Thinking about insect farming? Insect farming is expected to produce millions of tons of insects in coming years. Researchers recently studied whether insect frass could benefit crop production. Frass is the byproduct of insect farming and includes manure, shed insect skins, and leftover feed material.
The study from the Arkansas Agricultural Experiment Station focused on black soldier fly frass used as a soil amendment in soybean and switchgrass fields. Researchers compared frass with traditional poultry litter and untreated control plots. Results showed that frass performed as well as poultry litter, even when applied at lower rates.
“For every 1 pound of insect meal, you get up to four times more frass, so the question came up whether it could be used as a soil amendment,” said Helen Amorim, lead author of the study and the study’s lead author with the Arkansas Agricultural Experiment Station.
One important finding was that soybean plants grown with frass had significantly less insect damage. Leaf damage from pests was reduced by 38 to 45 percent compared to control plots and soybeans grown with poultry litter. This suggests frass may help improve natural plant resistance to insect feeding.
The researchers also found that frass improved nutrient efficiency. Low application rates of frass delivered two to four times greater nutrient efficiency than higher frass rates or poultry litter, while still supporting similar crop yields. This means farmers could achieve good results using fewer nutrient inputs.
Frass acted mainly as a soil amendment rather than a fertilizer. Soil amendments improve soil structure, organic matter, and microbial activity, which supports healthier root growth and long-term soil health. Researchers believe beneficial microbes present in frass may play a role in both plant growth and pest resistance.
“Typically, these organic sources like insect frass have a much lower nutrient concentration to be considered a fertilizer, but more often they have greater organic material, like carbon, so it also has other benefits associated with increasing organic matter, or the overall soil health,” said Gerson Drescher, an assistant professor of soil fertility in the department of crop, soil and environmental sciences and a co-author of the study.
The frass used in the study was heat-treated to remove pathogens and came from insects raised on agricultural food waste. This process supports sustainability by recycling waste, reducing landfill use, and creating valuable agricultural inputs.
While frass is not expected to replace synthetic fertilizers, it may be useful for small-scale farmers, organic systems, or as a growth-promoting amendment in larger row crop operations. Researchers say more studies are needed to better understand frass microbiology and nutrient release.
Overall, the study highlights insect frass as a promising tool to improve soil health, support sustainable protein production, and reduce pesticide use in modern agriculture.