"Farmers have come from other parts of the country to see what is happening here. I no longer depend on seasonal rainfall. I produce three times more maize and have a surplus to trade," says Mr Beltran.
The project involves building earthen dams to form reservoirs or ponds that can collect surface water run-off from the hills during the rainy season.
The water is then used for irrigation during periods of drought.
"The problem in Nicaragua and the majority of tropical areas in Latin America is that you have a huge contrast between the rainy and the dry season," says Gonzalo Zorrilla, who is directing the project.
"In Nicaragua's case, you have a lot of rain for six months and then six months when there is practically none."
Catching the rain The idea for the initiative stemmed from work in southern Brazil, Argentina and Uruguay by the Latin American Fund for Irrigated Rice (FLAR) and supported by the International Center for Tropical Agriculture (CIAT).
In these countries, more than 1m hectares (2.5m acres) of rice have been irrigated with water collected by the farmers themselves.
"With our partners in Nicaragua, the local rice farmers' association, we thought it could be possible to use the same technology to help small farmers in the tropics," said Mr Zorrilla.
"We convinced a UN agency, the Common Fund for Commodities, CFC, to fund the project."
The idea is to construct the reservoirs as cheaply and simply as possible.
A dam is built between two hillsides to catch the rainwater run-off and create a pool of water.
An outlet tube reinforced with steel bars lies underneath the dam, so all the farmer has to do to irrigate his crops is open the valve.
"If you go anywhere in northern Costa Rica, Panama or Nicaragua, there is massive unemployment during six months of the year. People have no income, no crops, and in severe cases their cattle are dying," says Edward Pulver, agricultural scientist at FLAR.
When the project started, he says, many farmers were not optimistic about their future.
"But as soon as we started mentioning irrigation, their eyes lit up like Christmas tree lights because they had hope.
"They saw they didn't have to be poor, there was a way out. It is incredibly impressive to see that."
Fourteen dams have been completed or are being built in Nicaragua, and similar projects are under way in Costa Rica and southern Mexico.
"We are getting the same yields of maize in Nicaragua that you get in the Midwest in the US," says Mr Pulver.
"Fresh corn was not available in the dry season. Now, because of irrigation, some farmers sell their whole production as fresh corn for human consumption," says Mr Zorrilla.
This means a potential income of several thousand dollars per hectare, an amount that was "completely unimaginable in the past", according to Mr Zorrilla.
The project has also helped farmers to vary their diet, as some of them have introduced a small fish, tilapia, to the reservoirs.
Farming's future? Many countries in Latin America, including Mexico, Colombia, Ecuador, Bolivia and Costa Rica have the right topography and conditions to harvest water, says Mr Pulver.
"In Latin America we have excess water. Our problem is we have flooding, so if we can just capture this water, store it and plant crops during the dry season, we can feed ourselves very easily.
"This technology can work in the poorest of countries, and the CFC wants us to take the idea to Africa."
A key aim of the pilot project, which ends in 2012, is to train local people and officials so they can build their own dams and reservoirs.
"If we finish with just 14 dams in Nicaragua, nothing would have change there because too few farmers would have benefited," says Mr Zorrilla.
"Globally, despite the challenges of growing populations, water is really under used.
"The intelligent, sustainable use of water could give rise to a water revolution, a blue revolution," he says.
One key factor seems already guaranteed: the conviction of the farmers themselves.
"If you expand access to this technology, you can help to lessen the impact drought has in Nicaragua," says Mr Beltran.
"Farmers can have a balanced diet, money for their farm and for their children's education. On my farm, there's now work for four of us.
"This project has really changed the way we think."
24 November 2011 Last updated at 10:53 GMT