Relação de pedoambientes com as formas carbono, nitrogênio e fosfóro em classes de solo do estado da Paraiba

Abstract

There are few studies on the influence of climate gradient, especially rainfall, in the dynamic of C, N and P in soils of Paraiba State, which are critical informations for planning soil management. In this context, the objective was to evaluate the influence of climate gradient in the C and N stocks, and in the forms of C, N and P, in three representative soil orders of Paraiba State. Eight areas were selected considering two climatic gradients (Hot and semi-humid, and hot and semi-arid) in three soil orders (Solonetz , Luvisol and Leptosol – FAO/WRB). Was evaluated the levels and stocks of C and mineral N (NH4 + and NO3 - ), the particulate organic carbon (POC), organic carbon associated with silt and clay minerals(COam), light organic matter (LOM), and the phosphorus fractioning (P-Al, P-Fe and P-Ca). The POC content varied between soil types and climatic gradients, with higher levels in the climate hot and semi-arid in Luvisol (Cabaceiras) and COam in the climate hot and semi-arid in Luvisol (Taperoá); the LOM contents behaved differently in each soil order, in which the surface horizons had the highest C content, except in Leptosol of the hot and semi-arid climate (Picuí), while stocks did not follow this behavior, and can relate this fact with different densities and thicknesses of the horizons.Regarding stocks of N, the behavior was different in Leptosol, where the largest stocks were found in the deeper horizons, different from the others, indeed related to the ease of leaching presented by this soil, but in Planosol was observed higher stock of N in hot and semi-arid climate in Luvisol, the highest stock of C was in hot and semi humid climate in Leptosol; stocks of C and N were higher in hot and semi-arid climate.The highest levels of P fractions were found in Luvisol in the hot and semi-arid climate, with predominance of P-Al and P-Fe, this may be associated with low levels of Ca2+ and pH of soil, taking into account that P-Al and P-Fe are higher in most developed soils, while the P Ca predominates in alkaline soils; the N fractions contents were low in all soils and horizons, with exception on the hot and semi-arid climate in Luvisol that had higher levels of nitrate, due to the accumulation of organic matter from leaf litter; with increased rainfall occurs an increase in fractions of P and N in Planosol and Luvisol; the parental material influenced more than rainfall.