Previous field studies simulating atmospheric nitrogen (N) deposition generally apply N once or twice (large and infrequent N pulses) during the growing season. However, atmospheric N deposition occurs in more frequent events of smaller doses of N to ecosystems.

Dr. WANG Ruzhen, an associate professor from Institute of Applied Ecology, Chinese Academy of Sciences conducted a study to investigate whether frequency of N addition can affect soil chemical properties.

Dr. Wang and his co-authors simulated N deposition in a temperate steppe by changing the frequency (2 versus 12 applications yr^-1) and rate (ranging from 0 to 50 g N m^-2 yr^-1) of N addition with and without a common grassland management practice of mowing.

They found that soil pH, exchangeable base cations and soil pH buffering capacity decreased with increased N application rates as expected, but these decreases were generally larger when application rates were applied in large doses, particularly in unmown plots. In contrast, many of the soil micronutrient concentrations increased with increased N application rate, similarly with a larger extent under large N doses.

Their results suggest that simulating atmospheric N deposition with large and infrequent N addition events may overestimate loss of base cations, soil acidification and mobilization of micronutrients, especially under low N inputs in the short term, but that these effects also depend on the intensity of N addition and how these grasslands are managed through mowing or grazing.

The study entitled “Intensity and frequency of nitrogen deposition alter soil chemical properties depending on mowing in a temperate steppe” has been published in Journal of Environmental Management.

The study is financially supported by the National Key Research and Development Program of China and the National Natural Science Foundation of China.