Dynamics of phosphorus in the rhizosphere and efficiency of phosphate sources and filter cake in sugarcane

Abstract

In tropical soils, phosphorus is adsorbed onto the oxide surface, reducing its availability to plants. Thus, the best exploitation of the soil becomes important in rhizospheric region where the roots of plants and soil microorganisms are constantly interacting. The aim of this study is evaluate the effect of filter cake on the structure of microbial communities associated to the sugarcane root system to understand how the community of microorganisms can contribute to the availability of phosphorus for plants, especially under fertilization with low solubility sources, so that the plants can access it and how it can improve the fertilizer use efficiency and identify the contribution of each source in shaping the microbial structure of sugarcane rhizosphere. The experiment will be held in an Oxisol from Piracicaba - SP, in a greenhouse, at Soil Science Department - ESALQ-USP in randomized blocks with 4 replications. The treatments are going to be in a 2x3 factorial, with or without filter cake (10 t DM ha-1), and phosphate sources: soluble phosphate, rock phosphate and no phosphate fertilizer. The rhizospheric soil will be collected 0-2 mm from the root. These soil samples will be subjected to extraction of total DNA, with subsequent use of direct sequencing for fungi and bacteria, using Polymerase Chain Reaction (PCR) approach and Terminal Restriction Fragment Length Polymorphism (TRFLP) technique. The fractionation of phosphorus will be carried out in these soil samples, as well as the accumulation of phosphorus in plant tissue. The molecular data, phosphorus fractionation and phosphorus concentration in plant tissue will be analysed by appropriate multivariate techniques. The correlation between these data will allow inferences about changes in the structure of microbial communities associated with the cultivated soils with sugarcane, under different managements of phosphorus fertilization. (AU)