A Novel Approach to Grow and Mechanically Kill Cover Crops On Beds and in Furrows for Reduced Tillage of Organic Vegetables.

Long-term, organic systems research in Salinas, California, showed that annual winter cover cropping improves soil quality, pest management, nutrient cycling, and yield of high-value, high-input vegetables.  However, cover crop residue management in these rotations is challenging and expensive because extensive tillage is used to soil-incorporate the residue, and the residue decomposition period delays subsequent vegetable plantings.  An alternative approach may involve mechanically killing the cover crop and transplanting vegetables through the mulch, although the feasibility of this approach in organic cool-season vegetables is unknown.  A two-year study of fall-planted cover crops evaluated the first phase of this strategy with ‘Merced’ rye (Secale cereale L.) planted at three seeding rates on bed tops and ‘Ida Gold’ mustard (Sinapsis alba L.) planted in furrows.  Roller-crimping alone, versus roller-crimping + grain drill-crimping, were compared for killing the cover crops.  Above ground cover crop biomass and nitrogen uptake during cover cropping period (October to April) increased with seeding rate early in the season.  Rye regrowth after crimping varied with seeding rate and year, and was significantly lower in the roller-crimping + grain drill-crimping treatment.  Mustard was unaffected by rye seeding rate.  Mustard guided the tractor wheels in the furrows during crimping and was killed by crimping from the wheels.  The study illustrates a novel approach to grow and kill cover crops on beds and in furrows with standard implements, and showed the benefits of higher rye seeding rates for maximizing N uptake and reducing regrowth in some years.  Roller crimping + drill-crimping was most effective because it crimped rye that laid either parallel or perpendicular to the beds.  More research is needed to develop organic methods to control weeds that grew rapidly through the mulch after crimping, and implements for injecting organic fertilizers under cover crop mulch before planting transplanting vegetables.