Changes in soil chemical properties and corn response to lime and gypsum applications

Root growth and crop yield can be affected by chemical modifications of the soil profile owing to lime and gypsum applications. A field trial was carried out on a dystrophic Clay Rhodic Hapludox in Ponta Grossa, Parana State, Brazil, aiming to evaluate the changes in the chemical soil properties and corn response to lime and gypsum applications at the installation of a no-tillage system. A randomized complete block design was used, with three replications, in a split-plot experiment. The main plots received dolomitic limestone treatments (no lime; 4.5 t ha(-1) of lime applied on the surface supplying the total demand, 113 of the total demand applied on the surface during three years; total demand incorporated into the soil) and the subplots received gypsum rates (0, 3, 6, and 9 t ha(-1)). The treatments with lime were applied in July 1998 and the rates of gypsum in October 1998. Corn was evaluated in the agricultural year of 2001/02. The applied surface liming, at full or split rates, provided a more accentuated soil acidity correction in the superficial layer (0-0.05 m), and there was a stronger reaction in the 0.05-0.10 and 0.10-0.20 m layers, when lime was incorporated into the soil. Gypsum improved the subsoil, increasing the concentrations of Ca and S-SO42-, raised N, K, and Ca concentrations in the corn leaves, while it reduced the Mg concentration in soil and corn leaves. Liming and gypsum treatments did not affect the corn root growth. Liming (whether surface applied, at full or split rates, or incorporated into the soil) and gypsum increased the corn yield, due to an increase in the Ca soil saturation of the superficial layers. The application of gypsum associated to liming was an effective strategy to maximize grain yields.