Mid-Term Effects of Dry Leucaena Leaf Application on Cassava Growth and Yield in a Nutrient-Poor Loamy Sand Soil

Low soil fertility remains a major constraint to cassava (Manihot esculenta Crantz) production, particularly in sandy soils with limited nutrient-holding capacity. While Leucaena leucocephala has been studied as green manure, evidence on the mid-term application of dry Leucaena leaves under field conditions remains limited. This four-year field experiment (2011–2015) evaluated the effects of dry Leucaena leaves application, alone and in combination with urea, on cassava growth, yield, and soil fertility in loamy sand soil. A randomized complete block design with four replications was used, with treatments supplying 25–100 kg nitrogen (N)/ha from dry Leucaena leaves, urea, or their combinations. In the first two years, no significant differences in biomass or root yield were observed among treatments. However, in the third year, root yields were significantly higher in plots receiving 100 kg N/ha from dry Leucaena leaves or 50:50 kg N/ha combinations of dry Leucaena leaves and urea compared with the control and urea alone. Similar trends were observed for starch yield in the fourth year, although root yields did not differ significantly. This mid-term field evidence demonstrates that dry Leucaena leaves can partially substitute for synthetic N fertilizers without adverse soil effects, providing a practical, sustainable nutrient management option for cassava grown in nutrient-poor sandy soils.