Submitted to: USDA Symposium on Greenhouse Gases & Carbon Sequestration in Agriculture and Forestry
Publication Type: Abstract Only
Publication Acceptance Date: 1/1/2005
Publication Date: 3/1/2005
Citation: Carbon Dynamics in Corn-Soybean Crop Sequences: Tillage Effects and Evidence of C Priming. Huggins, D.R. Allmaras, R.R., Clapp, C.E., Lamb, J.A., Randall, G.W. Third USDA Symposium on Greenhouse Gases and Carbon Sequestration in Agriculture and Forestry. March 21-24, 2005, Baltimore, Maryland. http://soilcarboncenter.k-state.edu/conference/Technical_Sessions_Oral_Presentations.htm Interpretive Summary:
Technical Abstract: Carbon dynamics of agroecosystems are largely regulated by soil disturbance (cultivation) and crop rotation. Interactions between cultivation and crop rotation may be significant in the sub-humid region of the Corn Belt. Our objective was to assess tillage and crop sequence effects on SOC storage and dynamics using natural 13C abundance in corn (Zea mays L., a C4 species) and soybean [Glycine max (L.), Merr., a C3 species]. A randomized, split-plot design (four replications) with main plots consisting of tillage treatment: moldboard plow (MP), chisel plow (CP) and no-tillage (NT) and subplots of crop sequence: continuous corn (CC), continuous soybean (SS) and alternating corn-soybean (CS) was established in 1981. Soil samples were collected in each treatment after 14 y and analyzed for bulk density, pH, delta13C values and SOC. Crop sequence effects on total SOC (0 to 45 cm) occurred in CP and NT. The CP treatment had 16% greater SOC in CC than SS, while NT had 15% greater SOC in CC than SS. In contrast, no crop sequence effects on SOC occurred in MP, where overall SOC was least and similar to SOC in continuous fallow. Tillage effects on SOC were greatest in CC, where CP had 26% and NT 20% more SOC than MP. In CS, SOC averaged 23% more in CP than MP, while SOC in NT tended to be more than in MP, but was not significantly different. Continuous soybean was the only crop sequence where tillage had no influence on SOC. Interaction between tillage and crop sequence on SOC was expressed by marked differences in SOC (0 to 45-cm depth) for CP treatments with corn and NT continuous corn which averaged 164 Mg ha-1, compared to all MP and SS treatments, and NT treatments with soybean where SOC averaged 137 Mg ha-1. We concluded that soybean sequences accelerated C decomposition (priming effect) and resulted in similar SOC storage across all tillage treatments and fallow.