Nitrogen Faculty Workgroup

A portion of funding from the David and Lucile Packard Foundation helped to fund UC Davis faculty researchers who are studying nitrogen in a variety of forms.  The funding aimed to encourage institutional development and nitrogen-related scholarship on campus and to help build a diverse network of researchers. 

Much of the research is nearing its completion and faculty have submitted grant reports with some of their initial findings.  While journal articles and final results are still forthcoming, these reports will give some insight on the current nitrogen research happening around the UC Davis campus. 

Nitrogen faculty workgroup final reports

 Impacts of management and environmental conditions on the roles of different plant species play in altering nitrogen inputs, recycling, and retention. 

Principal Investigator: Valerie Eviner, Dept. of Plant Sciences

Executive Summary:

Conventional agricultural practices have decoupled N supply from plant demand, and have compromised and/or overwhelmed many natural ecosystem services, including: nutrient provision and retention, erosion control, water infiltration and storage, soil carbon storage and maintenance of biodiversity. The most effective way to provide multiple services is to restore the plant-soil interactions that naturally provide and retain nutrients, particularly by: rebuilding soil organic matter, increasing plant cover, increasing the diversity of plants to ensure high plant uptake and root C inputs (to fuel microbial immobilization and nutrient turnover) across the growing season, and fostering key plants that play important roles in providing key services. This study will investigate the potential for different plant types to restore these services to agricultural soils. 

California Nitroscapes: An environmental, social, and economic evaluation of the fate and consequences of excess nitrogen 

Principal Investigators:

  • Alissa Kendall, Dept. of Civil and Environmental Engineering
  • Benjamin Houlton, Dept. of Land Air, and Water Resources
  • Mike Springborn, Dept. of Environmental Science and Policy

Executive Summary:

This collaborative research project sought to examine the environmental, social, and economic impacts of excess N in California – tracking N from creation to fate, and toward its ultimate influence on regional-scale economies and environments. Our approach attempted to create strong linkages between innovative models of key N-cycle processes, life cycle analysis (LCA) methods, and environmental-economic assessments.  

 Inferring the effects of nitrogen management policies using a fully calibrated programming model of California agriculture

Principal Investigator: Pierre Merel, Dept. of Agricultural Resource Economics

Executive Summary: Our work addresses ex ante policy evaluation as it relates to nitrogen management in agriculture, in particular the reduction of nitrogen losses from field crops. We build a bio-economic model of crop production at the regional scale to predict the effects of nitrogen-related policies on agriculture and the environment. The model is calibrated against economic data on observed crop acreages and yields, as well as predetermined supply responses. In addition, crop-speci c production functions are calibrated to exogenous agronomic information on yield responses to nitrogen and irrigation. Environmental outcomes are tracked using the biophysical model DAYCENT.

The model is applied to the study of a nitrogen tax in Yolo County, California, intended to mitigate non-point source nitrogen pollution from eld crops. At low tax levels, the behavioral and environmental responses to the nitrogen tax appear to be largely due to the reduction in fertilizer use and irrigation on each crop. However, as the tax level increases, reductions in input intensities start to level out due to unfavorable yield e ects, and acreage reallocation among crops begins to play a sizable part in the total response. From a methodological standpoint, our study illustrates the need to accurately model input intensity adjustments in regional models of crop supply intended for agri-environmental policy analysis. From a policy standpoint, our study shows that sizable reductions in nitrogen
application, and attendant reductions in nitrogen losses, can be achieved at the regional scale at a moderate social cost. Overall, the induced reduction in nitrate leaching appears larger than the reduction in nitrous oxide emissions.

Investigating the influence of biochar on the soil nitrogen cycle, carbon sequestration, and stabilization with soil minerals

Principal Investigator: Sanjai J. Parikh, Dept. of Land, Air, and Water Resources

Executive Summary: 

Due to increased urbanization and population growth during the 20th and 21st centuries, the need for higher food production on smaller land areas has lead to a marked increased in the use of N fertilizers for agronomic production. The use of biochar, the byproduct of the pyrolysis of biomass in biofuel product, has received widespread attention as an agricultural amendment with the potential ability of reducing N leakage (increase N-fixation and decrease N2O emissions) while sequestering carbon (stabilize soil organic C and decrease CH4 emissions), improving soil fertility (increase cation retention), and increasing water retention in soil [1]. With the thrust for biochar use gathering steam, many in the agricultural field will soon be faced with evaluating if biochar application to their soil is prudent. Therefore, in order to assess the impacts of biochar soil amendments, on greenhouse gas (GHG) emissions and C and N sequestration in soil, our functional research objectives were to:

  1. Characterize the physical and chemical properties of biochar originating from various organic residue sources and pyrolysis condition;
  2. Examine the ability of biochar to influence soil N-cycles and C sequestration when applied to agricultural soils and under conditions favoring denitrification via lab incubation;
  3. Elucidate molecular-level interactions involved in the stabilization of biochar by soil minerals.