Tuesday, November 6, 2007
204-7
Total Soil Organic Carbon Change as Affected by Cropping Sequence and Bio-Cover Under No-till Production.
Fred Allen1, J.P. Wight1, Jennifer E. Noe1, and Donald Tyler2. (1) Dept. of Plant Sciences, University of Tennessee, 2431 Joe Johnson Drive, Knoxville, TN 37996-4561, (2) Dept. of Bioengineering and Soil Science, University of Tennessee, West Tennessee Research and Education Center, 605 Airways Blvd, Jackson, TN 38301
The objective of this research is to compare changes in total soil organic carbon (SOC) among different cropping systems and regions of Tennessee under no-tillage production. The experiment used a split-block treatment design with four replications at each site. The whole-block treatment was cropping sequences of Roundup Ready® corn (Zea mays), soybeans (Glycine max), and cotton (Gossypium hirsutum) combined with a split-block treatment of bio-covers using winter wheat (Triticum aestivum), hairy vetch (Vicia villosa), poultry litter, and winter weeds. Treatments were applied to fields at the University of Tennessee ’s Research and Education Center ’s at Milan (RECM) and Spring Hill (MTREC). Soil samples were taken before treatments began and after two and four years of experimentation. SOC was measured at the surface (0 - 5 cm) and subsurface (5 - 15 cm). Changes in SOC were calculated. Overall, both sites showed small but consistent loss in carbon over all treatments during the first two years, being largest in the surface layer, at the RECM site.
After four years, SOC began to recover, with total mean loss of SOC at the surface being 1.06 Mg ha-1 and 1.40 Mg ha-1 at RECM and MTREC, respectively. In the subsurface, mean SOC loss at RECM had increased to 1.43 Mg ha-1. The subsurface SOC at MTREC was 3.14 Mg ha-1 higher than pre-experiment levels. Sequence, cover, and their interactions were significant at RECM (P < 0.05). Sequences with high frequencies cotton lost significantly more SOC than others in the surface and subsurface regions. Plots under the poultry litter bio-cover lost less surface SOC (0.58 Mg ha-1) than those under vetch (1.33 Mg ha-1) or fallow 1.8 Mg ha-1). Vetch and poultry litter affected SOC differently, depending on the sequence. For these bio-covers, sequences high in soybean tended to lose less carbon than others.
After four years, SOC began to recover, with total mean loss of SOC at the surface being 1.06 Mg ha-1 and 1.40 Mg ha-1 at RECM and MTREC, respectively. In the subsurface, mean SOC loss at RECM had increased to 1.43 Mg ha-1. The subsurface SOC at MTREC was 3.14 Mg ha-1 higher than pre-experiment levels. Sequence, cover, and their interactions were significant at RECM (P < 0.05). Sequences with high frequencies cotton lost significantly more SOC than others in the surface and subsurface regions. Plots under the poultry litter bio-cover lost less surface SOC (0.58 Mg ha-1) than those under vetch (1.33 Mg ha-1) or fallow 1.8 Mg ha-1). Vetch and poultry litter affected SOC differently, depending on the sequence. For these bio-covers, sequences high in soybean tended to lose less carbon than others.