With the aim of improving soil productivity a shift in secondary natural vegetation was induced with cropped plants in a collaborative project utilizing improved fallows for maize production under a slash and burn system. A survey of 150 families, two experimentation peasant groups and three formal experiments was conducted. Family welfare depends on forage trees which support soil productivity and fertility. Within 4 years peasants working with improved fallows system found best results with Leucaena leucocephala, Caesalpina yucatanenses and Piscidis piscipula. Maize production was improved with Mucuna pruriens plus 100 kg/ha of P2O5. Two and 4 year-old improved fallows of M. pruriens and L. leucocephala did not improve maize production but weed competition was reduced.