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This chapter focuses on the various approaches to managing and maintaining soil fertility for organic vegetable production systems. Organic vegetable growers encounter many challenges when managing their fertility program. To build soil systems and enhance fertility, organic growers use several biological inputs such as animal and green manures, composts, cover crops, and animal byproducts. These inputs promote the decomposition of plant and animal material, which make nutrients available to plants. Managing soil fertility with biological inputs assures that organic production is a biologically dynamic process, which makes nutrient management in organic systems complex. Animal manures were one of the main sources of nutrients for vegetables before food safety issues became a major concern. Composting animal manure alleviates many of the concerns about food safety issues. However, compost is relatively low in plant nutrients, and large amounts must be used to supply enough nitrogen to succeeding vegetable crops. This problem can be greatly reduced by using cover crops or green manures (i.e., plants grown in a field to be turned under and used as fertilizer) usually grown during nonproduction periods of vegetables. Cover crops are used to add nutrients to the soil, improve soil structure, suppress weed growth, and protect the soil from erosion caused by wind and water. The overall challenge for organic growers is to time nitrogen release to coincide with the demands of the vegetable crop. Growers accomplish this by selecting appropriate combinations that fit the specific needs of their vegetable production system. |
