Componentes de rendimento da cultura da soja em função da aplicação de nitrogênio no florescimento

Abstract

Brazil has been consolidating as one leading global producer of food, and soybeans, Glycine max (L.) Merrill, the main grain crop grown in the country, and one of the great responsible for the economic performance of Brazilian agribusiness. Soybean cultivation became viable, in good part because of the ability of this species of fixing atmospheric nitrogen for their nutrition, together with nitrogen fixing bacterias. The continuous increase in soybean productivity, observed throughout the last two decades, is a reflection of the improvement of the system of soybean production in Brazil, due to the advances of genetic order, of control of crop pests and diseases, and especially efficient use fertilizers. Nitrogen is the nutrient required in greatest amount by soybean crop because the grains are very high in protein presenting an average content of 6.5% N. Currently many papers have been developed about to nitrogen supply, pointing out that the biological fixation alone might not be contributing with the amount required for the plant to express its productive potential. This study aims to evaluate the effect of nitrogen applied at soybean flowering, and their effects on plant height, the yield components (number of pods per plant, number of seeds per pod and thousand seed weight) and yield. The experiment was conducted at Escada Farm, located in the municipality of Irineópolis - SC, in 2012/2013 harvest, with cultivar SYN 1163, on no-tillage system. The experimental design used was a randomized block with five treatments and five replicates, totaling 25 plots of evaluation. When the soybean crop was in full flowering was applied Nitrogen, as urea according to the following treatments: 1) control - without N fertilization; 2) 22.5 kg ha-1 N, 3) 45.0 kg ha-1 N, 4) 67.5 kg h-1 N, 5) 90.0 kg ha-1 N. Was performed by analysis of variance F test, and when significant, the data were subjected to comparison of means by Duncan test at the 5% level of significance and regression. Significant difference was observed among the treatments only for the variable plant height, with the highest average (122.68 cm) was obtained with the dose of 45 kg ha-1 N. For the components of yield (number of pods per plant, number of grains per pod and thousand seed weight) there was no significant difference among the treatments. However increase was observed in all treatments with N fertilization for the number of pods per plant compared to control. In the component weight of 1000 seeds there was an increase in weight with increasing doses of 22.5, 45.0 and 67.5 kg ha-1 N. As to soybean productivity, there was no difference between treatments.