Vinasse and straw retention decrease fungal diversity and potentially pathogenic fungi in sugarcane soil

Abstract

Soil management practices used in sugarcane agriculture in Brazil require synthetic mineral fertilizers and full recycling of waste products from ethanol production to sugarcane fields in the form of organic fertilizer. Vinasse (V) is a by-product of the sugar-ethanol industry, and it has been used as a liquid organic fertilizer in combination with mineral nitrogen (N) and straw retention. Despite numerous benefits to the physical and chemical characteristics of the soil, the effects of these organic residues combined with mineral N fertilizer on the soil fungal community are still largely unknown. This study focused on the effects of V combined with mineral N fertilizer and straw retention on the fungal microbial community diversity, richness, evenness, composition and structure in sugarcane-cultivated soils in a greenhouse mesocosm experiment. The experiment consisted of a combination of V, mineral N and sugarcane-straw blanket. Soil samples were collected at 7 (T7), 157 (T157) and 217 (T217) days after planting, corresponding to maximum carbon dioxide (CO2) emissions from soil induced by the fertilizers after three repeated applications into the soil. Across 57 soil metagenomics datasets, it was revealed that the application the V in combination with mineral N and straw retention as a surface blanket decreased a diversity, evenness and richness of fungi at the community level in soil. Analysis of the soil fungal community composition based on the 20 genera most abundant in the soil revealed decrease in abundance for Blastomyces, Melampsora and Penicillium after the third application of V in combination with N fertilizer and straw blanket. An opposite response was revealed for Amauroascus, Cantharellus, Chrysosporium, Clavaria, Morchella, Puccinia, and Tuber in soils under this treatment. Shifts in fungal community composition were followed by increases in mycorrhizal and decomposers soil-borne fungi and decrease in potentially pathogenic fungi, but not by changes in community structure. Based on these results, it is possible to attest that repeated applications of V in combination with mineral N fertilizer and sugarcane-straw blankets affect ecological aspects of the soil fungal community composition and potentialfunctions played by fungi in sugarcane soil, which are essentials to ecosystem function and sustainable management of agricultural ecosystems.