Combining Lysimetric and Gaseous Nitrogen Loss Measurements for Assessment of Agroecosystem Sustainability.

Losses of reactive nitrogen (N) from agroecosystems negatively effect air and water quality, and greenhouse gas (GHG) emissions, ultimately degrading our environment. The nature of environmental degradation is dependent on the form and amount of N released, whether it is via ammonia (NH₃) volatilization, nitrous oxide (N₂O) emission, or nitrate (NO₃^-) leaching. Strategies such as diversifying annual crop rotations and use of cover crops are recommended to mimic natural ecosystems and are postulated to increase agricultural resilience to climate change, soil quality and provision of soil ecosystem services. However, diverse cropping systems could increase soil mineral N levels and lead to greater leaching and/or N₂O emissions; which raises the questions: (i) are diverse cropping systems actually beneficial for air and water quality? (ii) what are the trade-offs between soil, water, and air quality upon implementing a diverse cropping rotation? We are addressing these questions using a newly-funded soil lysimeter infrastructure by quantifying the role of agri-food practices on the amount, fate, and pathway of nitrogenous contaminant loss, and linking contaminant loss to soil microbial community structure (an indicator of soil health). The infrastructure is comprised of high-precision weighing lysimeters, nine for each of two soil types (silt loam, sandy loam), instrumented with automatic gas chambers coupled to a trace gas analyzer. An overview of the experimental site and planned experiments will be given. Preliminary results characterizing the variability within soil type will be presented and results from the two contrasting soil types will be discussed.