How much compost to use for growing produce may be a more pressing question for many growers than the timing of application. Soil testing, crop recommendations, nutrient budgeting and field observations are some of the common methods for determining compost rates. Although we have used all of these tools over the years, our guiding principle has been kind of arbitrary: we use the manure produced by our work animals. With three to four horses for 3 ½ acres of vegetables, that comes to one horse per acre and a current application rate of 5-6 tons/acre.
We have hesitated to go public with our potting mix, not because the formula is top secret, but because our greenhouse experience is limited in years and scale. Nevertheless, we would like to offer what we have learned in hopes of showing that something as seemingly insignificant as putting together a potting mix can be integrated into a systems approach to farming.
Our compost piles will age for at least a year before being added to the garden. We have learned that the slow aging is more beneficial to the decomposition process as well as not losing nearly as much nitrogen to off-gassing as happens with the hot and fast methods. Another benefit is the decomposition is much more thorough, destroying weed seeds, pathogens and any unwanted chemicals much better in a slower composting setup.