- Agronomic: potatoes
- Education and Training: demonstration, extension, on-farm/ranch research
- Farm Business Management: budgets/cost and returns
- Pest Management: mulching - plastic, soil solarization
- Production Systems: organic agriculture
- Soil Management: general soil management
Biofumigation, the managed release of degradation products from plant residues, is an alternative to soil fumigation. We evaluated traditional biofumigant crops like rapeseed and mustards, and others including forage pearl millet. Our intent was to combine crop amendments with solarization for managing Potato Early-dying Disease (PED) pathogens, but we found soil covers were not crucial for forage pearl millet. Forage pearl millet is frost sensitive so is best used in the upper Midwest as a full season cover crop or to follow early season vegetables. The mechanism for suppressing soilborne pathogens appears to be related to decomposition rather than to specific plant compounds.
Potato production systems are important in most states in the North Central region and potato is prominent in diets typical of the Midwest and the world. Potato production accommodates a range of cultural practices and strategies, but there is one practice that is common to 80% of the potato acreage in Wisconsin and a majority of acreage elsewhere – soil fumigation. Fumigation is done in the fall preceding potato for the purpose of decreasing two soil pathogens, the fungus Verticillium dahliae and the nematode Pratylenchus penetrans and the disease that they cause, potato early dying. Metam sodium is the most commonly used chemical in the North Central Region, but there is a growing interest in chloropicrin. Both metam sodium and chloropicrin are general biocides with the potential to harm a broad range of organisms, including humans if accidental exposure occurs. Soil fumigation is effective, profitable despite a relatively high cost (approximately $150-$300 per acre), and is accomplished as a one-time event during a period that doesn’t interfere with other farm activities. Despite the advantages of soil fumigation, there is a clear and growing interest among farmers to develop additional strategies for managing potato early dying disease.
Biofumigation, the managed release of degradation products from plant residues that are toxic to soil organisms, is an effective practice for pest and pathogen control. The principal components of biofumigation are appropriate plant material, tools to chop and incorporate the material into soil, and manipulation of the soil environment to affect the timed release of decomposition products. For all of the human effort involved, the success of biofumigation also rests with the soil microbial community. It is the activity of the rich parade of litter- and soil-dwelling microbes that release volatiles, break down organic matter, and change the fabric of the soil community to the credit of the microbial consortium responsible for litter breakdown, nutrient cycling, disease and pest suppression, and filtering ground water. These ecosystem services are an integral part of agriculture and are supplanted, in part, by anthropogenic inputs such as fertilizer, pesticides, and tillage.
Biofumigation might not match the profitability of fumigation in the short term, but developing practices that are both profitable and sustainable is a critical activity for improving the profitability of farmers. All of the cover crops used for biofumigation return organic matter to soil, and thus help sustain important ecological services that can supplement current management activities. Unlike soil fumigation which causes a fast sharp spike in biological activity of select organisms able to capitalize on dead colleagues, biofumigation promotes a continued release of volatiles in combination with carbon and nitrogen resources that support a diverse community. Biofumigation is a pest suppression practice that poses no risk of accidental release or exposure of the public to noxious chemicals. Accidents with metam sodium, chloropicrin, and other soil fumigants are rare, but such occurrences gain immediate and wide-spread attention that has an impact on public perception disproportionate to their real risk.
Pesticides are an important tool for sustaining profitable farming systems, but absolute reliance on pesticides increases the vulnerability of farms and farmers to changes that can be mandated with little warning or full consideration of consequences. Our long-term goal is to equip farmers with knowledge, confidence, and tools to maintain agricultural production systems that utilize the ecological services provided by the soil community to augment pest control and promote crop productivity. The short- and intermediate term objectives for this project were to:
1) Build a knowledge base among growers and agribusiness representatives about ecosystem services available in the soil and the organisms involved.
2) Increase the expertise of farmers about cover crop management and the practice of biofumigation.
3) Increase awareness of farmers, crop consultants, county agents, and industry representatives of the value of biofumigation relative to soil fumigation with synthetic chemicals.
4) Increase the use of cover crops in vegetable production systems in Wisconsin
5) Increase the number of growers who consider ecological principles when making management decisions.
6) Increase public awareness of biologically-based pest management alternatives and efforts by farmers to promote land stewardship.
1) Determine why covering soil enhances the efficacy of biofumigation.
2) Evaluate different cover crops, timing of biofumigation, and soil covering strategies