Correlations between the phosphorus fractions of soil and rhizosphere microbiome of sugarcane
Phosphorus is essential for life, but it is often limited in soil due to its high reactivity. Up to 80% of added phosphorus can be immobilized as low-labile compounds. Plants can solubilize non-labile phosphorus through organic acids synthesized by soil microorganisms, which also contribute to the mineralization of organic phosphorus through the production of enzymes. This study aimed to correlate changes in organic and inorganic phosphorus fractions in the rhizosphere of sugarcane plants with their microbiome structure and diversity. A total of 74 rhizosphere samples were analyzed. Plants were grown for 180 days in microcosms with different phosphorus sources, both with and without filter cake. The different phosphorus fractions were correlated with molecular data based on partial sequencing of the 16S rRNA gene. At 60 days, there was greater overall bacterial diversity, benefiting copiotrophic bacteria. At 120 days, diversity decreased in response to reduced labile phosphorus content, benefiting oligotrophic bacteria. The association of filter cake with monoammonium phosphate showed evidence of increased mineralization on the soil surface, with a strong correlation with an increase in Beta-Proteobacteria population. In general, filter cake changed the solubilization and availability of phosphorus in mineral sources, contributing to increases in organic and inorganic phosphorus fractions. These results showed that bacteria participate in processes that make phosphorus available in soil and that filter cake can modulate these transfers beneficially to plants by stimulating the activity of phosphorus-solubilizing microorganisms and mineralizing soil organic matter.