2013 Annual Report
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, CO; Ames, IA; St. Paul, MN; Pullman, WA; and Auburn, AL) 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.
Final analyses of the experiments conducted from 2008 through 2011 were completed to evaluate the effect of different forms of enhanced efficiency fertilizers on the nitrous oxide emissions and the agronomic responses. To quantify the agronomic responses, we measured plant biomass at the beginning of the grain-filling stage, yield, weight per 100 kernels, and leaf chlorophyll index, canopy reflectance, and leaf area index. The reflectance, leaf chlorophyll index, and leaf area index were measured repeatedly throughout the growing season. There was no effect of the use of enhanced efficiency fertilizers on plant biomass at the onset of the grain-filling period with the only effect between the use and no application of nitrogen fertilizers. There was an effect of the use of enhanced efficiency fertilizers on the final grain yield which was related to the change in the leaf chlorophyll index during grain-filling and the rate of canopy senescence. These two parameters could be estimated by remote sensing information and were consistent over the three years of the study when all treatment comparisons were made. The use of enhanced efficiency fertilizers decreased the nitrous oxide emissions during the initial period after application of the materials; however, over the total season enhanced efficiency fertilizers increased the total nitrous oxide emission because of the retention of nitrogen in the upper soil profile and the wet weather experienced during the late portion of the growing season induced nitrous oxide emissions. Losses of N2O to the atmosphere from fertilizer are offset by the advantage of using materials or management practices which increase the availability of nitrogen to the plant during the grain-filling period.