Designing and Evaluating Complex Cover Crop Mixtures

View the project final report

Commodities

• Agronomic: corn, grass (misc. annual), rapeseed, rye, soybeans, vetches

Practices

• Crop Production: application rate management, catch crops, conservation tillage, cover crops, crop improvement and selection, cropping systems, nutrient cycling
• Education and Training: extension, networking, participatory research

Cover crops are used by farmers to provide a range of ecosystem services including nitrogen scavenging and fixation, weed suppression, reducing soil compaction and increasing water use efficiency that can result in increased crop yield. Success with simple, two-species cover crop mixes has led to interest in more complex cover crop mixtures, with three or more species. But research on complex cover crop mixtures is inconsistent because it fails to capture all of the potential ecosystem services provided by complex mixtures. This research hoped to show the cumulative effect of the ecosystem services provided by cover crop mixes and to describe the best cover crop mixture. Rye, vetch, clover and radish cover crops were grown in 1, 3 and 9 species mixes. Corn yield, cover crop biomass and C:N ratio, soil compaction, weed pressure and soil moisture status were measured. A method of classifying ecosystem service interactions and ranking develop by Jopke et. al. (2015) was used to evaluate the cumulative ecosystem service contributions of cover crop mixtures. Multiple linear regression was used to estimate the individual species contribution of rye, vetch, oats and radish to each ecosystem service; which can be used in designing new complex cover crop mixtures. The expected results of this project were to develop a tool that can be used to evaluate a wider range of ecosystem services and ranking system for new cover crop mixtures as well as provide guidelines for mixing species in new cover crop mixtures.

1. Measure ecosystem services provided by monocultures and cover crop mixtures, including corn yield.
   1. Provisioning services of corn yield and cover crop biomass.
   2. Weed suppression.
   3. Reduced soil compaction.
   4. Nitrogen accumulation by cover crops.
   5. Increased soil water conservation to reduce irrigation needs.
2. Evaluate the range of ecosystem services provided by cover crop mixtures to select cover crop mixtures that provide the desired ecosystem services and the lowest amount of trade-offs.
3. Estimate the contribution of individual cover crop species or plant functional groups (legumes, small grains, brassicas and tap-roots) toward the desired ecosystem service to design new cover crop mixtures.