A farming experiment in western Kenya has produced an interesting result: combining crop diversification with fertilizer made from insect waste can increase farm productivity, improve carbon storage and raise economic returns.

The research, published in npj Sustainable Agriculture on September 2, tested different combinations of maize, cowpea, companion crops and black soldier fly frass, an organic fertilizer made from the waste left behind when black soldier fly larvae process organic material.

The study matters because many smallholder farmers face several problems at the same time. They need higher yields, healthier soils, better pest management and more reliable income, while also dealing with climate pressure and the rising cost of agricultural inputs.

Instead of trying to solve each problem separately, the researchers tested whether several relatively simple practices could work together.

What Is Black Soldier Fly Frass?

Black soldier fly larvae can consume large amounts of organic material. After the insects process that material, they leave behind a nutrient-rich residue known as frass.

Researchers have been studying frass as an alternative organic soil amendment because it can turn organic waste into an agricultural input rather than allowing that material to become a disposal problem.

In this experiment, researchers combined the frass with a farming method called push-pull agriculture.

How Push-Pull Farming Works

Push-pull farming uses different plants around the main crop to influence pests and improve the farm ecosystem.

In the systems tested in Kenya, maize was grown alongside or around plants such as Desmodium and Brachiaria. These plants can help manage insect pests while also producing useful forage for livestock.

The researchers also tested a more diversified version called vegetable-integrated push-pull, or VIPP, which incorporated cowpea into the system.

This means one field can perform several jobs at once.

It can produce food for people, provide forage for animals, support pest management and contribute organic material to the soil.

What Did the Researchers Find?

The team tested 12 different cropping systems across three locations in western Kenya over two years, covering the 2024 and 2025 growing seasons.

The results were striking.

Diversified systems produced substantially more total crop output than simple monocropping systems. When researchers added black soldier fly frass, the benefits generally increased further.

In the strongest maize based system, vegetable-integrated push-pull combined with cowpea and frass produced an 8.5-fold increase in total crop yield compared with untreated maize monocropping.

The researchers also found that diversified systems combined with frass produced more biomass and stored more carbon. Maize grain yields increased by more than two times in several diversified systems.

The benefits were not limited to crops.

The most productive diversified systems also generated higher protein yields, with cowpea making an important contribution to food protein and Desmodium providing valuable forage for livestock.

The Economic Side Is Just as Important

Sustainable agriculture only becomes practical at scale when farmers can make a living from it.

The study found annual economic benefits of roughly $6,864 to $7,681 in diversified systems. Adding black soldier fly frass increased the reported benefits further, reaching approximately $7,528 to $8,340 in the strongest systems.

That combination is particularly interesting for smallholder agriculture.

A farmer does not necessarily need to choose between productivity and environmental benefits. A well-designed farming system can potentially improve both.

Turning Waste Into Something Useful

There is another idea hiding inside this research.

Organic waste can become an input for insect production. The insects can then produce useful products, while their remaining material can return to agriculture as fertilizer.

That creates a small circular system.

Organic waste → insect production → frass fertilizer → healthier crops → more food and biomass

It does not eliminate every environmental problem associated with farming, but it demonstrates how agricultural systems can reuse materials instead of treating them as waste.

There Is Still a Long Way to Go

The researchers are careful about what their results mean.

This was a two-year, multilocation field experiment, not proof that the same results will automatically appear on every farm.

The researchers say longer studies are needed to understand the durability of the productivity, carbon and resilience benefits. They also recommend testing the systems on farm sizes that more closely represent real smallholder conditions before wider scaling.

That distinction matters.

The study provides strong evidence that the combination is promising. It does not mean every farmer should immediately replace existing practices with this system.

A Different Way to Think About Sustainable Farming

One of the most useful lessons from the research is that sustainable agriculture does not always require a completely new technology.

Sometimes the opportunity comes from combining several existing ideas more intelligently.

Crop diversification can make better use of land. Push-pull farming can help manage pests. Cowpea can add food and protein. Companion plants can provide livestock feed. Insect frass can return nutrients to the soil. Together, these elements can create a more productive farming system than relying on a single crop.

That is what makes this research worth watching.

The future of sustainable agriculture may not come from one miracle product. It may come from designing farms where waste becomes an input, different crops support one another and productivity works alongside environmental protection.