The sowing speed or planting speed is referred to tractor and seeder displacement speed during the sowing. It plays a crucial role intruding distribution of plants, and consecuently yield of soybean grain. Therefore, this paper endeavors to corroborate the repercussions of the sowing speeds on the plants distribuition and grain yield. The experimental design consisted of a randomized complete block design with five treatments and four replications, with the treatments comprising of five sowing speeds (2.0, 3.1, 6.1, 7.4, 9.0 km h-1). The following parameters were evaluated:(i) distance between plants, (ii) double spacing, acceptable spacing and failing spacing, (iii) number and dry mass of nodules, (iv) plant population, (v) shoot dry mass, (vi) mass of one thousand grains, and (vii) grain yield. With the increase in the sowing speed, the equidistance of plants in the row was changed, which in turn decreased the soybean yield. The results showed that seeding speeds close to 4.0 km h-1 provided better uniformity and distribution of plants in the row. The results also unveiled that sowing speed mainly influence the plants distribution, having greater influence on the productivity components, thereby affecting the overall soybean grain yield

The crop yield is related to several factors, among these, soil tillage, soil compaction and crop rotation. This study aimed to evaluate the winter cover crops and crop rotation influence on soil physical properties and grain yield of dry beans, maize and soybean for two growing seasons. Three experiments were conducted, corresponding to dry beans, maize and soybean crops. It was used the randomized block design with three treatments and four replications consisted by 3 × 10 m plots. The treatments were: two cover crops systems and crop rotation in no-till, and the control, consisting of winter fallow and conventional tillage. The cover crop dry matter, soil physical properties and grain yield for dry beans, maize and soybean in the two growing seasons were evaluated. Crop rotation systems and cover crops showed a trend to increase maize and soybean yields. Crop rotation in no-till increases soil compaction in the superficial layer compared to conventional tillage, but does not reduce the dry beans, maize and soybean yields.

Submetido em 11/02/2014 e aprovado em 16/12/2016. 1 Parte do trabalho de conclusão de curso da segunda autora.

A adubação orgânica é uma forma de reduzir a entrada de fertilizantes inorgânicos e baixar o custo de produção, manter o rendimento das culturas e a sustentabilidade do sistema produtivo. O objetivo do trabalho foi avaliar o crescimento e a produtividade do algodoeiro herbáceo em função da adubação orgânica. O delineamento experimental adotado foi o inteiramente casualizado, com três tratamentos e sete repetições. Os tratamentos foram compostos por três fontes de adubação: esterco bovino, palha de arroz carbonizada e solo sem adubação orgânica, totalizando 21 unidades experimentais. Cada unidade experimental foi composta por três vasos de polietileno preto de 18 litros cada, totalizando 63 vasos. Foi determinada a área foliar por planta, diâmetro do caule, altura de planta, número de ramos vegetativos, número de ramos reprodutivos, número de botões florais, número de maças por planta, massa seca da raiz e produtividade de pluma e caroço. De acordo com os resultados obtidos, a adubação orgânica melhorou o crescimento, desenvolvimento e a produtividade das plantas de algodão, sendo que o esterco bovino foi o que proporcionou os melhores resultados, incrementando em 101 e 108% a produtividade de fibra e caroço, respectivamente, em relação ao solo sem adubação orgânica.

Rice is an economically important and widely consumed cereal that achieves high yields under flood-irrigated cultivation. However, the amount of residual straw from the previous year may influence its growth and yield. This study evaluated the performance of flood-irrigated rice as affected by residual rice straw, in a greenhouse. A completely randomized design, in a 5 x 4 x 2 factorial scheme, with four replications, was used. Treatments were obtained from a combination of five rice straw amounts (0 t ha-1, 5 t ha-1, 10 t ha-1, 20 t ha-1 and 40 t ha-1), four application times (3, 2, 1 and 0 months before sowing) and two straw application methods (on the surface and incorporated into the soil). The number of panicles and shoot dry mass do not increase when residual straw remains on the soil surface. When the straw is incorporated into the soil on the sowing day, the number of panicles and the shoot dry mass increased by 20 % and 14 %, respectively, if compared to when it was added three months before. The addition of residual rice straw on the surface or incorporated into the soil resulted in a higher yield for flood-irrigated rice grains, when compared to the absence of straw. At 40 t ha-1 of residual rice straw, added at three months before sowing, there was a higher mass yield of rice grains, if compared to the lower amounts of straw.

Climatic variables affect soybean yield components. Understanding how they are interrelated is essential for planning and boosting crop productivity. The aim of this study was to evaluate whether the photothermal quotient can be used to predict the productivity and 1000-grain weight of soybean. Five experiments were carried out at the Federal University of Santa Maria in growing seasons of 2013/14 to 2017/18 using the main cultivars (154) sown in the state of Rio Grande do Sul (RS), Brazil. The experiments were organized in a randomized block design with four replicates, evaluating grain productivity and 1000-grain weight. The results showed that years with the highest grain productivity and 1000-grain weight were associated with regular rainfall and high photothermal quotients (approximately 2.3 MJ m-2). There was a positive and significant correlation between grain productivity and the average number of days without rainfall (r = 0.98). In addition, there was a negative correlation with air temperature (r = -0.8). Air temperature and days without rain are decisive factors for yield and grain weight. The photothermal quotient can be used as a basis for predicting soybean grain productivity.

RESUMO:Neste trabalho, é analisada a variação da temperatura atmosférica próximo à superfície considerando quatro diferentes cenários de concentração atmosférica de dióxido de carbono. É mostrado que as maiores variabilidades de temperatura ocorrem no estado desconectado na região transição entre os regimes. Os resultados indicam que a diminuição na variação de temperatura diurna pode estar associada à variabilidade de regimes na camada limite estável. ABSTRACT:In this work it is analyzed the temperature variation near the surface in four different scenarios of carbon dioxide concentration in the atmosphere. It is shown that the large temperature variations occur in the disconnected state, near the region of coupling. The results indicate that the decreasing of the diurnal temperature range could be associated to the regimes variability in the stable boundary layer. INTRODUÇÃONas últimas décadas, diversos trabalhos vêm mostrando, através de registros históricos, um aumento de temperatura em diferentes regiões do globo, fenômeno atualmente conhecido como aquecimento global. Um fato peculiar que chama atenção é que a elevação de temperatura ao longo do ciclo diurno não é homogênea, já que os valores observados para

Brazil is the largest exporter and second largest producer of soybean grains. Most of this production is from plants grown under no-tillage system (NT). This research evaluated the effect of soil compaction, and different amounts of black oat residues on the soil surface on soybean growth and grain yield in lowland under NT. The experiment was conducted in a completely randomized design with seven treatments and four replications, in the 2016/2017 and 2017/2018 crop seasons. The treatments consisted of: 1) winter fallow without soil compaction (WF); 2) winter fallow with soil compaction (WF-C); 3) black oats and complete removal of surface residues, with soil compaction (0R-C); 4) black oats and removal half of surface residues, with soil compaction (0.5R-C); 5) black oats without surface residue removal, with soil compaction (1R-C); 6) black oats without surface residue removal, plus the residues from treatment 3, with soil compaction (2R-C); 7) black oats without surface residue removal, without soil compaction (1R). When the soybean plants were at the phenological stage R2, they were evaluated nodule, root and shoot dry matter, nitrogen contents, plant height, and grain yield. The soil physical properties were evaluated in the 0.0-0.05, 0.10-0.15 and 0.20-0.25 m layers. The soybean aerial dry matter is > 38% in non-compacted soil in year with soil water excess, regardless of the amount of surface oat straw. In year with small water deficit, soil with more surface oat straw produced > 5% shoot dry matter and > 4% of soybean grain, regardless of compaction. The plant growth and grain yield soybean in lowland varied according to the water conditions, and were affected by soil compaction and amounts of black oats residues on soil surface.