Band applied K increases agronomic and economic efficiency of K fertilization in a crop rotation under no-till in southern Brazil

The effectiveness of potassium (K) fertilizer management strategies on sandy clay loam soils under no-till (NT) is essential to achieving economically viable yields. This study compared the agronomic and economic efficiency of K fertilization using band application versus broadcast distribution on a subtropical Acrisol under NT. From 2019–2023, five K rates (0, 50, 100, 150, and 200 kg ha⁻¹) were applied annually using band and broadcast methods during spring/summer at corn or soybean sowing. There was no increase in grain crop yield with K broadcast application. This resulted in economic loss and significantly increased the available K levels in the topsoil, hampering the use of this soil layer to diagnose K availability and the likelihood of response to K fertilizers. The optimum agronomic and economic K rate matched the output K rate when the fertilizer was banded. The application of 50 kg ha⁻¹ of K increased 20 % the partial factor productivity, 300 % the agronomy efficiency, 680 % the economic profit from applied K, and 100 % the value cost ratio compared to the broadcast application. Even with available K above the critical level in the soil of the 0–10 cm layer, low rates of K fertilizers should be applied banded in the seed furrow.