Kenya: Farmers grow soya beans to manage striga

| January 8, 2018

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It’s midday and Francis Babu is using a hoe to weed his maize and soya beans. The movements of his hands and hoe match the beat and lyrics of his favourite song, which he hums as he works.

Occasionally, he sets the hoe aside and squats to uproot weeds with his hands. All the while, he sings in the Luo language, “Kayongo ee kayongo; kayongo okadwar neni but puodha … kayongo in jajuok marich [Striga, I don’t want to see you near my farm … striga, you are a bad witch].”

Kayongo is a Luo word for striga, or witchweed, as it’s commonly known. Though the plant has beautiful pink flowers when mature, farmers say it’s a dangerous weed. They say it’s dangerous because it can stifle the growth of other plants, including maize and cowpea. The weed is common in many parts of Kenya and has long been a worry for Mr. Babu and many other farmers, especially in areas where farmers grow cereal crops like maize, finger millet, rice, and sorghum.

Mr. Babu is from Nyabisagwa village in Migori county, western Kenya, where he operates a one-and-a-half acre farm. For more than ten years, he hasn’t had to worry about striga because he practices intercropping and crop rotation. He rotates soya beans with cereal crops.

He has found intercropping and crop rotation more successful than other methods of controlling striga. At first, Mr. Babu tried using animal manure to suppress striga, but he was not very successful. He explains, “I did not have enough manure to apply on the entire farm because I had only two animals … [and they] could not provide enough manure.”

He later discovered that soya beans also manage striga.

Mr. Babu says farmers in his area who grow soya beans to manage striga are enjoying bumper harvests of maize, sorghum, and finger millet. 

Charles Omare Ochako is a farmer in the nearby village of Banana. Mr. Babu taught him to grow soya beans to manage striga. Mr. Ochako says, “I had almost given up farming because of striga. But now, I am a happy farmer.”

He says that, after trying intercropping and rotating soya beans with maize, he has better yields. While his two-acre farm used to yield just seven sacks of maize per season, since managing striga with soya beans, he can now harvest 18 or more sacks. Also, for the eighth year in a row, he has not seen striga in his three-acre field.

Mr. Babu says that farmers should intercrop soya beans with cereals in the second season after planting a cereal crop. He adds that farmers must be careful not to plant maize in the same field where they planted a cereal crop the previous season.

He adds: “A farmer can decide to plant two lines of soya between two lines of maize. [But] there must be permanent marks to guide the farmer on where the lines of maize were in the previous season to avoid planting in the same area.”

It’s important to plant soya beans in every part of the field during the first two seasons of intercropping in order to best manage striga. In the second season of intercropping, farmers should plant soya beans exactly where they planted maize the season before. In this way, maize—which is susceptible to striga—is planted in spots where striga populations have already been reduced.

Mr. Babu explains that marking the lines helps ensure that the soya beans effectively manage striga in every part of the field.

Eric Moturi is a plant scientist in the region. Mr. Moturi says striga seeds can live in the soil for up to 20 years. He explains, “The seeds can stay dormant for so many years until they find a host plant which can facilitate their germination.”

Striga is naturally parasitic, living off the nutrients and water from the roots of the host crop, which becomes withered or stunted.

Mr. Moturi explains that soya beans render striga less dangerous to the main crop. Soya has an allelopathic affect on striga, meaning that its roots produce a biochemical that induces striga to germinate, but then makes it unable to find a host crop on which to attach itself, which kills the striga plant.

With soya beans, Mr. Babu is sure that striga will not appear again on his farm. He says, “You can now find many farmers within our locality with healthy cereal crops, but mine are the best.”