Biofumigation is an agronomic practice that consists of finely grinding a plant cover set up during the fallow period and incorporate the chopped biomass into the soil. This practice is of interest because it releases organic compounds which are naturally produced during the development of certain plant species as a defence mechanism (allelopathic effects), and which are likely to reduce the biotic pressure of certain pests on the next crop.
The plants mainly used in biofumigation are from the Cruciferae family (mustard, radish, etc…). They produce glucosinolates which are sulfur-containing carbohydrate compounds, whose degradation in the presence of the myrosinase enzyme releases substances that have biocidal properties and help limit the proliferation of certain pathogens (bacteria, fungi, nematodes) and weeds. The production of glucosinolates reaches its peak at flowering. This is why the plant cover must be finely ground at this stage and immediately buried in order to release these substances into the soil. Re-compacting the soil in arable crops as well as mulching or covering in horticultural crops are tasks that, when carried out after the burial of crop residue, enable to limit the volatilization of the compounds. Plants from the grass family, such as forage sorghum, also have biofumigant properties that can be found through the release of dhurrin which degrades to a hydrocyanic acid, a gas that is toxic to certain soil pathogens.
Biofumigation is an agronomic lever in crop protection which could reduce the use of certain pesticides or even be a substitute. By bringing other benefits to the plot but also to the ecosystem (input of organic matter, improve soil structure, refuge for auxiliaries …), these intermediate crops which are used for biofumigation have a major part to play in the conception of innovative farming systems and in the transition to agroecology. However, there are many obstacles to such cultivation (possession of specific material, duration of the fallow period …). Setting up a plant cover must therefore be accompanied by practical changes at the farming system level.
References to explore
Brown, P.D., Morra, M.J. 1997. Control of soil-borne plant pests using glucosinolate-containing plants. Advances in Agronomy 61, pp 167–231. DOI: 10.1016/S0065-2113(08)60664-1
Couedel, A. 2018. Provision of multiple ecosystem services by crucifer-legume cover crop mixtures. PhD thesis 188p. University of Toulouse. DOI: 10.13140/RG.2.2.25222.01606
Matthiessen, J., Kirkegaard, J. 2006. Biofumigation and enhanced biodegradation: opportunity and challenge in soilborne pest and disease management. CRC. Critical Review Plant Science 25, pp 235–265. https://doi.org/10.1080/07352680600611543