Optimizing organic and mineral amendments to jatropha seed cake to increase its agronomic utility as organic fertilizer

Abstract

The agronomic utility of an organic residue, jatropha cake (Jc) was assessed according to the NPK requirement of selected crops. Fertilizer combinations were made by mixing jatropha cake (Jc), bone meal (Bm), tobacco dust (Td) and inorganic supplements ammonium Bi-carbonate (NH4HCO3), dicalcium phosphate (CaHPO4 · (H2O)2) and potassium chloride (KCl). The effects of combinations on the chemical and biological properties of soil and the growth of Jatropha curcas (used for non-edible oil or biofuel) and Cymbopogon martinii (essential aromatic oil used for anti septic, anti viral, bactericide, cytophylactic, digestive, febrifuge and hydrating properties) were studied. The combination of Jc with other residues turned it into an appropriate soil amendment to increase soil fertility. Utilization of these residues can also solve disposal related issues of these residues. Jc + CaHPO4 · (H2O)2 + KCl, Jc + Bm + Td, Jc + Bm and Jc + Td were most efficient combinations in terms of increasing soil fertility and growth of J. curcas and C. martinii. Most optimal organic combination of Jc + Bm + Td provided 182.4 kg N ha−1, 102.8 kg P ha−1 & 50 kg K ha−1 for J. curcas and 83.7 kg N ha−1, 19.8 kg P ha−1, 33.1 kg K ha−1 for C. martinii. The fertilizer combination gave significantly highest increase of 1.78 and 5.79 mg N g−1, 14.12 and 10.3 mg P g−1, 9.38 and 26.40 mg K g−1 and 9.06 and 4.42 mg C g−1 of experimental soils of J. curcas and C. martini, respectively. The combination also increased the extractable micronutrient content and soil enzymatic activity. Total plant biomass increased 5.9 and 10.5 times higher to control due to Jc + Bm + Td fertilizer combination in test crops of J. curcas and C. martini, respectively.