25. Biofumigation Certain Brassica cover crops, as well as mustard seed meal, contain high concentrations of isothiocyanates (ITCs) – derived from the degradation of glucosinolates (what gives them the pungent taste). The seed meal is also a significant source of nitrogen and other nutrients. When incorporated into the soil ITCs act as an effective biofumigant, reducing populations of pathogenic fungal species (Sclerotium, Rhizoctonia, and Phytium), nematodes, weeds, and certain insect species. UT/TSU 2003 In addition, the residues add important organic matter for soil building.