Gil Miguel de Sousa Câmara

Épocas de semeadura e densidade de plantas de soja: I. Componentes da produção e rendimento de grãos

Yield of three soybean cultivars and of three maturation dates, sowed on typical, late and autumn sowing dates was evaluated. Three individual and independent experiments, one for each sowing date, were carried out in a randomized block factorial design 3 x 3 with three replications (3 cultivars: IAC-12, IAC-17 and IAC-19; three planting densities: 10, 20, and 30 plants.m1). The yield components used for evaluation were: total number of pods and total number of grains, determined for 10 randomly choosen plants per plot. The weight 1,000 grains and grain yield were determined for each plot. Yield components showed differences among themselves, with a compensating effect among cultivars, densities, and sowing dates, providing a uniform grain yield. Cultivar IAC-19 showed the best grain yield performance in the autumn sowing date, independently of plant densities. Sowing date mostly affects grain yield.

The soybean yield gap in Brazil – magnitude, causes and possible solutions for sustainable production

Brazil is one of the most important soybean producers in the world. Soybean is a very important crop for the country as it is used for several purposes, from food to biodiesel production. The levels of soybean yield in the different growing regions of the country vary substantially, which results in yield gaps of considerable magnitude. The present study aimed to investigate the soybean yield gaps in Brazil, their magnitude and causes, as well as possible solutions for a more sustainable production. The concepts of yield gaps were reviewed and their values for the soybean crop determined in 15 locations across Brazil. Yield gaps were determined using potential and attainable yields, estimated by a crop simulation model for the main maturity groups of each region, as well as the average actual famers’ yield, obtained from national surveys provided by the Brazilian Government for a period of 32 years (1980–2011). The results showed that the main part of the yield gap was caused by water deficit, followed by sub-optimal crop management. The highest yield gaps caused by water deficit were observed mainly in the south of Brazil, with gaps higher than 1600 kg/ha, whereas the lowest were observed in Tapurah, Jatai, Santana do Araguaia and Uberaba, between 500 and 1050 kg/ha. The yield gaps caused by crop management were mainly concentrated in South-central Brazil. In the soybean locations in the mid-west, north and north-east regions, the yield gap caused by crop management was 2000 kg/ha. For reducing the present soybean yield gaps observed in Brazil, several solutions should be adopted by growers, which can be summarized as irrigation, crop rotation and precision agriculture. Improved dissemination of agricultural knowledge and the use of crop simulation models as a tool for improving crop management could further contribute to reduce the Brazilian soybean yield gap.

Estado nutricional e produção do capim-pé-de-galinha eda soja cultivada em sucessão em sistema antecipadode adubação

NUTRITIONAL CONDITION AND YIELD OF FINGER MILLET AND SOYBEAN GROWN IN SUCCESSION IN A SYSTEM OF ANTICIPATED FERTILIZATION Questions arise on the viability of the chemical management of soil being related to the fertilization of the cropping system (anticipated fertilization) aiming to increase organic matter in agroecosystem s due to their several advantages regarding soil conservation, natural resources preservation and nutrient recycling; or whether the traditional fertilization practices should be maintained. The objective of this research was to evaluate the effect of the anticipation of soybean fertilization on: (i) the dry matter yield and nutrients uptake of finger millet, and (ii) the dry matter yield, nutrients exportation, and grain yield of soybean cultivated after finger millet [Eleusine coracana (L.) Gaertn.]. The experiment was carried out in Piracicaba, State of Sao Paulo, during the 2001/2002 growing season, in a randomized complete blocks design with three replications. The anticipation of the soybean fertilization did not interfere in the dry matter yield, grain yield, and the nutrient exportation by soybean. Finger millet responded to the soybean fertilization increasing its dry matter yield and nutrient uptake. The management of fertilization to adequate the production system and optimize the sowing process performance can be used in order to install the soybean crop in the field within the proper time.

Épocas de semeadura, densidades de plantas e desempenho vegetativo de cultivares de soja

The present research was carried out in Piracicaba, SP, Brazil, to evaluate vegetative performance of three soybean cultivars at two sowing dates, at five plant densities. The cultivars used were: IAC-17, IAC-12 and IAC-19, with early, semi-early and medium maturation, respectively, sown at the typical planting date and late date. Each cultivar was sown at densities of 10, 15, 20, 25, and 30 plants.m-1. Experimental plots with five rows spaced 0.50 m and 5.0 m long were randomized in blocks, using a factorial design (3 cultivars x 5 plant densities), with three replications. Plant final height, main stem diameter, number of nodes, and number of branches per plant were evaluated. Reduction of cultivars cycle for the late sowing date occurred mainly during the reproductive phase. Independently of the planting date, the increase in plant density, implyed in an increased final plant height and in decreasing main stem diameter and number of branches per plant. Number of nodes in the main stem was reduced with the delay of the planting date.

Influence of photoperiod and air temperature on the growth, flowering and maturation of soybean (Glycine max (L.) Merrill)

Experimentos em casa-de-vegetacao visando estudar o comportamento de cultivares de soja perante fotoperiodo curto (12 horas) e longo (13 e 14 horas) e na presenca de temperaturas variaveis em funcao de diferentes epocas de semeadura, foram instalados na Universidade Federal de Vicosa, MG, Brasil, durante o periodo de junho de 1984 a dezembro de 1985. Delineado inteiramente ao acaso, cada experimento contou com doze cultivares de soja repetidos oito vezes por epoca. Avaliaram-se as seguintes caracteristicas: duracao do subperiodo emergencia - inicio do florescimento, altura de planta e numero de nos vegetativos formados por planta e duracao do subperiodo emergencia - maturidade fisiologica. Concluiu-se que a fase fenologica da soja compreendida entre a emergencia e o inicio do florescimento e significativamente influenciada pelas variacoes do fotoperiodo e da temperatura do ar; fotoperiodo e temperatura interferem com a duracao fenologica do periodo juvenil da soja e acrescimos de fotoperiodo e de temperatura antecipam o florescimento da soja e aumentam a altura de suas plantas.

Desempenho vegetativo e produtivo de cultivares e linhagens de soja de ciclo precoce no município de Piracicaba-SP

As part of the official network trials for soybean (Glycine max L. Merrill) cultivar screening in the State of Sao Paulo-Brazil, a field experiment was installed in Piracicaba, to evaluate the growth and yield performance of short maturity genotypes. The experiment was arranged in a randomized block design with 20 treatments (cultivars and breeding lines) and 4 replications on a Kandiudalfic Eutrodox soil. The plots were 2.50 m wide and 5.0 m long, with 4 planting lines spaced 0.50 m. The cultivar IAS-5 (the most used in the State of Sao Paulo) and IAC-17 (with high yields in the trials of the last years) were introduced as standards for comparision with the newly developed cultivars and lines. The following characteristics were evaluated: initial plant population, flowering date, maturation date, plant height at flowering and maturation, first pod insertion height, degree of lodging and grain yield. Lower plant population reduced plant height at maturation, first pod insertion height and grain yield. The lines BR 92-4428, BR 92-6528, IAC 93-680, IAC 90-938, IDS 413-F4, IAC 93-598 and IAC 90-1000 were the most productive, with yields above the standards. The lines FT 90-2687 and BR 92-5261 presented the lowest yields.

Soybean Seed Treatment with Nickel Improves Biological Nitrogen Fixation and Urease Activity

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 biological nitrogen fixation (BNF), directly by the 15N natural abundance method (δ15N‰) 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 Potencia 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 (δ15N ‰), were evaluated. The proportion of N derived from N2 fixation varied from 77 to 99% using the natural 15N 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.

Assessment of crop-management strategies to improve soybean resilience to climate change in Southern Brazil

Abstract. 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.