Farmers in Trans- Nzoia and West Pokot can harvest up to 20 tonnes per acre (60,000 tubers) by growing new high yielding varieties from the Kenya Agricultural and Livestock Research Organization.
A 98kg bag of sweet potatoes is currently retailing at Sh3500 in Nairobi according to soko+, an online digital trading platform that connects farmers to markets. In this, a farmer can earn Sh714,285 per acre with the high yielding varieties.
In lower altitude areas like Arror and Ortum, farmers of Marakwet, West Pokot County and KALRO scientists found that KSP20 and Sandak varieties do well when planted as a single crop.
In medium altitude areas like Kitale where sweet potato is intercropped with maize, Sandak variety is recommended. KSP20 also does well as a mono-crop in this region. Kembl0 and KSP20 produce the best vines, especially where farmers look after the crop well by weeding and planting on time at the onset of rains.
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Sweet potato farming in Kenya. Courtesy
For sole cropping, prepare the land immediately after the first rains. For intercropping with maize, prepare the land after harvesting beans. Use a hoe (jembe) to loosen the soil to at least six inches deep and remove all the weeds. Avoid stony soils because they limit tuber expansion. In drier areas, KALRO recommends one to plant when the top six inches of soil is wet.
In high rainfall areas like Kitale you can plant when the top three inches is wet. Cut the vines into one to two feet two pieces and bury two thirds in the wet soil. The leaves should point upwards.
You can plant the vines on the flat ground at two to three feet by one to two feet spacing or on ridges or mounds of soil at two to four feet by one to two feet. The mounds or ridges should be between six to 18 feet high.
Farmyard manure is then applied at the rate of 40 to 200 ‘debes’ per acre or 1/2 bag of DAR. If your major interest is vine production, apply half a bag of di-ammonium phosphate (DAP) per acre
After planting, the first weeding is done three weeks and the weeds are occasionally removed manually by hand.
To control pests such as weevils it is recommended to practice crop rotation and plant only on the land where sweet potatoes have not been grown for the last two years. Earthing the soil after four to six weeks also controls weevils.
KSP20 and Sanda varieties mature after three and half months in low and hot areas such as Arror and Sigor and four months in areas such as Kitale.
The tubers can be harvested at once or you can leave some in the ground for up to four months until you need them. One can locate the large tubers by cracks in the ground. To harvest, loosen the soil around the tuber with a sharp tool like a fork and lift the tuber from the ground. Use a jembe if you want to harvest the whole plot at once.
Besides being cooked and consumed as food, sweet potato vines are a good dairy animal feed supplement because they have high protein content (10 to 15 per cent) and are easily digestible.
In 2017, Kenya produced 1.15m metric tonnes of sweet potatoes with 1.036m metric tonnes consumed as food while rest went to waste according to the 2018 Economic Survey report.