Tephrosia, a herb more commonly referred to as ‘fish bean’, delivers a double blessing of repelling moles that clear out sweet potato farmers in Western Kenya and increasing crop yields in low fertility soils by almost the same amount as when using chemical fertilisers.
Mole rats are mainly found in East Africa and Central Africa with Tanzanian researchers finding that they cause damage to 79 per cent of bananas growing in highlands and 70 of maize in lowland areas. They also cost farmers hours controlling them and limited the time they had working on their farms. Tephrosia, a wild-growing shrub, which earns its name ‘fish bean’ or ‘fish-poison bean’ because it is used to poison fish making them easy to catch has been used by Maasai pastoralists to kill livestock ticks with researchers arguing, “There is not much of a difference between triatix dip– a store-bought acaricide that is most commonly used to fight ticks– and tephrosia in their effectiveness.” Tephrosia is not just a great pesticide, when grown in coffee fields, the nitrogen-fixing shrub increased yields by 23–36 per cent over two years making it nearly as effective as NPK fertilizer in delivering nutrients to the soil. The legume is also recommended by KALRO as a mole repellant.
Before being introduced to what she now describes as her miracle plant, Ruth Wanga had suffered repeated attacks by moles on her eighth-acre sweet potato plot throughout 2021. “I’d tried everything, pouring pig and cow urine into their holes, cleaning my fields, trapping them with baits, hiring trappers to get rid of them but nothing worked. They would nibble on my still-growing sweet potatoes and leave me with nothing after each growing season,” the Kakamega-based mixed farmer said.
Related News: Farmers use poisonous weeds & tree extracts to eradicate moles
Related News: Farmer applies pigs’ manure in celery farming to keep off moles
Moles can be extremely difficult to get rid of because they dig up to 4.6 meters of tunnels an hour deep into the soil where they are difficult to reach.
Two years ago she learned of the mole-repelling powers of Tephrosia while attending the Western Kenya Agricultural Show held at Kakamega showground. ”I’d seen the plant growing on many farms in Kakamega but thought it was just a weed,” she noted.
After getting seeds from neighbours she grew them as a hedge on her sweet potato plot and in the second year she said that the moles which were her biggest farming nemesis were as good as vanquished.
According to the agriculture research organisation International Center for Tropical Agriculture (CIAT), Tephrosia can be planted inside farms three meters apart or one meter apart along the farm’s borders to prevent moles and root rats from entering the farm. “Within one year, your farm will be free of moles and root rats and the Tephrosia which are planted inside the field can be removed leaving only those along the farm’s boundary,”– CIAT-Africa.
In the study done on two coffee fields in Gisagara in Rwanda and Kisumu in Kenya, Tephrosia grown within the coffee fields produced up to 1.9 tons a hectare of living organisms and decomposed material (biomass) and mulch which added 42–57 kg of nitrogen three kilograms of 13–16 kilograms of potassium and three kilograms of phosphorus per hectare. This increased yields by 400–500 kg per hectare.
Tephrosia grown on the edges of the coffee field of coffee fields produced 600-700 kilograms of biomass per hectare and much lower levels of nutrients as the plant struggled with high soil acidity and a lack of nutrients.
Related News: Sugar cane rats attacking neighbouring farms in crop wipeouts
Related News: Top snake center launches free helpline to treat snakebite victims across Kenya
In the second year, the Tephrosia was grown with NPK fertiliser and it produced 2.5 and 3.8 tons of biomass per hectare which gave the soil 103–150kg of nitrogen, 24–38kg of potassium, and five to 9kg of phosphorus per hectare. These added nutrients increased coffee yields by up to 700kg per hectare.
Tephrosia, which acts as a soil cover crop, also reduced labor demands for weeding by 30 fewer workdays for every hectare of coffee.