Maize is one of the most important crops for food security and livelihoods in Tanzania. Yet, while many farmers grow improved varieties, yields are far lower than their potential. Most farmers don't use mineral fertiliser and those that do don't apply enough to make an impact. More farmers use organic fertiliser such as manure but supplies are limited.
Wema Ako, a farmer from Long, a small village in the peaks of the East African Rift Valley Highlands, was brought up to believe mineral fertiliser is bad. He doesn't know where the belief came from but his father, from whom Wema inherited land, refused to use industrial fertiliser.
In fact, the belief is so old that only older generations remember how it started. Gabriel Leonse (59) from Seloto village remembers a visit from an extension worker more than 40 years ago.
Two years ago Isaac, along with partners from SARI, started working with farmers in Babati to test the suitability of different fertilisers on maize crops. It was the first time anyone had advised farmers about fertiliser since 1974.
The aim of the Africa RISING project is to discover optimal - and affordable - organic and mineral fertiliser combinations coupled with the most suitable maize varieties and most appropriate agronomic practices.
Rita Matias was nominated by her community to take part in the research.
"I've always used manure to fertilise my soil but I had to rotate it because there was never enough to go round," said Rita. "I never used mineral fertiliser because I didn't have any knowledge about it."
Since she has been using mineral fertiliser, Rita has noticed a big difference in her yields and has increased her income by 50 per cent or more, depending on the market.
"It is more work to use fertiliser," said Rita, referring to weeding, correct spacing, pest and disease control and other agronomic practices needed to get the best out of her investment. "But it's worth it."
Wema is also taking part in the trials. At harvest time it's easy to see which crop was fertilised and which wasn't. The cobs from fertilised plants are double the size of those that weren't.
The most promising combination of organic and mineral fertiliser is producing on-farm yields of up to six tons of maize grain per hectare. The regional average is less than one ton per hectare.
Education is only the first step in enabling farmers to make informed decisions about fertiliser.
Isaac is working with Corneleus Yangole, a researcher from SARI. "Once we have assessed the performance of each option we will carry out an economic analysis so that our final recommendations are based on the best and most financially affordable options," said Corneleus. "We can make all the recommendations we want, but if they are beyond a farmers financial means they are useless."
Stephanie Malyon / CIAT