Modeling the Nitrogen Balance and Nitrous Oxide Emission of Organic Grain and Forage Production Systems
Research Poster Engineering 2025 Graduate ExhibitionPresentation by Farzaneh Tahriri
Exhibition Number 160
Abstract
Assessing nitrous oxide (N2O) emissions from agricultural systems is critical for effective monitoring and developing mitigation strategies. Soil-plant-atmosphere continuum (SPAC) Models can be used for simulating agricultural practices and their effects on greenhouse gas emissions including N2O. Although these models have limitations due to the complexity of simulating N2O fluxes, they are considered promising tools for predicting the gas emissions. This study assessed the Cycles model in simulating nitrogen (N) balance components, aiming to evaluate NO fluxes in forage and grain organic systems. A three-year experiment in Pennsylvania involving four organic cropping systems with variations in tillage, manure application method, and cover crop incorporation timing, was modeled using Cycles and the results were compared with experimental data. The model reasonably simulated major N balance components such as N extraction at harvest. However, while it performed well for no-till corn silage with fall manure applications (Nash-Sutcliffe efficiency of 0.25 and 0.67 for daily and cumulative emissions, respectively), it failed to capture large N2O peaks in systems with spring manure application and incorporated cover crops (Nash-Sutcliffe 0). This discrepancy is attributed to the model's lack of representation of hypoxic conditions caused by the rapid decomposition of fresh residues and manure buried via tillage. These results strongly suggest that refining the simulation of oxygen consumption and diffusion in soil, as well as the generation and diffusion of N2O into and out of the soil are of critical importance to simulate N2O emissions accurately.
Importance
Increasing awareness of the environmental damage caused by some conventional farming practices, including soil degradation and pesticide contamination, along with concerns about the health risks of agrochemicals, has driven a shift toward organic farming methods. Organic agriculture is not, however, exempt from causing environmental damage. Among the concerns related to the input of organic nitrogen sources is the emission of nitrous oxide (N2O) from soils in organically fertilized fields. Nitrous oxide is the third most impactful long-lived greenhouse gas and its global warming potential is 298 times greater than that of carbon dioxide on a 100 year time scale. Assessing emissions of nitrous oxide (N2O) from agricultural systems is critical for effective monitoring and for developing strategies to reduce emissions.