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Title: Cover crops in mixtures do not use water differently than single-species plantings

Author
item Nielsen, David
item LYON, DREW - Washington State University
item HERGERT, GARY - University Of Nebraska
item HIGGINS, ROBERT - University Of Nebraska
item Calderon, Francisco
item Vigil, Merle

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2015
Publication Date: 3/27/2015
Publication URL: http://handle.nal.usda.gov/10113/61933
Citation: Nielsen, D.C., Lyon, D.J., Hergert, G.W., Higgins, R.K., Calderon, F.J., Vigil, M.F. 2015. Cover crops in mixtures do not use water differently than single-species plantings. Agronomy Journal. 107:1025-1038.

Interpretive Summary: Claims have been made that cover crops grown in mixtures use far less water than single-species plantings of cover crops. An additional claim is that cover crops grown in mixtures will use less water than is lost by evaporation from fallow. This study shows that cover crops grown in mixtures use water similarly to cover crops grown in single-species plantings. Additionally cover crops grown in mixtures or as single species will use, on average, 1.8 times more water than is lost from fallow by evaporation. Hence, farmers in the semi-arid central Great Plains should be cautious when considering implementing the use of cover crops in their farming operations as there is a high likelihood that subsequent crop yields will be decreased due to the cover crop water use.

Technical Abstract: Some recent statements have been made about the benefits of growing cover crops in mixtures as compared with single-species plantings of cover crops. One of those stated benefits is greatly reduced water use by cover crops grown in mixtures. The objectives of this study were to characterize soil water extraction patterns and determine water use of cover crops grown in single-species plantings and in a 10-species mixture and compare cover crop water use to evaporative water loss from no-till fallow. The study was conducted at Akron, CO and Sidney, NE during the 2012 and 2013 growing seasons on silt loam soils. At each location there was a dryland and an irrigated treatment. Soil water contents were measured by neutron scattering and time-domain reflectometry at six depths from 0 to 165 cm. There were no consistent significant differences in soil water contents or growing season crop water use with the single-species plantings compared with the 10-species mixture. Cover crop water use (244 mm) averaged 1.8 times greater than evaporative water loss (135 mm) from the no-till fallow treatment with proso millet (Panicum miliaceum L.) residue. There appears to be no evidence from data collected in this semi-arid environment, even when irrigated to simulate higher rainfall environments, to support the conclusion that cover crops grown in multi-species mixtures use water differently than single species plantings of cover crops.