The Nitrogen Budget of DRW in the Northeastern China

The nitrogen (N) budget is studied to evaluate N inputs and outputs of DHF Reservoir Watershed (DRW), where it is cold semiarid climate in northeastern China. Using the data of 2003 as a typical calculation year, the input of N is quantified from the aspects of atmospheric deposition, fertilizer use, biological fixation, net food and feed input, output of N from ammonia volatilization, denitrification and runoff export, respectively. It is addressed that the atmosphere deposition, fertilizer use and food and feed input dominates more than 90% of the total input. In the output side of N, the ammonia volatilization and denitrification are the main items, which account for 55% of the total N input and 95.1% of the total N output. However runoff N export is 6.49% of the total N input. This is owing to the more water retention time in reservoir for N settling and more sites for denitrification. Over the whole watershed, the budget of N is positive (13.52 kg ha^–1 yr^–1), which results in the N accumulation in landscape and the TN concentration increase in DHF Reservoir.