Sustainability in agriculture is gaining popularity as we become more cognizant that natural resources are not unlimited, yet sustainable agriculture has been practiced by successful growers for decades.
Sustainability is basically ensuring good stewardship of land, air, and water while providing a quality of life for those in agriculture who are growing our food sources. Tending sustainable gardens is a way that the average plant enthusiast can contribute to good stewardship.
Maintaining soil health is top on the list of good stewardship.
Cover crops serve as green manure crops, those that, when properly managed, provide living organic matter to a soil. Green manure crops are planted in the off seasons, either in the winter months before the summer gardens or in the summer before the fall gardens. Seeds are sown, germinate, become established and grow, producing root systems below ground and lush, green foliage above ground. The below ground parts and above ground parts combine to produce biomass that will be tilled under before seeds are set. Crops that are left to set seed will actually cause a weed problem, so it is critical to till under the foliage before seeds mature.
Legumes and grasses are both excellent cover crops. The lush foliage of both types of growth are low in carbon and are high in nitrogen, providing a favorable carbon to nitrogen ratio which will rapidly breakdown once tilled into the soil. Legumes, unlike grasses, have the added benefit of fixing atmospheric nitrogen in the soil.
The use of cover crops as green manures has a role in crop rotation schemes. Cover crops can be annuals, biennials, or perennials. Each can fill specific niches in a season. Winter-annual legumes are planted in the fall, overwinter, and produce most of their biomass when growth resumes in the spring. These can be sown following the summer garden. They are tilled under before planting of the summer garden.
The most common summer-annual legume is blackeyed peas, often called cowpeas. Black-eyed peas produce nitrogen in the foliage and fix nitrogen in the soil; when seed is broadcasted or drilled thickly the peas can make ground cover for weed control.
Sustainable Agriculture Research and Education (sare. org) suggests these crops: Winter cover crops: Trifolium species (clovers), oats, ryegrass, wheat, triticale, barley and field peas.
Summer cover crops: cowpeas, small grains, soybeans, sorghum, sudan grass, millet.
Ellen Peffley Harp, a retired professor of horticulture at Texas Tech University, writes about gardening for several Texas newspapers.
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