Frass pre-treatment and application method impact spring wheat vegetative growth and nutrient concentration

Abstract The house cricket ( Acheta domesticus ) is a widely farmed edible insect species, and its by-product – frass – has potential as a sustainable soil amendment. However, the efficacy of frass may depend on how it is pre-treated and applied. This study evaluated the effects of cricket frass on the vegetative growth and nutrient concentration of spring wheat ( Triticum aestivum ) under different frass pre-treatments and application methods. Wheat was pot-grown in a greenhouse for eight weeks — from seed germination to flowering — with one control (no frass) and six experimental treatments, combining two pre-treatments (non-heated and heat-treated frass) and three frass application methods (surface application, mixed into the substrate, and 2-week delayed application). Germination, plant height, shoot biomass, leaf chlorophyll content, and shoot nutrient concentration were measured. Frass pre-treatment and application method significantly influenced wheat growth and nutrient concentration. Germination reached 100% with heat-treated frass mixed into the substrate and delayed application of no-heat frass but dropped to 60% with surface-applied heat-treated frass. The tallest plants grew with no-heat frass mixed into the substrate, while surface application, regardless of heat treatment, produced the greatest shoot biomass. Delayed application, regardless of pre-treatment, resulted in the highest leaf chlorophyll content. Surface-applied heat-treated frass increased plant nitrogen and potassium concentrations, whereas no-heat mixed frass enhanced phosphorus levels. These findings demonstrate that cricket frass can improve wheat growth and nutrient concentration, but its effects vary by pre-treatment and application method. Optimising these factors could maximise its potential as a sustainable soil amendment in crop production.