Skip to main content
ARS Home » Research » Publications at this Location » Publication #313302
Title: High plains cover crop research

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

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/2/2015
Publication Date: 1/20/2015
Citation: Nielsen, D.C., Lyon, D.J., Calderon, F.J., Hergert, G.W., Higgins, R. 2015. High plains cover crop research. Cover Your Acres Winter Conference Proceedings. 12:7-12.

Interpretive Summary: Cover crops may have many beneficial effects on crop production. Recently many claims have been made stating that cover crops grown in mixtures use far less water than single-species plantings of cover crops and that cover crops grown in mixtures will use less water than is lost by evaporation from fallow. Additionally other claims have been made that cover crops grown in mixtures will result in enhanced soil microbiological activity, increased biomass productivity, and enhanced water use efficiency by cover crops grown in mixtures compared with single-species plantings of cover crops, and that growing cover crops will have no adverse effects on subsequent crop yields. These claims have not been tested under the semi-arid environment of the central Great Plains, and previous research has indicated that cover crop production results seen in more humid environments may not be seen in the drier central Great Plains environment. 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. In this environment we saw no evidence of enhanced microbiological concentrations or of increased water use efficiency in cover crop mixtures compared with single-species plantings of cover crops. We found that growing cover crops decreased subsequent winter wheat yields. Hence, farmers in the semi-arid central Great Plains should be cautious when considering implementing the use of cover crops in their farming operations. Use of cover crops in mixtures appears to produce no added benefits compared with single-species plantings of cover crops.

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. Those stated benefits have included greatly reduced water use, enhanced soil microbiological activity, increased biomass productivity, and enhanced water use efficiency by cover crops grown in mixtures compared with single-species plantings of cover crops. The objectives of this proceedings paper were to report the findings of a study that compared cover crop water use, soil microbiological populations, biomass production, and effect on subsequent winter wheat production for four single-species cover crop plantings and a 10-species mixture. The study was conducted at Akron, CO and Sidney, NE during the 2012-2014 growing seasons on silt loam soils under both rainfed and irrigated conditions. Soil water contents were measured by neutron scattering and time-domain reflectometry at six depths from 0 to 165 cm. Soil microbiological community composition was measured through the use of fatty acid methyl ester (EL-FAME) analysis. Cover crop biomass production was quantified through periodic destructive sampling. Seed yield and water use of the following winter wheat crop were measured. 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 (9.6 inches, 244 mm) averaged 1.8 times greater than evaporative water loss (5.3 inches, 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. Cover crop biomass production occurred with the same water use efficiency for the 10-species mixture as for each of the single-species plantings. Total fatty acids and arbuscular mycorrhizae concentrations were lower in the plots that had been fallowed for nine months than for the cover crop plots. The microbiological community concentrations were not different for the 10-species mixture than for the single-species plantings at cover crop termination, nor at subsequent wheat planting or wheat harvest. The water use by the cover crops generally reduced subsequent winter wheat water use resulting in lower yield that followed a previously reported water use/yield production function rate of 4.7 bu/a per inch of water use (12.43 kg/ha per mm of water use). Growing cover crops in mixtures did not change this relationship. It is difficult to justify the expense associated with the implementation of cover crops (particularly mixtures) in semi-arid dryland cropping systems based on the results of this and previously conducted studies in this regions with legume cover crops.