Organic phosphorus changes with land use change in Brazil

Abstract

Land use changes, especially those which disturb the soil and alter redox reactions, affect directly the phosphorus (P) dynamics and lability for plant uptake in the soil through changes in P losses via runoff or leaching and by changing the proportions of P accumulated in more recalcitrant pools. Since P is highly limited in tropical soils, turnover of organic P and the rapid recycling of P from litterfall are the main processes for providing P to plants in natural ecosystems. Organic P is extremely important in humid tropical soils as it is an active fraction influencing P availability to plants and should be considered in studies of the P dynamics and bioavailability. It is necessary, therefore, to understand the dynamics of organic forms of P in the soil in order to develop manure and fertilizer management strategies to improve P use efficiency in pastures and sugarcane fields. Eight sites have been selected for this study, three in São Paulo State (from thematic project 2015/18790-3, Soltangheisi et al., in press) regarding land use change from degraded pasture to intensified pasture and sugarcane, two in Western Amazon (from Soltangheisi et al., 2019) regarding land use change from forest to pasture, and three in São Paulo State regarding different tillage systems and straw removal in sugarcane fields. Nuclear magnetic resonance spectroscopy (31P-NMR) to explore the distinct organic P pools in the soil is very helpful for a better understanding of P dynamics over the time with land use change. This technique combining with P fractionation methods will be used to investigate the changes in organic P species with land use change. The results obtained from these techniques will be also analyzed by path analysis (Soltangheisi et al., 2019) to investigate the dynamics of organic P in the soil. (AU)