ASA Southern Branch 2008 Annual Meeting
February 3-5, 2008
Dallas, TX
Monday, February 4, 2008 - 1:15 PM
Cover Crop Management Effects on Microclimate and Soil Biological Activity.
Larry Zibilske and Donald Makus. USDA-ARS, 2413 E. Hwy. 83, Weslaco, TX 78596-8344
Cover crops are often evaluated for their effects on succeeding crop productivity or by their effects on soil structure and fertility, but their effects on the soil microclimate factors affecting soil biological properties are not well documented. We assessed soil moisture, temperature, and several soil biological parameters in soil under replicated black oat cover crop plots managed by sickle-bar mowing, vertical flail mowing, or on which the residues were left standing (non-mown). Oats were was sown in November and allowed to develop and die naturally following spring. Over the course of the summer, significant increases in soil cellulase and alkaline phosphatase activities, and for soil total N were detected for the non-mown treatment, compared to both mown treatments. Later in the summer, microbial biomass and dissolved organic C (DOC) were significantly higher for the flail-mown treatment, probably reflecting decomposition of residues in contact with the soil in those treatments. Soil temperatures (surface IR) were ~14 °C higher (56° C vs. 42° C) in flail-mowed compared to standing residues in the heat of the summer. Results indicate significant differences in microbial activities with management of cover crop residues and appear to be affected differently by temperature differences over time. Few soil moisture differences were detected, presumably due to the unusually wet year (2007) in South Texas. Cover crops may sufficiently affect the microclimate of hot soils to warrant a consideration of these aspects in management practices.