2012 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.
Experiments were conducted to evaluate the agronomic performance and nitrous oxide emissions of different forms and rates of nitrogen fertilizers. Combined results across the three years of the experiment conducted in Ames, Iowa, on 16 different forms and rates of nitrogen in both continuous corn and corn-soybean production systems. There were differences among treatments; however, the most consistent treatment was the SuperU applied as a 150 lb A-1 preplant or as 50 lb A-1 preplant and 100 lb A-1 sidedress and urea ammonia nitrate (UAN) with a nitrogen stabilizer added to both the 50 lb A-1 preplant and 100 lb A-1 sidedress nitrogen applications. In these treatments there was increased leaf chlorophyll content along with a greater duration of green leaf area during the grain-filling period compared to the responses in the other forms. The result of this change was a larger weight per 100 seed. The effect of stabilized forms of nitrogen has a positive physiological impact on corn and this increased the efficiency of grain development. The stabilized forms of nitrogen did not reduce the amounts of nitrous oxide emissions because of the occurrence of wet soil conditions during the late summer; however, the increase in agronomic efficiency in nitrogen use outweighed the loss of nitrous oxide. Understanding the effects of forms of nitrogen will be enhanced by focusing on the physiological processes along with the yield components. Improvement of nitrogen-use efficiency by corn production would decrease the potential for nitrogen loss into the environment.