Ação residual e interação entre calagem e gessagem superficial na fertilidade de um solo arenoso e no estado nutricional da soja

Abstract

Limestone and surface gypsum is an excellent correction option without modifying the system, as it allows the movement of the corrective to the deeper layers of the soil. In this way, the improvement of the chemical characteristics of the soil, in depth, resulting from the surface limestone will be proportional to the used dose of the corrective. The objective of the work was to evaluate the availability of the fertility of a sandy soil in the system, in view of the application of doses of dolomitic limestone in the absence and presence of gypsum as a subsurface conditioner. The experiment was carried out, at the Experimental Farm of the Universidade do Oeste Paulista - Unoeste, in Presidente Bernardes-SP, on a soil classified as dystrophic Red ARGISOLO with smooth wavy relief. The experiment was structured according to the experimental design in bands with subdivided plots, in a 4x2 factorial scheme, with three replications, with the plots consisting of four limestone doses (0, 2, 4 and 8 Mg ha-1) and the subplots by doses of agricultural gypsum (0 and 4 Mg ha-1). The plots and subplots comprised an area of 400 m² and 200 m², respectively, and in 2014 received the unique and superficial application of dolomitic limestone (CaO - 36%, MgO 15.8% and PRNT 90%), with and without plaster. (CaSO4) which is an excellent source of Ca - 20% and S - 16%. The following were evaluated: chemical analysis of the soil, soybean plant tissue and soybean yield. The data were subjected to analysis of variance and, in case of significant effect for limestone and plaster doses, regression analysis (linear or polynomial) was performed to verify the effect of limestone doses on the surface. In the case of a significant effect for the doses of superficial gypsum, the data were compared using the Tukey test (P≤0.05), using the Sisvar software. It was concluded that the dose of 4 Mg ha-1 of dolomitic limestone maintained base saturation close to 60% and Mg2+ above the critical level for culture. Agricultural gypsum contributed to the increase in the levels of Ca2+ and Mg2+ up to 0.40 m in depth. There was a greater movement of K+ and SO42- in the soil profile due to the increase in limestone doses in the presence of gypsum. The residual action of limestone and gypsum was observed over the years of management. Despite improvements in soil fertility, limestone and gypsum did not promote significant gains in soybean yield.