Alley cropping agroforestry as a climate change resiliency strategy for vegetable production in the southeastern US

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Commodities

• Vegetables: cucurbits, greens (lettuces)
• Additional Plants: trees

Practices

• Crop Production: agroforestry, alley cropping, nutrient management
• Soil Management: soil quality/health

Alley cropping agroforestry systems are multifunctional land use systems that are well-established as effective systems for mitigating climate change and restoring essential ecosystem services. In alley cropping systems, herbaceous annual crops like vegetables are grown in wide alleys between rows of trees or large shrubs (typically leguminous, fruit, nut, or biomass tree species). Such systems are designed and managed to optimize resource-use efficiency and facilitative interactions between species. Given increasing frequency of extreme weather events induced by climate change in the southeastern USA, the ability of trees (with higher biomass and more spatially extensive aboveground and belowground structure than herbaceous species) to buffer many of these extremes is likely to increase resiliency of regional vegetable production. In particular, vegetable crops are especially susceptible to stress induced by heat extremes, which can significantly reduce yields and quality. Microclimate modification can effectively mitigate vegetable crop heat stress, but research on alley cropping systems as a microclimate modification strategy for vegetable production in the region is largely unexplored. Further, there are existing social and technical barriers that limit farmer adoption, including a lack of information on how to implement and integrate alley cropping systems into existing enterprises and a lack of information about the economic feasibility of adopting these systems. The overarching goal of this project is to establish alley cropping as a viable solution for organic and similarly managed vegetable production systems in the face of climate extremes in the southeastern USA. Our specific objectives are to 1) evaluate microclimate [e.g., soil, air, and crop canopy temperature, humidity, soil moisture, crop canopy light (PAR)], crop performance (growth, yield, quality and physiological parameters), vegetable crop mycorrhizal associations, and nutrient (carbon, nitrogen and phosphorus) cycling effects of leguminous tree alley cropping systems [nodulating black locust (Robinia psuedoacacia), or non-nodulating honey locust (Gleditsia triacanthos)] compared to open field systems on two model vegetable crops (winter squash and lettuce) at two soil nitrogen fertilization rates on an established alley cropping site in replicated research farm trials; 2) evaluate vegetable crop management on an established alley cropping site through deployment in a working university student farm; 3) assess the long-term profitability and risk of the leguminous tree alley cropping systems using capital budget valuation models and scenario analysis; 4) evaluate on-farm alley cropping system establishment and management and provide grower outreach through on-farm workshops in each cultural/geographic region of Tennessee (East, Middle, West), including rural and urban locations; and 5) extend knowledge through open-access data and open-access refereed journals, research station field days, and extension publications and videos. Our work will provide innovative research results related to vegetable crop microclimate, crop performance, nutrient cycling, and economic outcomes of leguminous tree alley cropping vegetable systems as compared to open-field systems and extend these results to researcher and grower communities. Our work involves farmers, as well as student farm interns, in the establishment, maintenance, and evaluation of alley cropping systems, and we will provide workshops for interested growers related to tree establishment and vegetable crop management in these systems.

Objective 1. Evaluate herbaceous crop microclimate [e.g., soil, air and crop canopy temperature, humidity, soil moisture, crop canopy light (PAR)], crop performance (growth, yield, quality & physiological parameters), vegetable crop mycorrhizal associations, and nutrient (carbon, nitrogen & phosphorus) cycling effects of leguminous tree alley cropping systems [nodulating black locust (Robinia psuedoacacia), or non-nodulating honey locust (Gleditsia triacanthos)] compared to open field systems on two model vegetable crops [winter squash (Cucurbita pepo var. turbinata) and lettuce (Lactuca sativa)] at two soil nitrogen fertilization rates on an established alley cropping site in replicated research farm trials.

Objective 2. Evaluate vegetable crop management on an established alley cropping site through deployment in a working university student farm. We will train student interns in alley cropping system vegetable production and management, and we will assess intern wellness, satisfaction, and productivity associated with alley cropping systems compared to open-field systems using semistructured interviews and follow up with a questionnaire interns will complete using TurningPoint Technologies.

Objective 3. Assess the long-term profitability and risk of the leguminous tree alley cropping systems evaluated in Obj. 1 using baseline capital budgeting valuation, scenario analysis, and stochastic simulation.

Objective 4. Evaluate on-farm alley cropping system establishment and management at four on-farm sites and provide grower outreach through on-farm workshops in each cultural/geographic region of Tennessee (East, Middle, West), including rural and urban locations.

Objective 5. Extend knowledge through open-access data and open-access refereed journals, research station field days, Extension agent in-service trainings, and Extension publications, webinars, and other forms of social media.