Biochar is a black solid with stable carbon that has many positive effects on the physical, chemical, and biological properties of soil. One of the important positive effects of biochar on the soil is affecting the mobility and dynamics of nutrients, including nitrogen, in the soil. Biochar has negatively charged surfaces and can adsorb and store ammonium ions (NH4+) and small nitrogen-contained organic molecules. Also, releasing amounts of nitrogen into the soil and changing the ratio of carbon to nitrogen (C/N), can affect the mineralization-immobilization balance of nitrogen in the soil. In addition, biochar indirectly affects the cycle and dynamics of nitrogen in soil by changing soil pH, cation exchange capacity, electrical conductivity, organic carbon, biological activity, availability of nutrients, porosity, ventilation, water relations, and other soil characteristics. In addition, providing water, air, and nutrients needed by soil microorganisms can act as a suitable habitat for soil microorganisms and improve nitrogen biological fixation. Biochar also reduces the emission of greenhouse gas N2O from the soil by reducing soil nitrogen sublimation. In general, biochar has a synergistic interaction with nitrogen and can reduce the nitrogen use efficiency of nitrogen fertilizers. However, the biochar induced soil nitrogen changes especially in calcareous soils are not yet well known and more research is needed to investigate the effect of biochars produced from different biomass and under different temperature conditions on the mobility and availability of nutrients, especially nitrogen, in calcareous soils. |