Explorations into Site Suitability and Cover Crop Management for Dry-farmed Vegetable Production

Commodities

• Vegetables: cucurbits, tomatoes

Practices

• Crop Production: cover crops, drought tolerance
• Production Systems: dryland farming

Dry-farmed vegetable production is practiced in coastal California (Leap et al., 2017) and increasingly in western Oregon and Washington, where and beginning farmers are adopting dry-farmed vegetable production to grow high-value crops without irrigation.

However, there is a lack of knowledge regarding practices and site factors associated with successful dry-farmed vegetable production, which increases risk of crop failure and inconsistent yields. This project will evaluate subsoil constraints, weather, wind exposure, and cover cropping in their effects on dry‑farmed vegetable performance in the Willamette Valley, Oregon.

One knowledge gap that many farmers have is how to evaluate site suitability for dry farming. This is especially important to small and beginning farmers, as they may be growing on more marginal land. Dry farm site suitability is related to soil available water holding capacity, soil nutrients and pH (Davis et al. 2023). However, other factors, including subsoil constraints, weather, and wind speeds, still need to be explored. Subsoil constraints are physical and chemical properties of the subsoil that restrict water and nutrient availability. It is possible that cover crops can be used to ameliorate the effects of subsoil constraints (Chatterjee et al. 2024). Additionally, site factors may influence crop flavor intensity (Davis et al. 2025).

In addition to site factors, farmers also want more information on site prep, particularly how to manage fall-planted cover crops, including appropriate species/mixtures and optimum termination practices. Current recommendations are to terminate cover crops

during a break in rainfall during early spring. If cover crop termination occurs too early, it may result in soil compaction, while late cover crop termination may result in the loss of residual soil moisture to cover crop transpiration. Early cover crop termination may also limit its positive effects on soil structure and fertility.

This project aims to explore the effects of tillage timing, cover crops, subsoil constraints, wind, and weather with OSU research farm and on-farm trials with producer collaborators. Data collected will include crop yield, fruit quality, soil water tension, root length density, soil profile assessments, soil nutrient concentrations, wind run, temperature, and relative humidity.

The results of this research will be disseminated to farmers through field days, publications, and videos. Farmers will better understand how cover crop species and termination dates affect dry-farmed vegetable production. They will also develop a better understanding of how site factors like subsoil constraints and weather affect yield and flavor intensity for four different crops on their farms: tomatoes, grafted tomatoes, melon, and winter squash. Finally, they will test whether cover crops can ameliorate subsoil constraints on their farms.

This research and education grant will help farmers successfully dry farm vegetables in the Willamette Valley and other areas with similar growing conditions. Farmers adopting dry farmed vegetable production may benefit from high value market opportunities and reduced costs associated with water use, increasing on-farm profitability as well as in-stream flows. Furthermore, it will help farmers on lands with no or limited irrigation rights to grow crops with decreased risk, thereby increasing profitability and quality of life.

The objectives are as follows:

1. Determine the effects of subsoil constraints, wind, and weathert on a diversity of different dry-farmed crops
2. Develop methods for ameliorating subsoil constraints to improve dry farm productivity
3. Determine how cover crop termination dates affect soil moisture loss and dry-farmed vegetable production
4. Determine how cover crop species affect soil moisture loss and dry-farmed vegetable production
5. Market/promote dry-farmed vegetables
6. Engage other farmers in project and its outcomes