Comparison of Rye and Legume-Rye Cover Crop Mixtures for Vegetable Production in California

Rye (Secale cereale L.) is an important cover crop in high-value vegetable production in California. A 2-yr winter study on organic farms in Salinas and Hollister, CA evaluated cover crop population densities, ground cover, aboveground dry matter (DM), and N content of rye and five legume-rye mixtures. Mixtures had 60 or 90% legumes by seed weight and included two or more of the following legumes: faba bean (Vicia faba L.), vetches (V. benghalensis L., V. dasycarpa Ten., V sativa L.), and pea (Pisum sativum L.). Seeding rates were 90 (rye) and 140 (mixtures) kg ha(-1), and densities were 142 to 441 plants m(-2). Early-season ground cover was usually greater in monoculture rye and the 60% legume mixtures than the 90% legume mixtures. Total DM, and legume and rye DM in mixtures differed by year, site, harvest, and cover crop. Total DM was usually at least two times higher at season end than mid-season. The 90% legume mixtures generally produced more legume DM than the 60% legume mixtures, but legume DM usually declined after mid-season. Rye DM increased with rye density. Total cover crop N uptake was greater in Hollister than Salinas; however, legume DM and legume N uptake were greater in Salinas. Interactions between site, year, cover crop, and harvest illustrate the complex growth dynamics of legume-rye mixtures. The 90% legume mixtures appear most suitable for vegetable production in California because they had a better balance of legume and rye DM at season end.