Effects of pasture-sugarcane conversion and intensification on soil microbiota
Brazil is a global leader in the production of sugarcane and ethanol with an area of approximately 8.7 million hectares dedicated to sugarcane harvest. Despite the constant increase in sugarcane production, to prevent its expansion over native Brazilian biomes, the conversion of underutilized pasture to sugarcane is one approach to be considered. Soil microbial community involved in nitrogen cycling in pasture and sugarcane fields, fertilized or not, may provide information about nitrogen transformation in soils. To evaluate the effects of pasture-to-sugarcane conversion as well as the intensification of both systems, by nitrogen fertilization, soil properties, ammonium and nitrate concentration in soil, abundance, diversity and taxonomy of target genes, nifH, amoA, nirK, nirS and nosZ clade I and clade II, and microbial groups associated with nitrogen cycling were measured. The abundance and composition of soil microbial communities, including nitrification- and denitrification-associated genes, were influenced by the conversion from pasture to sugarcane but remained unaffected by fertilizer application. The amoA genes from both archaea and bacteria were more abundant in sugarcane soils, while nirS and nosZ (clade I) genes were more dominant in pasture soils. Land-use change also led to an increase in archaeal populations, whereas fungal abundance showed no response to either fertilization or land use. These findings indicate that nitrogen-cycling soil communities are more sensitive to land-use change than to fertilizer application.