Substantial weed growth often occurs in legume-cereal cover-crop mixes commonly grown on organic vegetable farms. A 2-yr study at the USDA-ARS in Salinas, CA, was conducted to test the effect of zero, one, and two passes with a rotary hoe on weed control in a mixed cover crop of 10% rye, 15% common vetch, 15% purple vetch, 25% peas, and 35% bell bean. Rotary hoeing occurred 14–15 days after planting (DAP) in the one-pass treatment, and 14 and 28 DAP in the two-pass treatment. Rotary hoeing did not affect total cover-crop density or biomass in either year, but reduced rye density and biomass in year 2. One pass reduced total weed density by 69% in year 1 and 49% in year 2. A second pass did not affect weed density in year 1 but reduced weed density an additional 33% in year 2. One pass decreased weed biomass in year 1, whereas two passes were required to reduce weed biomass in year 2. Rotary hoeing reduced seed shed by chickweed and shepherd's-purse seeds, the two predominant weed species, by 80 to 95% in both years. Rotary hoe efficacy depended on weather conditions directly before and after cultivation. The decision to repeat rotary hoeing should be based upon field scouting and weather conditions following the initial pass with the rotary hoe.
Nomenclature: Chickweed, Stellaria media (L.) Vill. #3 STEME; shepherd's purse, Capsella bursa-pastoris (L.) Medic. # CAPBP; rye, ‘Merced’ Secale Cereale L.; common vetch, Vicia sativa L.; purple vetch, Vicia benghalensis L.; peas ‘magnus’, Pisum sativum L.; bell bean, Vicia faba L.
Additional index words: Weed seed, organic, Senecio vulgaris, Lamium amplexicaule, Solanum sarrachoides, Poa annua.
Abbreviations: GDD, growing degree days