Priority 2: Reducing Chemical Inputs
Sustainable strawberry production in the absence of soil fumigation
- Thomas Gordon, University of California, Davis
- Jenny Broome, Driscoll's Strawberry Associates
- Scott Scholer, Lassen Canyon Nursery
- Jack Chambers, Sonoma Worm Farm
- Jim Cochrane, Swanton Berry Farm
California produces more than 80 percent of fresh strawberries in the United States. Pre-plant soil fumigation using methyl bromide has been critical to this success. However, international regulations require growers to phase out methyl bromide. Consequently, non-chemical alternatives are necessary. Previous work shows promise for managing pathogens responsible for black root rot through compost amendments. Black root rot is not a problem in fumigated soil, and therefore, little was known about the susceptibility of the day-neutral cultivars that dominate the California industry. Therefore, both day-neutral and short-day strawberry germplasm were evaluated in compost. The objectives of this project were to 1) evaluate the performance of two strawberry cultivars with and without compost amendments in the central coast, north coast and central valley of California; 2) evaluate four types of composts for effect on root health, suppression of black root rot, and effect on microbial communities; 3) develop recommendations for compost application and cultivar selection to induce disease suppressive soils based on geographic region; 4) evaluate flavor differences between cultivars based on geographic region and compost amendments; and 5) extend information to growers and other stakeholders through field days and publications.
Project Outputs and Impacts
The four types of composts used in this study --yard trimmings, manure, vermicompost, and mushroom compost -- significantly increased microbial activity and led to greater root development in the field. Over time, the effects of microbial populations of each type of compost on field soil were similar no matter the origin of the native soil. The use of vermicompost led to significantly more root development than the other composts in both field and potted trials. Detailed nutrient and microbial activity profiles for pure compost and compost-amended field soil were generated and published. Additionally, significant differences were observed in the growth habits of the two types of strawberry germplasms. By April, the short-day cultivar ('Chandler') had much more vigorous and rapid growth than the day-neutral cultivar ('Albion') at all sites, which was largely attributed to root health. Information generated from this project has been shared through the project website and at professional meetings, reaching more than 130 growers, researchers and industry professionals.