Soil quality indicator responses to row crop, grazed pasture, and agroforestry buffer management

Soil enzyme activities and water stable aggregates have been identified as sensitive soil quality indicators, but few studies exist comparing those parameters within buffers, grazed pastures and row-crop systems. Our objective was to examine the effects of these land uses on the activities of selected enzymes (b-glucosidase, b-glucosaminidase, fluorescein diacetate (FDA) hydrolase, and dehydrogenase), proportion of water stable aggregates (WSA), soil organic carbon and total nitrogen content. Four management treatments [grazed pasture (GP), agroforestry buffer (AgB), grass buffer (GB) and row crop (RC)] were sampled in 2009 and 2010 at two depths (0 to 10- and 10 to 20-cm) and analyzed. Most of the soil quality indicators were significantly greater under perennial vegetation when compared to row crop treatments. Although there were numerical variations, soil quality response trends were consistent between years. The b-glucosaminidase activity increased slightly from 156 to 177 lg PNP g-1 dry soil while b-glucosidase activity slightly decreased from 248 to 237 lg PNP g-1 dry soil in GB treatment during 2 years. The surface (0–10 cm depth) had greater enzyme activities and WSA than sub-surface (10–20 cm) samples. WSA increased from 178 to 314 g kg-1 in row crop areas while all other treatments had similar values during the 2 year study. The treatment by depth interaction was significant (P\0.05) for b-glucosidase and b-glucosaminidase enzymes in 2009 and for dehydrogenase and b-glucosaminidase in 2010. Soil enzyme activities were significantly correlated with soil organic carbon content (r C 0.94, P\0.0001). This is important because soil enzyme activities and microbial biomass can be enhanced by perennial vegetation and thus improve several other soil quality parameters. These results also support the hypothesis that positive interactions among management practices, soil biota and subsequent environmental quality effects are of great agricultural and ecological importance.