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Title: Cover crop and irrigation effects on soil microbial communities and enzymes in semiarid agroecosystems of the Central Great Plains of North America

Author
item Calderon, Francisco
item Nielsen, David
item Acosta-Martinez, Veronica
item Vigil, Merle
item LYON, DREW - Washington State University

Submitted to: Pedosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2015
Publication Date: 4/1/2016
Citation: Calderon, F.J., Nielsen, D.C., Acosta Martinez, V., Vigil, M.F., Lyon, D. 2016. Cover crop and irrigation effects on soil microbial communities and enzymes in semiarid agroecosystems of the Central Great Plains of North America. Pedosphere. 26(2):192-205.

Interpretive Summary: In this work, we document the effects of cover crops and irrigation on soil microbial communities and soil function in dryland wheat-fallow systems in the Central Great Plains. Recently there has been a discussion in the scientific community regarding the benefits of cover crops on semiarid agroecosystems. There have been claims that cover crops have profound effects on soil microbiology and soil functioning, which can quickly improve the water use efficiency even in semiarid soils. Our results show that while the type of crop or fallow does affect microbial community structure, irrigation has a lasting effect on soil enzyme activities in these severely water limited systems.

Technical Abstract: The objective of this study was to compare a fallow-winter wheat (Triticum aestivum L.) rotation to several cover crop-winter wheat rotations under dryland and irrigated conditions in the semiarid US High Plains. We carried out a study that included two sites (Sidney, NE, and Akron, CO), and three sampling dates spanning the summers of 2012 and 2013, which included cover crop termination, wheat planting, and wheat maturity. The experiment included four individual cover crops, a 10-species mixture, and a fallow treatment. The variables measured were soil C and N, soil community structure by fatty acid methyl esters (FAME), and soil ß-glucosidase, ß-glucosaminidase, and phosphodiesterase activities. At the time of cover crop termination, FAMES were mostly affected by the presence of fallow, which reduced the concentration of most fatty acids. Total FAME was correlated with cover crop biomass regardless of the cover crop type (R=0.62 at Sidney, and 0.44 at Akron). By the time of wheat planting, there was a beneficial effect of irrigation, which caused a 17% increase in total FAME. At wheat maturity, the cover crop and irrigation effects on total FAME had subsided, but irrigation had a positive effect on the ß-glucosidase and phosphodiesterase activities at Akron, which was the drier of the two sites. Our results show that cover crops have a short-lived effect on soil microbial communities in semiarid wheat-based rotations. Irrigation can enhance enzymatic activity, an important soil function attribute.