Crescimento e fenologia da soja em função da adubação potássica

Abstract

In Brazil, soybean cultivation has stood out due to the adoption of high level of technology and crop management, and the nutritional requirements such as potassium fertilization of great importance for increasing agricultural productivity. In this sense, the aim with this study was to evaluate the growth and phenology of soybeans due to the potassium. The experiment was conducted in a greenhouse in the Amazon Federal Rural University in Belem, PA. The soil used was dystrophic Yellow Latosol. The experimental design was randomized blocks in a factorial 5 x 12, with five repetitions, and the factors consisted of five doses of potassium (0, 40, 80, 120 and 140 kg ha-1) in the form of potassium chloride and 12 phenological stages (VE - cotyledon above the soil surface, VC - open cotyledons, V1 - developed unifolioladas leaves, V2 - first developed trifoliate leaf, V3 - second fully developed trifoliate leaf, V4 - developed third trifoliate leaf, V5 - fourth developed trifoliate leaf, V6 - fifth developed trifoliate leaf, V7 - sixth developed trifoliate leaf, R1 and R2 - bloom and R7 - plant maturation). We evaluated the phenology from the monitoring point. The maximum agronomic efficiency was achieved with the estimated dose of 72 kg ha-1 potassium, getting height estimated at 38 cm. There was a decrease in height from the rate of 80 kg ha-1 potassium. Therefore, the soybean plants are usually developed independent of potassium levels, with no dose effect on soybean stages.