Biofumigation Potential and Considerations for the Desert Southwest

The use of biofumigant, or bioactive, cover crops for soil-borne pest suppression is a management tool that has demonstrated, although often inconsistent, success in rain-fed cropping systems. However, less information is available regarding biofumigant cover crop species and their culture in arid regions, including the desert southwest of the United States. While irrigated agriculture can add an additional level of control to water management of biofumigant crops, the unique and diverse cropping systems can simultaneously add a layer of complexity. This complexity creates roadblocks to adoption of biofumigant cover crops, although alternatives to chemical fumigation are desired among agricultural producers. The desert southwest, and specifically southern New Mexico, present unique soil (calcareous, low organic matter), water (salinity, pH), and climatic conditions (24 cm of precipitation/year, high summer temperatures, mild winters, and intense sunlight) that can impact biofumigation protocols adapted for use in other parts of the country. Here, we outline the attributes of a successful biofumigant crop for southern New Mexico as well as the potential pitfalls and considerations that are specific to our unique environment. Some of these considerations include: the biofumigant crop must be a non-host for economically important viruses, nematodes, and soil-borne fungal and bacterial pathogens; high biomass production over winter, high glucosinolate content with a wide range of functional groups to manage multiple pests; a harvestable primary product (ie- broccoli or cabbage); low cost and readily available; and it will not become weedy itself. Initial studies indicate that brassica biofumigant crops can yield up to 5,400 kg/hectare dry weight, over winter successfully, and contribute to significant dicot weed reduction from direct competition in the fall. We use this information to develop a set of protocols that are economically viable as well as an effective management tool for a wide range of soil-borne pests common to the desert southwest. We outline specific recommendations for southern New Mexico, but with potential application to other parts of the country and arid parts of the world.