Insect Frass, a sustainable plant nutrient product

Black soldier fly larvae frass – their solid digestate – is the only substance to contain a form of chitin that is  plant available. This chitin produces antimicrobial compounds in stress conditions that act as a protective barrier. The chitin blocks pathogenic organisms and their access to mineral nutrients while blocking the release of pathogenic mycotoxins.

Insect frass

The role of biology in nutrient uptake, ecosystem biodiversity and resilience as well as plant immune response to pests and disease is becoming more studied and understood. Cultivators are looking to inputs that will support this living soil system known as the soil food web that maintains soil structure, mineralises organic nutrients into plant available form and outcompetes pests, pathogens and disease. Insect frass is an incredible organic fertiliser that not only supports and stimulates the soil food web while providing plant available mineral nutrients but also contains itself, huge levels of biology in all beneficial functional groups.

Unlike chemical N fertilisers that burn carbon into the atmosphere and pollute waterways, Insect Frass stores carbon and nitrogen directly in the soil. Frass prevents atmospheric loss of nitrogen via its bacteria. Nitrogen fixing bacteria in frass such as Bacillus and Pseudomonas fix atmospheric nitrogen while other nitrifying bacteria convert the N in soil to plant available form to optimise photosynthesis. Frass contains the biology needed to help optimise the nitrogen cycle and keep the nitrogen in the soil.

Insect frass contains very low levels of heavy metals, sodium and other chemicals which can accumulate in plant tissue and the environment as well as causing undesirable soil conditions. Frass is an excellent input to use in place of chemical or high sodium organic fertilisers not only due to the presence of all major nutrients vital for plant growth but its incredible defense properties for plants.

Rates for deficient or low fertility soils can be higher, up to 500kg per hectare (500g per square metre). Below are some best practice application rates for various growing systems and styles.

Garden beds: Spread 100 to 250g per m2 and gently incorporate into the soil before planting and again after seedlings are established. Apply mulch on top to maintain moisture.

Top dress: Sprinkle a handful around the rootzone. Water in to activate.

Fertigation/root drench: Add 2 Tbsp 9L water.

Potting soil: Apply and mix at 1.5% to 2% or 15-20mL per litre of potting media.

Hydroponics: Top dress directly to any grow media (rockwool, coco, hydroton) or add 1/2 cup per 100L of water (strain for drip systems). For best results, brew insect frass tea for 24 hours before use. Add directly to the reservoir for flood to drain systems.

To conclude, frass is a highly effective and affordable, long lasting fertiliser that will improve soil biological diversity, soil fertility, increase plant yields and defend against plant pathogens while minimising environmental impact.