Nutrient release from rice and rubber biochar tablets with and without embedded fertilizers

An alternative to agricultural residues management is to convert them to biochar because this organic amendment can act as a superior soil conditioner that improves soil productivity. Nevertheless, the low density of biochar poses a challenge in the handling biochar. Tableting of biochar can mitigate the aforementioned problems associated with biochar. The objectives of this study were to determine the physico-chemical properties, nutrient release and soil ammonia volatilization of biochar tablets with and without embedded fertilizers. The different rates of biochar tablets with and without embedded fertilizers impact on selected soil chemical characteristics and nutrient use efficiency (NUE) of sweet corn (test crop) were also determined. Next planting cycle was conducted to determine the effects of combination biochar and fertilizers with and without tableting on selected soil chemical characteristics and NUE of sweet corn (test crop). The composition of biochar mixture was 50% charred rice husk, 30% charred rice straw, and 20% charred rubber twigs. The NPK fertilizers used for this study were ammonium sulfate (AS), triple superphosphate (TSP), and muriate of potash (MOP). The biochar tablet (BT) was produced by blending a biochar mixture with starch followed by tableting using a single punch tablet press whereas the fertilizer embedded biochar tablet (BF) was prepared using the same procedure except that NPK fertilizers were added during blending. Similarly, a combination of biochar and NPK without tableting (Biochar + NPK) was prepared. The ratio of biochar to fertilizers mixture used for the BF and Biochar + NPK production was 2:1. Standard procedures were used to characterize BT, BF, Biochar + NPK, and NPK. The nutrient release of the biochar and fertilizers with- and without- tablets were determined using the water incubation over 30 days. The daily loss ammonia was measured using a closed dynamic air flow system model for 10 days. A pot experiment with six f