Evaluation of Spent Coffee Grounds as an Ecological Fertilizer for Enhancing Soil Fertility and Radish Nutrition (Raphanus sativus L.)

Globally, rising coffee consumption has led to an increase in coffee grounds waste. This study evaluated the feasibility of using spent coffee grounds (SCG) as an alternative fertilizer in agriculture from an environmental perspective. To this end, various application rates of coffee grounds (0, 7.5, 15, and 30 t ha⁻¹) were tested to determine their effects on the yield and nutrient content of red radish, as well as on selected physical and chemical soil properties. Coffee grounds applications significantly increased the organic matter content and the amounts of N, P, K, Mg, and Zn in loamy sand soil following radish cultivation. Compared with the control, 30 t ha⁻¹ of SCG raised soil organic matter by 50% and enhanced P, Mg, and Mn contents by 27.5%, 14.6%, and 55.5%, respectively. SCG treatments significantly improved the P, Mg, Zn, and Mn contents in radish leaves and tubers, as well as K and vitamin C levels in the tubers. Notably, the 30 t ha⁻¹ dose increased tuber Mg and Mn contents by 32% and 55%, respectively, while the 15 t ha⁻¹ dose increased vitamin C content by 35%. However, these applications did not affect radish tuber yield, dry matter content, leaf N, Fe, and Cu levels, or tuber N, Ca, and Fe concentrations. Consequently, the application of spent coffee grounds enriched the mineral profile of radish, an important nutritional source, thereby enhancing its overall nutritional value. The findings indicate that spent coffee grounds applications to soil can improve the mineral content of both plants and soil while also enhancing soil properties, suggesting significant potential as an alternative fertilizer. Additionally, repurposing large quantities of coffee grounds in agriculture contributes to sustainable soil fertility and offers environmental benefits.