Veum,K.S., Goyne,K.W., Holan,S.H. and Motavalli,P.P.(2011): Assessment of soil organic carbon and total nitrogen under conservation management practices in the Central Claypan Region, Missouri, USA. Geoderma, 167-168, 188-196.

『米国ミズーリ州のセントラル・クレーパン・リージョン(中央粘土盤地域)における保全管理実施下での土壌有機炭素と全窒素の評価』


Abstract
 Conservation management practices including upland vegetative filter strips (VFS) and no-till cultivation have the potential to enhance soil carbon sequestration and other ecosystem services in agroeosystems. A modified two-factor analysis of variance (ANOVA) with subsamples was used to compare SOC and TV on a concentration, soil volume and soil mass basis in claypan soils planted to different conservation management practices and as a function of landscape position. The three conservation management practices (no-till cultivation, grass VFS and agroforestry VFS) and four landscape positions (summit, shoulder. backslope and footslope) investigated were compared 10 years after VFS establishment in a no-till system planted to maize (Zea mays. L.)-soybean (Glycine max (L.) Merr.) rotation. Two soil depth increments (0-5 cm and 5-13 cm) were modeled separately to test for treatment effects. In the surface layer, mean SOC concentration was significantly greater in the VFS soils compared to no-till. On a soil volume or mass basis, no significant differences in SOC stocks were found among treatment means. Concentration and mass based TN values were significantly greater in the grass VFS relative to no-till in the surface layer. A rapid slaking stability test, developed to separate particulate, adsorbed and occluded organic carbon (PAO-C) and nitrogen (PAO-N), showed that VFS soils had significantly greater mean PAO-C and PAO-N concentrations, soil volume and soil mass based stocks than no-till. In addition, comparison of SOC:TN and PAO-C:PAO-N ratios suggest reduced decomposition and mineralization of SOC in the PAO fraction. no significant treatment effects were detected in total or PAO soil fractions in the subsurface layer or among landscape position in either depth increment. Study results emphasize the need to compare soil carbon and nitrogen stocks on a soil volume and/or soil mass basis using bulk density measurements. Additionally, the rapid PAO separation technique was found to be a good indicator of early changes in SOC and TN in the systems studied. Overall, this research indicates that grass VFS may sequester TN more rapidly than agroforestry VFS and that a greater proportion of SOC and TN may be stabilized in VFS soils compared to no-till.

Keywords: Bulk density; Conservation management; Nitrogen; No-till; Organic carbon; Vegetative filter strips』

1. Introduction
2. Materials and methods
 2.1. Study site
 2.2. Soil sampling and laboratory analyses
 2.3. Statistical analysis
3. Results
 3.1. Bulk density, total SOC and TN
 3.2. Particulate, adsorbed and occluded organic carbon (PAO-C) and nitrogen (PAO-N)
 3.3. SOC and TN ratios
4. Discussion
5. Conclusions
Acknowledgments
Appendix
 1. Statistical analysis
References


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