1a. Objectives (from AD-416):
The fertilizer industry and the USDA-Agricultural Research Service's (USDA-ARS) GRACEnet project need scientifically sound N2O emissions data from field research plots treated with various N sources across the U.S. The USDA-ARS GRACEnet cross location project has (1) a research network in place; (2) established cross location protocols for greenhouse gas sampling; (3) the facilities and personnel; and (4) the initial instrumentation required to expand its collection of this type of data. GRACEnet objective 2 includes the collection of CO2, N2O and CH4 greenhouse gas data, in addition to soil carbon sequestration. This research project will evaluate the effects of controlled release and stabilized nitrogen sources on nitrous oxide emissions in rainfed and irrigated cropping systems at several ARS research locations compared with the commonly used urea and urea-ammonium nitrate fertilizer sources.
1b. Approach (from AD-416):
Nitrogen source studies will be conducted at five ARS locations (Fort Collins, Colorado; Ames, Iowa; St. Paul, Montana; Pullman, Washington; and Auburn, Alabama) to collect greenhouse gas emissions data from corn, cotton, wheat, and potato cropping systems (varies with location). Several N fertilizer sources (a controlled release polymer-coated urea (ESN); a stabilized urea source, SuperU or UAN treated with AgrotainPlus; UAN and/or Urea as conventional sources) will be applied as a minimum to a cropping system at each location. Except for the irrigated Fort Collins site and one irrigated site at St. Paul, all sites are rainfed cropping systems, with either conventional tillage or no-tillage management practices, or both. Nitrogen rates at each location will include at least a near optimal N rate (for greenhouse gas data collection) for the crop and cropping system. The N sources will be applied using normal farming practices at each location. Nitrous oxide emissions (and possibly CO2 and CH4 emissions) from each N source treatment and a check (zero fertilizer N applied) treatment will be monitored several times each week during the growing season. Methods used for greenhouse gas measurements will follow those established for the ARS GRACEnet program. Crop yield data, needed soil water and temperature data, and other necessary data needed to interpret the greenhouse gas emissions results will be collected. A scientifically sound experimental design with a minimum of 3 replications will be used at each location.
3. Progress Report:
Progress on this project contributes directly to Sub-objective 3b “Determine biogeochemical dynamics of Soil Carbon (C) and Nitorgen (N) including nitrous oxide flux as influenced by agroecosystem drivers (e.g., soil, topography, micro-climate, organisms, management)” of the parent project. Limited information is available on the effects of nitrogen fertilizer sources on greenhouse gas emissions from cropping systems. Our project objective is to evaluate the effects of fast and slow release fertilizer nitrogen sources on emission of nitrous oxide, a greenhouse gas, from wheat grown in the Palouse region of eastern Washington. The fertilizers tested were ESN and SuperU (slow release fertilizers) and Urea (a fast release fertilizer). The slow release fertilizers showed potential for reducing nitrous oxide emissions in spring and winter wheat. For example, nitrous oxide emissions from winter wheat fertilized with a fast release fertilizer were higher than from wheat fertilized with slow release fertilizer. In contrast, nitrous oxide emissions were lowest from winter wheat that received no fertilizer. Slow release fertilizers have been shown to reduce nitrous oxide emissions in irrigated systems, but this is one of the first studies to show slow release fertilizers reduce emissions from dryland cropping systems.