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Title: Chemical stabilization of organic carbon pools in particle size fractions in no-till and meadow soils

Author
item LORENZ, K - THE OHIO STATE UNIV.
item LAL, R - THE OHIO STATE UNIV.
item Shipitalo, Martin

Submitted to: Biology and Fertility of Soils
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2008
Publication Date: 5/27/2008
Citation: Lorenz, K., Lal, R., Shipitalo, M.J. 2008. Chemical stabilization of organic carbon pools in particle size fractions in no-till and meadow soils. Biology and Fertility of Soils. 44:1043-1051.

Interpretive Summary: No-till management practices for crop production can reduce runoff and erosion and increase the amount of organic matter in the soil. This organic matter improves soil quality and can help offsite the rise in atmospheric levels of carbon dioxide attributable to the burning of fossil fuels. Nevertheless, the processes that lead to the increase in soil organic matter and how it is protected from decomposition in no-till soils are poorly understood. Therefore, we used chemical extraction techniques to determine how organic matter is protected from decomposition in a no-till corn production system (with and without added animal manure) and in a similar soil used to produce hay. The no-till soil with added manure had more soil organic matter than all the other management practices even in the lower horizons, probably due to redistribution of manure and crop residues by earthworms. Association of organic matter with sand particles was the most effective mechanism protecting organic matter from decomposition. Nevertheless, since there was much more silt in these soils than sand, most of the increase in soil organic matter was due to organic matter binding to silt particles. Our results indicate that the best way for farmers to achieve long-term increases in organic matter levels in their soils is through continued use of no-till practices, particularly if they are able to add animal manure.

Technical Abstract: Land use and soil management affects soil organic carbon (SOC) pools associated with particle size fractions and their chemical stabilization. No-till (NT) production of corn (Zea mays L.) is a recommended management practice that reduces erosion and increases SOC concentration, but the knowledge about the relevance of physical and chemical fractionation methods to SOC stabilization mechanisms is fragmentary. Therefore, our objective was to compare the stabilization of the SOC pool in coarse (0.25-2.00 mm dia.) and fine (0.05-0.25 mm dia.) sand, silt (0.002-0.050 mm dia.) and clay (<0.002 mm dia.) particle size fractions by oxidative degradation with disodium peroxodisulfate and destruction of the mineral phase by hydrofluoric acid (HF). The uppermost two horizons of three pedons from the same soil series under three different long-term management practices were studied: (i) meadow converted from NT corn in 1988 (Meadow), (ii) continuous NT corn since 1970 (NT); and (iii) continuous NT corn with beef cattle manure since 1964 (NTm) at the North Appalachian Experimental Watershed near Coshocton, Ohio. Land use and soil management had no significant effects on particle size distribution among horizons. Coarse sand and clay size particles, however, were quantitatively more effective in enriching SOC than the other size fractions. The SOC pool (Mg/ha) in silt size particles from 0-30 cm was greatest in NTm (27.1) and progressively smaller in NT (15.5), and Meadow (14.9), representing 44, 39, and 39% of the total SOC pool, respectively. The pools of oxidizable C in 0-30 cm depth were comparable among particle size fractions and pedons, as indicated by treatment with disodium peroxodisulfate. The amounts of C preferentially associated with soil minerals were also comparable among pedons, as indicated by treatment with HF to release mineral-bound SOC. However, the NTm pedon stored the largest pool (12.6 Mg/ha) of mineral associated C in 0-30 cm depth. The silt associated and mineral-bound SOC pool in NT with manure was greater compared to NT corn without manure due to increased organic matter (OM) input and most likely by promoting earthworm activity. Thus, the silt particle size fraction at NAEW has the potential for SOC sequestration by increasing OM inputs. Mineralogical and molecular level analyses on a larger set of fractions obtained from entire rooted soil profiles are required, however, to compare the SOC sequestration capacity of the land uses.