Formas de alumínio no solo, disponibilidade denutrientes e produtividade de culturas anuais em função de doses de calcárioincorporadas a 0,40 m de profundidade

Abstract

Recent studies have shown the importance of deeper soil correction (0 to 0.40 m) in increasing productivity, as well as in crop resilience to water deficits. However, the optimal limestone doses have been much higher than those obtained by multiplying the values calculated for the 0 to 0.20 m layer by two, as suggested in the recommendation bulletins. Thus, the objective of this study was to evaluate the effects of incorporating high doses of limestone up to 0.40 m in depth on nutrient availability and grain productivity, in addition to evaluating the effects of liming on acidity correction and on the forms of exchangeable Al (AlKCl), Al associated with OM (AlCuCl2 - KCl) and the relationship of these forms of Al with crop productivity. The experiments were conducted independently, in DBC with four replicates, in the cities of Uberlândia (Site 1), Araguari (Site 2), São João del Rei (Site 3) and Formiga (Site 4), in soils with sandy loam to very clayey texture. The treatments consisted of six limestone rates (0.0, 4.0, 8.0, 12.0, 16.0 and 20.0 Mg ha-1) at sites 1, 2 and 3 and eight limestone rates at Site 4 (0.0, 4.0, 8.0, 12.0, 16.0, 20.0, 24.0 and 28.0 Mg ha-1), incorporated at 0.40 m. In the first study (article 1), liming increased pH and reduced H+Al at different soil depths at all sites. The largest increases in pH (pH >7.0) occurred at sites 1 and 3. AlKCl levels were higher at sites 2 and 4 and decreased with increasing pH. Likewise, AlCuCl2 and Al (CuCl2 – KCl) levels were inversely related to increasing pH. The observation of higher pH values in soils that naturally presented the lowest AlCuCl2 levels and also the positive relationship between these amounts of AlCuCl2 and H+Al indicated that these forms may be associated with pH buffering in these soils. Liming increased accumulated productivity, with maximum yields obtained with doses of 13.2 (Site 1), 17.1 (Site 2) and 18.7 Mg ha-1 (Site 4). In the second study (article 2), carried out at Site 3, liming positively influenced pH and V% values and Ca and Mg levels. In the soil, reductions were only observed in Fe in the first two years and in B in the second year of evaluation. Reductions in foliar concentrations were observed for Fe in soybean and corn, while B and Mn were reduced only in legumes, without harming crop nutrition. Soybean productivity, grown under water stress, was increased by lime rates, with the maximum at the estimated rate of 15 Mg ha-1. In turn, corn productivity, in two crops with high volumes of accumulated precipitation, was not influenced by liming.