Agronomic Effectiveness of Jatropha Seedcake as an Organic Fertilizer

Zambia has embraced bio-diesel processing from jatropha ( Jatropha curcas ) and, therefore, disposal of de-oiled residue of jatropha seeds(Jatropha seedcake) from the growing bio-diesel industry is likely to present challengesbecause it cannot be utilized as livestock feed. In this study, we explored the agronomic effectiveness ofthe seedcake as an organic fertilizer. We evaluated the rate of nitrogen release from the seedcake and maize crop performance in soils fertilized with the seedcake. The seedcake had a nitrogen mineralization rate of 0.14 wk -1 and its improvement to plant soil nutrient supply was evident in the vigorous growth and higher maize grain yields observed in plants grown in soils where seedcake was applied. Maize grain yields of 2.29, 2.32 and 2.75 ton ha -1 were obtained from plots treated with 2, 4 and 6 ton ha -1 of seedcake, respectively, compared to a yield of 1.4 ton ha -1 where no seedcake was applied.We, therefore, concluded that jatrophaseedcakefrom bio-diesel processing could be safely disposed on land and be a valuable organic fertilizer. Nevertheless, further study needs to be done to ascertain possibilities of utilizingseedcake from processes where solvents are used for extracting oil from the seeds.