『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