Potentials of Jatropha Seed Cake in Soil Fertility: A Case Study with Cucumber (Cucumis Sativa .L.)

ABSTRACT

An attempt to mitigate rapid soil fertility and productivity decline has led to the application of organic and inorganic fertilizers. However, the availability of inorganic fertilizers for crop production is a challenge to many farmers in developing countries. Thus, the use of organic fertilizers is becoming more popular among farmers in recent decades. In this study, a two-year field experiment was conducted to compare the efficacy of Jatropha seed cake (JSC), Tithonia (Tithonia diversifolia), compost, and the most common compound inorganic fertilizer in Nigeria – NPK. 15:15:15 on growth, yield, and some soil physico-chemical parameters and yield of cucumber (Cucumis sativus L.). The treatments were laid out in Randomized Complete Block Design, with three replicates and were applied at the rates of 80 and 120 kg N ha⁻¹. Two-way ANOVA was used to determine the effects of fertilizer, rate, and year on some soil macro and micronutrients. Structural equation model (SEM) was used to reveal the direct and indirect effects of fertilizer and rate of application on soil physicochemical properties and the performance of cucumber. The results showed that organic amendments (JSC and Compost) significantly increased the yield of cucumber, JSC improved the soil pH, available nitrogen (AN), and available phosphorus (AP), while Compost better improved organic carbon (OC) than the NPK. 15:15:15. The SEM showed that fertilizer had direct significant positive effects on the yield of cucumber, magnesium, and sodium and a direct significant effect on the yield of cucumber. Also, organic carbon had direct and significant effects on both available phosphorous and total nitrogen. Jatropha seed cake and compost proved to be better than mineral fertilizers NPK 15–15-15, thus proving these organic wastes as better alternatives to NPK fertilizer in producing cucumber.

KEYWORDS:

• Jatropha seed cake
• npk fertilizer
• organic amendment
• structural equation model (SEM)
• Tithonia (Tithonia diversifolia)

Acknowledgments

Thanks to the management of the National Horticultural Research Institute (NIHORT), Ibadan, Nigeria, for allowing the field experiment to take place in their Institute. Appreciation also goes to the management of the University of Ibadan, through the Department of Agronomy, Faculty of Agriculture, for supporting the laboratory aspect of this study.