Chapter 15. COMET2.0-Decision Support System for Agricultural Greenhouse Gas Accounting

Abstract

Improved agricultural practices have a significant potential to mitigate greenhouse gas (GHG) emissions. A key issue for implementing mitigation options is quantifying emissions practically and cost effectively. Web-based systems using process-based models provide a promising approach.

COMET2.0 is a further development of the web-based COMET-VR system with an expanded set of crop management systems, inclusion of orchard and vineyards, new agroforestry options, and a nitrous oxide (N2O) emissions estimator, using the Century and DAYCENT dynamic ecosystem models.

Compared to empirical emission factor models, COMET2.0 accounted for more of the between site variation in soil C changes following no-till adoption in Corn Belt and Great Plains experiment sites. Predicted N2O emission rates, as a function of application rate, timing (spring vs. fall), and use of nitrification inhibitors, were consistent with observations in the literature. Carbon dynamics for orchard and agroforestry compared well with field measurements but limited availability of data poses a challenge for a fuller validation of these systems.

Advantages of a practiced-based approach, using dynamic process-based models include integration of interacting processes and local conditions for more accurate and complete GHG accounting. Web-based systems, designed for non-experts, allow land managers and others to evaluate trade-offs and select mitigation options for their particular conditions. Experimental networks such as GRACEnet will play an important role in improving decision support tools for implementation of agricultural GHG mitigation.