Combined Sulfur and Boron Fertilization Improves Peanut Yield and Kernel Nutrient Composition in Tropical Sandy Soils

Sulfur (S) and boron (B) deficiencies are increasingly reported in sandy soils with low nutrient retention, potentially limiting peanut yield and kernel quality. This study evaluated the individual and combined effects of S and B fertilization on peanut yield, plant nutritional status, kernel nutrient composition, and nutrient distribution within the soil profile. Two field experiments were conducted during the 2022–2023 growing season in São Paulo State, Brazil, in a randomized complete block design with four replications and a split-plot arrangement. Treatments comprised B alone, S alone, and combined B + S, each at four rates: zero, low (0.83 kg B ha -1 and 30 kg S ha -1 ), intermediate (1.7 kg B ha -1 and 60 kg S ha -1 ), and high (3.3 kg B ha -1 and 120 kg S ha -1 ). Applied individually at intermediate rates, S or B increased pod yield by approximately 750 kg ha -1 . Combined application increased yield by approximately 920 kg ha -1 at the lowest rates (0.83 kg B ha -1 + 30 kg S ha -1 ), with no further benefit at higher rates; the highest B rate applied alone reduced yield at one location. Fertilization also increased N, S, and B concentrations in leaves and kernels. Soil analyses indicated high mobility of both nutrients and limited residual accumulation within the profile. Combined application of 0.83 kg B ha -1 + 30 kg S ha -1 was sufficient to achieve high pod yield in both tropical sandy soils, whereas higher rates conferred no additional benefit and, in the case of B, reduced yield. The high mobility and limited residual accumulation of both nutrients favor moderate annual applications over high rates aimed at building soil reserves.