MITIGATING NITROGEN LOSSES IN SUSTAINABLE AGRICULTURE

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: NEW
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1018808
• Project No.: NC02762
• Project Start Date: Feb 13, 2019
• Project End Date: Sep 30, 2023

Project Director
Woodley, AL, LA.

Recipient Organization
NORTH CAROLINA STATE UNIV
(N/A)
RALEIGH,NC 27695

Performing Department
Crop & Soil Sciences

Non Technical Summary
Agriculture practices, particularly soil management (fertilizer and manure applications) account for 74% of the nitrous oxide (N2O) emitted in the USA. Nitrous oxide is a potent greenhouse gas, 300 times more effective than CO2. Nitrous oxide is produces mainly through a processes called denitrification, which convert nitrate nitrogen to nitrous oxide or N2 gas (atmospheric nitrogen). Denitrification occurs typically after large rain events when the soil stays saturated for several days at a time. Several countries around the world are beginning to create N2O emission factors for different agricultural management practices. An example of an emission factor would be to what degree does injecting manure versus broadcast applying it reduces or increases N2O emissions or what increase in N2O emissions do you observe when you apply (x) amount of nitrogen fertilizer above what the crop requires. These emission factors will be important in regulation and policy making and a similar requirements to quantify these emissions may occur in the USA in the near future. The most common way to measure N2O in the field is called the static chamber method. Here a chamber is placed in the field and left for 30 minutes and air sampled from within the chamber 4 times. The air is analyzed for N2O and the daily flux of N2O is calculated and eventually can be interpolated for the whole growing season, linking together regular samplings during the growing season. The concern with static chambers is that when you sample you don't know if you have missed a large emission event or if you measure large emissions you don't know if that is that is the highest part of the flux emission. This could lead to over or underestimation of N2O emission estimates. It is critical that we have measurements representative of field conditions for emission factor estimates, as well when these results are used in large climate change models. To address these concerns we are developing a method of continuous N2O measurements using automated chambers that sample the soil every 150 minutes rather than once or twice a week. We run the air into a trailer that has a N2O analyzer, which produces real-time results transmitted back to us at North Carolina State University. We are going to compare these results the static chamber method to determine if there is significant over or under estimation of emissions. In addition, we are going to develop a method of incorporating the continuous measurements into a static chamber study, this would only require only a limited number of auto-chambers. The chambers would be used to guide researchers on when the main N2O flux events is occurring and allow them to modify the static chamber calculations, making them more accurate to real world conditions.Using these newly developed methods we are going to evaluate different best management strategies used by farmers to mitigate nitrogen losses in the field. Anticipated evaluations will include comparing different organic amendment sources, legume cover crops and the use of enhanced efficiency nitrogen fertilizers. Enhanced efficiency fertilizers tend to slow the rate of nitrogen release into the soil either through physical barriers or modifying the nitrogen cycle. Slowing the release helps prevent nitrogen loss to the atmosphere through ammonia volatilization and could potentially reduce N2O emissions. In addition to the N2O measurements, we will measure ammonia volatilization and estimate nitrate leaching. By tracking the main nitrogen loss pathways as well was how much nitrogen is taken up by the plant we are able to create a nitrogen balance. This is used to determine nitrogen use efficiency. A higher nitrogen use efficiency means more of the nitrogen that is applied to being captured by the plant, rather than lost from the system. This is not only important economically to the farmer but also means the system is more sustainable from an air quality, greenhouse gas and water quality perspective.

Animal Health Component

0%

Research Effort Categories

Basic

10%

Applied

50%

Developmental

40%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	0110	1000	75%
102	0499	1000	25%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
0110 - Soil; 0499 - Atmosphere, general/other;

Field Of Science
1000 - Biochemistry and biophysics;

Keywords

sustainable agriculture

nitrous oxide emissions

nitrogen management

nitrogen use efficiency

ammonia volatilization

Goals / Objectives
The major goal of this project is to improve nitrogen (N) use efficiency of various N inputs (inorganic/organic fertilizers and cover crops) in sustainable and organic farming systems by reducing ammonia volatilization, nitrous oxide emissions and nitrate leaching and increasing plant N uptake. In addition, to fully understanding the efficacy of best management practices on reducing N losses we need to accurately quantify the temporal and spatial N loss dynamics, through the development of innovative measurement techniques. The objectives to accomplish these goals are as follows: Develop a continuous monitoring system for nitrous oxide emissions providing high temporal resolution flux events and compare this to the traditional approach for quantifying N2O emissions (static chambers).Evaluate various best management practices for improved mitigation of N losses, including enhanced efficiency fertilizers, anaerobic digestate by-products as compared to untreated manure and the interaction between soil fertility and legume based cover crops

Project Methods
Methods uses in Objective 1: The most commonly used method for measuring N2O emissions is using the static chamber method. Static chambers involve placing a collar buried in the soil and when sampling occurred a chamber lid is placed over the collar. To sample the chamber gas is extracted using syringes and 130 mL of air is injected into evacuated container, air samples are taken at 0, 10, 20 and 30 min. The samples are analyzed for N2O through an electron capture detector within a gas chromatograph. The time series of samples allows for a flux rate estimating using linear regression. Cumulative growing season N2O emissions were calculated using the Trapezoid rule with linear interpolation between consecutive sampling periods. The main constraint with this method of sampling is poor temporal resolution. Using the GRACEnet protocol N2O is supposed to be sampled 12-24hrs after sufficiently large rain events to capture N2O emissions. To address the low temporal resolution we are developing a method that continuously measures N2O emissions in the field. Continuous measurement is achieved using an auto-chamber developed by LiCor. A PVC collar is buried in the field 20 cm and the auto-chamber pivots onto this ring for 25-30 min, while sealed, air is being pulled into an air conditioned chamber at a rate 2.96 LPM. At the same time supply air is being pumped back into the chamber at the same rate to ensure pressure differentials are not occurring. There is a 5 minute ambient flush between each chamber and ambient sampling. Adruino ® microprocessor used to control the sampling rotation. The N2O is analyzed on a Teledyne 320U N2O analyzer (Gas Filter Correlation) and CO2 is measured on a LiCor 840A analyzer. The chambers are assumed as continuous stirred reactors and at steady state, flux equals sample flow multiplied by the difference in concentration from ambient divided by chamber area.We aim to compare methods and determine the significance of low temporal resolution between sampling times using the static chamber methods. We also want to develop an integration of the two methods. The advantages of static chambers is that they are easy to make, deploy and sample and they are cheap to create. They can be used on field sites with many treatments. Whereas the auto-chambers may be cost prohibitive to deploy many in the field. We want to use a limited number of chambers within each replication (block) as background guidance for static chamber calculations. The auto-chambers can provide us with an idea of where on the flux peak the sampling occurred using that static chambers and we can modify our extrapolation through either modifying the start time of the flux and continuing the linear interpolation or placing the static chamber measurements on a derived peak and exponential decay model determined by the continuous measurements.Methods uses in Objective 2: The method development as outlined in objective 1 will occur nested within experiments that evaluate different nitrogen sources and best management practices aimed at mitigating nitrogen losses from the field and increase nitrogen use efficiency in crop uptake. The field site will be a randomized complete block design with 4 replications of each treatments. Anticipated treatments are enhanced efficiency fertilizers that use urease and nitrification inhibitors to mitigate N losses through N2O emissions and ammonia volatilization. In addition application method is an important management strategy for mitigating loss via ammonia volatilization and in the North Carolina Urea Ammonium Nitrate is still mainly applied via surface streaming, a method shown to increase ammonia losses as compare to injection. In addition nitrate leaching estimates will be determined using seasonal deep soil core nitrate extractions. Ammonia volatilization will be measured using passive samplers initially, which entails covering the surface of the soil with a chamber and having acid embedded filter paper within the chamber. Any free ammonia in the air will be captured by the acid paper. The acid paper will be changed daily and rinsed in the lab and analyzed for ammonium through a flow injection analyzer. If additional grant funding is acquired for ammonia volatilization then the construction of wind-tunnels will be considered. These have the advantage of being more representative of field conditions by simulating the movement of wind over the surface. The air is collected through acid traps and any free ammonia will be captured as ammonium and analyzed using the same method as the passive ammonia samplers. Frequent plant and soil tests taken during the growing season will be used to follow nitrogen dynamics. By measuring nitrogen uptake in the crop, N2O emissions, ammonia volatilization and an estimate of nitrate leaching we can develop a fairly comprehensive nitrogen balance. This balance is key for our determination on the effectiveness of various best management practices. This template can be used for a variety of nitrogen management studies and the exact nature of what will be studied will be dependent on grant availability, grower needs and issues highlighted by commodity groups.

Progress 02/13/19 to 09/30/19

Outputs
Target Audience:The target audience is the scientific community, organic and conventional agricultural producers and potentially policy makers.In addition, classes taught incorporate this research, with a target audience of students in sustainable agricultural majors. In the 2019 reporting period. Research relevant to this outlined work was disseminated at the following national and regional meetings. National: Pagan-Caballero, I., A.L. Woodley, W. Robarge. Ammonia Volatilization by an Inorganic-Organic Hybrid Nitrogen Product Used As a Slow Release Fertilizer Corn in North Carolina As Compared to UAN and Urea.ASA,CSSA,SSSA Meetings, San Antonio, TX Mathers, C., A.L. Woodley, J. Heitman, D. Osmond, W. Roper. (Linking Long-Term Corn Yield Stability and System Resilience to Agricultural Management Practices in North Carolina. ASA,CSSA,SSSA Meetings, San Antonio, TX Woodley, A.L., W. Robarge, C. Reberg-Horton, S. Hu.. Quantification of Nitrous-Oxide Emissions: Combining Semi-Continuous and Static Chamber Measurements. SSSA Meetings, San Diego, CA Robarge, W., A.L. Woodley. Metal-Binding Potential of Maleic-Itaconic Polymers Used in Enhanced Efficiency N-Fertilizers. SSSA Meetings, San Diego, CA Regional: Woodley, A.L. (2019, Feburary). What is soil health? Organic commodities and livestock conference. Raleigh, NC. Woodley, A.L. C.F. Drury, W. Calder, W. D. Reynolds and T. Oloya. (2019, January). Streaming Urea Ammonium Nitrate with or without Enhanced Efficiency. Soil Science Society of North Carolina, Raleigh, N.C. Extensions Documents: Woodley, A.L., L. Gatiboni, J. Heitman, A. Howard. 2019. Long-Term Tillage Effects on Corn and Soybean Yield in the Piedmont . Soil Facts. NCSU ExtensionCrozier,C.R., S.C. Reberg-Horton and A. L. Woodley. 2019. Certified Organic Farm Management Alternatives. 2020 N.C. Agricultural Chemicals Manual Teaching in 2019: SSC 427 - Biological Approaches to Sustainable Soil Systems SSC 720 - SSC 720 Soil and Plant Analysis Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Trained an undergraduate student fromNSF Research Experience for Undergraduates (REU): Basic and Environmental Soil Science Training (BESST) with an ammonia volatilization and nitrous oxide experiment Myself and my research technicianattending greenhouse gas training event hosted by LICOR How have the results been disseminated to communities of interest? Preliminary results from the 2018-2019 field season have been presented at a national conference. What do you plan to do during the next reporting period to accomplish the goals? Continue the planned second year of the intensive soil monitoring study Continue the planned second year of the cover crop and N reduction sweet potato research Continue to establish collaboration efforts in Denmark and Canada Expand our measurement capabilities by having a controlled column system in lab to allow for rapid evaluation of GHG emissions from a range of management choices (i.e. cover cropping, bio-char) before trialing the field Secure additional funds through USDA-NIFA grant opportunities?related to soil carbon research

Impacts
What was accomplished under these goals? Recently, soils have caught the attention of the general public and climate science community as a potential mitigation tool for drawing down atmospheric CO2 into the soil through soil carbon sequestration. The magnitude of sequestration can vary dramatically based on region, climate and soil type. In the southeast U.S. the soils tend to be low in carbon due to the hot humid climate which rapidly decomposed carbon additions and coarse textured soils that offer limited protection to soil carbon. It is likely that carbon sequestration rates will be modest when using best management practices such as no-till and cover cropping which have seen more dramatic success in the mid-west and northern states. It is essential that we evaluate field management in terms of net greenhouse gas emission to determine if management is a net contributor or a mitigation tool for climate change. How farmers manage their nitrogen fertilization can be the tipping point between helping and hindering tackling climate change. Agricultural soil management account for 78% of anthropogenic induced nitrous oxide (N2O) emissions in the U.S as of 2019. Poorly managed nitrogen can cause N2O emissions at levels that can negate modest increases in soil carbon sequestration. Therefore, for any meaningful contribution of soils to drawing down CO2 to occur accurate accounting of N2O emissions must occur. However, N2O emissions are difficult to measure, vary widely by region, within field and temporally. The impact of this research is the improvement of how N2O is measured in the field using innovative methods to set a foundation for assessing various soil management climate solutions emerging in the research landscape. In 2019, we expanded the continuous monitoring experiment to 12 chambers located within long-term plots at the Center for Environmental farming systems. We tracked emissions from conventional managed till and no-till plots and organically managed field crops and hay+field crops over the growing season. We compared this continuous method to traditional static chambers and monitored other controlling variables like soil moisture, soil nitrate and soil temperature. Preliminary data processing suggests that the continuous monitoring captures more estimated losses than the traditional method which has implication for GHG inventories and policy decision making regarding support for GHG reductions. In addition to this field study, we conducted additional work examining legume nitrogen contributions to sweetpotato and determining the nitrogen reduction rate possible when using these cover crops. Nitrogen substitution away from inorganic nitrogen sources is another strategy to reduce energy requirement to grow crops as the generation of inorganic N is an energy intensive process. Energy consumption can be equated to CO2 equivalents and be incorporated into life cycle analyses of farming systems. The inorganic N reduction research is in the first year of a 2 year study.

Publications

• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Woodley, A.L., W. Robarge, C. Reberg-Horton, S. Hu. (2019, January). Quantification of Nitrous-Oxide Emissions: Combining Semi-Continuous and Static Chamber Measurements. SSSA Meetings, San Diego, CA
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Mathers, C., A.L. Woodley, J. Heitman, D. Osmond, W. Roper. (2019, November) Linking Long-Term Corn Yield Stability and System Resilience to Agricultural Management Practices in North Carolina. ASA,CSSA,SSSA Meetings, San Antonio, TX
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Markey, K.E., D.L. Osmond, J.L, Heitman, A.L. Woodley. (2019, November). The Effect of Cover Crops and Tillage on Soil Health Three Years After Implementation ASA,CSSA,SSSA Meetings, San Antonio, TX
• Type: Theses/Dissertations Status: Published Year Published: 2019 Citation: 3) Pagan-Caballero, I., A.L. Woodley, W. Robarge. (2019, November). Ammonia Volatilization by an Inorganic-Organic Hybrid Nitrogen Product Used As a Slow Release Fertilizer Corn in North Carolina As Compared to UAN and Urea.ASA,CSSA,SSSA Meetings, San Antonio, TX