Gypsum Rates and Splitting Under No-Till: Soil Fertility, Corn Performance, Accumulated Yield and Profits

Gypsum is used in agriculture as calcium (Ca2+) and sulfur (S) source, and to mitigate native toxic levels of aluminum (Al3+). However, the effects on soil chemical attributes, corn leaf nutritional status, grain yield, and profitability should be better understood. Gypsum rates (0, 3, 6, 9, and 12 Mg ha−1) were applied at once (2009) or split in two (2009–2010) or three (2009–2010-2011) annual applications, to a Typic Hapludox under no-till from Southern Brazil. The use of gypsum increased Ca2+ and S-SO42− and reduced Al3+ levels in the soil up to 0.8 m depth. Increasing gypsum rates reduced Mg2+ levels up to 0.6 m. Corn leaf concentrations of Ca and S were increased, while Mg concentration was decreased by gypsum use. The maximum technical efficiency (MTE) rate of gypsum for corn (2013/2014) grain yield was 6.34 Mg ha−1. The most profitable rate for the period 2009–2014 growing seasons was achieved with 4.60, 5.63, and 6.08 Mg ha−1 of gypsum applied at once or split in two and three annual applications, respectively. The use of gypsum within the MTE interval improves chemical attributes in the soil profile, corn leaf nutritional status, corn grain yield, and land use profitability. The use of gypsum causes soil Mg2+ leaching. Split application reduces leaching process for S-SO42−, but not for Mg2+.