- Agronomic: grass (misc. annual)
- Nuts: almonds, pistachios, walnuts
- Animal Production: feed/forage
- Crop Production: alley cropping, cover crops, cropping systems, fertilizers, intercropping, irrigation, pollinator habitat
- Education and Training: decision support system, extension, on-farm/ranch research, technical assistance, workshop
- Farm Business Management: budgets/cost and returns
- Natural Resources/Environment: biodiversity
- Pest Management: competition, cultural control, integrated pest management, mulches - living, smother crops, weed ecology
- Production Systems: agroecosystems
Sustainable orchard production depends on effective orchard floor management to provide ecosystem services, such as limiting soil erosion, managing water cycling, and improving soil structure. While a growing body of literature has established the general sustainability of cover crops, few studies have investigated the importance of cover crops used specifically for weed management, and fewer still are applicable to perennial cropping systems in the arid west. Therefore, orchard growers have begun to recognize the need for research that will enhance specific ecosystem services from orchard floor vegetation. Weed-suppressing cover crops could contribute to an integrated weed management program by displacing weeds and reducing the need for chemical weed management. We intend to implement small plot cover crop trials in orchards in the Sacramento Valley of California to test a management-intensity gradient, including minimal cover crop management, multi-species mixtures, cut forage crops, and a harvested grain intercrop within the orchard. This research will help determine the level of management that best contributes to a competitive cover crop, including various combinations of agronomic factors like mowing, irrigation, and fertilizer applied to the cover crop. Results from this research will inform economic studies of cover crop intensification, and these data will be disseminated through professional scientific networks and Extension media and demonstrations. We will monitor outreach activities in order to understand the baseline level of awareness of cover crop benefits and identify knowledge gaps about weed-suppressing cover crops. The proposed research will make cover crops a more viable component of integrated weed management programs in western orchards, contributing to the general sustainability of orchard cropping systems and reducing the economic risk of orchard establishment.
Objective 1: Design and implement cover cropping systems for weed suppression in nonbearing orchards. Intentional orchard floor cover is relatively uncommon in young fruit and nut orchards. If intensified cover crops are viable in orchards, then winter cover crops will outcompete weeds but not negatively impact trees in a nonbearing orchard. Successful evaluation of this objective will integrate knowledge from existing cover crop research to develop systems that support orchard intensification while reducing negative externalities of orchard production.
Objective 2: Evaluate weed response to cover crop competition across a range of management intensities. Weed communities respond and adapt to the artificial selection imposed by agricultural management practices. If cover crops create a competitive environment that suppresses weeds, then orchards with a highly-competitive, highly-managed cover crop will be less weedy than those without. Successful evaluation of this objective will identify the relative advantages and drawbacks of high-intensity cover cropping and similar lower-intensity cover cropping programs.
Objective 3: Understand economic factors that motivate cover crop adoption. Realistically, broad adoption of integrated weed management requires an economic improvement over current practices. If cover crops can provide weed management services at a lower net cost to comparable weed management practices, then growers will be eager to adopt cover crops. Successful evaluation of this objective will include quantification of the economic costs and benefits of various cover crop systems in orchards.