Soil Organic Carbon Maintenance in Corn (Zea mays L.) and Soybean (Glycine max L.) as Influenced by Elevation Zone

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Landscape processes may impact the amount of carbon (C) required to maintain soil organic C levels. The objective of this study determined the influence of elevation zones on soil organic C maintenance and C-budgets. Research conducted between 1995 and 2003 in a 160 ac (65 ha) east-central South Dakota field measured spatial and temporal biomass [corn (Zea mays) and soybean (Glycine max)] production and changes in soil organic C and ^sup 13^C isotopic discrimination (Δ). Results from this study showed that: 1) data collected through precision farming practices (yield and grid soil samples analyzed for soil organic C) can be used to determine soil organic C maintenance requirements; 2) the corn - soybean rotation may not return enough biomass-C to maintain soil organic C levels at all landscape positions; 3) calculated maintenance rates were dependent on the approach used to estimate below ground biomass; 4) footslope areas had higher maintenance rates than summit/shoulder areas; and 5) 1.84 percent and 1.21 percent soil organic C measure in 1995 (SOC^sub 95^) were mineralized annually in elevation zones less than 527.3 and greater than 527.3 m, respectively. To maintain soil organic C levels, areas where mineralization is high (footslopes) will require higher biomass-C additions than areas where soil organic C mineralization is low (shoulders). The potential benefits of increasing biomass-C additions to footslope areas at the expense of summit/shoulder areas must be balanced against the potential effects on erosion.

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Journal of Soil and Water Conservation





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