Studying agronomic effects of cover cropping and its effect on greenhouse gas emissions

The Texas High Plains (THP) region is one of the largest upland cotton-producing regions in the world. Conservation management practices such as no-tillage and cover crops have been used to reduce wind erosion on the THP but also to help mitigate and reduce greenhouse gas (GHG) emissions from soil.

There was however a need for more information on the effects of these practices within the first few years of implementation, especially in semi-arid systems under agricultural production. This led Dr Katie Lewis to start a study* at Texas A&M AgriLife Research in Lubbock, Texas in 2015 with graduate student, Mark McDonald.

Cover cropping and its agronomic effects and impact on Co2 and N2O emissions

“The information from the research would allow us to make better recommendations to producers in the THP region regarding best practices for soil management to maintain agronomic production while mitigating their environmental impact,” says McDonald

The specific objectives of this study were threefold. First, to determine the effects of cover crops/no-tillage and altered nitrogen application timing on agronomic production and nitrogen use efficiency of a continuous cotton cropping system. Second, to determine the differential effects of these implemented treatments on the production of GHG (CO2 and N2O) emissions and the carbon balance of the system.

Thirdly, the study aimed to determine whether the implementation of these treatments would alter the soil biogeochemistry, increasing N2O mitigation potential of semi-arid agricultural systems.

Our analyzers provide key technological functions to suit research objectives

The ability of Gasmet analyzers to simultaneously measure soil surface emissions of multiple GHG emissions and ammonia in real-time played a large part in the researchers’ decision to use the devices in the gas/flux analysis research.

“Being able to measure gas concentrations and calculate flux rates with a large number of data points increased our confidence in the rate of CO2 and N2O production, and also when observing small but significant consumption of N2O at the soil surface,” says McDonald.

The ability to run our analyzer for several hours in the field and monitor the health of the machine and the validity of measurements in real-time gave the researchers the confidence to expand their gas-sampling program to other research projects.

The portability of the Gasmet DX4040 (predecessor of GT5000 Terra) was also a big advantage — allowing a single person to conduct measurements at two locations in a single week.

“This strengthened our research by adding another site for the evaluation of conservation practice and nitrogen timing effects on greenhouse gas emissions and agronomic productivity while also maintaining a consistent measurement schedule,” says McDonald.

Gasmet portable gas analyzer offers insights on production of GHG from soil surface

The research conducted using the Gasmet analyzer has revealed interesting information about the production of GHG emissions from the soil surface of a semi-arid agricultural production system.

The capability of agricultural soils to consume N2O was determined from the surface-emission measurements. The consumption of N2O represents a potential GHG mitigation effect based on the timing of N fertilizer application, with the net consumption of N2O being determined for the control treatment where inorganic-N was only applied with irrigation, the study revealed.

“Conservation farming practices outperformed the more common practices in terms of GHG mitigation (CO2 production mitigation, no increase in N2O emissions) while also not resulting in a reduction in agronomic productivity within this study,” sums up McDonald.

Key findings on GHG emissions from agricultural production in the THP region

From the initial study, it was determined that gross emissions of CO2 were greater where a wheat cover crop was grown, however, the consumption of CO2 by the wheat cover crop over the winter was greater than the increase in emissions between the cover cropped and non-cover cropped treatments.**

This indicates the potential for carbon sequestration in the soil with a wheat cover crop, but the true amount of carbon sequestration the wheat cover can provide is yet unknown.

It was also noted that the choice of tillage system has little effect on the production of nitrous oxide (N2O), which is beneficial for this region. However, it was determined that the timing of the N fertilizer application significantly impacted the production of N2O within the first two years of implementation.***

Although the research conducted so far has specifically focused on the first few years of implementation of conservation practices, it is predicted that the effect of GHG mitigation with conservation farming practices will further improve with the maturation of conservation systems.

*This research was conducted with funding through the Texas A&M AgriLife Air Quality Initiative and the Texas A&M AgriLife Strategic Initiative Assistantship. In addition, field locations were managed by Dr. Katie Lewis at Texas A&M AgriLife Research Lubbock and Dr. Paul DeLaune at Texas A&M AgriLife Research Vernon. Lab work was conducted under the guidance of Dr. Terry Gentry at Texas A&M University and Dr. Katie Lewis.
**This research was published in AIMS Agriculture and Food in March 2019: “Carbon dioxide mitigation potential of conservation agriculture in a semi-arid agricultural region” doi: 10.3934/agrfood.2019.1.206
***This research was published in Frontiers in Environmental Science in November 2021: “Nitrous Oxide Consumption Potential in a Semi-Arid Agricultural System: Effects of Conservation Soil Management and Nitrogen Timing on nosZ Mediated N2O Consumption” doi: 10.3389/fenvs.2021.702806

Greenhouse gas flux measurements

The measurement of GHGs from soil represents an important part of climate change research. GHGs, such as Carbon Dioxide (CO2), Methane (CH4) and Nitrous Oxide (N2O), released from soils into the atmosphere are primarily biogenic by origin.

Learn more about our solution for measuring greenhouse gases from soil

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