Biofumigant seed crops for pest and disease control
Green manure crops can be used not only to add nutrition and control weeds in your garden, but also to interrupt pest and disease cycles, much the same way as crop rotation does. This practice is known as biofumigation.
Growing a biofumigant crop can be used to manage issues such as root knot nematodes and root rot fungal pathogens, which consequently reduces the need to use toxic chemicals for soil fumigation. Plants which are particularly effective at doing this are: Brassica napus & Brassica campestris; mustard; and French marigold (Tagetes patula). In order for these crops to be successful biofumigant crops, they need to be dug into the soil where they release natural gases as they break down.
Brassica napus and Brassica campestris:
These species of brassica contain high levels of biofumigant compounds and have similar growing requirements to Canola. They also produce high levels of organic matter, perfect for the garden. Their strong taproots help to break up clay soils. Sow early autumn and early spring by evenly scattering seed across cultivated soil then lightly covering or raking in. Maintain reliable moisture, particularly until germination occurs.
The merits of marigolds have long been recognised, particularly in relation to their medicinal properties and as a food source to beneficial insects. It is now also known that French marigold, Tagetes patula, assist in the control of soil-borne diseases such as Verticillium Wilt and nematodes. This can be achieved by interplanting susceptible crops such as tomatoes with the species, as well as digging them in at the end of the growing season. Sow marigolds during spring and summer.