An automated flux chamber system at the Farming Systems Research Unit.

Greenhouse Gas Emission Monitoring Project

Developing a continuous monitoring protocol for nitrous oxide and carbon dioxide emissions rate

Overview

In recent years, more pressure has been directed towards agriculture to find solutions to climate change. With farming being a major contributor to anthropogenic Greenhouse Gases (GHG) emissions, the potential to develop mitigation practices have become a major focus for agricultural researchers and farmers.

The challenges for agricultural systems to adapt to and mitigate climate change in the Southeast U.S. are unique. Specific climatic conditions and soil types impact the amount of greenhouse gases that are released by different farming systems, especially nitrous oxide (N2O) and carbon dioxide (CO2). For these reasons, any attempt to reduce GHG emissions from farming must be informed by precise and site-specific data.

Nitrous Oxide

One of the obstacles to collecting precise data about GHG emissions from agricultural land is the difficulty of measuring N2O and CO2 emitted cumulatively by soils. Nitrous oxide is particularly difficult to research, but extremely relevant when it comes to GHG emissions and agriculture. In fact, agriculture accounts for 78% of N2O in the US. The gas is typically released after rain events when the soils become saturated and anaerobic, for this to occur soil nitrogen needs to be present, either by nitrogen applied to agricultural fields in the form of fertilizers, manures or naturally available soil organic nitrogen. Existing technology to measure GHG emissions from soils only enables sampling at specific times, when researchers can physically collect gas samples on the field. Developing protocols to continuously collect data will allow for more precise models to be analyzed, and for variables such as differences in farming practices or soil structure to be more significant in comparative studies.

Project Goals

The goal of this project is to answer the question, “Can we automate nitrous oxide and other greenhouse gas sampling?”

Dr. Alex Woodley, Assistant Professor in the North Carolina State University Department of Crop and Soil Sciences, is leading a team of scientists in developing research protocols that allow for continuous monitoring of GHG emissions. The Farming Systems Research Unit at CEFS’ Field Research, Education, and Outreach Facility located at Cherry Research Farm in Goldsboro, N.C. is one of the sites where these protocols and technologies are being developed and tested. This project will guide future GHG studies on data collection methods and timing.

Project Design

Sample collection is performed by utilizing the LI-8100A Automated Soil Gas Flux System. The system works similarly to a more traditional static flux chamber, an established research protocol to collect samples by trapping gases emitted from the soil surface. The main difference is that by using an automated system, precise data can be collected at discrete intervals of time. This is particularly important during and after a rain event, when N2O emissions are highest. The use of automatic chambers can also inform researchers in real time about peaks in flux of GHG emissions. This is extremely important for  other researchers that are interested in other areas of study that are linked to GHG emissions from soils.

Dr. Woodley notes the advantages the Cherry Research Farm fields have over most other research plots. Because the fields have been under the same style of management for 20 years, this study can show the results those management styles have on land over a long period of time. The systems under comparison at the Farming Systems Research Unit are four management systems: Best Management Practices (BMP) in a conventional cash cropping system (BMP), organic cropping system, conventional agronomic crops with no-till, and conventional agronomic crops with tillage.

The large acreage also yields practical data for farmers, demonstrating what happens on realistically sized fields. Even production challenges at Cherry Research Farm are proving to be a novel advantage. The research site is in a floodplain and has flooded twice in the past five years after extremely powerful hurricanes. Data from these years can show farmers how different farming systems respond to adverse conditions which are common in the Southeastern United States, and are becoming more intense because of climate change.

Results

Preliminary results from the experiment show an extremely detailed temporal resolution, and demonstrate that the use of traditional static chamber protocols underestimates the amount of N2O released by the systems. The analysis demonstrated that poorly drained, saturated soils or excess fertilizer application lead to higher emissions of this GHG.

 Preliminary results from 2018, show N2O emission events from 4 positions in a no-till long-term plot at CEFS . This data shows that emissions events are driven by rain events (top axis) when soils become saturated and how pre-plant nitrogen fertilization induced emissions (Day 125-145).

Preliminary results from 2018, show N2O emission events from 4 positions in a no-till long-term plot at CEFS. This data shows that emissions events are driven by rain events (top axis) when soils become saturated and how pre-plant nitrogen fertilization induced emissions (Day 125-145).

Policy decisions can be informed by this study. Measuring GHG emissions on both conventional and organic fields can advise regulations, and inform how – for example –  to distribute subsidies for farms that implement sustainable farming practices. Dr. Woodley believes the research conducted at CEFS’ Field Research, Education, and Outreach Facility will be key for county, state, or even Southeast regional policy decisions.

Dr. Shuijin Hu is Adjunct and Associate Faculty in Plant and Microbial Pathology at NC State University. His study focuses on plant-microbial interactions and how soil microorganisms mediate plant and ecosystem responses to elevated atmospheric CO2, O3 and N inputs. Knowing exactly when peak flux of GHG emission takes place provides essential information to Dr. Hu’s team. By looking at the fluxes of N2O the team can identify at what time of day or when during the season to take microbial samples. The goal of the study is to identify what microbes contribute to the N2O release and what changes occur within the microbial communities.