Influence of Conservation Management Practices On Indicators of Soil Quality In a Claypan Agroecosystem.

Conservation management practices, including no-till cultivation and vegetative filter strips (VFS) impact soil organic matter (SOM) quality and enhance profitability and sustainability in agroecosystems. This study compared indicators of SOM quality from three conservation management practices (i.e. no-till, grass VFS and agroforestry VFS) and four landscape positions (i.e. summit, shoulder, backslope and footslope) in a claypan agroecosystem. Variables included water stable aggregates of field-moist (FM-WSA) and air-dried (AD-WSA) soil, dehydrogenase activity (DHA), phenol-oxidase activity (POA), permanganate oxidizable organic carbon (KSOC), water-extractable organic carbon (WEOC) and ultraviolet (UV) absorbance of water extracts. Additionally, for more meaningful, ecosystem level comparisons, variables were expressed on an areal basis (by soil volume and soil mass) and on a soil carbon basis where appropriate. In the surface layer (0-5 cm), this study found that VFS soils had significantly greater AD-WSA, WEOC and KSOC than no-till, suggesting increased labile SOM fractions and enhanced soil structural stability under VFS relative to no-till. The grass VFS soil had the greatest DHA, POA and UV₂₈₀/UV₃₆₅ (E2/E3) ratio, indicating enhanced overall microbial activity and increased aliphatic, lower molecular weight moieties in water-extractable SOM. The agroforestry VFS exhibited the greatest carbon normalized UV₂₅₄ (SUVA), indicating increased aromaticity and humification in this fraction. Depending on how it was expressed, FM-WSA was either significantly greater under no-till than VFS or exhibited no significant difference among treatments, suggesting greater aggregate stability under no-till during moist field conditions. Overall, these results show that labile and water-extractable SOM has increased under VFS relative to no-till. These results also indicate that grass VFS experience the greatest microbial activity and SOM turnover and that under agroforestry VFS, microbial activity and SOM decomposition may be inhibited relative to grass VFS and no-till.