Modeling N₂O flux from an Illinois agroecosystem using Monte Carlo sampling of field observations
2009
Tonitto, Christina | David, Mark B. | Drinkwater, Laurie E.
We modeled the expected range of seasonal and annual N₂O flux from temperate, grain agroecosystems using Monte Carlo sampling of N₂O flux field observations. This analysis is complimentary to mechanistic biogeochemical model outcomes and provides an alternative method of estimating N₂O flux. Our analysis produced a range of annual N₂O gas flux estimates with mean values overlapping with results from an intermodel comparison of mechanistic models. Mean seasonal N₂O flux was 1-4% of available N, while median seasonal N₂O flux was less than 2% of available N across corn, soybean, wheat, ryegrass, legume, and bare fallow systems. The 25th-75th percentile values for simulated average annualized N₂O flux rates ranged from 1 to 12.2 kg N ha⁻¹ in the conventional system, from 1.3 to 8.8 kg N ha⁻¹ in the cover crop rotation, and from 0.8 to 9.3 kg N ha⁻¹ in the legume rotation. Although these modeling techniques lack the seasonal resolution of mechanistic models, model outcomes are based on measured field observations. Given the large variation in seasonal N gas flux predictions resulting from the application of mechanistic simulation models, this data-derived approach is a complimentary benchmark for assessing the impact of agricultural policy on greenhouse gas emissions.
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