A technical bulletin released detailing the feasibility of cover crops in southwest Colorado and southeast Utah painted a mix picture, but still drew some favorable conclusions for the future.
The objective was to test the growth and performance of different cover crop species/mixtures across distinct sites, and assess the impacts of cover crops on soil fertility, soil moisture, cash crop yields, and overall farm profit. You can read the results of this study here, but I’ll relay a summary of what they found.
Colorado State University established two field trials at the Southwest Colorado Research Center (SWCRC) and eight research and demonstration trials on farmers’ fields. The trials encompassed two crop rotations (winter wheat/fallow and winter wheat-safflower-fallow), two tillage regimes (conventional tillage and no-till), as well as conventional and organic crop production systems.
At the time of this bulletin’s filing, 19 summer or early-fall-planted and five spring-planted cover crop mixes were tested. Some key preliminary findings are:
• Late summer or early fall-planted cover crops produced considerably more biomass than the spring-planted cover crops. For example, plant biomass of spring-planted mixtures averaged 713 pounds an acre in 2017, while fall-planted mixtures exceeded 4,000 pounds an acre in 2016 at the SWCRC.
• If cover crops are planted too early after wheat harvest and before adequate moisture is available then volunteer wheat tended to dominate plant canopy and biomass.
• Some species such as flax, sunnhemp and balansa clover performed poorly and “the notion that the more species in the mix the better may not hold true in the project area,” researchers said. “We also note that climate in the region (semi-arid with short growing season), seed cost and proper management are all key considerations for developing high performance cover crop mixtures.”
• Results from one experiment at the SWCRC showed a 27% yield penalty for wheat following cover crops vs. fallow, likely due to temporary immobilization of soil nitrogen and reduced soil moisture at planting. The yield penalties were lower (19% and 22%) for two on-farm trials. No fertilizer was applied to the wheat in this project, a decision that will be reconsidered moving forward, researchers said.
Colorado State says project concepts and highlights have been presented at multiple events. Many of the presentations can be found here. They noted attendance to outreach events has been generally good and attendees appear to have gained knowledge on cover crops, soil health and management practices.
I think the important takeaway here is that management decisions on cover crops in semi-arid environments need to be precise, as there isn’t as much margin for error as regions that have more annual precipitation. Yes, cover crops use water — so do cash crops! The nutrient value of some cover crops can also have positive impacts on grazing economics and animal health and that should not be dismissed.
Knowing the volatile conditions that Great Plains farmers face, I don’t think it’s wise to dismiss the ability of cover crops to, in the long run, improve the resiliency of our farms. If you’re on the fence about seeding covers, set aside a field or two and do your own trials. You must write your own recipe for what works on your individual farm, climate, soil types and rotations.