Prospect of Deoiled Jatropha curcas Seedcake as Fertilizer for Vegetables Crops – A Case Study

The biodiesel from Jatropha curcas had been received much attention in these past decades. The seed was accountable for its high oil content. Through the development of oil expeller machine, the remains of an oil extraction were subjected to this study in order to examine the potential of deoiled Jatropha curcas seedcake (JSC) for being used as an organic fertilizer. However, the main concern was the presence of a toxic compound named phorbol ester in the JSC. The bio-safety questions were often regarded as the main concerns for the utilization of JSC as fertilizer. Therefore, the Chinese kale, tomato, and sweet potato were chosen to represent as the leaf, fruit, and tuber vegetable, respectively, which were subjected to the application of JSC as fertilizer. Here, the aspects of plant growth, yield, nutrient, and amount of phorbol ester in such plant parts as well as in the soil were analyzed. Although the treatments in each crops were practically the same, the specified details namely an exact rate of chemically fertilizer were slightly varied. The effects of half rate of chemical fertilizer mixed with high rate of JSC as fertilizer on the yields of Chinese kale and tomato were proven to be on the increase. This same treatment had mostly affected the growth characteristics of sweet potato. The total percentages of nitrogen (N), phosphorous (P), and potassium (K) in the vegetable products were subsequently inspected. Not only the qualities of pre-planting soil, in terms of pH, organic matter, and available P and K were analyzed, but also that of postharvest. Analytical measurements of phorbol ester via both HPLC and LC-MS/MS, were performed in all the samples from both harvested plant parts as well as soil. From all the postharvest propagations, the toxicity of phorbol ester could not be found, neither from the plant products nor the soil. Therefore, utilization of JCS as organic fertilizer for vegetable crops was marked as a safe practice, both for the consumer consumption and soil environment. This outcome can be of choice to solve the problem of rising fertilizer prices.