Brassica juncea or Sinapis alba Annual broadleaf. Up to 5'. Moderately frost resistant. Produces large amounts of biomass containing high levels of glucosinates that break down into compounds toxic to nematodes and soil-borne pathogens (such as Verticilium wilt, Rhizoctonia, powdery scab, and common scab on potatoes), a phenomenon known as “biofumigation.”
Does not tolerate drought. Allow the plants to grow fairly large to maximize the glucosinate concentration, and then chop fine and incorporate into the soil. Allow 2 weeks for the plant to break down before planting a new crop. Plant 1½" deep in a firm moist seed bed at 15–25#/acre, 1#/1000 sq ft.
As cover crop: Best as a fall-planted cover crop to retain nutrients, suppress weeds and improve water penetration. Plant in the spring as a green manure and to suppress nematodes and diseases. (Some years ago, a lot came in bags featuring a cartoon knight dubbed “The Nematode Slayer!”) ②