F.W.
Kentucky

Answer: Thank you for your recent request for information from ATTRA, the National Sustainable Agriculture Information Service. I am pleased to provide you with information on the application of compost.

There are several different thoughts on when the best time to apply compost is. Although several factors attribute to these differences, the main factor in deciding when to apply compost to the soil depends on the compost's condition, age, and degree to which the composting process is complete. Nutrients in the compost are released slowly and small amounts are available to germinating and young crops. If compost is applied too early before a crop is planted, nutrients may escape in to the air. Incorporating compost in to the soil close to planting time allows for the release of nutrients to take place in the soil.

Unfinished compost will continue to generate heat and decompose. This compost is best applied in the fall of the year so that it is ready to supply nutrients to spring planted crops. The preferred time to apply fully matured compost is around the time of seeding or transplanting. For a single crop, the compost can be applied a few weeks in advance. For succession plantings, it is best to apply the compost just before planting. It is recommended that the closer to the planting time the compost is applied, the finer it should be and more thoroughly incorporated into the soil.

Although compost is most often applied to an entire field or plot at one time, it is important to have a crop plan as some vegetable crops react differently to compost. For example, research suggests that tomatoes, cabbages, and most root crops yield better with compost applications taking place every-other-year, while beans, peas, corn, and squash do better with a compost application each year. In fact, applying compost to some crops should be avoided in the same season. This includes potatoes, which have a greater tendency to scab, and carrots as compost can cause them to become "hairy." A crop plan will allow you to plan your crop rotations accordingly. For example, you can apply compost prior to a planting of beans followed by tomatoes the following year that do not receive a compost treatment.

Based on the information you have provided regarding your plantings of fall cover crops, you can either apply the compost before the cover crops are seeded or in the spring once the cover crops are terminated and you are preparing for spring planting.