Incorporation of biochar and semi-interpenetrating biopolymer to synthesize new slow release fertilizers and their impact on soil moisture and nutrients availability

Chemical fertilizers (CFs) are indispensable nutrients source for plants replenishing them with essential nutrients. However, their over-utilization imposed destructive consequences of excessive loss of major nutrients resulting in low nutrient use efficiency and further environmental concerns. Therefore, to counter excessive application of CFs and to regulate sustainable agriculture, a novel biochar (BC)-based slow-release fertilizer (SRF) was developed by incorporating mica (MI) and semi-interpenetrating chitosan polymer (Semi-IPN) via graft co-polymerization. Fabricated SRFs were characterized and their nutrient release dynamics as well as soil water holding (WH) and water retention (WR) capacity were investigated. The results revealed that BC-based SRFs, particularly BC-SRF and BCMI-SRF, enhanced soil WH capacity by 40.61% and 47.80%, respectively, whereas the highest soil WR capacity was recorded as 32.55% and 35.52% respectively, after 30 days. The nutrients (NH₄⁺-N, P, K) release ratio of CF and MI was recorded in the range of 85-100%, however BC and MI incorporated SRFs showed splendid slow release nutrients dynamics and release 75.53% of NH₄⁺-N, 65.66% of P and 71.83% of K in a 30 days incubation experiment. Nutrient release kinetics exhibited diffusion and mass transport as the major nutrient release mechanisms, which was confirmed by the best fitted parabolic diffusion and first order kinetics models. Hence, current study inclusively demonstrated new routes for synthesis of innovative and eco-friendly SRFs with substantial slow-release performance to overcome excessive nutrient loss by application of CF.