Stabilization of organic carbon in chemically separated pools in no-till and meadow soils in Northern Appalachia

Land use and soil management affects soil organic carbon (SOC) pools, chemical composition of stabilized SOC fractions, and the depth distribution. No-till production of corn (Zea mays L.) is a recommended management practice that reduces soil losses and increases SOC concentration, but the scientific knowledge of the mechanisms of C sequestration and protection is scanty. Therefore, the objective of this research was to compare the SOC pool, C pool in fine roots, and chemically separated C fractions with depth in three pedons from the same soil series: (i) meadow converted from no-till corn in 1988 (Meadow), (ii) continuous no-till corn since 1970 (NT); and (iii) continuous no-till corn with beef cattle manure since 1964 (NTm) at the North Appalachian Experimental Watershed near Coshocton, Ohio. The SOC pool (Mg ha- 1) from 0-69 cm was the highest in NTm (76.2) and progressively smaller in NT (49.3) and Meadow (46.6) pedons. The SOC concentrations and pool sharply decreased with depth, but were always more in NTm than NT soil. Fine root C pool (Mg ha- 1) was much larger in the pedon with perennial vegetation (Meadow, 1.28) than in those under corn (NT, 0.21; NTm, 0.09). The pool of chemically separated C fractions and their depth distribution varied depending on the separation technique. The amounts of C preferentially bound to soil minerals in 0-69 cm depth were comparable among pedons, as indicated by treatment with HF to release mineral-bound SOC. The NTm pedon had a larger pool of recalcitrant non-hydrolyzable C (58.4 Mg ha- 1), as indicated by HCl treatment. The Meadow pedon stored the smallest pool (3.4 Mg ha- 1) of oxidisable C, as was indicated by treatment with disodium peroxodisulfate (Na2S2O8). The relationship between chemically separated C fractions and turnover time of SOC at depth, however, warrants further studies. Nevertheless, the results indicate that no-till corn with added manure has a high potential for C sequestration by increasing the size of the SOC pool in the subsurface horizons.