Manejo da adubação potássica na cultura da soja e efeito residual na cultura do milho em sistema plantio direto no Oeste do Paraná

Abstract

The fertilization with potassium in the soybean crop has been carried out most of the time in the planting groove; however, potassic fertilization techniques that are usually recommended in sandy soils have been adopted in clayey soils. The aim of this work was to evaluate the response of potassium fertilization in soybean crop in different management systems with two sources of potassium (K) and the residual effect on corn cultivation in an eutroferric soil. Two sources of K, potassium chloride and KCl-polymer were tested. The experiment was installed in the municipality of Formosa do Oeste-PR. The design was a randomized complete block design in a factorial scheme (2x5) +1 with 2 sources of potassium, KCl and KCl-polymer and the K2O dose split in five application periods. At the time of sowing, all treatments received phosphate fertilization in the form of simple superphosphate to provide 60 kg ha-1 of P2O5. For the soybean, KCl-polymer was more efficient for the haul application before sowing the crop. The application of KCl was better when applied at the V3 stage of the culture. The higher K content in the leaf and higher fertilizer use efficiency and recovery efficiency indicate superiority of the KCl-polymer source. With regard to corn, the highest residual content of potassium in the soil reflected in higher potassium content in the leaf, in the grain and higher productivity for both sources. Only when KCl-polymer was used at the V3 stage of the soybean crop that the productivity was significantly higher than the control. For both sources, the residual potassium content in the soil after corn harvesting was considered Low and medium.