Brassicas
The plant family Brassica includes radishes, mustards, turnips, and cabbages, among many others. In the context of cover crops, the Brassicas are an excellent way to prevent weeds and reverse soil compaction.
Dean Baas and Elizabeth Schulthuis of Michigan State write:
Brassicas are leafy and grow very rapidly. Because of this rapid growth, you get a lot of shading of the soil very quickly, which helps prevent the growth of weed species. Unique to the Brassica family is the production of glucosinolates, or chemical compounds that are natural inhibitors of weed species. Because of these chemicals and their fast growth, you will see very few weeds growing in plots containing Brassica cover crops.
Some Brassicas feature large tap roots which can effectively reverse soil compaction at different soil depths, depending on the species. It goes without saying that these roots, which can grow to depths of more than six feet, are also excellent safeguards against erosion.
The Center for Agriculture, Food, and the Environment at UMass Amherst emphasizes both the efficacy of Brassicas to control pests, bacteria, and weeds as well as the ongoing research that these complicated interactions make necessary:
All Brassicas have been shown to release biotoxic compounds that exhibit broad activity against bacteria, fungi, insects, nematodes, and weeds. Brassica cover crops are often mowed and incorporated to maximize their natural fumigant potential. This is because the fumigant chemicals are produced only when individual plant cells are ruptured. The timing and method of incorporation seems to be a key factor in how effective they are at suppressing pests. University studies have shown Brassica green manures to suppress Rhizoctonia, Scab, and Verticillium in potatoes and Phtophthora blight in cucurbits. It has also shown efficacy in reducing nematode and weed populations in various cropping systems. The use of Brassica cover crops for disease and insect control is still very much a work in progress.
At Scout Seed, we are at the forefront of research into Brassica use in the Coastal Plains and would be happy to share our findings in how best to implement these incredible cover crops into your working farm.