Your Organic Gardening Primer
Lesson 3: Jumpstart your garden with compost tea
Your organic garden will need a jumpstart. Organic gardening relies entirely on the release of nutrients from the decomposition of organic matter and the bodies of the microorganisms that digest the organic matter in the soil. In cold soils, nutrients are not readily available.
Room temperature — a consistent 72 degrees — is the starting point for analyzing the situation. With 72-degree soil temperature, the rate of the mineralization of organic matter is approximately eight to 10 percent. If the soil contains three percent organic matter, it releases 24 to 30 pounds of nitrogen per acre per year. Producing a respectable crop takes between 80 and 100 pounds of nitrogen per acre.
In summer, when soils are at room temperature and above, it takes a soil with five to 10 percent organic matter to produce a respectable crop. Even if soil temperatures increase above 72 degrees, the mineralization rate increases only a few percentage points. To grow a crop in soils containing less than five percent organic matter, you’ve got to add organic fertilizers, including compost. As the microorganisms that digest the carbon of the organic matter die, the minerals in their bodies and in the cells of the organic matter are released.
The cooler the soil, the slower the process. Mineralization of nutrients from organic matter stops when the ground freezes. In spring, the mineralization rate of organic matter is not nearly up to summer’s eight percent. Even if the soil contained five to 10 percent organic matter, it would not supply sufficient nutrients to grow early spring crops such as cabbage, broccoli, cauliflower, celery and lettuce.
Traditional agriculture uses starter fertilizers with early spring transplants. Starter fertilizers are made of water-soluble minerals that are instantly available to the roots of plants, regardless of soil temperature. Applying these fertilizers near the roots of new transplants helps establish them quickly in the soil and resume normal growth.
Compost tea can be used as starter fertilizer. Brew the compost tea at room temperature three or four days prior to transplanting. Partially fill a five-gallon pail up to half capacity with mature compost. To assure maturity, I strongly recommend using commercial compost. Top with water and stir vigorously. Stir the compost three or four times daily to provide adequate aeration for nutrient release from the compost. Or you can aerate the compost using an aquarium air filer as a substitute.
When you transplant three or four days later, irrigate each plant with one to two cups of compost tea.
A second batch of tea can be made using the same compost by filling the pail again with water and repeating the process. The second batch will not be as concentrated as the first unless you allow a week or more for it to release its nutrients into the water.