Organic liquid fertilizers deliver highly available, water-soluble nutrients derived exclusively from natural sources. These preparations bypass the slower breakdown of solid organic matter, providing a rapid boost to plant health. They function as quick nutrient supplements and soil conditioners, feeding plants directly through the leaves or indirectly through the root system. Creating these amendments typically involves extracting compounds from plant materials or multiplying beneficial microorganisms from finished compost.
Creating Simple Nutrient Teas (Steeping Method)
Simple nutrient teas are traditionally made using an anaerobic (oxygen-starved) steeping process that draws out macronutrients from plant matter. This method focuses on creating a concentrated, mineral-rich liquid fertilizer rather than cultivating a microbial community. High-nitrogen materials like stinging nettle and mineral accumulators such as comfrey are prime sources for this liquid feed. Comfrey contains high levels of potassium, which supports flowering and fruiting.
To begin, you need a non-reactive container, such as a plastic bucket with a lid, and dechlorinated water. Harvest fresh plant material, like nettle or comfrey, and loosely pack the container halfway to two-thirds full with the chopped greens. The general ratio for a strong concentrate is one part plant matter to three parts water.
Submerge the plant matter completely with water and secure the lid, allowing it to steep for one to three weeks. Since this is an anaerobic process, the mixture will ferment, leading to a potent odor. This smell indicates that the plant tissues have broken down and released their soluble nutrients into the water.
The resulting liquid concentrate is rich in raw N-P-K (Nitrogen, Phosphorus, Potassium) that plants can readily absorb. Once steeping is complete, strain the liquid to remove the remaining solids, which can be added to a compost pile. This nutrient-dense liquid is ready to be diluted for application.
Brewing Aerated Compost Tea (Microbe Extraction)
Aerated compost tea (ACT) prioritizes the extraction and multiplication of beneficial aerobic microorganisms from high-quality compost or worm castings. Unlike the anaerobic steeping method, ACT requires a constant supply of oxygen to maintain an active population of bacteria and fungi. The primary purpose of ACT is to enhance soil structure and plant immunity by introducing a living microbial inoculant.
The equipment includes a five-gallon bucket, a small aquarium air pump, and an air stone or bubbler to ensure high dissolved oxygen levels. Begin by filling the bucket with dechlorinated water; tap water can be left uncovered for 24 hours to allow chlorine to dissipate. Place a small amount of finished, high-quality compost or vermicompost (worm castings) into a fine mesh bag, creating a “tea bag.”
Suspend the mesh bag in the water and begin aeration by submerging the air stone and turning on the pump. A simple food source, such as a tablespoon of unsulfured molasses or sugar, is added to encourage the rapid growth of the microbial population. The ideal brewing time is between 24 and 48 hours, during which the microbes multiply exponentially, resulting in a dark, earthy-smelling liquid.
The constant bubbling keeps the environment aerobic, discouraging the proliferation of undesirable anaerobic bacteria and potential pathogens. After the brewing cycle, the resulting liquid is a microbial suspension that acts as a biostimulant, improving nutrient cycling efficiency in the soil.
Dilution Rates and Application Methods
Proper dilution is necessary when applying homemade liquid fertilizers to prevent phytotoxicity, or “burning,” plant tissues with an overly concentrated mixture. The strong anaerobic nutrient teas derived from comfrey or nettle require significant dilution before use. A common ratio is one part concentrated tea to ten parts water (1:10), though dilution up to 1:20 is used for sensitive plants.
Aerated compost teas, which are primarily microbial extracts, can be applied with minimal or no dilution. These teas are safer to use, as their value is in the living microbes, not the raw nutrient load. Applying the tea directly to the soil or foliage is common practice, though a slight dilution (such as 1:1) can be used if desired.
Application can be done in two primary ways: root drenching or foliar feeding. Root drenching involves applying the liquid fertilizer directly to the soil around the base of the plant, which benefits soil health and allows nutrient uptake through the roots. Foliar feeding involves spraying the diluted liquid directly onto the plant leaves, providing a fast pathway for nutrient absorption.
Foliar applications are effective for quick nutrient deficiencies, as leaves absorb nutrients rapidly through their stomata. Applying foliar sprays during the cooler parts of the day (early morning or late afternoon) prevents rapid evaporation and maximizes absorption. Root drenching is preferred for improving the microbial life and long-term vitality of the soil ecosystem.
Storage and Shelf Life of Liquid Fertilizers
The shelf life of a homemade liquid fertilizer depends on the creation method. Anaerobic nutrient teas, such as those made from steeped nettle or comfrey, are highly concentrated and stable. Because they are preserved by the low-oxygen, high-nutrient environment, they can be stored in an airtight container in a cool, dark location for several months.
In contrast, aerated compost teas have a short shelf life once the constant supply of oxygen is removed. The beneficial aerobic microbes cultivated during the 24- to 48-hour brewing process die off rapidly without aeration. For maximum efficacy, these microbial teas should be applied within four to six hours of turning off the air pump.
Allowing aerated compost tea to sit unused will cause it to quickly turn anaerobic, which can lead to the proliferation of harmful microbes. If the tea develops a putrid smell, it indicates the aerobic organisms have died and the liquid should be discarded. Due to this time sensitivity, it is best to only brew the volume of aerated tea that can be used immediately.