Although organic fertilizers represent an environmentally friendly choice for your gardening chores, choosing them for edible crops, such as vegetables, reduces the amount of chemical residue in your family's diet. Organic fertilizers may be as inexpensive as your backyard compost or as pricey as exotic mail-order bat guano. Each fertilizer offers a different combination of nutrients. Consult your local extension service to determine common nutrient deficiencies in your region's soils as well as specific vegetable crops' needs.
Cover crops, also known as "green manures," feed vegetables before they are planted by adding nitrogen to the soil, notes "Rodale's Ultimate Encyclopedia of Organic Gardening." Some crops, such as red clover and sweet clover, also mine phosphorus from subsoil, bringing it closer to the surface to benefit vegetable growth. Gardeners may choose to seed their vegetable gardens with cover crops in the fall for the following year's garden or sow quick-growing crops in early spring. In either case, gardeners till the low-growing plants back into the soil several weeks before planting their vegetables to allow the plants to decompose in the ground, adding nutrients and building soil structure. Popular cover crops include soybeans, several clover varieties, buckwheat, oats, hairy vetch, alfalfa and winter rye.
Whether you make your own or buy it bagged from the garden center, rely on compost to organically feed your vegetables throughout the growing season as well as to create the perfect soil texture for root growth prior to planting. According to the Environmental Protection Agency, compost also provides higher yield for food crops. It may protect vegetables from diseases, such as root rot --- an especially important concern for root vegetables, such as potatoes and carrots. Compost may be spread over the soil and worked into the garden a few weeks before planting as well as added to planting holes in small quantities when establishing seedlings. During the growing season, heavy feeders, such as tomatoes, corn and peppers, benefit from a 1/2-inch layer of compost applied in circles around each plant or in straight lines along row plantings. (See References 1)
Dried manure comes in bagged form from the nursery. If you have your own chickens, rabbits, cows or horses, age manure for several months before adding it to the vegetable garden, because fresh manure can pass harmful bacteria to food crops. Manure adds nitrogen to the soil as well as potassium and phosphorus. As with compost, manure can be added to the vegetable garden before planting as well as during the growing season. Excess amounts of manure may result in more foliage and less fruit or flower, so use it sparingly in the weeks before such plants as tomatoes and peppers set fruit. On the other hand, all-leaf plants, such as lettuce and cabbage, benefit from extra manure. (See References 1)
Some gardeners create their own liquid fertilizers by soaking bags of aged compost in water and straining the resulting liquid. Garden centers also offer organic liquid formulas based on fish emulsion or seaweed. Liquid fertilizers are especially useful for feeding vegetables by applying it to the plants themselves rather than the soil. The method, known as foliar feeding, quickly delivers nutrients to the plants through its leaves. The Rodale volume recommends liquid fertilizers for container-grown vegetables and for mid-season feeding of vegetables, such as pole beans and tomatoes, that bear crops over a period of several weeks.
Dry fertilizers, such as fish meal, kelp meal and rock phosphate, usually deliver specific nutrients to the soil. They are useful for addressing soil deficiencies of major nutrients or trace minerals or for adding to specific vegetable crops that benefit from specific nutrients. Blood meal, cottonseed meal, fish meal and soybean meal add nitrogen, while bone meal and rock phosphate supply phosphorus. Granite meal, greensand and kelp meal add potassium. Some gardeners supplement dry store-bought fertilizers with home-produced plant foods. Powdered eggshells deliver calcium, coffee grounds are rich in nitrogen and wood ashes are rich in potassium. (See References 1)
- "Rodale's Ultimate Encyclopedia of Organic Gardening"; Fern Marshall Bradley, et al.; 2009
Ellen Douglas has written on food, gardening, education and the arts since 1992. Douglas has worked as a staff reporter for the Lakeville Journal newspaper group. Previously, she served as a communication specialist in the nonprofit field. She received her Bachelor of Arts from the University of Connecticut.