treatments were created that compared NT rotations with CC monocultures, CC mixtures of 3-9 species, and without CC. In the third year corn was grown in all 12 rotations and four N rates were applied (0, 56, 112 and 156 kg N ha-1). To evaluate CC mixture performance in rotations, CC biomass, CC N accumulation and corn and soybean yield was measured over three years. To evaluate changes in soil quality, nine soil physical, chemical and biological soil properties were measured after three years of NT and CC. Biomass production varied significantly each experimental year (5633 kg ha-1 in year 1, 755 kg ha-1 in year 2, 5370 kg ha-1 in year 3) due to climate and agronomic differences, but CC mixtures were the highest biomass producing CC each spring and accumulated the highest amount of N. Cover crop mixtures had equal corn and soybean yield as CC monocultures. In year 3 corn yield and was greater in treatments with CC than in treatments without CC and was greater in legume dominated monocultures and mixtures than majority grass CC mixtures and monocultures. After 3 years of CC and NT, some soil quality parameters improved. Indicators of soil biology (soil respiration, earthworm populations, and soil microbial biomass C) increased in CC treatments. However, some soil physical and chemical properties (infiltration rate, bulk density, pH and EC) did not improve. In conclusion, adding CC mixtures to crop rotations shows promise for producing high CC biomass, accumulating N, and increasing crop yields, while also improving some soil quality parameters that are important for agricultural systems.

Orientador: Jairo Osvaldo Cazetta / Banca: José Lavres Junior / Banca: Felipe Campos Figueiredo / Banca: Domingos Fornasieri Filho / Banca: Wanderley Jose de Melo / Resumo: O estudo de aspectos químicos e bioquímicos associados ao desenvolvimento das diferentes partes das plantas permite o entendimento das reações que refletem na produção de grãos. O presente trabalho buscou avaliar dois híbridos de milho com potencial produtivo distintos, a fim de determinar as diferenças na biomassa de raízes, colmo, folhas e grãos e suas respostas bioquímico-fisiológicas. Para isso, foram montados três experimentos: O primeiro foi realizado em casa de vegetação, por 20 dias, em solução nutritiva, com quatro doses de nitrogênio e três repetições, com o intuito de estudar a diferença nas raízes e parte aérea; Um ensaio em campo, com o plantio dos mesmos híbridos, submetidos a quatro doses de N; O terceiro experimento consistiu do cultivo de grãos in vitro, submetidos a quatro doses de N e cinco repetições, a fim de avaliar a diferença de eficiência de absorção de N pelos grãos. No experimento I, a parte aérea das plantas apresentou as maiores diferenças entre os genótipos, comparados com a raiz. Na raiz, a atividade da redutase do nitrato foi a que proporcionou as maiores diferenças entre os híbridos; na parte aérea, houve maior acúmulo de biomassa seca para o genótipo AS1596. No experimento II, o genótipo AS1596 foi superior ao AS1522 para a atividade da redutase do nitrato, acúmulo de N nos grãos e biomassa seca do caule e grãos; houve acúmulo no teor de aminoácidos livres totais no híbrido AS1596. No experimento III, observou-se que o híbrido AS1596 possui maior capacidade de absorção de N pelos grãos, sendo mais responsivo às doses de N que o AS1522 / Abstract: The study of chemical and biochemical aspects associated with the development of different plant parts allows the understanding of reactions that reflect on kernels production. This study evaluated two corn hybrids with different yield potential in order to determine the differences in root biomass, stem, leaves and grains and their associated biochemical and physiological responses. Three experiments were carried out: The first was conducted in a greenhouse for 20 days with nutritive solution, with four nitrogen levels, in order to study the difference in the roots and shoots; The second essay was conducted in the field subject on four N levels; and the third experiment consisted of growing kernels in vitro subject to four N levels, in order to evaluate the difference in efficiency N uptake by kernels. In the first experiment, the shoots showed the greatest differences between genotypes. In the root, the activity of nitrate reductase activity provided the greatest differences among the hybrids; in the shoot, there was a greater accumulation of dry biomass for genotype AS1596. In experiment II, the genotype AS1596 was higher than AS1522 for nitrate reductase activity, N accumulation in the grain, and stem or grain dry biomass, the total free amino acid content was greatest in hybrid AS1596. In experiment III, the hybrid AS1596 has a greater capacity for N uptake being more responsive to N levels than AS1522 / Doutor

O uso de fertilizantes nitrogenados de eficiência aumentada, em especial o blend de ureia convencional tratada com NBPT e ureia revestida com enxofre elementar e polímeros (U+UREP) consiste em uma alternativa para fornecer nitrogênio (N) nos estádios fenológicos do milho garantindo a sustentabilidade agrícola, além de ser uma opção válida para reduzir os custos em comparação ao uso exclusivo de fertilizantes de liberação controlada. Os objetivos do trabalho foram: (1) avaliar o manejo da adubação nitrogenada em um sistema de sucessão cana-de-açúcar/milho com blend de U+UREP, comparados com fertilizantes nitrogenados convencionais, além de avaliar a viabilidade econômica do custo da adubação nitrogenada e a margem de lucratividade nesse sistema de manejo; (2) avaliar os modos de aplicação e doses de N utilizando o blend de U+UREP no mesmo sistema de cultivo anteriormente citado, além de avaliar o custo e a rentabilidade desse manejo; (3) avaliar o destino do N-fertilizante dentro das plantas de milho proveniente do blend de U+UREP por meio do método isotópico (15N) e do método da diferença, além de avaliar a volatilização de NH3, a viabilidade econômica do custo da adubação e outros parâmetros de crescimento das plantas quando comparados com a U e o NA em um sistema de sucessão Brachiaria ruziziensis/milho. No primeiro estudo, a conversão de um sistema de cultivo de cana-de-açúcar para milho com alto aporte de palha tem influência marcante nas transformações do N no sistema solo-planta-atmosfera, sendo que a produção de biomassa seca (BS) foi pouco influenciada entre os fertilizantes avaliados aplicados no estádio V4 do milho, diferindo-se apenas do tratamento controle. As condições climáticas (intensidade e distribuição das chuvas) se apresentaram como um fator limitante para o rendimento da cultura. No segundo estudo, a viabilidade econômica no sistema de sucessão cana-de-açúcar/milho mostrou que o custo da adubação nitrogenada foi impulsionada pelo preço dos fertilizantes nitrogenados e aumento das doses de N, sendo que a adubação com o blend de U+UREP não mostrou-se ser uma alternativa economicamente viável no cultivo do milho, independentemente das doses e dos anos de cultivo avaliados. A adubação com 300 kg de N ha-1 na forma de U promoveu a maior margem de lucratividade. No terceiro estudo, quando o blend de U+UREP foi aplicado em cobertura no sistema de cultivo de cana-de-açúcar/milho foi observado as maiores médias de produção de BS e acumulo N, independentemente da dose de N avaliada, sendo que a aplicação de 194 kg de N ha-1 do blend de U+UREP proporcionou a máxima produtividade de grãos de milho. No quinto capítulo, o estudo do custo e rentabilidade do modo de aplicação do blend de U+UREP mostrou que a aplicação em cobertura de 300 kg de N ha-1 proporcionou os maiores valores de produtividade de grãos, receita bruta e custo operacional total, enquanto que o maior lucro operacional e índice de lucratividade foi obtido com a aplicação incorporada de 150 kg de N ha-1. No sexto capítulo, o blend de U+UREP foi capaz de reduzir as perdas por volatilização de NH3, entretanto, as condições climáticas podem ter influenciado a produção de BS, o acumulo de N e a ausência de resposta na produtividade de grãos em ambas as safras. O N proveniente do solo foi a principal fonte de N para as plantas durante o ciclo de cultivo, sendo que a % NBPTUplanta foi de 14% e a % URPplanta de 23%. / The use of nitrogen fertilizers of increased efficiency, especially the blend of conventional urea treated with NBPT and urea coated with elemental sulfur and polymers (U+UREP), is an alternative to provide nitrogen (N) in the phenological phases of maize, guaranteeing sustainability agriculture, as well as being a valid option to reduce costs compared to the exclusive use of controlled release fertilizers. The objectives of the study were: (1) to evaluate the management of nitrogen fertilization in a sugarcane/corn succession system with blend U+UREP, compared to conventional nitrogen fertilizers, and to evaluate the economic viability of fertilization cost nitrogen balance and profit margin in this management system; (2) to evaluate the application modes and N doses using the blend U+UREP in the same cultivation system mentioned above, besides evaluating the cost and profitability of this management; (3) to evaluate the fate of the N-fertilizer within the corn plants from the blend U+UREP using the isotopic method (15N) and the difference method, besides evaluating NH3 volatilization, the economic feasibility of the cost of fertilization and other plant growth parameters when compared to U and NA in a Brachiaria ruziziensis/maize succession system. In the first study, the conversion of a sugarcane cultivation system to corn with high straw yields had a marked influence on N transformations in the soil-plant-atmosphere system, and the production of dry biomass (DB) was little influence among the evaluated fertilizers applied in the stage V4 of the corn, differing only from the control treatment. The climatic conditions (intensity and distribution of rainfall) were presented as a limiting factor for crop yield. In the second study, economic viability in the sugarcane/corn succession system showed that the cost of nitrogen fertilization was driven by the price of nitrogen fertilizers and increase of N rates, and the fertilization with the blend U+UREP did not prove to be an economically viable alternative to maize cultivation, regardless of the doses and the years of cultivation evaluated. Fertilization with 300 kg of N ha-1 in the U-form promoted the highest profit margin. In the third study, when the blend U+UREP was applied under cover in the sugarcane/maize cultivation system, the highest production averages of DB and N accumulation were observed, regardless of the N dose evaluated, and the application of 194 kg of N ha-1 from the blend U+UREP provided the maximum yield of corn grains. In the fifth chapter, the study of the cost and profitability of the application of the blend U+UREP showed that the application in coverage of 300 kg of N ha-1 provided the highest values of grain yield, gross revenue and total operating cost, while the highest operating profit and profitability index was obtained with the incorporated application of 150 kg of N ha-1. In the sixth chapter, the blend U+UREP blend was able to reduce NH3 volatilization losses; however, climatic conditions may have influenced DB production, N accumulation and lack of response in grain yield in both crops. N from the soil was the main source of N for the plants during the growing cycle, with the % NBPTUplant was 14% and the % UREPplant was 23%.

A field experiment was conducted to examine the responses in growth, total dry matter (TDM), seed yield and nitrogen (N) accumulation of Kabuli chickpea cv. Principe and narrow-leafed lupin cv. Fest to different irrigation levels and N fertilizer on a Templeton silt loam soil at Lincoln University, Canterbury, New Zealand in 2007/08. The irrigation and fertilizer treatments were double full irrigation, full irrigation, half irrigation and nil irrigation and a control, full irrigation plus 150 kg N ha⁻¹. There was a 51 % increase in the weighed mean absolute growth rate (WMAGR) by full irrigation over no irrigation. The maximum growth rates (MGR) followed a similar response. The growth rates were not significantly decreased by double irrigation. Further, N fertilizer did not significantly improve crop growth rates. With full irrigation MGRs were 27.6 and 34.1 g m⁻² day⁻¹ for Kabuli chickpea and narrow-leafed lupin, respectively. Seed yields of fully-irrigated crops were trebled over the nil irrigation treatment. With full irrigation, seed yield of chickpea was 326 and that of lupin was 581 g m⁻². Seed yield of the two legumes was reduced by 45 % with double irrigation compared with full irrigation. Nitrogen fertilizer did not increase seed yields in either legume. Increased seed yield with full irrigation was related to increased DM, and crop growth rates, seeds pod⁻¹ and seeds m⁻². Crop harvest index (CHI) was significantly (P < 0.05) increased by irrigation and was related to seed yield only in narrow-leafed lupin. With full irrigation, the crops intercepted more than 95 % of incoming incident radiation at leaf area indices (LAIs), 2.9 and 3 or greater in Kabuli chickpea and narrow-leafed lupin, respectively. In contrast, without irrigation the two legumes achieved a maximum fraction of radiation intercepted of less than 90 %. With full irrigation, total intercepted photosynthetically active radiation (PAR) was increased by 28 % and 33 % over no irrigation for Kabuli chickpea and narrow-leafed lupin, respectively. Fully-irrigated Kabuli chickpea intercepted a total amount of PAR of 807 MJ m⁻² and fully-irrigated narrow-leafed lupin intercepted 1,042 MJ m⁻². Accumulated DM was strongly related to accumulated intercepted PAR (R² ≥ 0.96**). The final RUE was significantly (P < 0.001) increased by irrigation. With full irrigation the final RUE of Kabuli chickpea was 1.49 g DM MJ⁻¹ PAR and that of narrow-leafed lupin was 2.17 g DM MJ⁻¹ PAR. Total N accumulation of Kabuli chickpea was not significantly affected by irrigation level. Kabuli chickpea total N was increased by 90 % by N fertilizer compared to fully-irrigated Kabuli chickpea which produced 17.7 g N m⁻². In contrast, total N accumulated in narrow-leafed lupin was not increased by N fertilizer but was decreased by 75 % with no irrigation and by 25 % with double irrigation (water logging) compared to full irrigation with a total N of 45.9 g m⁻². Total N was highly significantly related to TDM (R² = 0.78** for Kabuli chickpea and R² = 0.99** for narrow-leafed lupin). Nitrogen accumulation efficiency (NAE) of narrow-leafed lupin was not affected by irrigation or by N fertilizer. However, the NAE of Kabuli chickpea ranged from 0.013 (full irrigation) to 0.020 (no irrigation) and 0.017 g N g⁻¹ DM (full irrigation with N fertilizer). The N harvest index (NHI) was not affected by irrigation, N fertilizer or legume species. The NHI of Kabuli chickpea was 0.50 and that of narrow-leafed lupin was 0.51. The NHI was significantly (r ≥ 0.95 **) related to CHI.