Improving Soil Health Through Cover Crop Based No-Till Organic Vegetable Production

Improving Soil Health Through Cover Crop Based No-Till Organic Vegetable Production

Summary

No-till techniques have gained attention as a means to reduce the negative impacts of intensive tillage, which is routinely used by organic farmers for weed control, but significant questions remain about the viability of no-till techniques in organic vegetable systems. The Improving Soil Health Through Cover Crop Based No-Till Organic Vegetable Production project is comparing cover crop species used in organic no-till vegetable systems, as measured by impacts on vegetable quality, yield, and soil health. Outcomes will include the development of best management practices for organic no-till vegetable production in the upper Midwest. Long-term impacts include increased no-till adoption among growers, leading to more effective organic weed management, improved soil health, and greater long-term financial and environmental sustainability. Research will be conducted on a university research station with input from a grower advisory committee. Outreach will be conducted through field days and information disseminated through websites, conference presentations, and publications directed toward grower audiences. Evaluation will be conducted at the field days, and through the grower advisory committee and data collected with distribution of publications and web resources.

Objectives/Performance Targets

Improve soil health (long term) and reduce soil and nutrient loss by erosion (short term): The use of no-till and cover cropping practices have been shown to increase soil organic matter, improve soil biology and soil health, reduce erosion, and improve soil aggregate structure. Research to identify successful applications of no-till on organic farms will lead to increased knowledge among growers about successful practices, in turn allowing increased implementation of this technique, ultimately resulting in improved soil health and reduced erosion and nutrient run-off.

Increased environmental sustainability and farmer profitability: In the short term, this research will provide data, education and outreach that will provide farmers with reliable information about vegetable specific no-till systems, leading to increased farmer adoption of sustainable no-till techniques. Implementation of organic no-till and mulching practices will provide farmers with a more cost effective and environmentally sustainable tool for weed management and a low-cost source of slow release soil organic carbon resulting in increased farmer environmental sustainability and profitability.

Increase productivity and profitability on organic farms: Increased adoption of no-till vegetable systems will reduce labor costs associated with tillage, weed management, and spreading mulch (medium term). In addition to reducing labor requirements and associated costs, no-till retains soil nutrients, minimizing the need for off-farm fertility and weed management inputs and fuel.

Accomplishments/Milestones

The field research portion of this project was completed in the fall of 2014. A summary of findings follows.

Cereal rye produced greater amounts of biomass than the other cover crop treatments. Hairy vetch germination and survival through the winter was extremely poor and this treatment was replaced by a straw mulch treatment using straw obtained from off-farm as a positive control. Greater numbers of weeds were found in the wheat mulch as compared to the cereal rye. Early season weed density was significantly greater in the control plots than in the rye plots, although later in the season density was comparable. This impacted the in-season labor required for weed management, with wheat plots requiring the most labor and rye plots having management needs similar to the control plots.

The peppers in the straw mulch had greater yields than the other treatments, while pepper yield in the wheat mulch was comparatively poor. Peppers in both rye plots performed well in comparison to the control plot. Bean yield was far greater in the control plot relative to the other mulch treatments. In 2014, weed pressure due to volunteer oats in the straw mulch probably impacted this treatment so as to significantly decrease yield. Pepper yield in the rye plots was good, but these plots were not quite as productive as the control plot.

Potato yields we very similar among treatments in 2013. Wheat treatments showed a lesser potato yield than the other mulch treatments. In 2014, however, there was a greater yield from the control plot. Although weed pressure may be a factor, damage caused by potato leafhoppers and rodents decreased the harvest of marketable potatoes. There was a greater incidence of loss due to these factors in the mulched plots, probably due to their providing a preferable habitat for pests. Overall, adequate cover crop biomass production was found to be a key factor in determining the extent of weed suppression and productivity of this system.

These results suggest the fruitfulness of future work with winter rye as a cover crop, together with other varieties of winter hardy vetch or red clover to add nitrogen fixation to the benefits of this system. One shortcoming of this experiment was that it only ran for two seasons, in adjacent but different fields, preventing us from effectively measuring impacts on soil health. Given the high weed density both years, it would be prudent to manage the initial weed seed bank before attempting this method for long-term weed control. Cooler soil, production of allelopathic compounds by rye, and slower cycling of organic matter from the cover crops to replenish soil nutrients may also impede growth in cover cropped plots. Future research should take into account the impacts of these factors. It would also be helpful to experiment with other vegetable crops.

Initial bacterial assays do not show a significant difference in enzymatic activity or production of plant-growth promoting compounds between rye and control plots. As expected there is greater incidence of these phenotypes in samples taken from the root surface than in the bulk soil. Laboratory work with bacterial samples is ongoing and will be completed by this summer. Only one set of samples were taken late in the season both years and the cover crop was, for the most part, intact. Impacts of this method on microbial activity over the course of the season, impacts on mycorrhizal growth, longer term effects, once the organic matter of the cover crops is fully broken down and corroboration with other techniques to measure impacts on the microbial community, would be advisable for future research.

Impacts and Contributions/Outcomes

Initial findings were presented at a 2013 Organic Field Day at the West Madison Agricultural Research Station. Feedback on this research was solicited from farmers interested in utilizing cover-crop based reduced tillage in urban areas at the Growing Power Small and Urban Farmer’s conference in Milwaukee and from several organic vegetable farmers in southeastern Wisconsin. This research was presented at the 2014 American Society of Agronomy-Crop Science Society of America-Soil Science Society of America meetings in Long Beach, CA and discussed with from organic researchers working with these methods within the Organic Management Systems Community. A poster presentation of soil microbiology aspect of this work was presented at the 2014 American Phytopathological Society-Canadian Phytopathological Society meeting in Minneapolis. Eric Bietila will participate in a panel at the Organic Agriculture Research Symposium this February in La Crosse to discuss this research, and has submitted a proposal for a research poster to be presented at the MOSES Organic Conference that follows. Final results from this study will be included in Eric Bietila’s Master thesis and publication will be sought in appropriate academic journals and extension publications.

Collaborators: