Temporal variation in phosphorus dynamics under different soil management and phosphate fertilizers

Abstract

Fractions and forms of Phosphorus (P) accumulated in the soil and its distribution depends on many factors, especially on the management adopted in the system. Thus, the general aim of this research is to evaluate the legacy P dynamics in different managements of the soil and phosphate fertilization. To this end, three experiments will be conducted. The first is a long-term experiment with 17 years of P fertilization and eight years without P fertilization, aiming to indicate the kind of management that accumulates more P and that favors the P use by plants. The treatments consisted by two soil tillage systems (No-Tillage - NT and Conventional Tillage - CT) and four phosphate fertilization management strategies, with two P sources (Triple Superphosphate - TSP and Reactive Rock Phosphate - RRP) and two application methods (band-applied in the plant row and broadcast spread). The second experiment, also long-term (21 years), aims to evaluate the dynamics of P fractions and forms accumulated in the soil under different management. The treatments are set up in a factorial scheme, with two soil tillage systems (CT and NT) x three P doses (0, 50 and 100 kg ha-1 of P2O5) x two P sources (TSP and RRP). The third experiment will be conducted in a greenhouse, with the aim to estimate how much P which accumulated in the soil is useful to be explored in crops. The treatments will consist of the three P fertilizer doses (0, 50 and 100% of plant absorption) and three species: soybean, maize and brachiaria, being composed of 12 successive crops. Chemical fractionation of P, speciation of P by XANES and nuclear magnetic resonance, successive resin extractions will be carried out, in addition to the microbiological analysis, legacy P stocks in the soil, and efficiency of P use by plants. With this project, it is expected to indicate which management results in the most efficient use of legacy P by plants and to estimate how much of this P may be economically exploited in agricultural crops. (AU)