Location: Soil Management and Sugarbeet Research
Project Number: 3012-12210-001-009-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 21, 2021
End Date: Aug 31, 2025
Objective:
The first short-term objective is to assist ARS in assessing the greenhouse gas mitigation potential of enhanced efficiency fertilizers deployed in various cropping systems across the USA. The second long-term objective is to improve the nitrogen gas submodel in DayCent. These efforts will facilitate collaborative research between ARS and the Cooperator to continue simulation model development, testing, and application, to better predict current greenhouse gas emissions from agricultural soils, and quantify the effects of improved management practices on emissions, nutrient use efficiency, and crop yields.
Approach:
The DayCent ecosystem model is used to estimate soil GHG fluxes reported in national inventories compiled by EPA and USDA. ARS has collaborated with the Cooperator to develop, test, and apply DayCent. In addition to expertise, ARS provides vital observational data from the Agricultural Collaborative Research Outcomes System (AgCROS) while the Cooperator houses the hardware and software required to assemble model input data bases, execute simulations, and process model outputs. Enhanced efficiency fertilizers can reduce nitrous oxide (N2O) emissions and other nitrogen losses while maintaining or enhancing cop/forage yields. However, the amount of mitigation potential is uncertain if there is widespread use of these fertilizers. DayCent was recently extended to represent slow release fertilizers as well as formulations with urease and nitrification inhibitors. ARS will collaborate with the Cooperator to leverage existing infrastructure for the GHG inventory and conduct simulations of currently used and enhanced efficiency fertilizers for cropped and grazed systems across the country. Model outputs under business as unusual conditions will be compared with improved management scenarios to estimate the GHG and N loss mitigation that could be supplied by improved fertilizers alone and in combination with other practices such as reduced tillage intensity.
In addition to assessing mitigation potential using the current version of DayCent, ARS will collaborate with the Cooperator to improve how soil nitrogen dynamics are represented in the model. Specifically, the nitrification submodel will be enhanced. Nitrification is an important biochemical process that contributes to N2O emissions as well as producing nitrate which is vulnerable to losses from leaching and runoff and compromises water quality. Current representation of nitrification is simplified, and evidence suggests that more explicit representation of process reactions will improve soil nitrogen dynamics. Nitrification modeling equations developed by ARS will be integrated into the DayCent model and the enhanced version will be compared with observational data sets to evaluate overall model performance. Anticipated improvements will increase the accuracy of soil GHG emissions reported in national inventories as well as increase confidence in model estimated mitigation potentials.
