Data and code for "Resin-coated urea effectively simulates the chronic dynamics of natural nitrogen deposition"

1. Atmospheric nitrogen (N) deposition has more than tripled globally since the Industrial Revolution. Observational studies have shown that this chronic and continuous N deposition is altering a range of ecological functions and processes, but these studies are affected by confounding variables. Experimental studies attempt to address this limitation by simulating N deposition using fast-release N fertilizers applied once or several times a year. However, these pulses differ from the continuous N supply of natural deposition, which may lead to different outcomes. There is an urgent need for methodologies that more accurately replicate continuous N deposition to better understand its causal impacts on future biological outcomes.

2. We developed a resin-coated slow-release urea that simulates the continuous dynamics of N deposition under semi-arid grassland conditions. Resin was chosen as the coating material because it does not contain plant nutrients. We designed three sizes of urea fertilizer balls with varying resin coating thicknesses to achieve a combination that would release urea continuously over the course of a year in semiarid ecosystems. We then compared the N release rate of the resin-coated urea to the natural N deposition rate to determine the effectiveness of the resin-coated urea in replicating the temporal pattern of N deposition.

3. Our results showed that under the semi-arid conditions of our site, the resin-coated urea with a 0.5 mm coating on 4 mm diameter balls released urea continuously for approximately 12 months. The temporal pattern of N release rate from the chosen coated urea was very similar to local atmospheric N deposition. There was a strong positive relationship between N release rates and N deposition (R2 = 0.80), with both exhibiting simultaneous peaks and valleys.

4. Our results indicate that resin-coated urea with a pellet size and coating thickness determined by local site conditions can effectively simulate the temporal dynamics of N deposition. Coated urea provides a far more effective approach for experimentally simulating future impacts of elevated N deposition on ecosystem function and processes compared to fast-release fertilizers.