Impacts of Leucaena leucocephala as a fallow improvement crop in shifting cultivation on the Island of Mindoro, Philippines

In 1977 a fallow improvement program was initiated in Occidental Mindoro, Philippines using Leucaena leucocephala to shorten the fallow period in local shifting cultivation practices. Evaluation of the programme in 1989 suggests that the practice of planting leucaena as a fallow improvement crop has been adapted and widely adopted by farmers. Farmers using leucaena have successfully shortened fallow periods from over 6–8 years to 2–4 years with no reported reduction in crop yields. The leucaena psyllid has had little or no effect on farmer acceptance and use of the system. Soil properties under burned and unburned leucaena and natural bush fallows were analyzed. Exchangeable calcium was significantly lower at 50 cm soil depth under the natural bush fallow. Soil pH in the 0–10 cm horizon was significantly higher under the bush fallow, suggesting that Ca extraction and deposition at the soil surface was greater under the natural bush fallow. No significant difference between natural and leucaena fallows were found for other soil properties. Surface soils of burned leucaena fallows were significantly lower in organic mattern and Mg than unburned fallows.