Gesso ou intervenção mecânica nas melhorias do gradiente de cátions do solo e na produtividade da soja e milho em plantio direto

Abstract

The No-Tillage (NT) diffused in about 70 % of producing grain crops and has emerged as an alternative to soil losses due to the conventional tillage. However, it has been observed in recent years that the basic assumptions of this system are not being considered, reflecting in densification of layers and therefore lower infiltration and soil water storage. Furthermore, due to the characteristics of the system itself, it has been observed the formation of a fertility gradient with high nutrient concentrations in the superficial layers of the soil. With this, the highest goal to be accomplished is to create physical and chemical soil conditions, able to permit greater infiltration and water storage, root growth and absorption capacity of both water and nutrients in depth, depending the vulnerability of soybean and maize recurrent water deficits in the state of RS. The gypsum has been touted as enhancing the chemical characteristics of the subsoil, as his ability to deliver cation and sulphur to lower layers of the listing, in addition to eliminating toxic forms of aluminium to plants. Farmers from the northern region of RS are speculating using this product without observing large returns to grain production, which lacks scientific technical soil and climate in the local conditions. In this sense, this study aimed to verify the effect of gypsum combined with mechanical interventions of a consolidated system of zero tillage on the gradient of cation in the soil profile and the cultivation of soybeans and corn. Application rates of gypsum were performed on the soil surface, with and without mechanical intervention, making it the cultivation of soybeans/corn plants under cover for four seasons (2009/10, 2010/11, 2011/12 and 2012/13). The results showed that the mechanical operations of the soil did not influence the effects of gypsum on the gradient of cations in the soil profile and grain yield of corn and soybeans; Intervention soil with plowing+disking alters the Ca2+ gradient in the soil under NT and the plaster has little potential to mobilize cations vertically soil, and the effects are limited to 0.10 m depth; Use of gypsum shows little maximizing soybean production and maximizing good for corn production, being the contribution of sulfur in soil maximizing main factor.