Agroforestry and grass buffer effects on soil quality parameters for grazed pasture and row-crop systems

摘要

Establishment of buffers and incorporation of trees and shrubs are believed to improve soil quality and thereby improve water quality from grazed pasture systems. Although enzyme activities and water stable aggregates have been identified as measurable soil quality parameters for early responses to changes in soil management, the literature lacks information on those parameters for grazing systems with agroforestry buffers. The objective of this study was to examine the activities of fluorescein diacetate (FDA) hydrolase, dehydrogenase, beta-glucosidase and beta-glucosaminidase, the percentage of water stable aggregates (WSA) and soil organic carbon and nitrogen 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). The WSA was determined by wet sieving method while the enzyme activities were colorimetrically quantified using a spectrophotometer in laboratory assays. Soil organic carbon (SOC) and total nitrogen (TN) contents were also determined. Two soil depths (0-10 and 10-20 cm) were analyzed for all treatments. The row-crop treatment showed significantly lower activities compared to all other treatments for beta-glucosidase and beta-glucosaminidase enzymes along with lower WSA. The dehydrogenase activities were significantly higher in GP treatment compared to RC treatment. The FDA hydrolase activities were not significantly different among treatments. Surface soil revealed higher enzyme activities and higher WSA than the subsurface soil. The treatment by depth interaction was significant for beta-glucosidase and beta-glucosaminidase enzymes. The soil organic carbon and total nitrogen data strongly supported the results of enzyme activities and WSA. Implications can be made that perennial vegetation enhances organic matter accumulation in the soil, has minimum disturbance to the soil and will have positive impacts on the ecosystem