Quantifying the total airborne nitrogen input into agroecosystems in the North China Plain

Nitrogen (N) input from atmospheric deposition is a concern in the North China Plain (NCP). To quantify the magnitude of the problem, the total airborne N deposition to agroecosystems in the NCP was quantified using a manual ITNI (integrated total nitrogen input) system and a long-term experiment (LTE). Total estimated N deposition averaged 83.3 kg N ha−1 across the sites Dongbeiwang (DBW) of Beijing, Wuqiao (WQ) and Quzhou (QZ) of Hebei, with atmospheric N input 14 kg N ha−1 in the period from flowering to maturity, when maize (Zea mays) was the monitoring crop. The 15N-supply level in the ITNI system seemed not to affect the estimation of N deposition significantly. However, the N deposition value was only 48.6 kg N ha−1 on average when ryegrass (Lolium multiflorum) was cultivated during the same period of maize (May–September), suggesting that total airborne N input varies with the monitoring crop, largely because of the different surface areas. The total annual N deposition obtained from zero-N plots of LTE at Changping (82.8 kg N ha−1) supported the N deposition results from the maize-based ITNI systems.