Wednesday, November 15, 2006

Maintaining Agroecosystem Health in an Organic Strawberry/Vegetable Rotation System (Part 5).

Joji Muramoto1, Stephen R. Gliessman1, Steven T. Koike2, Carol Shennan3, Daniel T. Schmida4, Robert Stephens5, and Sean L. Swezey1. (1) Univ of California at Santa Cruz, 1156 High St., Santa Cruz, CA 95064, (2) Univ of California Cooperative Extension, 1432 Abbott St, Salinas, CA 93901, (3) Un ic of California at Santa Cruz, 1156 High St., Santa Cruz, CA 95064, (4) Sandpiper Farms, P.O.Box 3597, Freedom, CA 95019, (5) Elkhorn Ranch, P.O. Box 270, Moss Landing, CA 95039

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 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 will be tested after 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) will be monitored during all five years. In the first four years, strawberries, vegetables and cover crops had moderate yields and no major disease problems. No significant differences were found between any treatments in yields of any crops during this period. Broccoli residue incorporations consistently reduced Verticillium dahliae propagules in soils, whereas mustard incorporations did not. Even in the continuous strawberry-cropping plot, fruit yield has been consistent probably due to the effect of broccoli incorporations under low soil-borne disease pressure. The N monitoring in strawberries suggested: 1) the maximum N-loss during the rainy season reached 214 kg/ha, and 2) adjusting basal/supplemental N rates and pre-plant plastic mulch application can reduce N-loss during the rainy season to less than 20 kg/ha, while maintaining fruit yield. Results from the final year will also be presented.

Handout (.pdf format, 283.0 kb)