What about “green manures” and composting them in place by turning them under?
A month or so before killing frost, the vegetable-garden soil that fed me gets a meal, or at least the promise of one. I sow soil-sustaining cover crops (always from non-GMO, organic seed) as the various food crops are harvested, gradually turning my vegetable beds into mini-fields of winter cereal rye (above) and mammoth red clover for the colder months.
Come spring, several weeks before I plan to plant each area, I’ll cut the grain and legume down or mow them, depending on where they’re located, then turn under the remains—like composting in place, with the foliage and underlying root system decomposing to improve soil texture and fertility.
Cover crops can serve other purposes: Some specialized ones, like various Brassicas, can also provide not just biomass but other benefits like pest and disease control; the subject is much wider than this simple explanation but stated most simply:
- Grasses (like rye, sorghum-sudangrass crosses, and wheat) add organic matter to the soil very effectively (note that I don’t list buckwheat, another great cover crop, here; that rhubarb and sorrel relative is not technically a grass or grain, though we think of it as such because of how we use it food-wise);
- Legumes (clovers, cow and field peas, vetch) with their inherent Nitrogen-fixing capability, provide Nitrogen effectively;
- Brassicas and Mustards (rapeseed or canola; radish; mustard) have proven effective against various nematodes, fungi and insects.
Cover crops—there are varieties for each season and each climate—also serve as a living mulch, protecting the soil from erosion, and thwart other weeds, making the management of fallow garden areas (such as during crop rotations) easier than just standing back and watching undesirable plants take over.
Depending where you live, and what your purpose and timing is, here are some sources of high-quality seed
TERRITORIAL SEED, in Oregon, breaks its list down by season;
BOUNTIFUL GARDENS in California calls them “compost crops;”
JOHNNY’S SELECTED SEED in Maine offers many varieties, too.
CORNELL UNIVERSITY has a longer list of sources, many commercial and geared to organic farming.