Resumo

The variability of factors that can affect the development of sugarcane is an actual issue, being the sugarcane productivity mostly limited by the presence of nutrients in soils on available forms. Major problems of such limitations are found for the plant nutrition with nitrogen, potassium and especially phosphorus. Phosphorus (P) is one of the most limiting nutrients for plant cultivation in Brazilian soils, being retained by high adsorption forces in the soil Al and Fe oxihidroxides. An alternative to improve P fertilizer efficiency could be the use of less soluble sources (rock phosphate) combined with microbial inoculants, where mycorrhizal fungi could act to increase plant P uptake. The aim of this study was to evaluate the effect of phosphate sources on mycorhizal fungal colonization, development of sugarcane and changes in microbial communities associated. The experiment was conduct in a greenhouse, using as P sources: simple superphosphate (SS), rock phosphate of Catalão - Brasil (CA) and reactive rock phosphate of Bayóvar - Peru (BA). All sources were submitted to with or without mycorrhizal fungi inoculation. Sugarcane was cultivated for three months, being collected root and shoot system for dry mass and tissue analysis. The microbial community in the rizospheric soil was analyzed using bacterial and fungi based in Denaturing Gradient Gel Electrophoresis (DGGE). The phosphate source has affected the root colonization index, the dry mass accumulation by sugarcane and the structure of rhizospheric microorganism community. Shoot and root dry mass accumulated by sugarcane increased according to the solubility of the phosphate fertilizer, exception under more soluble P sources and inoculated, which reduced the root system compared to the less soluble sources. The fertilization with natural rock phosphates has promoted less effect in root colonization than acidulated soluble P fertilizers. Regardless the inoculation, the community of fungi and bacteria are highly affected by the phosphate source.