Efeito residual da aplicação de fontes e doses de potássio na cultura da soja

Abstract

Potassium is an essential nutrient for soybean crops, directly influencing plant growth, development, and productivity. The objective of this study was to evaluate the residual effect of potassium sources and rates on nutritional traits, morphological characteristics, and yield components of soybean. The experiment was conducted under field conditions during the 2024/2025 growing season in Ipameri, Goiás, Brazil, using a randomized block design in a 3 × 5 factorial scheme, with three potassium sources (potassium chloride, phonolite, and hydrothermally treated phonolite) and five rates (0, 50, 100, 150, and 200 kg ha⁻¹), with four replications. Leaf nutrient contents, relative chlorophyll index, morphological traits, and yield components were evaluated. Potassium sources did not influence most variables, except for leaf potassium content. Residual potassium rates affected leaf nitrogen, potassium, and silicon contents, as well as the chlorophyll index. Morphological characteristics were not affected, except for the insertion of the first pod. The 100-grain weight responded to potassium rates, while yield did not differ among treatments. It is concluded that alternative potassium sources show a residual effect similar to potassium chloride, maintaining satisfactory yield levels in soybean crops.