GLOBAL MICROBIAL ACTIVITY AS SOIL HEALTH INDICATOR IN MOLLISOLS OF THE SOUTHEASTERN BUENOS AIRES PROVINCE

Abstract

Soil biological activity (i.e. mineralized carbon (C) (Cmin)) is a crucial property to evaluate soil health and its changes due to soil use. In the southeastern Buenos Aires province (SEB) there is scarce information about how agriculture ecological intensification (IEA) affects soil global biological activity and the potentially mineralized C (C₀) to improve the comprehension of the mechanisms that regulate soil C dynamics. It would be relevant to determine the adequate incubation time at which the determination of Cmin can predict C₀ in soils from the SEB. Moreover, the Cmin determined in early incubation days has been proposed as a quick alternative to estimate C₀. It has been hypothesized that it is necessary to run longer incubations to correctly evaluate C₀ of soils of the SEB and that the CO₂ emitted during short incubation periods is a good estimator of C₀. Soil samples were taken (0-5 and 5-20 cm) from a long-term experiment on crop-pasture rotations on Mollisols at Balcarce with different levels of IEA under conventional tillage and no-tillage (SD). Total (COT), particulate (COP) and associated organic C were determined, as it was the Cmin from aerobic incubations under controlled conditions at 2, 4, 6, 10, 16, 22, 28, and 63 days. The C₀ was estimated from the Cmin at 22, 28, and 63 days. The Cmin and C₀ showed similar patterns among cropping systems. The estimations of C₀ from the Cmin at 63 days were the most trustable (mean of C₀ 466,9 and 517,8 mg C kg^-1 from Cmin(28) and Cmin(63), respectively). Furthermore, the Cmin at a few days of incubation showed high correlation coefficients with C₀ (r between 0.68 and 0.92 at 0-20 cm for 2 to 10 incubation days) and therefore short incubations would be promising to estimate C₀.