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Title: STOCK AND DISTRIBUTION OF TOTAL AND CORN-DERIVED SOIL ORGANIC CARBON IN AGGREGATE AND PRIMARY PARTICLE FRACTIONS FOR DIFFERENT LAND USE AND SOIL MANAGEMENT PRACTICES

Author
item PUGET, P - OHIO STATE UNIVERSITY
item LAL, R - OHIO STATE UNIVERSITY
item IZAURRALDE, C - BATTELLE PACIFIC NW LAB
item POST, M - OAK RIDGE NAT'L. LAB
item Owens, Lloyd

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2004
Publication Date: 4/1/2005
Citation: Puget, P., Lal, R., Izaurralde, C., Post, M., Owens, L.B. 2005. Stock and distribution of total and corn-derived soil organic carbon in aggregate and primary particle fractions for different land use and soil management practices. Soil Science. 170(4):256-279.

Interpretive Summary: Soil organic matter is an important part of the global carbon (C) cycle and the impacts that C has on global climate change. It has been estimated that the global amount of soil organic C is twice the amount of C in the atmosphere. The length of time that C is stored in soil varies from several months to millennia. Agricultural management practices and land use changes strongly affect soil organic C storage. Soil organic C was quantified in silt loam soils under secondary forest, meadow converted from no-till corn, continuous no-till corn, continuous corn-soybean rotation, and conventional plow till corn in eastern Ohio. The distribution of C stored in different sizes of soil aggregates and different soil particle classes (e.g. clay and silt) was also evaluated. Management induced differences in soil organic C storage were largely confined to the upper soil layer. Conversion of cropland to meadow may not necessarily increase stored soil organic C, especially when hay is removed. Soil organic C concentrations decreased with decreasing soil aggregate size. Soil organic C had a longer turnover time when located deeper in the soil profile. The association of soil organic C with soil aggregates and soil depth needs much more study, especially in relationship to management practices and soil type. This information is important to other scientists and policy makers, especially those make who decisions based on a global scale.

Technical Abstract: Land use, soil management, and cropping systems affect stock, distribution, and residence time of soil organic carbon (SOC). Therefore, SOC stock and its depth distribution and association with primary and secondary particles were assessed in long-term experiments at the North Appalachian Experimental Watersheds near Coshocton, Ohio, through [delta]13C techniques. These measurements were made for five land use and soil management treatments: (1) secondary forest, (2) meadow converted from no-till (NT) corn since 1988, (3) continuous NT corn since 1970, (4) continuous NT corn-soybean in rotation with rye grass since 1984, and (5) conventional plow till (PT) corn since 1984. Soil samples to 70-cm depth were obtained in 2002 in all treatments. Significant differences in soil properties were observed among land use treatments for 0 to 5-cm depth. The SOC concentration (g C kg-1 of soil) in the 0 to 5-cm layer was 44.0 in forest, 24.0 in meadow, 26.1 in NT corn, 19.5 in NT corn-soybean, and 11.1 in PT corn. The fraction of total C in corn residue converted to SOC was 11.9% for NT corn, 10.6% for NT corn-soybean, and 8.3% for PT corn. The proportion of SOC derived from corn residue was 96% for NT corn in the 0 to 5-cm layer, and it decreased gradually with depth and was 50% in PT corn. The mean SOC sequestration rate on conversion from PT to NT was 280 kg C ha-1 y-1. The SOC concentration decreased with reduction in aggregate size, and macro-aggregates contained 15 to 35% more SOC concentration than microaggregates. In comparison with forest, the magnitude of SOC depletion in the 0 to 30-cm layer was 15.5 Mg C/ha (24.0%) in meadow, 12.7 Mg C/ha (19.8%) in NT corn, 17.3 Mg C/ha (26.8%) in NT corn-soybean, and 23.3 Mg C/ha (35.1%) in PT corn. The SOC had a long turnover time when located deeper in the subsoil. Additional research is needed to understand association of SOC with particle and aggregate size fractions and temporal changes and depth-distribution with regard to land use and soil management.