RESUMOO experimento teve por objetivo avaliar o tempo de fechamento das entrelinhas e o índice de área foliar da cultura da soja (Glycine max (L.) Merrill), com a identificação do arranjo populacional mais adequado ao manejo da cultivar MG/BR 46 (Conquista) com alta produtividade agrícola. O experimento foi desenvolvido em área experimental da Escola Superior de Agricultura "Luiz de Queiroz" (ESALQ/ USP), no município de Piracicaba (SP), durante o ano agrícola de 2001/2002. Os 30 tratamentos, delineados em blocos ao acaso com parcelas subdivididas e com três repetições, constaram de diferentes arranjos espaciais, obtidos pela combinação de seis espaçamentos entre linhas (0,20; 0,30; 0,40; 0,50; 0,60 e 0,70 m) e cinco populações (70.000; 140.000; 210.000; 280.000 e 350.000 plantas/ha). As características avaliadas foram: tempo de fechamento de entrelinhas; índice de área foliar e produtividade agrícola. Concluiu-se que: a) Na cultivar Conquista, semeada em linhas espaçadas entre si de 0,20 a 0,60 m, o índice de área foliar é máximo no estádio fenológico correspondente ao início de granação das vagens (R 5 ); b) O índice de área foliar é aumentado proporcionalmente com o aumento da população de plantas; c) o fator de mais influência na velocidade no fechamento entrelinhas é o espaçamento.Palavras-chave: densidade de semeadura, espaçamento entre linhas, cobertura do solo, dossel cultural. ABSTRACT CLOSED CANOPY AND LEAF AREA INDEX OF SOYBEAN IN DIFFERENT SPACE ARRANGEMENTSThis research had the purposes to evaluate the time to achieve closed canopy and leaf area index of soybean (Glycine max (L.) Merrill) and identify the best space arrangements for higher grain yields of cultivar MG/BR 46 (Conquista). The experiment was carried out at the experimental fields of Escola Superior de Agricultura "Luiz de Queiroz" (USP/ESALQ), São Paulo State University, in Piracicaba, State of São Paulo, Brazil, during the 2001/2002 growing season. The 30 treatments consisted of different space arrangements, combining 6 row spacing (0.20; 0.30; 0.40; 0.50; 0.60; 0.70 m) with 5 different populations (70,000; 140,000; 210,000; 280,000; 350,000 plants ha -1 ), in a complete randomized blocks design with subdivided plots and three replications. The evaluated characteristics were: time to achieve closed canopy; leaf area index and grain yield. The conclusions are: a) in the cultivar MG/BR -46 (Conquista) cultivated under 0.20 to 0.60 m row spacing, the leaf area index maximum is at the beginning of seed-filling stage (R 5 ); b) the leaf area index becomes higher proportionally with the increase of population; c) the factor that more influenced to shorten the time to achieve closed canopy was the spacement.

A ocorrência das doenças foliares de final de ciclo em soja (Glycine max) causadas pelos fungos Septoria glycines e Cercospora kikuchii é facilmente observada no campo. Entretanto, são necessárias informações precisas sobre a quantificação de danos e perdas na produtividade. A falta de um método padrão de quantificação visual para essas doenças pode levar a estimativas imprecisas da severidade das mesmas, induzindo a conclusões erradas. Com o objetivo de elaborar uma escala diagramática para quantificar a severidade dessas doenças, foram coletadas em campo, folhas apresentando diferentes níveis de severidade. A área de cada folha e sua correspondente severidade foram determinadas e, obedecendo-se a "Lei do estímulo de Weber-Fechner", foi elaborada uma escala com os níveis de severidade de doença: 2,4; 15,2; 25,9; 40,5 e 66,6%. A validação foi realizada por nove avaliadores, sem experiência na avaliação das doenças de final de ciclo, os quais estimaram a severidade de 30 folhas de soja com sintomas destas doenças. A precisão das avaliações variou de acordo com o avaliador (0,84<R²<0,65), bem como a acurácia (0,00<a<3,40; 0,90<b<1,29), não ocorrendo erro sistemático na superestimativa ou subestimativa da doença entre os avaliadores, demonstrando que a escala desenvolvida é adequada para a avaliação das doenças de final de ciclo em soja.

Avaliou-se o desempenho produtivo de três cultivares de soja, pertencentes a diferentes ciclos de maturação, instalados em épocas de semeadura normal, tardia e safrinha. Cada época constituiu experimento individual delineado em blocos casualizados num fatorial 3 x 3 (três cultivares: IAC-12, IAC-17 e IAC-19; três densidades de plantas: 10, 20 e 30 plantas.m-1), com três repetições. Os componentes da produção, destinados à avaliação do rendimento, número total de vagens por planta e número total de grãos por planta, foram determinados em 10 plantas aleatórias na parcela útil. A massa de 1000 grãos e o rendimento de grãos foram determinados com base na população final de plantas na área útil de cada parcela. Concluiu-se que: os caracteres componentes do rendimento apresentam variações entre eles, com efeito de compensação, no sentido de uniformizar o rendimento de grãos, entre cultivares, densidades e época de semeadura; o cultivar IAC-19 apresenta melhor desempenho para rendimento de grãos em época de semeadura safrinha, independente das densidades; a época de semeadura é o fator que mais influencia no rendimento de grãos.

Nickel (Ni) is an essential micronutrient required for plants' metabolism due to its role as a structural component of urease and hydrogenase, which in turn perform nitrogen (N) metabolism in many legume species. Seed treatment with cobalt, molybdenum and Bradyrhizobium strains has been widely practiced to improve crops. Additionally, seed treatment together with Ni fertilization of soybean might improve the efficiency of biological nitrogen fixation (BNF), boosting grain dry matter yield, and N content. The objective of this study was to evaluate the effect of soybean seed treatment with Ni rates (0, 45, 90, 135, 180, 360, and 540 mg kg −1 ) on BNF, directly by the 15 N natural abundance method ( 15 δ N‰) and by measurement of urease [E.C. 3.5.1.5] activity, as well as indirectly by nitrogenase (N-ase) activity [E.C. 1.18.6.1]. Soybean plants (cultivar BMX Potência RR) were grown in a sandy soil up to the R7 developmental stage (grain maturity), at which point the nutrient content in the leaves, chlorophyll content, urease, and N-ase activities, Ni and N content in the grains, nodulation (at R1-flowering stage), as well as the contribution of biological nitrogen fixation (BNF; 15 δ N ‰) were evaluated. The proportion of N derived from N 2 fixation varied from 77 to 99% using the natural 15 N abundance method and non-nodulating Panicum miliaceum and Phalaris canariensis as references. A Ni rate of 45 mg kg −1 increased BNF by 12% compared to the control. The increased N uptake in the grains was closely correlated with chlorophyll content in the leaves, urease, and N-ase activities, as well as with nodulation. Grain dry matter yield and aerial part dry matter yield increased, respectively, by 84 and 51% in relation to the control plants at 45 mg kg −1 Ni via seed treatment. Despite, Ni concentration was increased with Ni-seed treatment, Ni rates higher than 135 mg kg −1 promoted negative effects on plant growth and yield. In these experimental conditions, seed treatment with low Ni rates caused higher dry matter yield of plants and grains, N content in the grains, and in the aerial part by increasing of BNF.

Management is the most important handle to improve crop yield and resilience under climate change. The aim of this study was to evaluate how irrigation, sowing date, cultivar maturity group and planting density can contribute for increasing the resilience of soybean (Glycine max (L.) Merr.) under future climate in southern Brazil. Five sites were selected to represent the range of Brazilian production systems typical for soybean cultivation. Yields were obtained from a crop-model ensemble (CROPGRO, APSIM and MONICA). Three climate scenarios were evaluated: baseline (1961–2014), and two future climate scenarios for the mid-century (2041–70) with low (+2.2°C, A1BLs) and high (+3.2°C, A1BHs) deltas for air temperature and with atmospheric [CO2] of 600 ppm. Supplementary irrigation resulted in higher and more stable yields, with gains in relation to a rainfed crop of 543, 719, 758 kg ha–1, respectively, for baseline, A1BLs and A1BHs. For sowing date, the tendencies were similar between climate scenarios, with higher yields when soybean was sown on 15 October for each simulated growing season. Cultivar maturity group 7.8 and a plant density of 50 plants m−2 resulted in higher yields in all climate scenarios. The best crop-management strategies showed similar tendency for all climate scenarios in Southern Brazil.

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A Deus À minha família, em especial à minha mãe, Lília Sichmann e filhos, Karoline e Eduardo André. Ofereço e Dedico"O degrau de uma escada não serve simplesmente para que alguém permaneça em cima dele, destina-se a sustentar o pé de um homem pelo tempo suficiente para que ele coloque o outro um pouco mais alto." Thomas Huxley AGRADECIMENTOS EVALUATION OF THE PLASTICITY OF SOYBEAN (Glycine max (L.) Merrill) UNDER EFFECT OF VARIABILITY OF SPACE ARRANGEMENTS

To study the infl uence of temperature on seed protein and oil concentration, soybean seeds from cultivar Williams 82 were grown in vitro at temperatures of 17, 21, 25, 29 e 31° C in liquid medium for 8 days. There was an inverse relationship between Dry Growth Rate (DGR) and protein and oil concentration. Since oil and protein concentrations were the lowest when DGR was the greatest, dilution accounted for much of the variation in concentrations. At extremes temperatures the dry matter reduction occurred on whole seed, not only on oil and protein contend, but also on other seed components, then oil and protein concentration increased. The temperature effect was mainly on total dry matter accumulation and not directly on oil and protein synthesis. The oil and protein concentration were positively related when the supply of nitrogen and carbon were constant. ln the second in vitro experiment, glutamine concentrations of 20, 40, 60 and 80 mM were used in the medium. At 20 mM glutamine the protein concentration was 294 mg g-1 and at 80 mg g-1 glutamine it reached up to 445 mg g• 1 , which is higher than the normal protein concentration of 400 mg g-1 , that typically occurs in in vivo mature soybean seed. Oil and protein concentrations were inversely xií related (r 2 = 0,43*). These results indicate that the negative relationship between oil and protein is related to the balance of carbon and nitrogen supply to the seed. When nitrogen becomes more abundant the preferences was to make protein instead of oil and carbon was used in this purpose. Therefore, nitrogen availability can regulate seed protein concentration. ln the fi eld experiments, in spite of the significant results of the linear regression of protein and oil versus temperature, within the sarne Iocation, variation on protein concentration were best explained by the rain distribution during seed filling. Among locations, there was a trend that seed collected at locations with milder average temperatures (21 to 23° C) and higher altitude (>650m), present higher protein concentration than those collected in locations with higher temperatures (23 to 27 º C). When this trend was not observed, the rain distribution during the seed filling and seed yield, again best explained the results. Due the differences obtained among years and locations, the geographic pattem based only on temperature variations was not sufficient to explain the variations on protein concentration. The rain distribution during the seed filling period as well as the nitrogen availability to the seeds, are the key factors to the best understanding of the variations in protein and oil concentrations in soybean seeds.