Soil management, phosphate fertilizers and green manure effects in organic phosphorus

Abstract

The different agricultural system management affects the dynamics of legacy phosphorus (P) in the soil, and its use by plants. Thus, the objectives of this work plan are: to evaluate of long-term soil management and phosphate fertilizers effects on the dynamics of legacy organic P (Po) in Brazilian Savanna soils; and to investigate the ability of different plant species to increase the mobilization of recalcitrant legacy Po. For this, three experiments will be evaluated. The first is a long-term experiment (17 years with P fertilization and 8 years of P fertilizer suppression), constituted by two soil management systems (no tillage-NT and conventional tillage-CT), two P sources (triple superphosphate-TSP and phosphate rock-PR) and two methods of application (seed furrow and broadcasted). The second experiment, also long-term (more than 20 years), is composed by factorial design 2 x 2 x 2 + 2, that are, 2 soil managements (NT and CT) x 2 P doses (50 and 100 kg ha-1 of P2O5) x 2 sources (TSP and PR) + 2 controls (0 kg ha-1 in SPD and SPC). The third experiment will be carried out in a glasshouse during six months, with 5 green manures (1: blue lupin; 2: pea; 3: barley; 4: mix blue lupin and barley; 5: mix pea and barley) x 2 soils (collected of long-term experiment with biomass retention and biomass removal). Solution 31P nuclear magnetic resonance (31P-RMN) will be performed in soil samples of the first two experiments; and the following analyzes will be carried out on the samples of the last experiment: foliar P content; microbial biomass P, phosphatase enzyme measurements and chemical sequential P fractionation in soil samples. With this, a broader understanding of P speciation and P dynamics under distinct managements is expected, correlating the changes in soil Po with the management, aiming at the optimization of P use in the long-term. (AU)