Maintaining Agroecosystem Health in an Organic Strawberry/Vegetable Rotation System
(Part 5): Final Results*

by J Muramoto1*, SR Gliessman1, ST Koike2, C Shennan1, D Schmida3, R Stephens4, and S Swezey1.
Univ. of California-Santa Cruz1, Univ. of California-Cooperative Extension2, Sandpiper Farms3, Elkhorn Ranch4

Abstract: Continued growth of organic strawberry and vegetable production in California faces two challenges: soil-borne disease management without use of synthetic chemical fumigants, and fertility management to optimize fertility input use while ensuring protection of surrounding vulnerable habitats. The goal of this project is to demonstrate effects of diverse organic strawberry/vegetable rotations and integrated ecological practices on agroecosystem health. In 2001, we initiated a replicated on-farm trial in a field with low Verticillium pressure at Moss Landing, California with number of years between strawberry crops as main plot (5 levels) and strawberry cultivar as sub-plot (2 levels). Ecological practices such as biofumigation with broccoli or mustard residues, compost application, use of vegetables that do not host Verticillium dahliae (spinach and broccoli) as rotational crops, and choosing strawberry cultivars that are less sensitive to disease are used in an integrated manner. While the main-treatment effects were tested in the fifth year, soil health indicators(Verticillium dahliae propagule number, soil inorganic N, and other physicochemical indicators) and agroecosystem health indicators (yield, disease incidence, and N loss) were monitored during all five years. Strawberries grew well without any major pests and diseases in all plots. Generally, regardless of cultivar, the longer the years between strawberries, the greater the marketable fruit yield, though significant difference was found only between continuous strawberry plot and 7-year break rotation plot. Therefore under low Verticillium pressure and by using the integrated ecological practices, organic strawberries can be grown in 1 to 3 year-break rotation without significant yield difference from 7 year-break rotation. Broccoli residue incorporations consistently reduced Verticillium dahliae propagules in soils. The N monitoring in strawberries suggested the maximum N-loss during the rainy season reached 214 kg/ha and adjusting basal/supplemental N rates can reduce the N-loss to less than 20 kg/ha, while maintaining fruit yield.

* Presented at the Annual Meetings of the ASA-CSSA-SSSA, Indianapolis, Indiana - Nov 13-16, 2006. 

Full Poster: Maintaining Agroecosystem Health in the Organic Management of a Strawberry/Vegetable Rotation System (Part 5) Final Results. poster_2006.pdf