Green manure and cover cropping are relatively synonymous; both describe plants we purposefully plan on knocking down and digging into the soil without harvesting from them. In fact, the harvest is the plant itself, feeding the soil from which it grew.
Where I'm hired to maintain an organic vegetable garden, I planted part of the beds with a summer mix of buckwheat and cowpeas. In other seasons and for other purposes, I'd plant something different.
|Cover crop just after emerging from the soil.|
|The plants in bloom, just before cutting down.|
Cover cropping can solve a myriad of garden problems. Some crops can protect soil from erosion, some can fight against root knot nematodes, others build tilth and inhibit the growth of weeds, but the most common use for cover cropping is to increase soil fertility by adding organic matter and often nitrogen. In my client's garden, I wanted to keep soil that wasn't growing food during the summer as healthy as possible, housing microbes and beneficial critters. I also wanted to continue to add nitrogen, so the buckwheat and cowpea combo was perfect. The plants grow well in the heat; the buckwheat builds organic mass very quickly; working in symbiosis with mycorrhizae, the cowpeas collect nitrogen from the atmosphere.
|The felled crop.|
|Nitrogen nodules on cowpea roots.|
Sustainable Agriculture Research and Education's Write-up of Cover Crops
Sustainable Agrigulture Research and Education Program's Explanation of Cover Crops
Rodale's Organic Life on Cover Crops