Introduction to Compost Tea

Compost tea is compost extract brewed under actively-aerated aerobic conditions. Brewing compost tea extracts beneficial microorganisms from the compost material and encourages the growth of these microorganism populations during the brewing process. As part of the tea brewing process, a variety of additives are added to encourage the growth of microorganisms. Depending on brewing conditions, ingredients used and a variety of other factors, the brewing process can potential increase the original microbial population extracted from the compost by over 1000 fold. This compost tea is then applied as a soil drench or sprayed on plant surfaces (aka foliar application) to inoculate root zones and plant surfaces with beneficial microorganisms.

Benefits of Compost Tea

Ideally, brewed compost tea contains both an abundance and diversity of beneficial microorganisms that is only found in high-quality, properly processed compost. When applied to the soil, compost tea can contribute to improving the soil biological diversity, thereby enhancing the soil food web. Presence of an active soil food web leads to positive changes in soil conditions that makes possible the functions and benefits of healthy soil. 


When used as a foliar spray, compost tea can provide an inoculum of beneficial microorganisms to plant surfaces that can function to outcompete pathogenic organisms for resources (food, space), and thus suppress diseases by reducing opportunities for disease-causing organisms.

Compost tea can be applied in home gardens, commercial agricultural production systems, landscapes, and golf courses. Brewed compost tea is economical to make and easy to apply.  As little as 15 to 20 gallons of brewed tea can be applied to one acre. Frequency of application will depend on environmental and plant conditions; however compost teas are often applied once or twice per month. Applications of compost teas have shown to improve soil structure, improve nutrient cycling, reduce water-use, reduce long-term fertilizer applications, build and sustain fertile soils, increase crop yield, improve plant health, promote plant growth, reduce or eliminate the occurrence of diseases, increase root development, and yield better tasting fruits and vegetables. 

Depending on the compost material used to brew tea, the brewed tea can contain the following components: soluble plant nutrients in plant available form, humic substances that are present in compost, microorganisms (bacteria, fungi, protozoa, nematodes), plant growth promoting bacteria, and metabolites that may be responsible for pathogen antagonism and microbial metabolites.   

Brewing and Applications of Compost Tea

Compost tea should only be brewed from high-quality compost that has gone through a proper and complete thermophilic decomposition process under aerobic conditions, and allowed to cure.  The aerobic thermophilic decomposition and curing process ensures the compost is pathogen-free, safe, and provides an abundance of microorganisms in the finished compost material. High-quality compost is characterized by a dark brown color (not black) when moist, soil-like in texture and has an earthy fragrance.  Immature or partially composted products should never be used to brew compost tea.

How can you tell if the "compost" is appropriate for tea brewing?  If the "compost" material retains some form of the raw ingredients, has an odor not characterized as earthy, is black in color, and/or contains foreign objects (trash, plastic), then the "compost" product is immature and/or has not been composted properly, and is not to be used to make compost tea.  

Compost tea brewing is a simple process when you have the right equipment.  The appropriate equipment and materials are required to ensure a high quality tea is brewed. Brewing equipment typically includes a container to hold the tea, a mesh bag to contain the compost during the brewing cycle, an aerator to provide oxygen in the tea, and a lid to prevent the tea from splashing out of the container. The aerator must be sized appropriately to ensure enough oxygen (air) is pumped into the tea to maintain sufficient aerobic conditions (measured by dissolved oxygen levels) throughout the brewing process. An important characteristic of the brewing system is that all parts are easy to clean; dirty brewers will negatively affect tea quality. 

Making compost tea involves a few simple steps, summarized below:

1. High-quality compost is placed in a mesh bag, which is suspended in the brewer containing water.

2. An aerator, connected to the brewer by way of plumbing parts, is turned on to start the brewing process. The aerator remains on during the entire brewing process.

3. Food sources are added to the tea brewing process to encourage microbial activity.

4. After the brewing cycle, the compost tea is applied as a soil drench and/or foliar spray within 6 to 8 hours. Applications are quick and easy when using a hose end sprayer (or back-pack sprayer or spray equipment for larger or commercial applications).

The brewing cycle can vary from 18 hours to 48 hours, depending on the ambient temperature.  In warmer temperatures, generally less time is required to brew the tea. Whereas in cooler temperatures more time will be required. Proper brewing methods will also utilize organic microbial food sources such as kelp, hydrolyzed fish, molasses, and other ingredients to promote growth of beneficial microbial populations. 

Compost tea is ready for use straight out of the tea brewer but can also be diluted with water (up to 1 part tea with 10 parts water) to spread out its application across a larger area. For example, just five gallons of compost tea can be used to cover the landscaping around a typical home. Is it possible to use too much compost tea? No. Frequency of compost tea applications will vary, and is often dependent on environmental conditions and how much time you have. Home-use and small-scale applicators have found benefits from applying compost tea with just few applications per year. Golf courses and commercial agricultural operators find benefits from bi-weekly applications as part of a nutrient maintenance program. 

Applications of GrowBetter™ pelletized organic fertilizers help build long-term soil quality, increases soil fertility and enhance soil biodiversity. In pellet form, GrowBetter™ All-Purpose Organic Fertilizer & Soil Conditioner can be applied in a number of way.  The pellets can be incorporated in the soil to provide long-term feeding of plant nutrients while conditioning the soil. Additionally, GrowBetter™ pellets can also be safely used as the primary compost ingredient in brewing compost tea.  As little as one-third of a pound can be used to brew 5 gallons of compost tea that can be applied up to 1/3 of an acre or the entire landscaping (lawn and gardens) for a typical home. 

GrowBetter™ Organic Fish Plus Kelp Fertilizer Concentrate is a high-quality, cold-processed organic liquid fertilizer approved for use in organic production. Cold-processing retains the fish oils, proteins and carbohydrates in the liquid fertilizer and serve as organic food sources to encourage soil microbial activity when applied as a soil drench. Weekly small-dose applications will also provide quick feeding of plant nutrients in the root zone.  When brewing compost tea, one fluid ounce of GrowBetter™ Fish Plus Kelp Fertilizer Concentrate can be added to a 5-gallon brew to encourage beneficial microbial growth. 

GrowBetter™ Organic Sea Kelp Concentrate is a high-quality, cold-processed sea kelp extract approved for use in certified-organic production. GrowBetter™ Organic Sea Kelp Concentrate is derived from Norwegian kelp (Ascophylium nodosum) extract, known to be one of the most effective sources of kelp extract for plant applications. Weekly small-dose applications promotes budding, flowering and fruiting.  GrowBetter™ Organic Sea Kelp Concentrate is also formulated for use as an ingredient in actively-aerate compost tea brewing; add one fluid ounce to a 5-gallon brew as a food source to encourage beneficial microbial growth.  

​Applications of compost teas brewed with GrowBetter™ products is not only cost effective (less than $0.50 per gallon brewed), but also proven to increase crop yield, improve plant and crop quality, improve soil quality, reduce the occurrence of diseases through competition of a diverse soil microbial population, improve soil water-holding capacity, and curtail long-term applications of inputs (both fertilizers and pesticides).  

Whether you are a new or seasoned expert compost tea brewer, you can purchase compost tea brewing equipment and ingredients at our website. 

What is compost tea?  It's benefits?  How is it made? 


Brewing Compost Tea with GrowBetter™ Products

​GrowBetter™ products are formulated to enhance the soil food web by promoting soil microorganisms and soil fertility, resulting in productive and beautiful gardens, turf systems, landscapes, and commercial crop systems.  

GrowBetter™ All-Purpose Organic Fertilizer & Soil Conditioner is made from pure chicken manure that is fully-composted and cured. Approved (by the Organic Materials Review Institute and California Department of Food & Agriculture) for use in certified organic production, it is safe, low-odor (has an earthy fragrance, not a strong chicken manure smell), and does not contain fillers. Chicken manure is an excellent fertilizer used by many generations of farmers and home gardeners because it is rich in nutrients and organic matter. Not only does chicken manure contain essential primary plant nutrients such as nitrogen, phosphorus, and potassium, but also secondary plant nutrients such as calcium, iron, magnesium, and other trace elements. 

Fortify Plants, Enrich the Soil.

GrowBetter™ compost tea brewing ingredients and equipment are available at our online store.