A new black market has sprung up in Ivory Coast for Niger's onions.
By Ben Sutherland
BBC News Online in Kyoto
Two years ago, the United Nations Food and Agriculture Organisation (FAO) launched a project to help Niger's farmers near the town of Keita, focusing on the use of onions as a "cash crop".
The FAO helped show the farmers better irrigation and soil techniques.
Niger is one of the world's driest countries
And the high-quality vegetables that emerged have become a prized commodity 800 kilometres away.
"The end result was very surprising," Reto Florin, chief of the FAO
Water Service, told BBC News Online.
"In Ivory Coast, they have created a sort of Mafia for Keita-produced onions.
"Nowadays, other farmers cannot go and sell onions on the market if they are not from Keita. I find this a real success."
Mr Florin says there are three reasons why Nigerien onions do so well in Ivory Coast: good transportation; effective marketing and "good quality product".
"Onions just seem to be very popular in that area," he said.
And the demand for Keita's onions has continued despite the six-month conflict in Ivory Coast.
If we managed to improve the efficiency by 1% in one hectare, this will provide drinking water for 150 people for a whole year
The FAO project in Niger was one of a number that have been highlighted at the Third World Water Forum in Kyoto as helping farmers in the developing world use water much more effectively.
Agriculture is very much under the spotlight at the forum, as it is by far the biggest user of the world's fresh water reserves.
"Why are we here in Kyoto? Everyone cries 'water shortage, why do we still need to have agriculture still on board'?" said Mr Florin. "But agriculture is using 70% of all the fresh water available.
"We know that we are not very efficient at the moment. We have losses that are above 50%, similar to inefficient towns in Latin America and southern Europe.
"But if you are the number one user, it's better to start reducing and using water better."
'Water not oil'
He added that in South America, for example, "conservation agriculture" has successfully been launched, where farmers are encouraged to plough only minimally rather than automatically every year.
This helps keep moisture in the soil, and lessens the need for more water.
And he said that even a small improvement in the use of water could massively help conserve supplies.
"If we managed to improve the efficiency by 1% in one hectare in
Africa, this will provide drinking water for 150 people for a whole year," he said.
"Water is different to oil.
"Oil will one day be finished. Water does not finish - we have a cycle, we have the same amount of water - but we have a population which increases, which means we have to use the water more efficiently."