Nanobiochar reduces ammonia emission, increases nutrient mineralization from vermicompost, and improves maize productivity

Recently nanobiochar (NB) has been getting more attention than bulk biochar due to its ultrafine particles, desired chemical composition, and negatively charged surface. These properties make NB a great nano-additive to improve the agro-environmental value of any conventional fertilizer. However, the production of smart organic fertilizer with the help of NB is still not investigated. This study aims to synthesize NB and analyze its concentration dependent influence on ammonia emission, nitrogen (N), phosphorus (P), potassium (K) mineralization and the aforementioned nutrients uptake by maize from the vermicompost and nanobiochar mixture. The NB was synthesized from farmyard manure using pyrolysis (500 °C) and ball milling techniques. X-ray diffraction data confirmed the synthesis of nanobiochar, showing clear carbon peaks. In addition, FTIR spectroscopic analysis indicated the existence of OH, C-O, NH, and C-C functional groups on the NB surface. The electron microscopy images revealed the bi-model size and morphologies of synthesized NB particles. Different nanobiochar concentrations (2, 5, and 10% of applied N) were mixed with vermicompost and applied to maize. The lowest and intermediate NB concentrations did not affect any soil and plant parameters. The highest NB concentration decreased ammonia emission by 43% (68 vs 120 μg m−3) from vermicompost. This treatment increased soil microbial biomass carbon and N, mineral N (Nmin), P, and K by 71%, 120%, 95%, 72%, and 11%, compared to vermicompost. The highest concentration of NB in vermicompost also increased maize shoot dry matter (DM) yield by 32% (16,631 vs 12,562 kg ha−1), as well as N, P, and K uptakes by 42, 30, and 54%. This confirmed that NB acts as a nano-additive and improves vermicompost fertilizer efficiency, soil quality, and maize productivity. Hence, NB can be recommended as an additive in conventional fertilizers to achieve higher economic and environmental benefits.