Does Organomineral Fertilizer Combined with Phosphate-Solubilizing Bacteria in Sugarcane Modulate Soil Microbial Community and Functions?

Soil bacterial and fungal communities are suitable soil ecosystem health indicators due to their sensitivity to management practices and their role in soil ecosystem processes. Here, information on composition and functions of bacterial and fungal communities were evaluated at two phenological stages of sugarcane (six and twelve months, equivalent to the most intensive vegetative stage and to final maturation, respectively) when organomineral fertilizer, combined with phosphate-solubilizing bacteria (PSB), was added into the soil. Organic compost enriched with apatite (C + A) or phosphorite (C + P) and compost without phosphate enrichment (C) were used in the presence or absence of PSB. In addition, we used a control fertilized with soluble triple superphosphate. The differences were more related to the sampling period than to the type of organomineral fertilizer, being observed higher available phosphorus at six months than at twelve months. Only in the C treatment we observed the presence of Bacillaceae and Planococcaceae, while Pseudomonadaceae were only prevalent in inoculated C + A. As for fungi, the genera Chaetomium and Achroiostachys were only present in inoculated C + P, while the genus Naganishia was most evident in inoculated C + A and in uninoculated C + P. Soliccocozyma represented 75% of the total fungal abundance in uninoculated C while in inoculated C, it represented 45%. The bacterial community was more related to the degradation of easily decomposable organic compounds, while the fungal community was more related to degradation of complex organic compounds. Although the microbial community showed a resilient trait, subtle changes were detected in microbial community composition and function, and this may be related to the increase in yield observed.

Experimental validation under controlled conditions of real time PCR to quantify arbuscular mycorrhizal colonization in root.

Mycorrhizal colonization of roots is traditionally evaluated by empirical methods, such as root microscopy. We compared this method with data from using a real time PCR technique, and determined the correlation between methods, indicating particularities of a promising system for a quick and accurate molecular diagnostic of arbuscular mycorrhization.