Residual Effect of Polyhalite Fertilizer for Corn Grown on Sandy Soil.

Sandy soils in Brazil presents low amounts of nutrients, as phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S). Normally the soybean and corn fertilizations are made to supply only P and K, besides nitrogen (N) for corn. Use of fertilizers containing these other nutrients (S, Ca and Mg) is important to the management of crops in order to get greater sustainability of the yields. The aim of the research was to evaluate the residual effect of the mineral fertilizer Polyhalite applied in the previous soybean crop, on the corn yield. Polyhalite is a natural fertilizer extracted from is a single crystal complex with two molecules of water of crystallization, and the chemical formula of the mineral is: K2Ca2Mg(SO4)4.2(H2O). Polyhalite contains 19.2% S, 14% K2O, 17% CaO, 6 % MgO. Trial was conducted at Farm Alvorada, in Luis Eduardo Magalhaes, Bahia, Brazil. Soybean was sown under no-till on November, 2015. Seven treatments were installed to compare three rates and two sources of potash, KCL and Polyhalite. Soybean was harvested on March,2016, and corn was sown on October, 2016, and all treatments had received same fertilization, 150 kg/ha N as urea, 100 kg/ha P2O5 as MAP, and 60 kg/ha K2O as KCl, in order to evaluate residual effect of potash sources applied on previous soybean fertilization. Corn was harvested on March, 2017 and yield was 6% higher in function of residual of Polyhalite in comparison with KCl fertilization, showing importance of the S, Ca and Mg in the management of the crops.