Cover Crops and Green Manures

Two ways of enriching the soil involve growing your own fertilizer. This can be done through a class of plants that are able to extract nitrogen from the air, and through the growing of “green manure.”


Cover crops are also known as green manures. In contrast to crops grown for their fruit or flower, cover crops are grown for the express purpose of being tilled back into the soil.


Tilling these crops into the soil has the effect of improving the physical structure of the soil, increasing the organic matter content, and increasing the soil’s fertility.

Cover cropping is a common practice on farms and ranches, but the use of cover crops can also benefit the home gardener.

Examples of cover crops

In addition to the legumes mentioned above, the following crops make excellent green manures in the geographical areas listed. In the northern states, ryegrass (Lolium multiflorum); in the southern states, crimson clover (Trifolium incarnatum), horse bean (Vicia faba), and rough pea (Lathyrus hirsutus); in the West, bitter vetch (Vicia ervilia) and common vetch (V. sativa).

Using Cover Crops to Improve Soil

Cover crops should be tilled into the soil shortly before the crop reaches full maturity. If grown on soils of very low fertility, an application of a commercial fertilizer during the growing season will greatly improve growth of the crop and its eventual benefit to the soil.

In the home garden, cover crops can be used to improve the soil (How to improve Soil for New Gardens) before planting. Kill any weeds, then prepare the soil and sow a cover crop. When it begins flowering, cut it, let it lay in the sun for a day to wilt, then till it into the soil. If you have time, repeat for greater benefit.