Conventional nitrogen (N) fertilizers used in crop production typically have use efficiencies of only 30 to 40%. While reduced efficiency can be a result of multiple factors (rate, placement, source), mismatched timing between N availability and N crop demand is a significant cause of reduced efficiency. This study aims to develop a biochar-based controlled release nitrogenous fertilizer (BCRNF) from relatively low-cost renewable materials to improve N availability when needed by the corn crop thus reducing N losses and improving nitrogen use efficiency. Ammonium sulfate was impregnated in biochar and then pelletized into particles. Three concentrations (3%, 6%, and 10%) of polylactic acid (PLA) solutions were used to coat the particles to produce BCRNF. The effects of different PLA concentrations on N release and physical properties of BCNRFs were investigated in both water and soil conditions. Water absorption and retention, thermal stability, and microstructures of BCRNFs were also analyzed to determine the N release mechanism of BCRNFs. The BCRNF coated by 10% and 6% of PLA both released 70% of N over 12 days in water and 25 days in soil. The biochar held 14% N that was not released into the water. However, coating with PLA, increased N holding to 16% inside BCRNF particles. The thermal properties of BCRNFs were stable under 230 °C. The PLA concentration of the coating layer significantly affected not only the N releasing time and rate but also the morphology and thermal properties of BCRNFs. Higher PLA concentrations resulted in a longer releasing time at lower N release rates. This study demonstrates that a biochar-based controlled-release nitrogen fertilizer (BCRNF) can enhance N release time and rate in both water and soil environments through the integration of biochar absorption and a PLA coating. Further development could yield a BCRNF that can optimally synchronize timing and amount of available N with crop N demand to increase N use efficiency.

作物生产中使用的常规氮（N）肥料的使用效率通常仅为30％至40％。虽然效率降低可能是多种因素（比率，放置，来源）的结果，但氮素供应量与氮素作物需求之间的时间安排不匹配是造成效率降低的重要原因。这项研究旨在从相对低成本的可再生材料中开发一种基于生物炭的控释氮肥（BCRNF），以在玉米作物需要时提高氮的利用率，从而减少氮的流失并提高氮的利用效率。将硫酸铵浸渍在生物炭中，然后制成颗粒。三种浓度（3％，6％和10％）的聚乳酸（PLA）溶液用于包覆颗粒以生产BCRNF。在水和土壤条件下，研究了不同PLA浓度对BCNRFs氮释放和物理特性的影响。还分析了BCRNFs的吸水率和保留率，热稳定性和微观结构，以确定BCRNFs的氮释放机理。分别用10％和6％的PLA涂覆的BCRNF在水中12天和在土壤中25天都释放了70％的氮。生物炭含有14％的氮，但并未释放到水中。但是，用PLA涂层可将BCRNF颗粒内部的氮含量提高至16％。BCRNFs的热性能在230°C下稳定。涂层的PLA浓度不仅显着影响N释放时间和速率，而且显着影响BCRNFs的形貌和热性能。较高的PLA浓度导致较低的N释放速率导致更长的释放时间。这项研究表明，基于生物炭的控释氮肥（BCRNF）可以通过整合生物炭吸收和PLA涂层来提高水和土壤环境中的氮释放时间和氮释放速率。进一步的发展可能会产生出一种BCRNF，它可以最佳地将氮素的施用时间和数量与作物的氮需求同步化，以提高氮素的利用效率。