Difference Between Green Manure And Cover Crops

Green Cover Crops
cover crop
(Image credit: Wylia Santoso)

The name may be misleading, but green manure has absolutely nothing to do with poop. However, when used in the garden, cover crops and green manure provides a number of benefits to the growing environment. Read on to learn more about using cover crops vs. green manure.

What are Cover Crops?

Cover crops are plants grown strictly to improve soil fertility and structure. Cover crops also provide insulation that keeps the soil cool in summer and warm in winter.

What are Green Manures?

Green manure is created when fresh cover crops are incorporated into the soil. Like cover crops, green manure increases the level of nutrients and organic matter in the soil.

Cover Crops vs. Green Manure

So what's the difference between green manure and cover crops? Although the terms “cover crop” and “green manure” are often used interchangeably, the two are actually different, but related, concepts. 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 are sometimes known as “green manure crops.” They are planted to improve soil structure, suppress growth of weeds and protect the soil from erosion caused by wind and water. Cover crops also attract beneficial insects to the garden, thus reducing the need for chemical pesticides. Green manure provides similar benefits. Like cover crops, green manure improves soil structure and releases important nutrients back to the soil. Additionally, the organic matter provides a healthy environment for earthworms and beneficial soil organisms.

Growing Cover Crops and Green Manures

Most home gardeners lack space to dedicate an entire growing season to a cover crop. For this reason, cover crops are usually planted in late summer or autumn, and then the green manure is tilled into the soil at least two weeks before the garden is planted in spring. Some plants, which reseed themselves prolifically and become weeds, should be worked into the soil before they go to seed. Plants suitable for planting in the garden include peas or other legumes, which are planted in either spring or early autumn. Legumes are a valued cover crop because they fix nitrogen in the soilRadishes are a fast-growing cover crop planted in autumn. Oats, winter wheat, hairy vetch and ryegrass are also planted in late summer or early autumn. To plant a cover crop, work the soil with a garden fork or rake, then broadcast the seeds evenly over the surface of the soil. Rake the seeds into the top of the soil to ensure the seeds effectively contact the soil. Water the seeds lightly. Be sure to plant the seeds at least four weeks before the first expected frost date.

Mary H. Dyer

A Credentialed Garden Writer, Mary H. Dyer was with Gardening Know How in the very beginning, publishing articles as early as 2007.