Research shows the byproduct of black soldier fly production supports crop and soil health
Research shows a key to improving crop and soil health lies in frass, a byproduct of black soldier fly production.
“Frass can be defined as a mixture of insect manure, leftover feed from insect rearing, and also the skins that they release while they’re growing,” Helen Amorim, a Research Scientist at the University of Arkansas, told Farms.com.
These insects are primarily grown for poultry and fish feed. Use in swine and pet food, and as ingredients in energy bars for human consumption, is also being researched.
And the black soldier fly produces more frass than it does protein.
“For every kilogram of insect protein they produce, you can get four times more frass,” Amorim said. “That residue is rich in plant important nutrients like nitrogen, phosphorous, potassium, and calcium. And it doesn’t have a lot of pathogens or heavy metals, so it’s a clean and very good amendment to be used in agriculture.”
Ty-Pro, a joint venture between Tyson Foods Inc. and Protix, an insect ingredient manufacturer, supported the study.
This experiment was initiated by Dr. Amanda Ashworth of USDA’s Agricultural Research Service (ARS), along with Dr. Amorim who studied the use of frass as a soil amendment in soybeans and switchgrass at the ARS’s Dale Bumpers Small Farms Research Center in Booneville.
The field trials conducted between April and October 2024 included plots with low and high rates of frass, a low rate of poultry litter, and untreated controls. The soybean research also included irrigated and non-irrigated land.
The soybeans and switchgrass each received four treatments.
Throughout the season Amorim and her team measured multiple data points.
Helen Amorim
These included changes in soil nutrients before and after harvest, microbial activity, and plant growth. And they measured leaf damage in soybeans with an app called LeafByte.
After harvest, they looked at yield, nutrient removal, and biomass.
The results showed the frass improved soybean and switchgrass production as well as the poultry litter but with some added benefits.
“When applying frass, we found 50 percent less leaf damage in those plots compared to the ones receiving poultry litter,” Amorim said. “That shows the frass may have beneficial microbes and may be able to enhance plant resistance to insect leaf damage.”
For comparison, the published study says irrigated soybeans treated with poultry litter had the highest rates of leaf damage.
The data also showed plants receiving lower frass rates were more efficient in removing the nutrients from the soil to produce biomass or grains.
“We saw more phosphorous in soybean grains, and more potassium in switchgrass when applying frass,” Amorim said. “Forages need potassium for drought tolerance and water dynamics, so it’s a very necessary nutrient.”
Further research into frass will compare the insect byproduct to other commercial fertilizers.
That data will include multiple pieces of information including a cost analysis, Amorim said.
Overall, black soldier flies help support a circular agricultural system.
These insects recycle food waste which is used to produce the frass, and related byproducts.
With the benefits shown in the research, more startups emerging, and farmers looking for ways to improve their crops, insect farming could become a large industry in the next few years, Amorim said.
“There’s indication that in the next five to seven years we’ll have about 5 million tons of frass available,” Amorim said. “We’ll continue our research to show farmers the benefits of frass.”
For context, U.S. farmers used about 20 million tons of fertilizer in 2023, USDA data shows.
Amorim and her team’s work on frass continues this year.
They’re currently studying frass from mealworms and crickets on edamame and sorghum to show how the frass differs between insect species. Studies on using frass on different vegetables are planned.