Relationships of Nitrous Oxide Emissions to Fertilizer Nitrogen Recovery Efficiencies in Rain-fed Corn Systems: Research Foundation Building


01 Sep 2015

Project Description

Nitrous oxide (N2O) emissions from corn production systems are a large societal concern because so much of the N fertilizer applied to crop production in the United States is applied to corn, and because agriculture alone accounts for the majority of N2O emissions from all sources. The IPCC (2006) has estimated that an average of approximately 1.0% of the N fertilizer applied is lost as N2O, but we know from our own studies in rain-fed corn production that estimated emissions can sometimes exceed the equivalent of 5% of the N in the N fertilizers applied (e.g. Omonode et al., 2010).

Over the years of scientific monitoring of N2O emissions, the predominant reporting method has been to quantify episodic and/or cumulative growing season N2O emissions per unit land area. Later refereed publications included acknowledgement of the importance of reporting yield-scaled N2O emissions, but not until relatively recently has there been a plea to focus on emissions within the context of actual N use efficiencies (e.g. Snyder et al., 2014). The recent meta-analysis by Decock (2014) highlighted the low proportion of past N2O emission studies that included critical information on treatment effects on crop N export (let alone any mention of crop N uptake).

Unfortunately, very few greenhouse gas researchers in field crop systems have measured more than grain yield in their evaluations of crop response to N management. While grain yield responses to N fertilizer –especially in experiments were a zero N rate is included – permit calculation of an overall N use efficiency (NUE), they don’t account for the actual N uptake by plants. Determination of whole-plant biomass at maturity followed by grinding and plant-component N concentration measurements are the only pathway to calculating the overall gain in whole-plant N uptake (NU) for a particular N management system comprising a specific N source, N rate (versus a zero N control), N timing, and N placement combination. The difference in whole plant N at harvest is characterized, relative to the control N treatment, as N recovery efficiency (NRE). The ultimate N efficiency parameter, therefore, that means the most to understanding the production system context of fertilizer N fate and associated N2O emissions is NRE and not simply NUE alone.

Fertilizer industry associations such as IPNI and TFI have been strong proponents of the 4R’s (source, rate time and place) with respect to N management for many years. Further advances in promotion of sustainable nutrient practices are being discussed with other industry and university partners associated with the Field to Market (FTM) efforts. Sustainability of a particular N management practice, for example, can be quantified based on online resources like the “FTM Fieldprint Calculator for N2O” as long as there is a valid data base supporting those sustainability assessments in different environments and production systems. In a separate proposal, we seek to complete a review of existing knowledge about the relationships between whole-plant N recovery in corn and N2O emissions by November 20, 2015 based primarily on data already gathered in Colorado and Indiana.

The overall data base on corn whole-plant N uptake related to N2O emissions is especially weak in the rainfed corn production systems. Individual year-to-year variability in precipitation quantities and intensities following N fertilizer applications have huge impacts on the N lost as N2 or N2O to the atmosphere and the NO3- lost to leaching. In this proposal, we propose to take advantage of ongoing trials at Purdue University that are already supported by to gather both N2O and whole-plant N uptake data by corn treatments at maturity. These trials include those on intentional late-split N timing being supported by the 4R Nutrient Stewardship program, Pioneer Hybrid, and the Indiana Corn Marketing Council, as well as the long-term tillage plots (now 40 years old) that have been maintained at Purdue by a small amount of USDA support. In Indiana, we hope that this new project will enable us collect the complementary whole-plant N data and the N2O emission data from an additional 200 or more corn N management plots over the 2015 and 2016 field seasons.

  1. Analyze corn stover and grain N concentrations from whole-plant biomass samples taken at the R6 stage in ongoing Indiana studies involving N source (UAN and NH3 with and without nitrification inhibitors), N rate (from a 0 N control to as much as 240 pounds N/acre), and tillage system interactions with N losses.
  2. Expand the N timing research already underway in Purdue’s 4R Nutrient Stewardship research (2015-2017) to include intensive sampling of both growing-season N2O emissions as well as whole-plant N uptake at maturity in our late-season supplemental N experiments (where pre-plant or standard sidedress of 75-80% of the intended N rate is followed by a late-stage V12-V14 sidedress application of the remaining 20-25% of total N).

Primary Methodology:
During the field seasons of 2015 and 2016, we will accumulate new N2O emissions data, together with whole-plant N uptake data at maturity, in Indiana corn experiments involving N management variables such as N fertilizer timing (e.g. late-split N application at multiple total N rates in experiments established with 4R Nutrient Stewardship, Pioneer Hybrid, and Indiana Corn Marketing Council financial support), long-term tillage systems relying on side-dress UAN with and without a nitrification inhibitor (40-year old experiment at West Lafayette), and N rate/timing and nitrification inhibitors (e.g. Global Maize study funded by IPNI).

These studies will follow the methodologies for N2O emissions already utilized in our previous research (Burzaco et al., 2013; Omonode et al., 2010, 2015) except that we will be sampling more intensively. We have learned that bi-weekly sampling for N2O emissions, particularly in the first 6 weeks following N applications, is superior to once-per-week sampling in better characterizing the cumulative season N2O emissions from corn N management systems.

These studies will also follow the whole-plant corn N determination methods that we have reported on extensively in our corn physiology studies (e.g. in papers by Ciampitti and Vyn).

These studies will also characterize soil nitrate and ammonium levels to depths of 0-12” and 12-24” following N applications (during the intensive N2O emission measurement period) and at physiological maturity. The late-season N will be especially helpful to estimate potential leaching losses from the various N management systems.

  1. Quarterly progress reports will be distributed to all funding partners.
  2. By March 1, 2017, we will have submitted two publications for refereed publication on the topics of N2O emission patterns with variable corn NU and NRE resulting from recent Indiana experiments involving at least 2 years of intensive greenhouse gas, soil N, and plant N measurements following treatment applications involving N source, N rate, nitrification inhibitor presence, timing and/or tillage variables.
  3. Both investigators are expected to make oral and poster presentations in 2015 to 2017 to relevant science and industry sponsored meetings such as the Annual Meetings of the American Society of Agronomy, North-Central Extension-Industry Soil Fertility Conference, state-level CCA Conferences, and perhaps at a future 4R Nutrient Stewardship Summit (of course some of these events will depend on invitations by the respective program organizing committees).
  4. By June 30, 2017, all data collected with this project’s funding will be placed in a designated data repository.

Partial List of Background References:
Burzaco, J.P., D.R. Smith, and T.J. Vyn. 2013. Nitrous oxide emissions in Midwest US maize production vary widely with band-injected N fertilizer rates, timing and nitrapyrin presence. Environ. Res. Lett. 8:1-11.
Burzaco, Juan P., Ignacio A. Ciampitti, and Tony J. Vyn. 2014. Nitrapyrin impacts on maize yield and nitrogen use efficiency with spring-applied nitrogen: Field Studies vs. Meta- Analysis Comparison. Agron. J. 106:753–760; doi:10.2134/agronj2013.0043.
Decock, C. 2014. Mitigatin nitrous oxide emissions from corn cropping systems in the Midwestern U.S.: Potential and data gaps. Environ. Sci. Technol. 48: 4247-4256.
Hernandez-Ramirez, G., S.M. Brouder, D.R. Smith, and G.E. Van Scoyoc. 2009. Nitrous oxide production in an Eastern Corn Belt soil: Sources and redox range. Soil Sci. Soc. Am. J. 73:1182-1191.
Hernandez-Ramirez, G., S.M. Brouder, D.R. Smith, and G.E. Van Scoyoc. 2011. Nitrogen partitioning and utilization in corn cropping systems: Rotation, N source and N timing. Eur. J. Agronomy 34: 190-195.
Halvorson, Ardell D., and Stephen J. Del Grosso. 2013. Nitrogen placement and source effects on nitrous oxide emissions and yields of irrigated corn. J. Environ. Qual. 42:312–322; doi:10.2134/jeq2012.0315.
IPCC: Intergovernmental Panel on Climate Change Guidelines for National Greenhouse Gas Inventories. Volume 4: Agriculture, Forestry and Other Land Use, Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from. Lime and Urea Application. 2006
Maharjan, Bijesh. Rodney T. Venterea, and Carl Rosen. 2014. Fertilizer and irrigation management effects on nitrous oxide emissions and nitrate leaching. Agron. J. 106:703–714; doi:10.2134/agronj2013.0179.
Omonode, R.A., A. Gál, D.R. Smith and T.J. Vyn*. 2010. Nitrous oxide fluxes in corn following three decades of tillage and rotation treatments. Soil Sci. Soc. Am. J. 75:
Omonode, R.A., P. Kovacs, and T.J. Vyn. 2015. Tillage and nitrogen rate effects on area and yield-scaled nitrous oxide emissions from pre-plant anhydrous ammonia. Agron. J. 107:605–614.
Venterea, Rodney T., Bijesh Maharjan, and Michael S. Dolan. 2011. Fertilizer source and tillage effects on yield-scaled nitrous oxide emissions in a corn cropping system. J. Environ. Qual. 40:1521–1531. doi:10.2134/jeq2011.0039.
Snyder, C.S., E.A. Davidson, P. Smith, and R.T. Venterea. 2014. Agriculture: Sustainable crop and animal production to help mitigate nitrous oxide losses. Current Opinion in Environmental Sustainability. 9-10: 46-54.