Assessment of Soil Quality for Grazed Pastures with Agroforestry Buffers and Row Crop Systems.

Incorporation of trees and establishment of buffers are believed to enhance soil quality.  Soil enzyme activities and water stable aggregates have been identified as good indices for assessing soil quality to evaluate early responses to changes in soil management.  However, studies comparing these parameters for grazed pastures and row crop systems are limited.  The objective of this study was to examine the activities of selected enzymes (fluorescein diacetate (FDA) hydrolase, dehydrogenase, β-glucosidase and β-glucosaminidase), the percentage of water stable aggregates (WSA) as soil quality parameters for grazed pasture and row-crop systems.  The study consisted of four management treatments: grazed pasture (GP), agroforestry buffer (AgB), grass buffer (GB) and row crop (RC). Soil organic carbon (SOC), total nitrogen (TN) contents and soil bulk density were also determined.  Two soil depths (0-10 and 10-20 cm) were analyzed for all treatments for two consecutive years, 2009 and 2010.  The row-crop treatment showed significantly lower β-glucosidase and β-glucosaminidase activity and significantly lower WSA compared to all other treatments.  The FDA hydrolase activities were not significantly different in 2009 but were significant in 2010. There were numerical variations of parameters in two years but patterns were consistent. Surface soil revealed higher enzyme activities and higher WSA than the sub-surface soil.  The treatment by depth interactions were significant for β-glucosidase and β-glucosaminidase enzymes in 2009 while the interactions were significant for dehydrogenase and β-glucosaminidase enzymes in 2010.  Implications can be made that permanent vegetation will improve soil quality by enhancing organic matter accumulation in the soil and increasing microbial activity with minimum soil disturbance which will have a positive effect on the ecosystem.