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, Minnesota; 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. 5402-11000-008-00L: GRACEnet: An Assessment of Soil Carbon Sequestration and Greenhouse Gas Mitigation by Agricultural Management Cross Location Participants listed under 5402-11000-008-00L/411610: 3625-11000-004-00D/409178: Trace Gas Exchanges in Midwest Cropping Systems National Soil Tilth Research Laboratory (Ames, Iowa) 3640-12000-007-00D/410684: Farming Practices for the Northern Corn Belt to Protect Soil Resources, Support Biofuel Production and Reduce Global Warming Potential Soil and Water Management Research (St. Paul, Minnesota) 5348-11000-005-00D/414427: Quantifying and Predicting Emission of PM10 and Greenhouse Gases from Agricultural Soils Land Management and Water Conservation Research (Pullman, Washington) 5402-12130-008-00D/410759: Improving Soil and Nutrient Management Systems for Sustained Productivity and Environmental Quality Soil, Plant, Nutrient Research (Fort Collins, Colorado) 6420-12610-003-00D/410823: Conservation Systems Research for Improving Environmental Quality and Producer Profitability Soil Dynamics Research (Auburn, Alabama)
3. Progress Report:
This is a final report for project 5348-11000-006-01T which ended in April of 2013, and contributes to the ARS GRACEnet cross-location objective 4 of the inhouse project, "Develop agricultural PM10/PM2.5 and GHG mitigation strategies and management decision aids for Pacific Northwest cropping systems". Limited information is available on the effects of nitrogen fertilizer sources on greenhouse gas (carbon dioxide; nitrous oxide) emissions from rainfed cropping systems. Little information is available on how these controlled release and stabilized nitrogen fertilizers might affect nitrous oxide emissions from wheat cropping systems. Preliminary results from current studies indicate that these nitrogen sources may reduce nitrous oxide emissions. Enhanced nitrogen use efficiency by crops and reduced nitrous oxide emissions from using these fertilizer products would greatly benefit environmental quality. Our project objective is to evaluate the effects of controlled release and stabilized nitrogen sources on nitrous oxide emissions in rainfed wheat cropping systems. This study was conducted at the Palouse Conservation Field Station (PCFS) 1 mile northwest of Pullman, Washington, USA. The region has a semi-arid temperate climate with typical mean temperature of 27.8oC in August and -5.0 oC in January and rainfall of 530 mm per year (average from 1940 to 2005). The soil at the site is a Palouse silt loam classified as fine-silty, mixed, superactive, mesic Pachic Ultic Haploxerolls. Soil organic matter content of about 3.5%; pH of 5.6; and clay, silt, and sand content of 20, 59, and 21%, respectively. The cropping system is no-till winter wheat-pea rotation. For 3 years winter wheat was planted and the 4th year spring wheat was planted. The fertilizers tested were ESN®, (44% nitrogen) a polymer coated urea; SuperU® (46% nitrogen) urea containing urease inhibitors; Urea (46% nitrogen) and a no nitrogen applied treatment was included. The application rate was 100 lbs/ac for all crop years. The precipitation for the growing season was 470, 559, 432, and 635 mm for 2008, 2009, 2010 and 2011, respectively, the wettest year being the spring wheat planting year. This water increase over the normal 530 mm may affect nitrous oxide flux from the soil from different fertilizers. Cumulative growing season nitrous oxide emissions for spring wheat for each nitrogen source was lower than the 2008-2010 emissions from winter wheat which was expected. The enhanced efficiency fertilizers (polymer-coated, and urease inhibited) sources showed potential for reducing nitrous oxide emissions in no-till winter and spring wheat. An example for winter wheat shows Super U and urea with the highest nitrous oxide emissions approaching 45 g / ha, compared to ESN at 20 g / ha and the control emitting 5 g / ha. Slow release and coated urea based fertilizers have been shown to reduce nitrous oxide emissions in irrigated systems, however this is one of the first studies to show reduced emissions under dryland conditions in both winter wheat and spring wheat systems.