The impact of the nitrification inhibitor calcium cyanamide and an icrease of soil pH on N2O emission and soil bacterial community composition

Calcium cyanamide is the main component of lime nitrogen. Calcium cyanamide is gradually hydrolyzed into urea and the nitification inhibitor dicyandiamide in soil. In addition, Calcium cyanamide increase soil pH. The aim of this study was to elucidate the impacts of calcium cyanamide and an increase of soil pH on N2O emission and soil bacterial community composition. Soil incubation experiment was conducted with eleven treatments established in combination with five chemical amendments (i.e. urea [U], cyanamide [CN], calcium cyanamide [CaCN], calcium hydroxide [Ca], and urea with calcium hydroxide [CaU]) and two fertilization methods (i.e. whole mixing and local placement in the mid layer), and the control without fertilizer application [CT]. Soil was incubated up to 28 days, and the soil properties and N2O emission were monitored. Soil bacterial community compositions at 7th day were elucidated using the high throughput sequencing. In addition to CN and CaCN, CaU significantly suppressed N2O emission compared to U. The localization of the chemicals had less effect on N2O emission. CaCN, CN and CaU decreased soil bacterial alpha diversity, and Planococcaceae was the dominat family in these environments. Besides, bacterial communities of CaCN, CN and CaU were predicted to have less nitrification and denitrification genes. Compared to CT, bacterial beta diversities were gradually increased along with soil pH increase, whereas Ca showed smaller beta diversity to CT. Our results suggest that an increase of soil pH under high urea concentration could have an important role in shaping the bacterial community composition and suppress N2O emission.