Submitted to: North American Agroforestry Conference
Publication Type: Proceedings
Publication Acceptance Date: 4/10/2007
Publication Date: 6/10/2007
Citation: Udawatta, R.P., Kremer, R.J., Garrett, H.E., Anderson, S.H. 2007. Soil aggregate stability and enzyme activity in agroforestry and row-cropping systems. pp. 165-175 In A. Olivier and S. Campeau (ed.) When trees and crops get together: Economic Opportunites and Environmental Benefits of Agroforestry. Proceedings of the 10th North American Agroforestry Conference, June 10-13, 2007, University Laval, Quebec City, Quebec, Canada.
Technical Abstract: The proportion of water-stable aggregates (WSA) influences soil quality, crop growth, nutrient retention, water infiltration, and surface runoff. Roots, fungi, and bacteria as well as numerous chemical substances secreted by these agents play important roles in soil aggregate formation, persistence, and turnover. The objective of the study was to test the hypothesis that permanent vegetative buffers will increase WSA and contribute to increased microbial diversity and enzyme activity. Soil samples from agroforestry (AG), grass buffer (GB), grass waterway (GWW) and crop (CS) areas were collected from summit, middle, and lower landscape positions at the Paired Watershed Study, near Novelty, MO. Water stable aggregates (> 250µm diam; wet-sieving method), soil carbon, soil nitrogen, and soil enzyme activities were determined. Soils under permanent vegetative buffers and GWW had significantly more WSA than the crop areas. Soil carbon and nitrogen were highest in the GWW and lowest in the CS treatments. Fluorescein diacetate (FDA) hydrolase, '-glucosidase, and glucosaminidase enzyme activities were higher in AG, GB, and GWW soils than CS soils. Dehydrogenase activity was different between grass buffer or GWW and crop areas. The results of the study show that establishment of buffers with trees and grass as well as grass waterways increased WSA, soil carbon, soil nitrogen, microbial diversity, and enzyme activity. It is suggested that improved soil physical properties and increased microbial diversity resulting from these management practices help reduce nonpoint source pollution from row crop agriculture watersheds thus improving environmental quality.