Kenyan farmer George Muturi says the stinky wooden shack teeming with redworms has helped rescue his land from the soil degradation caused by chemical fertilizers. Agriculture is vital to east Africa’s economy, but a 2025 soil report by the Heinrich Boll Foundation, a German think tank, found that more than 40 per cent of the region’s soils were degraded -- in part by overuse of chemical fertilizers -- costing more than US$65 billion a year in lost productivity. Fertilizer prices have also increased this year due to the war in the Middle East, driving a search for alternatives. In Kenya, 32 per cent of cropland was classified as strongly acidic in the soil report. Changing climatic conditions and overly intensive farming practices are among the causes, but Muturi says moving away from chemical fertilizers has boosted his harvests at his farm in Lari, about 50 kilometres (30 miles) from the capital, Nairobi. He switched to “vermicompost” -- using redworms that turn food and crop waste into a natural, nutrient-rich form of fertilizer. “Vermicomposting was a breakthrough for us... our soil is much better in a way that we can be able to plant and sustain the crop even during dry season,” the 31-year-old farmer told AFP during a visit to his farm. About 70 beds, each filled with at least 5,000 redworms, hold layers of food and crop waste mixed with cow dung that the worms break down over six weeks, to create vermicompost. Multiple studies have shown that vermicompost can improve soil structure, organic matter and water retention. Muturi acknowledges that it is some way off being used on an industrial scale, since very large quantities are needed to match the effects of synthetic fertilizers. But he says he has seen positive results on his vegetables and has started selling the compost to other farmers around the country. According to agroecologist Harun Warui, chemical fertilizers address only one aspect of soil nutrition, while organic compost supports the soil’s broader biology, with benefits becoming apparent over time. “Vermicompost is providing a solution of farmers’ dependency on synthetic input. It’s saving our soils in terms of improving the health,” Warui told AFP. While adoption will take time, he said, “farmers are going to realize that year in, year out dependence on (chemical) fertilizer is not the solution.” Circular agriculture About 200 kilometres away in Nakuru County, Robert Mwangi has taken a similar approach with the larvae of black soldier flies. He collects waste from the city’s main market and feeds it to the larvae, which break it down into frass, an organic fertilizer. The mature larvae are dried and used as animal feed. In a nylon structure, a pungent smell hangs over drums of shredded food waste, which are emptied into plastic boxes where the larvae feed for about two weeks before the frass is harvested. “With conventional fertilizers, the more you use it, the more the productivity of the soil goes down, because (it) creates an acidic environment which is not good for the microbes that are responsible for maintaining and improving the soil fertility,” Mwangi said. “The organic fertilizer is a very good soil amendment so farmers are able to experience increased productivity over time and improved soil fertility which reduces their cost of production,” he said, adding that it also helps deal with food waste. As global and domestic demand for organic food grows, Kenyan farmers are seeking alternatives to chemical fertilizers. Muturi processes about 40 tonnes of food waste per month, selling the resulting compost to farmers across the country while Mwangi says: “demand has overwhelmed what we can produce.”
