CHEMICAL ATTRIBUTES OF A SOIL AND RESPONSE OF WHEAT AND SOYBEAN TO GYPSUM IN NO-TILLAGE SYSTEM

The application of gypsum can make Al unavailable to plants and provide soil nutrients, improving conditions for high crop yields. This study evaluated the chemical characteristics of Red Latosol, with or without exchangeable Al as influenced by gypsum rates (0, 1000, 2000, 3000, 4000, and 5000 kg ha(-1)) applied to the soil surface, and the effect of gypsum on mineral nutrition and wheat and soybean yields under no-tillage. Gypsum was applied to the surface six months after liming. Six and twelve months after gypsum application, soil samples were collected from the layers 0-0.10, 0.10-0.20 and 0.20-0.40 m. The use of up to 5000 kg ha(-1) gypsum resulted in increased levels of Ca2+ and SO42- and leaching of K+ to a depth of 0.20 m and Mg2+ down to 0.40 m, one year after gypsum application. The rate of 3000 kg ha(-1) resulted in greatest Al3+ level reduction. The application of gypsum induced increased Ca and Mg contents for soybean and reduced Ca and Mg content in wheat and increased contents of S in both crops, while K contents increased in soybean up to the 3170 kg ha(-1) gypsum rate. Gypsum increased wheat yields (cultivar CD 104), in soil with presence of Al, but did not influence soybean yield in either soil, with and without Al.