In the wind-swept plains of Kishapu, in Tanzania's northern Shinyanga region, Himelda Tumbo has for a few years struggled to grow maize on her farm.
"I have suffered huge losses due to drought. The seasonal rains are not enough and the crops are drying up," she complained. “Maize once grew easily,” she said, “but now I can hardly get enough to feed my family".
The 53-year-old farmer's other traditional crops, such as beans, groundnuts and yams, are also struggling, she said - one reason she has now turned to planting drought-resistant orange sweet potato.
"Unlike maize, orange potato can brave most conditions and is also resistant to rust diseases," she said.
Tumbo is among hundreds of farmers in the district who have switched to growing sweet potato as a strategy to cope with drought and improve food security. In Tanzania's lake regions, thousands are now growing the potatoes, with support from local researchers.
The potato has already been in widespread use in Uganda, where 55 000 households now grow it and 237 000 are expected to grow it by 2018, according to a US State Department initiative to cut global hunger and improve food security.
Kenya's Nyanza region, similarly is switching to orange sweet potato, after farmers in 2012 lost more than 80 percent of their maize crop to a lethal maize disease.
A TOUGH ALTERNATIVE
Researchers say orange sweet potato is more resilient than other crops to extreme weather problems such as drought and flooding caused by heavy rains, and it can stay in the ground for a long time after maturity, making the time of harvest less critical.
The crop was first introduced in Tanzania in 2002 by the International Potato Centre as an alternative staple crop in the wake of increasingly severe drought that had ravaged maize harvests in many parts of the country.
It is included in drought-coping strategies supported by the Mwanza-based Ukirigulu Agriculture Research Institute (UARI), which has worked on producing and distributing quality vines.
Everina Lukonge, a senior researcher with the institute said small-scale farmers in the region are being trained to produce potato seed to use and sell.
"The trained vine growers produce the seeds on their fields in the dry season and sell them during the rainy season," she said.
Each bundle of 300 potato vines, enough to sow about a third of an acre, is sold for 5 000 Tanzanian shillings ($2.40) or more, said Tumbo, one of the growers.
"When I planted the vines for the first time, they grew very well and I had a lot of potatoes which helped me to feed my children," she said. “Now I get sufficient income from selling the vine and my life is better."
Orange sweet potatoes are particularly valuable in improving nutrition and food security, researchers say, because they are very productive, contain vitamins missing from other foods and are tolerant to extreme weather. With some varieties, the leaves can also be eaten as a green vegetable.
Despite their growing popularity, analysts say efforts to expand the use of orange sweet potatoes in East Africa face a number of challenges, including a shortage of high yielding vines, a poor delivery system for pest-free vines and lack of political support.
"Policymakers have mainly ignored this important crop because it is widely perceived as a poor person's crop that people turn to when maize fails" said Godfrey Pyumpa, a local government agriculture engineer based in Morogoro.
But Maulid Ali, a farmer in Itima village in Kishapu, said growing orange sweet potatoes has made a difference for his family - and the switch in staple crops wasn't difficult to accept.
"Since I started growing and eating orange sweet potatoes, my family's health has improved remarkably. Actually, my children like potatoes more than ugali (maize meal)," he said.