Elucidating the Combined Effects of Organic and Conventional Grain Cropping Systems with Tillage Methods on Soil Organic Carbon Distribution.

The effect of organic and conventional grain production systems under different forms of tillage management on the size of total and biologically active soil organic carbon (SOC) pools, which are key soil health determinants, is poorly understood. Our hypothesis was that utilizing both organic management together with no-tillage could benefit both total SOC accumulation and biologically-active fractions. The study was conducted at the Rodale Institute’s Farming Systems Trial in Pennsylvania with three soil amendment treatments: synthetic fertilizers (conventional), leguminous cover crops (legume-organic), manure plus leguminous cover crops (manure-organic); and two tillage treatments: conventional tillage and no-tillage. Soil samples were collected from three depth increments (0-10cm, 10-20 cm, and 20-30 cm) in June 2018 and total SOC and biologically-active C pools such as microbial-biomass C (MBC) and permanganate-oxidizable C (POXC) were determined. Results showed that neither total SOC nor biologically-active carbon was influenced by 10 years of tillage treatments. However, 37 years of organic and conventional soil amendment management had significant effects on all the measured properties. Total SOC, MBC, and POXC were the greatest under manure-organic management and the least under conventional management. This study suggests that organic cropping system management enhanced SOC accumulation, especially in the biologically-active fractions, which is critical for soil fertility and ecosystem sustainability.