Comparative evaluation of agricultural gypsum recommendation methods in tropical sandy soils under agropastoral systems

Agricultural gypsum is essential for soil correction, neutralizing toxic aluminum, and increasing fertility, thereby promoting more efficient and sustainable agriculture. A challenge lies in the variety of methodologies in the literature, which recommend different doses and generate distinct responses in the soil. This 2017–2020 randomized-block experiment (4 replicates) compared five gypsum recommendation methods on a sandy Ultisol under agropastoral management, evaluating chemical and physical soil attributes (0–0.20 and 0.20–0.40 m) and crop productivity (corn, Marandu, soybean). Gypsum increased the sum of bases (SB), base saturation (V%), cation exchange capacity (CEC), and organic matter (OM), benefiting soil aggregation. The improvement of the soil profile was effective in increasing OM at depth, which contributed to nutrient cycling and consequently to V% and CEC, particularly in treatments that received gypsum, mainly T3 (Vitti et al.) and T5 (Raij et al.). The Vitti methodology stood out by increasing the dry matter production of Marandu palisade grass and subsequent soybean crops, while Souza, Lobato and Rein, and Raij were more effective in reducing acidity and increasing pH. Over the agricultural years evaluated, different treatments alternated in their contribution to nutrient levels such as P, K, Ca, and Mg. However, treatments with gypsum use contributed most to the levels of these nutrients, including at depth. Treatments T2 (Souza, Lobato and Rein) and T5 (Raij et al.) were the most effective in altering the soil profile at depth, showing higher calcium levels and lower aluminum content. Thus, the use of gypsum proved essential for improving fertility and productivity in tropical sandy soils.