ABSTRACT:
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 13C 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 (SOC95) 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.
Footnotes
David E. Clay, Sharon A. Clay, C. Gregg Carlson, and Douglas D. Malo are professors in the Plant Science Department at South Dakota State University, Brookings, South Dakota. Jiyul Chang is a research associate in the Biology Department at South Dakota State University in Brookings, South Dakota.
- Copyright 2005 by the Soil and Water Conservation Society
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