Identification of effective cover crop varieties and integrated management practices for weedy and invasive plant suppression in the Western US

View the project final report

Commodities

• Agronomic: clovers, corn, peas (field, cowpeas), soybeans, vetches, wheat
• Additional Plants: native plants

Practices

• Crop Production: application rate management, catch crops, cover crops, crop rotation, cropping systems, double cropping, drought tolerance, intercropping, irrigation, no-till, varieties and cultivars
• Education and Training: decision support system, demonstration, display, extension, mentoring, on-farm/ranch research
• Farm Business Management: agricultural finance, budgets/cost and returns
• Natural Resources/Environment: biodiversity
• Pest Management: competition, cultural control, integrated pest management, mulches - living, weed ecology
• Production Systems: dryland farming, organic agriculture
• Soil Management: green manures
• Sustainable Communities: community services, employment opportunities, local and regional food systems, new business opportunities, public participation

Weedy and invasive plant species are one of the major causes of yield losses in agricultural systems (Flessner et al. 2019, Soltani et al. 2016, Soltani et al. 2017, Soltani et al. 2018, WERA-77). The arid Western US is lacking in cover crop research and the development of best management practices for weed suppression utilizing cover crops and integrated strategies. Producers have identified this need for understanding the competitive ability of cover crops against weeds, including most effective seeding rates and timing, and their incorporation into an integrated approach for Western US cropping systems (Cann et al. 2019). In this proposed two-year study, we will identify the types of cover crops and best-integrated strategies for the use of these practices in the Western US. Types of cover crops will be tested within different cropping systems using a range of management approaches. Integrated weed management tactics of seeding dates, rates, and cover crop types will be tested in an irrigated wheat system for suppressing weeds, specifically Kochia scoparia. We will measure cover crops competition with weeds and cash crops and also examine their potential future weed threat. The outcome of these studies will be the identification of cover crops best suited for practical use alone and in integrated weed management in the Western US. Results will be disseminated through fact sheets, educational meetings, the development of a regional cover crop selection tool, and partial budgets accounting for these practices. Surveys and interviews will be conducted to discern the likelihood of practice adoption.

The objectives are to 1) test cover crops types in terms of weed suppression, cash crop interference, and potential weediness and identify their optimum planting date in small grains crops and 2) identify optimal seeding rates for cover crops that can be used in an IWM approach in wheat.

For both objectives the following methods were used:

The determination of the cover crops with the greatest efficacy in weed suppression in arid regions of the Western US was measured through percent cover and biomass comparisons. The density and composition of weed species were measured once monthly across the growing period (May-July) each year by taking percent cover measurements. At the time of cash crop harvest (August), shoot growth from the plots was collected for biomass comparison. This was repeated a month later for comparison of post-harvest competitive suppression due to cover crop-weed interaction.

These metrics have also been applied to the cash crop to show any influence on cash crop development. Additionally, cash crop yield data has been calculated each year from the biomass samples taken. This has allowed for the identification of any cover crop influence on crop yield.