While cow or horse manure enriches and fertilizes the garden soil, proper application is vital. Food contaminated with manure results in potentially lethal foodborne diseases. Never add fresh manure to the garden, as it first needs to mature or cure. One way gardeners do this is to add the manure to a compost pile or compost just the manure. When composted, only add the manure to the soil during certain stages of the garden.
Test the soil prior to adding composted manure or any amendments. The soil may not need manure added, or it may need manure and a combination of other nutrients. Contact your local county extension office for soil sample information.
Plan to add manure to the soil in the fall, after harvesting, or in the spring, before planting.
Add 1 to 2 inches of manure to the top of the soil prior to sowing seeds and work into the soil, turning over the top 6 to 9 inches. According to "Garden Soil Management," published online by Iowa State University Extension, it will take between 500 and1,000 pounds of manure for each 1,000 square feet of garden.
Side dress the vegetable garden with composted manure, when appropriate for fertilizing the particular vegetable. This involves spreading the composted manure along the side of the rows and not directly on the plant.