The effect of reduced tillage agriculture on carbon dynamics in silt loam soils

Reduced tillage (RT) agriculture is an effective measure to reduce soil loss from soils susceptible to erosion in the short-term and is claimed to increase the soil organic carbon (SOC) stock. The change in distribution and total SOC stock in the 0-60 cm layer, the stratification of microbial biomass carbon (MB-C) content in the 0-40 cm layer and the carbon (C) mineralization in the upper 0-5 cm layer in silt loam soils in Western Europe with different periods of RT agriculture were evaluated. Ten fields at seven locations, representing the important RT types and maintained for a different number of years, and eight fields under conventional tillage (CT) agriculture with similar soil type and crop rotation were selected. RT agriculture resulted in a higher stratification of SOC in the soil profile than CT agriculture. However, the total SOC stock in the 0-60 cm layer was not changed, even after 20 of years RT agriculture. The MB-C was significantly higher in the 0-10 cm layer under RT agriculture, even after only 5 years, compared to CT agriculture. The higher SOC and MB-C content in the upper 0-5 cm layer of RT fields resulted in a higher C mineralization rate in undisturbed soil in the laboratory. Simulating ploughing by disturbing the soil resulted in inconsistent changes (both lower and higher) of C mineralization rates. A crop rotation with root crops, with heavy soil disturbance every 2 or 3 years at harvest, possibly limited the anticipated positive effect of RT agriculture in our research.