Conservation tillage methods been widely adopted for agronomic crop production but because they rely on herbicide use, organic vegetable growers have not adopted them. Legume cover crops offer the opportunity to capture N from the atmosphere through symbiotic fixation in the root nodules and possibly produce N at a lower cost. We are investigating cover crop mixtures and mechanical kill methods to maximize benefits in organic vegetable production systems.
Oats, Oats + vetch, and Phacelia + vetch produced similar amounts of average total biomass (4610, 4530, and 4600 pounds of dry matter per acre) compared to 620 lbs of dry matter per acre in the no cover crop fallow. Adding the vetch to the oat mixture, however, increased the average N content from 51 lbs/a in oats to 105 lbs/acre in the mixture. Cost per lb of N in the cover crops were: oats $0.82; oat-vetch $0.48; and phacelia-vetch $0.39. Mechanical suppression of the phacelia-vetch mixture was obtained by mowing with a flail mower and by rolling with a ring roller (cultipacker). We have also established a ridge till/strip-till experiment to evaluate conservation tillage systems for organic vegetable production. This experiment is currently established at the OSU Vegetable Research Farm and is being conducted in cooperation with Stalhbush Island Farm, a vertically integrated farm and processing company near Corvallis. We will be focusing on mechanical methods for killing cover crops, including more advanced rolling equipment, and novel weed suppression technologies and application of GPS-guided cultivation equipment.
