System Effects of Strip Tillage and Compost with Zonal Cover Cropping in Organic Broccoli

Strip tillage and zonal cover cropping are both strategies that tailor management to specific areas of the field, with the goal of improving system-level performance. As part of a long-term field trial in Michigan, a study was conducted over two seasons (2014 and 2015) to evaluate the effects of tillage and compost on organic broccoli (Brassica oleracea ’Belstar’) production following zonal cover cropping of vetch (Vicia villosa Roth) and rye (Secale cereale L.) planted to in-row and between-row areas, respectively. Experimental plots were arranged in a split-plot design with tillage as the main plot factor [full width conventional tillage (CT) vs. strip till (ST)] and compost application as the subplot factor (none vs. dairy compost). CT was accomplished using a rototiller, while ST was accomplished with a Hiniker 6000 two-row strip-tiller. Effects on broccoli yield and quality, weed pressure, and soil moisture, temperature, and inorganic N availability were evaluated. Conventional tillage and the addition of compost generally increased total broccoli yields. However, in 2015, the physiological disorder brown bead was particularly prevalent in CT treatments, with greater yields of high-quality marketable heads observed in ST. Soil and microclimate measurements suggest that the observed yield benefits from CT and compost application may be more attributable to soil N availability than to differences in soil moisture or temperature. Weeds were managed through a combination of hand weeding and cultivation using a Hillside rolling-spyder cultivator. Increased competition from weeds or cover crop regrowth may have also contributed to depressed yields in ST, but the rolling-spyder cultivator generally proved effective at managing weeds between crop rows, even in the presence of rye cover crop residue. The performance of ST is sensitive to crop, environment, and management. Continued research is needed to identify crop-specific best practices and to better understand production and conservation tradeoffs in organic vegetable systems.