Remineralizadores e KCL como fonte de potássio para a sucessão soja-milho

Abstract

Potassium is the second most absorbed mineral nutrient by plants and presents low residual effect in the soil due to the high solubility of potassium chloride, the most used source in agriculture. In this context, the objective of this study was to evaluate the effect of five doses and three sources of potassium on the chemical attributes of the soil, as well as on the productive and nutritional characteristics of soybean and maize, including the residual effect on second crop maize, in a dystrophic Red Latosol. The experiment was conducted at the Experimental Farm of Agricultural Sciences (FAECA) of the Federal University of Grande Dourados (UFGD) during the 2021/2022 and 2022/2023 seasons for soybean, and the 2022 and 2023 seasons for maize. A randomized block design was used, arranged in a 5 × 3 factorial scheme with four replications, totaling 60 experimental units. The treatments consisted of five K₂O doses (0, 25, 50, 75, and 100% of the recommended K₂O dose, corresponding to 0, 25, 50, 75, and 100 kg ha⁻¹ of K₂O) and three K sources [potassium chloride (60% K₂O), phonolite (8% K₂O; 25% Si), and hydrothermally treated phonolite (12% K₂O; 25% Si)]. Soil chemical attributes and potassium desorption were evaluated, as well as macro- and micronutrient concentrations in diagnostic leaves, yield components, and grain productivity. Data were subjected to analysis of variance; polynomial regression was applied for K doses, and Tukey’s test for K sources, using the SISVAR statistical software. For Ca, the highest levels were obtained with phonolite and hydrothermally treated phonolite, which promoted gradual nutrient release and improved cation exchange capacity. Phosphorus content was not affected by sources or doses, remaining within adequate levels. KCl increased Cu and Zn levels, whereas hydrothermally treated phonolite showed a more balanced effect on micronutrients and greater stability in Fe release. Application of K₂O sources and doses influenced nutrient availability and crop productivity. In soybean, hydrothermally treated phonolite stood out by maintaining higher yields under water deficit conditions (2021/22 season) and performance equivalent to KCl under favorable conditions (2022/23). Antagonism among K, Ca, and Mg was observed, especially with KCl, while hydrothermally treated phonolite reduced this effect, ensuring better nutritional balance. In maize, K₂O sources did not differ significantly, although phonolite showed a slight advantage at intermediate doses. Overall, hydrothermally treated phonolite proved to be the most efficient K₂O source, providing chemical stability, nutritional balance, and productivity comparable to or greater than KCl, establishing itself as a sustainable alternative for potassium fertilization.