Microbial community response to transition from no-till to conventional tillage, and vice versa, associated with soil-particles fractions

FRENE JP; GABBARINI L; WALL LG

Rosario

Congreso; 7th World Congress on Conservation Agriculture; 2017

CAAPAS-AAPRESID

An understanding of the distribution of soil microorganisms and enzyme activities in particle-size fractions is important in order to determine how tillage systems influence soil structure and function at microbial and biochemical levels. Conservation practices are used to improve soil nutrients and structure, providing habitat and substrate for biota, which is largely responsible for the mineralization of nutrients in the soil. No-till is the first step to conservational practices. The objective of this study was to determine if the microbial community composition and soil activity enzymes associated with different particle-size fractions changed with the transition to no-till or tillage after 3 years of management transition. Treatments involving no-tillage (NT0) and conventional tillage (CT0) with their respective new treatments, new no-tillage (n-NT) and new conventional tillage (n-CT) were sampling from a current agricultural field assay with more than 30 years with the original NT and CT managements. Size fractions of 2000-250µm, 250-63µm, 63-20µm, 20-2μm and 2-0.1µm were obtained by a combination of low-energy sonication, wet sieving, and repeated centrifugation. Soil fractions distribution, enzymatic activities and microbial abundances clearly differentiate historical treatments and shifted after soil management shift. Microbial groups at Bacterial, Archaea and Fungi level, measured by qPCR, were slightly different among treatments but show more differences at the aggregate level, depending on the size fraction. The fractions 2000-250μm, 250-63μm, and 20-2μm show particular changes in this groups according to change of soil managements. When main bacterial fillums were quantified at the fraction level, Acidobacteria, Actinobacteria and in a lesser extent Firmicutes appeared to be the most sensitive groups according to management. In conclusion, soil managements differentially structure microbial communities and play a key role to determine modifications at soil-particle fractions level enhancing bigger micro-aggregates in the no-till management in comparison to conventional tillage. Modifying, in consequence, the enzymatic profile and soil services as a whole.