Trees that help keep soils fertile could slow or stop deforestation in Brazil's "arc of destruction".
A project using inga trees hopes to show smallholders that they can earn a decent living from the land.
Inga trees, known as ice-cream bean trees, fix nitrogen into the soil, boosting productivity levels.
Scientists hope the scheme will convince smallholders not to sell their land to large agri-businesses and remain farmers in the Amazon.
Growth of the 'miracle tree'
"It's very much a kind of 'miracle tree' or a super tree because some of the species can do some amazing things," said Toby Pennington, professor of tropical plant diversity and biogeography at the University of Exeter, UK.
"They can grow really fast on very, very poor soils, even soils where a rainforest has been cut down and have become very degraded."
The trees (there are more than 300 species) are in the legume family and that means they can fix atmospheric nitrogen into the soil.