Abstract: Atmospheric N deposition has become an environmental concern in the North China Plain (NCP), because of the large anthropogenic reactive N emissions in this region since the 1990s. A manually integrated total N input (ITNI) method was developed using 15N-labelled monitor plants grown in pots to obtain accurate measures of total N deposition to the agroecosystems in the NCP and to improve N-fertilizer recommendations. In the NCP, total airborne N input into the maize-wheat rotation system is 80-90 kg N ha–1 yr–1, and the plant available N from deposition for maize and wheat plants is c. 50 kg N ha-1 yr–1. While total airborne N input measures at almost 100 kg N ha–1 yr–1 when ryegrass is used as the monitoring plant the plant available N from deposition for ryegrass is c. 76 kg N ha-1 yr-1, accounting for 77% of the total N deposition. Dry deposition is likely to be the major contributor to the total N deposition during the wheat growing season in the dry and dusty NCP. In order to obtain reliable N deposition results, especially when the plant density in small area pots (0.57 m2) is different from the density in the field, we found that a correction factor (0.54 in this study) had to be used for maize to rectify values obtained from pot area.

Key words:  air pollution, reactive N deposition, 15N dilution method, biomonitoring