Ron Krupp: How to use cover crops and green manure to improve the garden

This commentary is by Ron Krupp, author of “The Woodchuck’s Guide to Gardening,” “The Woodchuck Returns to Gardening” and his forthcoming book, “The Woodchuck’s Guide to Ornamentals & Landscape Plants.”

When I’m giving garden talks, one of the questions I’m asked is how to replenish the soil. My standard answer is to make compost, grow cover crops, and use green manures, which I will address in this commentary and my next.

As soon as my first crop of lettuce and spinach and other greens are harvested in early summer, I plant annual buckwheat. In early July and August, I plant annual rye, field peas, brassicas and oats. In fall, I plant winter rye and legumes in October — both perennial crops.


Cover crops are grasses, legumes and other forbs ( herbaceous flowering plants other than grasses) that are planted for erosion control; improving soil structure, moisture and nutrient content; increasing beneficial soil biota; suppressing weeds; providing habitat for beneficial predatory insects; facilitating crop pollinators; providing wildlife habitat; and providing forage for farm animals. 

Furthermore, cover crops can provide energy savings both by adding nitrogen to the soil and making more soil nutrients available, thereby reducing the need to apply fertilizer. Cover crops encourage beneficial insect populations, often minimizing or eliminating the need for other insect control measures. 

Green manures or living mulches improve soil conditions and provide nutrients for subsequent crops instead of using chemical fertilizers that can harm soil microorganisms. 

Compost and cover crops are the ideal way to improve soil fertility in your garden. The difference between green manure and cover crops is that cover crops are the actual plants, while green manure is created when the green plants are plowed into the soil.

Cover crops and green manures are important in building up soil fertility. A cover crop is simply a high number of plants, usually specific annual, biennial, or perennial grasses and/or legumes, growing and covering the soil surface.

Cover crops also attract beneficial insects to the garden, thus reducing the need for chemical pesticides. Green manure provides similar benefits.

The Magic Carpet Mix from Fedco Seeds in Maine includes a diverse cover crop of 11 different varieties, mostly clovers but also vetch, radish, chicory and alfalfa, millet and annual rye. You can use it as a ground cover beneath peas and pole beans. Trim the crop to 6 inches high; I use  my grass shears. Otherwise, it goes up to 3 or 4 feet!. These cover crop seeds are not expensive to purchase at garden and farm centers and in catalogs like Fedco of Maine. 

When preparing new beds of perennials, flowering shrubs and trees, home gardeners can plant cover crops. I realize that some gardeners don’t have room for cover crops, but if you’re preparing a new area or removing some beds because of invasives, it might be a good idea to consider putting in cover crops, especially if you are removing parts of your lawn. Many times gardeners have open spaces that fill up with weeds. That is another good reason to plant cover crops.. 

Farmers use green manures more than gardeners; however, the latter have just as much to gain from these crops, although on a smaller scale. Why import fertility with only compost, when soil fertility can be complemented with green manures: I spread animal and plant manure composts over cover crops in fall.For more information, go here.


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