Investigating the decomposition of jatropha (jatropha carcus. l.) seed cake

Author: 
Emmanuel Chidiwa Mbewe., Patson C. Nalivata., Wilkson Makumba and Venon H. Kabambe

Studies to evaluate the decomposition of Jatropha curcasL. (Jatropha) seed cake were carried out at Bunda College of Agriculture using a laboratory experiment. The major objective was to evaluate the decomposition of Jatropha seed cake with and without an inorganic N combination, by incubation.
The experiment was laid out in a 4 × 3 factorial design with 4 levels of Jatropha seed cake at rates equivalent to (0 kg N/ha, 46 kg N/ha, 92 kg N/ha and 184 kg N/ha) which corresponded to 0, 600, 1200, and 2400 mg, respectively, of dry matter per bottle containing 1000 g of soil and 3 levels of inorganic fertiliser at rates equivalent to (0 kg N/ha, 23 kg N/ha and 46 kg N/ha) which corresponded to 0, 20, and 40 mg of urea (46% N) fertiliser per bottle containing 1000 g of soil. Soils were incubated for 112 days with sampling and analysis done after 7, 14, 28, 56 and 112 days. It was found that the decomposition of Jatropha seed cake was affected by the amount of Jatropha seed cake and inorganic fertiliser while the combination of Jatropha seed cake and inorganic fertiliser (at the same level of Jatropha seed cake) did not affect the decomposition of Jatropha seed cake. However, the highest amounts of nutrients were released in the treatment combination of 2400 mg Jatropha seed cake and 40 mg of inorganic fertiliser.
It can be concluded from this study that the decomposition of Jatropha seed cake does not require the addition of inorganic source of N.

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