Dicyandiamide efficacy of inhibiting nitrification and carbon dioxide emission from calcareous soil depends on temperature and moisture contents

Dicyandiamide (DCD) has been extensively used to retard the nitrification process and decrease nitrogen (N) losses. However, its efficacy is variable and inconsistent depending upon the environmental conditions. The effects of temperature and moisture on DCD degradation and carbon dioxide (CO2) release from calcareous soil are not well-known. Therefore, an incubation experiment comprising three treatme ts (control, N fertilizer, and N fertilizer + DCD) was conducted for 67 d at different temperature (10 degrees C and 25 degrees C) and moisture (40% and 60% WFPS) levels. Results showed that nitrification activity and subsequent gaseous losses were increased with N addition and significantly affected by temperature and moisture levels. DCD effectively inhibited NH4 (+) oxidation, net NO3 (-) production (31-59%), and N2O emissions (69%). CO2 emissions increased with N fertilization but reduced (18-161%) significantly with DCD application. DCD efficiency of inhibiting nitrification and controlling CO2 emission was related to its residence time in the soil. DCD degraded quickly at high temperature (25 degrees C) and moisture (60% WFPS), that is why it was least effective in inhibiting nitrification and controlling gaseous fluxes. Accordingly, DCD is not equally effective everywhere and is more suitable for regions with low temperature and low moisture.

Automated summary

The study found that nitrogen addition increases nitrification activity and gaseous losses, which are significantly affected by temperature and moisture levels. DCD effectively inhibits NH4 (+) oxidation, net NO3 (-) production (31-59%), and N2O emissions (69%). CO2 emissions increase with nitrogen fertilization but significantly decrease (18-161%) with DCD application. DCD's efficacy in inhibiting nitrification and controlling CO2 emission is related to its residence time in the soil.