Efeito de doses de calcário aplicadas em superfície e incorporado na produtividade de grãos e nos atributos químicos de solos com diferentes teores de argila

Abstract

Brazil stands out in the global situation of food production due to its current grain production, as well as its potential to increase production in the coming years, due to the increase in crop yield. As most Brazilian soils are naturally acidic and have low Ca2+ and Mg2+ contents, it is necessary to carry out limestone doses correctly before implementing the no till (NT). As it is no longer desirable to disturb the soil after adopting NT, most of the time limestone is applied to the surface without incorporation. However, there are still many questions about the efficiency of liming in soils under NT, mainly about the need to incorporate the limestone with the reopening of production fields after a certain period of initial liming, especially in more clayey soils. Therefore, the goal of this study was to evaluate the efficiency of increasing doses of limestone applied to the surface, without incorporation, compared with an incorporated rate on crop yield and chemical conditions of soils under NT, with different clay contents. The experiments were conducted independently in three locations in the state of Minas Gerais, Site 1 (52% clay), Site 2 (41% clay), Site 3 (21% clay). A randomized block design was adopted, with four replications and six treatments, which were composed of five doses of limestone (0, 2, 4, 6 and 8 Mg ha-1), applied to the surface (without incorporation), and one dose of 8 Mg ha-1, with incorporation. Each plot was 10 m wide and 20 m long. The experiments were implemented before the 2019/20 harvest and soil analyzes were carried out three years after limestone application (2022). The effects of surface liming on the chemical attributes of soils with the highest clay contents (sites 1 and 2) were concentrated in the 0-0,10 m layer, while in the sandier soil (site 3) there was an increase in base saturation (BS) and pH up to the layer of 0,20-0,40 m. Furthermore, in all locations, the application of the highest doses on the surface (6 and 8 Mg ha-1) gave greater effects in depth than the lowest applied doses. When incorporated, limestone was more efficient in correcting the 0,10-0,20 m layer, especially in the more clayey soils (sites 1 and 2). Accumulated grain yield during the three years of study increased only in Site 2, which had the lowest BS in the 0,10-0,20 and 0,20-0,40 m layers, with the plot receiving the application of 8 Mg ha-1, followed by incorporation, showed greater grain yield. Therefore, the vertical movement of limestone in the soil profile was directly proportional to the applied dose and inversely proportional to the clay content of the soil.