Can You Over Fertilize With Compost Tea?

Types

• The traditional farm method of making compost tea is to put finished compost or aged manure in a burlap sack and suspend it in a barrel of water for several days. The water is stirred or agitated occasionally to release more of the compost into the water and to incorporate oxygen. The water turns the color of tea. It is used in a hand-held or backpack sprayer. The remaining compost or manure is added back onto the compost pile. Home gardeners with limited space use the same concept with smaller buckets of water and several handfuls of compost stirred in directly.

Content

• Compost tea inoculates the soil with billions of tiny organisms that assist in the nutrient cycling between plans and soil. Worm casing –vermicompost—is often added to increase the nutrient content of the finished tea. Compost tea has a very large, diverse community of organisms, depending on the quality of the compost it is made from. The bacteria, fungi, insects, worm by-products and humic acids in compost tea support healthy growth of plant life and has a positive, cumulative effect on soil nutrient levels(ref.1). Commercial compost tea catalysts contain kelp, humic acids, rock powders and botanical ingredients that support optimal microbial growth. Comfrey leaves soaked in water is another traditional farm source of compost tea. Comfrey is high in nitrogen and potassium and its leaves contain silica, calcium iron magnesium and other nutrients(ref.2).

Overuse

• Research studies have identified the overuse of compost tea as a potential problem in water runoff pollution(ref.3). The studies identified compost leachate –drippings direct from the compost pile—as a potential source of pollution problems because of the concentration of nitrogen, phosphorus and other nutrients. The over-application of either natural or synthetic chemicals is potentially harmful to ground and water ecosystems(ref.3). Homemade compost tea is not as nutrient-intensive as compost leachate but the same cautions apply.

Correct Rate of Use

• Compost tea is not a fertilizer and should not be used with the same application rates as compost or other types of fertilizer. Use the brewed tea to introduce additional microbial populations directly on plant foliage or topsoil. Spray foliage or drench the soil once or twice a month during the growing season(ref.1). Use a one to one strength dilution for houseplants and a one to three strength tea to water solution to cover larger outdoor areas.