Use of Gypsum for Crop Grain Production under a Subtropical No-Till Cropping System

Gypsum has been used in tropical and subtropical agriculture when subsoil acidity is an important yield-limiting factor. However, the conditions that promote increased crop yield as a result of gypsum addition in no-till (NT) systems still remain unclear. A field trial examined the effects of newly and previously surface-applied gypsum in a long-term NT system on the soil chemical properties and nutrition and yield of corn (Zea mays L.), wheat (Triticum aestivum L.), and soybean [Glycine max (L.) Merr.] on a clayey Rhodic Hapludox in Parana State, Brazil. Gypsum was surface-applied at 0 and 6 Mg ha−1 in 2004 on plots that had received gypsum previously at 0, 3, 6, and 9 Mg ha−1 in 1998. Surface-applied gypsum newly and previously improved exchangeable Ca and SO4–S availability throughout the soil profile, and increased the cumulative grain yield of the crops. Exchangeable K losses through leaching caused by gypsum application were low, and a larger mobility of exchangeable Mg as compared with exchangeable K in soil was found as a result of gypsum addition. An increase in Ca content in the corn, wheat, and soybean leaves, and in S content in the corn and wheat leaves occurred following the gypsum application. The use of gypsum showed economic viability to maximize crop grain production in a long-term NT soil with a sufficient level of exchangeable Ca (≥8 mmolc dm−3) and low levels of exchangeable Al (≤4 mmolc dm−3) and Al saturation (≤15%) in the subsoil layers (20–60 cm).