Atmospheric deposition as an important nitrogen load to a typical agroecosystem in the Huang-Huai-Hai Plain. 1. Measurement and preliminary results

Atmospheric nitrogen (N) deposition has been widely considered as an important N input into agroecosystems, but its measurement involves considerable uncertainties with various methods. In this study, a field sampler with distilled water as a surrogate surface was developed and trialed for the collection of dry and wet N deposition. The direct measuring results were compared with the value calculated by the N mass balance method (crop N uptake from plots receiving no N fertilizers of the long-term fertilization experiment in the monitoring station). The results indicated that exposure durations of 3–5 days and water volumes of 2000–2800 ml were tested to be suitable to collect dry N deposition, while water volumes of less than 1000 ml and sampling conducted immediately after rain event were found to be appropriate for wet N collection under the present experimental conditions. The monitoring work was conducted from June 2008 to May 2009, and annual N deposition totaled up to 40.32 kg N ha−1, of which dry deposition accounted for 62.45%. NH4–N was the dominant species in N deposition and contributed 62.68% and 66.00% to wet and dry deposition, respectively. Organic N (O-N) was found to make greater contributions than NO3–N in both dry and wet depositions. Total N deposition was parallel to the results estimated by the method of mass N balance from the long-term experiment, as 45.6 kg N ha−1. These results provide helpful knowledge to elucidate the N deposition scenario of a typical agroecosystem and can be of great importance for the calculation of fertilizer recommendations in the Huang-Huai-Hai Plain.