This project sought to develop an improved organic production system for broccoli and other crucifer crops by integrating high-biomass no-tillage (NT) systems to suppress weeds with farmscape plantings as food and habitat for beneficial insects. In 2004 and 2005, a total of four crops (two summer and two fall) and ten on-farm demonstration trials (five summer and five fall) were conducted, using in-situ high-biomass cover crop mulch and NT production systems to produce organic broccoli.
Research – High-biomass cover cropping systems are considered ideal to simultaneously build soil quality and achieve high marketable yields of organic vegetables. However, nitrogen availability and weed and pest management are often problems during transition form chemical to organic cover-cropping systems, especially with no-till. In 2004-2005, two summer and two fall broccoli (Brassica oleraceae L. Botrytis Group) crops were grown in twin rows on permanent (controlled traffic) raised beds (185-cm wide). Before transplanting broccoli, high-biomass cover crops were established in specific bed areas (zones), namely legume species on bed tops (grow zones) and grass species in the alleyways (bed shoulders and bottoms). Experimental treatments were tillage (conventional, CT; and no-tillage, NT), farmscaping (with and without), and nitrogen sidedressing (with and without), applied 3 weeks after transplanting, as a mixture of sodium nitrate (22 kg N/ha) and feathermeal (44 kg N/ha). Weed growth was held below yield-limiting levels with cultivation in CT plots and by periodic spot weeding to remove pesky perennial weed species in NT. High levels of beneficial insects kept broccoli insect pests low in all plots. Although the excellent insect pest management was attributed to the farmscape plantings, pest level and crop yield were not affected by farmscaping, possibly because the distance between + and – farmscape plots was insufficient to prevent migration of beneficial insects. Broccoli yield averaged 72% higher in fall than summer, probably because cool weather conditions during broccoli head development (October) favorably impacted both head size and quality (marketability). Broccoli yield in CT plots was either equal or slightly higher than NT. Nitrogen sidedressing improved yield in all plots and particularly in NT, indicating that availability and/or synchrony of nitrogen was a major factor limiting broccoli yield. Lower N response in CT probably occurred because incorporating high-N legume residues in the grow zones resulted in greater N availability. Yield in both CT and NT N-sidedresed fall broccoli was excellent, averaging 11.9 t/ha in 2004 and 13.6 t/ha in 2005. These data show that zone establishment of high-biomass cover crops on permanent raised beds, farmscaping, and N sidedressing are an effective combination for producing organic broccoli.
Outreach – A total of seven on-farm trials with organic no till (NT) broccoli were conducted in Virginia and three in western North Carolina, during 2004-05. Mixed results illustrated several potential constraints to organic no-till brassicas, including insufficient cover crop biomass or incomplete mow-kill, heavy weed pressure, drought, and grower lack of knowledge of best crop and nutrient management practices for these crops. Supplemental trials at Virginia Tech’s Kentland Agricultural Research Farm identified soybean, sunnhemp and three species of millet as most suitable cover crops to precede NT fall broccoli (high biomass generation between June and August, and susceptible to mow-kill). Other trials clarified but did not resolve problems with insufficient mulch persistence and winter weed control in winterkilled cover crops preceding early spring vegetables.
During the two-year period from early 2004 through early 2006, the project’s outreach component reached about 450 people through presentations at winter conferences and workshops, and about 125 through a three farm field days. In addition to presenting integrated minimum-till systems for organic brassicas, outreach efforts emphasized key components that can be adopted individually to considerable benefit, including high biomass cover crops to protect and build soil quality, farmscaping for biological insect pest control, and best management practices for organic brassicas. A survey showed that participants gained useful knowledge from these events, that a majority of farmers, market gardeners, home gardeners and agricultural professionals are adopting components of these systems in their crop production or education/outreach endeavors, and that at least several growers are adopting or experimenting with organic no-till. Two Virginia farmers who hosted field trials are in the process of acquiring no-till planting aids in order to implement these systems at a larger scale on their farms.
Objectives—Our hypothesis was that by integrating farmscaping with NT systems, broccoli production can be economically feasible without application of chemical pesticides. Our goal was to demonstrate that high-biomass cover crop mulch combined with farmscaping and timely use of the microbial pathogen Bt can suppress weed and insect pests to produce a profitable organic broccoli crop. Specific objectives were to (1) develop an improved prototype system for production of organic broccoli by integrating high-residue NT cover crop mulch to suppress weeds and supply organic nitrogen with farmscape plantings to attract and sustain beneficial insects; (2) evaluate the need for application of Bt in farmscaped systems for broccoli to control insect pests; and (3) facilitate the adoption of high-biomass NT production systems and farmscaping and other education and outreach methods.
Performance targets—By December 2005, four fact sheets and a comprehensive leaflet on organic NT-farmscaping broccoli production will be available in both electronic and printed form. Within one year after completion of the project, (1) two of the five organic growers hosting on-farm demonstrations will adopt NT-farmscape systems, and (2) ten of the 200 or more growers who will attend workshops and field days will explore NT-farmscape systems for production of organic broccoli or other crops.