Paul Wolfowitz, president of the World Bank, recently returned from a tour of East Africa to reject the view that a country' s traditional culture is a barrier to economic progress. An innovative horticultural project in northern Tanzania supports his point: sustainable economic health in Africa depends on working with local customs and practices

In the smallholder fields below Mount Kilimanjaro and Mount Meru in Tanzania are tiny plots planted with rows of peas so sturdy they grow upright, barely needing the support of the pink string that is wound carefully about stakes at either end of the rows. As I smile at a group of farmers who turn their gaze skywards towards a jet high above us, they tell me proudly: "Our peas go direct from Kilimanjaro to Heathrow. Daily."

For two days I walked these fields, discovering in Tanzania a project that is simple, traditional, yet so imaginative that it is changing the lives of people here. It brings prosperity and endorses their conventional way of farming. But at the same time it helps women by challenging African patriarchy.

The project is called MIMS and is a system of self-governance for smallholders, now involving more than 1,000 farmers and over 100 hectares of land. Twelve months ago, MIMS - an NGO whose full title is Market Intermediary Management - was set up by Hugo Titley, a one-time commercial tobacco farmer who lost his Zimbabwean land to the Mugabe regime.

"There is a tendency to over-manage in Africa," Mr Titley tells me as we bounce along roads in a Land Rover so ancient it threatens to shed its doors. He and his team have set up a series of horticultural societies that work alongside the smallholders enrolled in MIMS, actively encouraging them to show initiative and accept responsibility. Rather than impose commercial ideals on the smallholders - ideals which in the past have proved detrimental to the success of such enterprises - they have striven to marry commercial success with a smallholder ethos.

Mr Titley will not permit any farmer to commit more than 20 per cent of his or her land or time to the project, and in order to afford greater opportunity for other farmers to enrol, the largest area any farmer is permitted to dedicate is 0.15 hectares. The main reason for this is that ordinary farmers' days - especially those of the women - are filled with tasks such as fetching firewood, carrying water, collecting fodder for livestock and tending families. Mr Titley understands that the sustained success of the smallholders depends on having a system that accommodates their traditional lifestyles. Limiting size means limiting risk, but it does not exclude the chance to make good profits.

If this ethos is one secret of the project's success, then the choice of crop and, more importantly, its commercial value, is another. Smallholder projects typically fail because they are not commercially viable. The market is not guaranteed. The crop value is low and subject to price collapses in the event of glut. In this case the crop - peas, mostly (though in time, and at different times of the year, leeks, tender-stem broccoli, and baby corn will be grown) is destined for the shelves of Sainsbury's and Tesco. It is grown to order, if you like. It is harvested, pre-graded and collected in the field by truck. It is sold at a commercial rate between six and nine times higher than the traditional bananas, beans, potatoes, onions or tomatoes, which would be transported to a local market on the back of a bicycle or in a basket atop a woman' s head.

To guard against the pervasive African problem of money being diverted by corrupt means, the relationship between management, horticultural societies and farmers is structured so as to guarantee transparency and self-policing. Both the farmers, who know the price per kilogram at planting, and the management, are present when the crop is harvested and yields are recorded. Every cent goes back to the farmer who can average $700 over a 16-week programme.

Working within the parameters of the subsistence farming culture familiar to rural Africans, while accommodating the demands of their - and specifically the multi-tasking women's - day, the approach is not only sympathetic to local lifestyles, but hugely sympathetic to the environment in a way commercial farming almost never is.

Farmers are discouraged from cutting down trees or indeed removing any plants. The pea plants grow among a glorious variety of coffee trees, banana trees, and beans, the odd maize stalk, manioc, tomatoes, ferns and wild flowers. An anomaly seems at play here: this crop is destined for an international market and yet I am standing beneath a canopy of trees, through which I can see blue African sky and I can hear only birdsong.

The project strongly upholds cultural strengths such as that of family, for children are involved in the work as part of their schooling which includes good agricultural practice on the curriculum. But it also strongly challenges African patriarchy. Women are an integral part of the project, for the men cannot register unless their wives comply and countersign. As Mr Titley acknowledges, "this being Africa, the job's inevitably going to fall to her anyway. It's imperative she's aware of what she's letting herself in for."

Half of the project managers are women too. Dommy, who is just 22, oversees 80 farmers ("between 50 and 90 years of age", she told me) and this year will be responsible for administering over 100 hectares of peas. This does not simply entail signing farms on. It means supervision and education at every step. That education extends to introducing farmers to the principles of Eurepgap. This is a set of rules European supermarkets have laid down for farmers to follow. Eurep is the Euro-Retailer Produce Working Group, while Gap stands for internationally recognised Good Agricultural Practices. Eurepgap's criteria ensure harmonisation of agricultural standards, and promote the health, safety and welfare of the grower, the environment and the consumer.

Dommy, like the other managers, supports the farmers from planting to fertilising, irrigating to stringing and finally harvesting and grading, by encouraging, teaching and providing technical know-how. I watched her as she patiently explained to one man of over 60 why it was important for him to string his peas (so that they are supported and the plants don't collapse, for this reduces the yield). He listened intently and did as he was told. "Doesn't he mind being told what to do by you?" I asked. "Of course not," retorts Dommy. "He wants to learn how to grow peas well."

Dommy has recently introduced the project to a number of schools which have land lying fallow outside classrooms or behind dormitories. It was her idea, not Mr Titley's. I wanted to know why she felt it was important to do this. "Because", she said, "these children can go home to their parents and teach them how to farm properly. Even if they are not growing peas, they will understand the importance of good farming practices." And, she adds, gesturing towards the girls' secondary school we have just visited, "these girls will learn something valuable, something practical, something they can work on after they have left school rather than just falling pregnant."

Farmers are clamouring to join the project: "Every day", said Dommy, "farmers ask me if they can grow peas for me. The queue is very long."

In the fields are children removing weeds and an elderly couple arguing over whether the strings are secure enough. I inspected the shamba of an old man who proudly showed me the first flowers on his crop, and told me he was working in the field, with his son and daughter, because "my wife cannot do this all by herself. And anyhow, she is busy preparing my lunch".

I listened to a village chief - responsible for giving the yea or nay as to whether a community can involve itself thus - telling me "we are fighting poverty, we are trying". And I listened in astonishment to a young man who, indignantly, told the smallholder management that paying for a fertiliser store to be built was not the way to go. "Talk to the community," he urged. "Get them to find a local building to rent ... See all these buildings," he said, gesturing to some kiosks and shops nearby, "there must be something here." He drew breath impatiently. "Mr Titley," he continued, "how will this project ever be sustainable if we do not learn to help ourselves?"

Anthea Rowan is a journalist based in Africa.