Comparative nutrient leaching capability of cattle dung biogas digestate and inorganic fertilizer under spinach cropping condition.

A field experiment was used to determine leaching capability of biogas digestate used as soil amendment in comparison to inorganic fertilizer under spinach cropping condition. The biogas digestate used in this experiment was obtained from a biogas production plant that used cattle dung as feedstock. Spinach was cultivated under three treatments, namely, biogas digestate (BD), inorganic fertilizer (IN) and control (no fertilizer or biogas digestate). All the treatments were replicated three times. Irrometer soil solution access tubes were inserted in the middle of each plot for the collection of the nutrient leachates. The leaf area of spinach was significantly higher in IN treatment than BD and control at the harvest stage; BD produced higher fresh mass (479 g/plant) than IN (468 g/plant) and control (201 g/plant). The leachates of inorganic fertilizer showed higher nutrient concentration compared to biogas digestate and control treatments. Twenty-eight days after transplanting, the leachate consisted of 3670.7, 12.12 and 8.5 mg/l of ammonium and 408, 83 and 39 mg/l of phosphate at IN, BD and control treatments, respectively. The study demonstrates that cattle dung biogas digestate can be applied on soil as fertilizer for crops with little or no environmental consequences to water resources and still have the same product quality as inorganic fertilizer.