Animal production is part of a larger agricultural nutrient recycling system that includes soil, water, plants, animals and livestock excreta. When inefficient storage or utilization of nutrients occurs, parts of this cycle become overloaded. The U.S. Beef industry has made great strides in improving production efficiency with a significant emphasis on improving feed efficiency. Improved feed efficiency results in fewer excreted nutrients and volatile organic compounds (VOC) that impair environmental quality. Anabolic steroids are used to improve nutrient feed efficiency which increases nitrogen retention and reduces nitrogen excretion. This study was conducted to determine the methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O), odorous VOCs, ammonia (NH3), and hydrogen sulfide (H2S) production from beef cattle manure and urine when aggressive steroid implants strategies were used instead of moderate implant strategies.
What Did We Do?
Two groups of beef steers (60 animals per group) were implanted using two levels of implants (moderate or aggressive). This was replicated three times, twice with spring-born calves and once with fall-born calves, for a total of 360 animals used during the study. Both moderate and aggressive treatment groups received the same initial implant that contain 80 mg trenbolone acetate and 16 mg estradiol. At second implant, steers in the moderate group received an implant that contained 120 mg trenbolone acetate and 24 mg estradiol, while those in the aggressive group received an implant that contained 200 mg trenbolone acetate and 20 mg estradiol. Urine and feces samples were collected individually from 60 animals that received a moderate implant and 60 animals that received an aggressive implant at each of three sampling dates (Spring and Fall 2017 and Spring 2018). Within each treatment, fresh urine and feces from five animals were mixed together to make a composite sample slurry (2:1 ratio of manure:urine) and placed in a petri dish. There were seven composite mixtures for each treatment at each sampling date. Wind tunnels were used to pull air over the petri dishes. Ammonia, carbon dioxide, and nitrous oxide concentrations were measured using an Innova 1412 Photoacoustic Gas Analyzer. Hydrogen sulfide and methane were measured using a Thermo Fisher Scientific 450i and 55i, respectively. Gas measurements were taken a minimum of six times over 24- to 27-day sampling periods.
What Have We Learned?
Flux of ammonia, hydrogen sulfide, methane, nitrous oxide, and total aromatic volatile organic compounds were significantly lower when an aggressive implant strategy was used compared to a moderate implant strategy. However, the flux of total branched-chained volatile organic compounds from the manure increased when aggressive implants were used compared to moderate implants. Overall, this study suggests that air quality may be improved when an aggressive implant is used in beef feedlot animals.
Table 1. Overall average flux of compounds from manure (urine + feces) from beef feedlot cattle implanted with a moderatea or aggressiveb anabolic steroid.
Hydrogen Sulfide
Ammonia
Methane
Carbon Dioxide
Nitrous Oxide
Total Sulfidesc
Total SCFAd
Total BCFAe
Total Aromaticsf
µg m-2 min-1
——–mg m-2 min-1——–
Moderate
4.0±0.1
2489.7±53.0
117.9±4.0
8795±138
8.6±0.1
0.7±0.1
65.2±6.6
5.9±0.5
2.9±0.3
Aggressive
2.7±0.2
2186.4±46.2
104.0±3.8
8055±101
7.4±0.1
0.8±0.1
63.4±5.7
7.6±0.8
2.1±0.2
P-value
0.01
0.04
0.01
0.01
0.01
0.47
0.83
0.05
0.04
aModerate treatment = 120 mg trenbolone acetate and 24 mg estradiol at second implant; bAggressive treatment = 200 mg trenbolone acetate and 20 mg estradiol at second implant; cTotal sulfides = dimethyldisulfide and dimethyltrisulfide; dTotal straight-chained fatty acids (SCFA) = acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, and heptanoic acid; eTotal branch-chained fatty acids (BCFA) = isobutyric acid and isovaleric acid; fTotal aromatics = phenol, 4-methylphenol, 4-ethylphenol, indole, and skatole
Future Plans Urine and fecal samples are being evaluated to determine the concentration of steroid residues in the livestock waste and the nutrient content (nitrogen, phosphorus, potassium and sulfur) of the urine and feces.
Authors
mindy.spiehs@ars.usda.gov Mindy J. Spiehs, Research Animal Scientist, USDA ARS Meat Animal Research Center, Clay Center, NE
Bryan L. Woodbury, Agricultural Engineer, USDA ARS Meat Animal Research Center, Clay Center, NE
Kristin E. Hales, Research Animal Scientist, USDA ARS Meat Animal Research Center, Clay Center, NE
Additional Information
Will be included in Proceedings of the 2019 Annual International Meeting of the American Society of Agricultural and Biological Engineers.
USDA is an equal opportunity provider and employer.
Acknowledgements
The authors wish to thank Alan Kruger, Todd Boman, Bobbi Stromer, Brooke Compton, John Holman, Troy Gramke and the USMARC Cattle Operations Crew for assistance with data collection.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2019. Title of presentation. Waste to Worth. Minneapolis, MN. April 22-26, 2019. URL of this page. Accessed on: today’s date.
Ionophores are a type of antibiotics that are used in cattle production to shift ruminal fermentation patterns. They do not kill bacteria, but inhibit their ability to function and reproduce. In the cattle rumen, acetate, propionate, and butyrate are the primary volatile fatty acids produced. It is more energetically efficient for the rumen bacteria to produce acetate and use methane as a hydrogen sink rather than propionate. Ionophores inhibit archaea forcing bacteria to produce propionate and butyrate as hydrogen sinks rather than working symbiotically with methanogens to produce methane as a hydrogen sink. Numerous research studies have demonstrated performance advantages when ionophores are fed to beef cattle, but few have considered potential environmental benefits of feeding ionophores. This study was conducted to determine if concentrations of greenhouse gases, odorous volatile organic compounds (VOC), ammonia, and hydrogen sulfide from beef cattle manure could be reduced when an ionophore was fed to finishing cattle.
What Did We Do?
Four pens of feedlot cattle were fed an ionophore (monensin) and four pens received no ionophore (n=30 animals/pen). Samples were collected six times over a two-month period. A minimum of 20 fresh fecal pads were collected from each feedlot pen at each collection. Samples were mixed within pen and a sub-sample was placed in a small wind-tunnel. Duplicate samples for each pen were analyzed. Ammonia, carbon dioxide (CO2), and nitrous oxide (N2O) concentrations were measured using an Innova 1412 Photoacoustic Gas Analyzer. Hydrogen sulfide (H2S) and methane (CH4) were measured using a Thermo Fisher Scientific 450i and 55i, respectively.
What Have We Learned?
Table 1. Overall average concentration of compounds from feces of beef feedlot cattle fed diets with and without monensin.
Total CH4 concentration decreased when monensin was fed. Of the VOCs measured, only total sulfide concentration was lower for the manure from cattle fed monensin compared to those not fed monensin. Ammonia, N2O, CO2, H2S, and all other odorous VOC were similar between the cattle fed monensin and those not fed monensin. The results only account for concentration of gases emitted from the manure and do not take into account any urinary contributions, but indicate little reduction in odors and greenhouse gases when monensin was fed to beef finishing cattle.
Future Plans
A study is planned for April – July 2019 to measure odor and gas emissions from manure (urine and feces mixture) from cattle fed with and without monensin. Measurements will also be collected from the feedlot surface of pens with cattle fed with and without monensin.
Authors
Mindy J. Spiehs, Research Animal Scientist, USDA ARS Meat Animal Research Center, Clay Center, NE
Bryan L. Woodbury, Agricultural Engineer, USDA ARS Meat Animal Research Center, Clay Center, NE
Kristin E. Hales, Research Animal Scientist, USDA ARS Meat Animal Research Center, Clay Center, NE
Additional Information
Dr. Hales also looked at growth performance and E. coli shedding when ionophores were fed to finishing beef cattle. This work is published in Journal of Animal Science.
Hales, K.E., Wells, J., Berry, E.D., Kalchayanand, N., Bono, J.L., Kim, M.S. 2017. The effects of monensin in diets fed to finishing beef steers and heifers on growth performance and fecal shedding of Escherichia coli O157:H7. Journal of Animal Science. 95(8):3738-3744. https://pubmed.ncbi.nlm.nih.gov/28805884/.
USDA is an equal opportunity provider and employer.
Acknowledgements
The authors wish to thank Alan Kruger, Todd Boman, and the USMARC Cattle Operations Crew for assistance with data collection.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2019. Title of presentation. Waste to Worth. Minneapolis, MN. April 22-26, 2019. URL of this page. Accessed on: today’s date.
Nitrous oxide (N2O) emissions from concentrated animal feeding operations, including cattle feedyards, have become an important research topic. However, there are limitations to current measurement techniques, uncertainty in the magnitude of feedyard N2O fluxes, and a lack of effective mitigation methods. There are uncertainties in the pathway of feedyard N2O production, the dynamics of nitrogen transformations in these manure-based systems, and how N2O emissions differ with changes in climate and feedyard management.
What Did We Do?
A literature review was conducted to assess the state-of-the-science of N2O production and emission from open-lot beef cattle feedyards and dairies. The objective was to assess N2O emission from cattle feedyards, including comparison of measured and modeled emission rates, discussion of measurement methods, and evaluation of mitigation options. In addition, laboratory, pilot-scale, and field-scale chamber studies were conducted to quantify and characterize N2O emissions from beef cattle manure. These studies led to new empirical model to predict feedyard N2O fluxes as a function of temperature and manure nitrate and water contents. Organic matter stability/availability was important in predicting manure-derived N2O emissions: inclusion of data for dissolved organic carbon content and Ultraviolet-visible (UV-vis) spectroscopic indices of molecular weight, complexity and degree humification improved model performance against measured data.
What Have We Learned?
Published annual per capita flux rates for beef cattle feedyards and open-lot dairies in arid climates were highly variable and ranged from 0.002 to 4.3 kg N2O animal-1 yr-1. On an area basis, published emission rates ranged from 0 to 41 mg N2O m-2 h-1. From these studies and the Intergovernmental Panel on Climate Change emission factors, calculated daily per capita N2O fluxes averaged 18 ± 10 g N2O animal-1 d-1 (range, 0.04–67 g N2O animal-1 d-1). Some of this variability is inherently derived from differences in manure management practices and animal diets among open-lot cattle systems. However, it was proposed that other major causes of variation were inconsistency in measurement techniques, and irregularity in N2O production due to environmental conditions.
For modeling studies, N2O emissions were measured during 15 chamber studies (10 chambers per study) on commercial Texas feedyards, where N2O emissions ranged from below detection to 101 mg N2O m-2 h-1. Numerous feedyard and manure data were collected and regression analyses were used to determine key variables involved in feedyard N2O losses. Based on these data, two models were developed: (1) a simple model that included temperature, manure water content, and manure nitrate concentration, and (2) a more complex model that included UV-vis spectral data that provided an estimate of organic matter stability. Overall, predictions with both models were not significantly different from measured emissions (P < 0.05) and were within 52 to 61% agreement with observations. Inclusion of data for organic matter characteristics improved model predictions of high (>30 mg m-2 h-1) N2O emissions, but tended to overestimate low emission rates (<20 mg N2O m-2 h-1). This work represents one of the first attempts to model feedyard N2O. Further refinement is needed to be useful for predicting spatial and temporal variations in feedyard N2O fluxes.
Future Plans
This work clearly identified that neither the magnitude nor the dynamics of N2O emissions from open-lot cattle systems were well understood. Five primary knowledge gaps/problem areas were identified, where current understanding is weak and further research is required. These include: (i) the need for accurate measurement of N2O emissions with appropriate and more standardized methods; (ii) improved understanding of the microbiology, chemistry, and physical structure of manure within feedyard pens that lead to N2O emissions; (iii) improved understanding of factors that influence feedyard N2O emissions, including manure H2O content, porosity, density, available nitrogen and carbon contents, environmental temperatures, and use of veterinary pharmaceuticals; (iv) development of cost-effective and practical mitigation strategies to decrease N2O emissions from pen surfaces, manure stockpiles, composting windrows, and retention ponds; and (v) improved process-based models that can accurately predict feedyard N2O emissions, evaluate mitigation strategies, and forecast future N2O emission trends.
Given the potential for future regulation of N2O emissions, feedyard managers, nutritionists, and researchers may play increasingly important roles in on-farm nitrogen management. Current management practices may need modification or refinement to balance production efficiency with environmental concerns. There is a need for data derived from both large-scale micrometerological measurement campaigns and small-scale chamber studies to assess the overall magnitude of feedyard N2O emissions and to determine key factors driving its production and emission. Refined empirical and process-based models based on manure physicochemical properties and weather could provide a dynamic approach to predict N2O losses from open-lot cattle systems.
Corresponding author (name, title, affiliation):
Heidi Waldrip, Research Chemist, USDA-ARS Conservation and Production Laboratory, Bushland, TX
Rick Todd, Research Soil Scientist, USDA-ARS Conservation and Production Laboratory, Bushland, TX
David Parker, Agricultural Engineer, USDA-ARS Conservation and Production Research Laboratory, Bushland, TX
Al Rotz, Agricultural Engineer, USDA-ARS Pasture Systems and Watershed Management Research Unit, University Park, PA
Andy Cole, Animal Scientist, USDA-ARS Conservation and Production Research Laboratory (retired), Bushland, TX.
Ken Casey, Associate Professor, Texas A&M AgriLife Research, Amarillo, TX
Additional Information
“Nitrous Oxide Emissions from Open-Lot Cattle Feedyards: A Review”. Waldrip, H. M., Todd, R. W., Parker, D. B., Cole, N. A., Rotz, C. A., and Casey, K. D. 2016. J. Environ. Qual. 45:1797-1811. Open-access article available at: https://dl.sciencesocieties.org/publications/jeq/pdfs/45/6/1797?search-r…
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.
Process-based models are increasingly used as tools for studying complex agroecosystem interactions and N2O emissions from agricultural fields. The widespread use of these models to conduct research and inform policy benefits from periodic model comparisons that assess the state of agroecosystem modeling and indicate areas for model improvement. The increasingly broad application of models requires an assessment of model performance using datasets that span multiple biogeophysical contexts. While limited in the capacity to identify specific areas for model improvement, general evaluations provide a critical perspective on the use of model estimates to inform policy and also identify necessary model improvements that require further evaluation.
What did we do?
The objectives of this model comparison were to i) calibrate and validate three process-based models using a large dataset; ii) evaluate the performance of a multi-model ensemble to estimate observed data; and iii) construct a linear model to identify and quantify possible model bias in the estimation of soil N2O flux from agricultural fields. We selected three models that have been used to evaluate N2O emissions from agricultural fields: DayCent, DNDC, and EPIC. Using data from two field experiments over five years, we calibrated and validated each model using observations of soil temperature (n = 887), volumetric soil water content (VSWC) (n = 880), crop yield (n = 67), and soil N2O flux (n = 896). Our model validations and comparisons consisted of commonly conducted statistical evaluations of root mean squared error, correlation, and model efficiency. Additionally, the large sample sizes used here allowed for more robust linear regression models that offered additional insight into relationships between model estimations and observations of N2O flux. We hypothesized that such a linear model would indicate if there was model bias in estimations of soil N2O flux. Ensemble modeling can reduce the error associated with climate projections and has recently been applied to the estimation of N2O flux from agroecosystems. Thus, we also constructed a multi-model ensemble to evaluate the use of multiple models to improve estimates of soil N2O flux.
What have we learned?
In a comparison of three process-based models, calibration to a large dataset produced favorable estimations of soil temperature, VSWC, average yield, and N2O flux when the models were evaluated using RMSE, R2, and the Nash-Sutcliffe E-statistic. However, an evaluation of linear regression models revealed a consistent bias towards underestimating high-magnitude daily N2O flux and cumulative N2O flux. Observations of soil temperature and VSWC were unable to significantly explain model bias. Calibration to available data did not result in consistent model estimation of additional system properties that contribute to N2O flux, which suggests a need for additional model comparisons that make use of a wide variety of data types. The major contribution of this work has been to identify a potential model bias and future steps required to evaluate its source and improve the simulation of nitrogen cycling in agroecosystems. Process-based models are powerful tools, and it is not our objective to undermine their past and future application. However, more work is left to be done in understanding the biogeophysical system that produces soil N2O and in harmonizing the process-based models that simulate that system and which are used to evaluate management and generate policy.
Future Plans
Future work should test our findings in additional agroecological contexts to determine the extent to which a bias towards underestimating peak N2O flux persists. A meta-analysis of published data may be the most direct method for doing so. New datasets will need to be collected that represent simultaneous observations of multiple system properties (e.g. soil NO3-, soil NH4+, and heterotrophic respiration) from different soil layers and at increased temporal frequencies. Model developers should use these rich datasets to identify the source of N2O estimation bias and improve the structure and function of process-based models.
Corresponding author, title, and affiliation
Richard K. Gaillard, Graduate Student, University of Wisconsin-Madison
Curtis D. Jones, Assistant Research Professor, University of Maryland; Pete Ingraham, Research Scientist, Applied Geosolutions;
Additional information
sustainabledairy.org
Acknowledgements
This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2013-68002-20525. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.
Additional Authors:
Sarah Collier, Research Associate, University of Wisconsin-Madison;
Roberto Cesar Izaurralde, Research Professor, University of Maryland;
William Jokela, Research Scientist (retired), USDA-ARS;
William Osterholz, Research Associate, University of Wisconsin-Madison;
William Salas, President and Chief Scientist, Applied Geosolutions;
Peter Vadas, Research Scientist, USDA-ARS;
Matthew Ruark; Associate Professor; University of Wisconsin-Madison
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.
This is a self-guided learning lesson about greenhouse gases (GHG) and their connections to livestock and poultry production. It is useful for self-study and for professionals wishing to submit continuing education credits to a certifying organization. Anticipated time: 60 minutes. At the bottom of the page is a quiz that can be submitted and a score of 7 out of 10 or better will earn a certificate of completion. (Teachers/educators: visit the accompanying GHG curriculum materials page)
Module Topics
Why does climate change?
How does US agriculture to compare to other industries and worldwide agriculture?
What greenhouse gases (GHG) are emitted by livestock and poultry farms?
What are mitigation and adaptation strategies
What is Climate Change?
Download and read “Why Does Climate Change?” (PDF; 8 pages). Includes basics and terminology about natural and man-made drivers of climate change.
US Agriculture Comparisons to Other Industries and Worldwide Agriculture
Watch this short video “Agriculture and Greenhouse Gases: Some Perspective” (5 minutes). This also includes some very good reasons why farmers, ranchers, and ag professionals should care about the topic of climate change, regardless of political stances on solutions.
Greenhouse Gases Emitted by Livestock, Poultry. and Other Agricultural Activities
Watch this short video discussing the most important gases produced through livestock, poultry, and cropping activities on farms and ranches. (8 minutes)
When you have completed the above activities, take this quiz. If you score at least 7 of 10 correct, you will receive a certificate of completion via email. If you are a member of an organization that requires continuing education units (CEUs), we recommend that you submit your certificate to them for consideration as a self-study credit (each individual organization usually has a certification board that decides which lessons are acceptable). Go to quiz….
American Registry of Professional Animal Scientist (ARPAS) members can self-report their completion of this module at the ARPAS website.
Acknowledgements
Author: Jill Heemstra, University of Nebraska-Lincoln
Why Study Nitrous Oxide and Methane at Cattle Feedyards?
Accurate estimation of greenhouse gas emissions, including nitrous oxide and methane, from open beef cattle feedlots is an increasing concern given the current and potential future reporting requirements for GHG emissions. Research measuring emission fluxes of GHGs from open beef cattle feedlots, however, has been very limited. Soil and environmental scientists have long used various chamber based techniques, particularly non-flow-through – non-steady-state (NFT-NSS) chambers for measuring soil fluxes. Adaptation of this technique to feedyards presents a series of challenges, including spatial variability, presence of animals, chamber base installation issues, gas sample collection and storage, concentration analysis range, and flux calculations.
What did we do?
Following an extensive review of the literature on measuring emissions from cropping and pasture systems, it was decide to adopt non-flow-through – non-steady-state (NFT-NSS) chambers as the preferred measurement methodology. However, the use of these NFT-NSS chambers had to be adapted for use in conditions of beef cattle feedyards and open corral dairies.
What have we learned?
Trials of various techniques for sealing the chamber to the manure surface including piling soil/manure around the chamber and various weighted skirts were trial, however no technique was as good at sealing the chamber as a metal ring driven 50-75 mm into the underlying substrate.
Chamber bases could potentially injure animal in the pen and/or animal could disturb the measurement installation, so measurements were only conducted in recently vacated pens.
Gas samples were drawn from a septa in the chamber cap using a 20 ml polyethylene syringe and immediately injected into a 12 ml evacuated exetainer vial for transport, storage and analysis. Trials of alternative vials led to sample loss and contamination issues.
Gas samples were analyzed using a gas chromatograph equipped with ECD, FID and TCD detectors for nitrous oxide, methane and carbon dioxide determination, respectively.
The metal rings or bases must be installed at least 24 and preferably 48 hours before measurements are commenced as the disturbance caused when installing the bases will result in a temporarily enhanced emission flux.
Ten, 20 cm dia chambers constructed from PVC pipe caps are deployed in a pen and yield a reasonable approximation of the average emission fluxes from the pen.
The range of gas concentrations measured in the chamber at the end of a 30 minute deployment was up to 2 orders of magnitude greater than that typically measured in cropping systems research. This required careful choice of calibration gas concentrations and calibration of the gas chromatograph. The response of the ECD detector used for determining N2O concentration may not be linear over the entire range experienced.
The rate of increase in concentration in the chamber is often curvilinear in form and a quadratic approach was adopted for determination of the flux rate.
Future Plans
On-going studies are quantifying N2O and CH4 flux rates from pen surfaces in a cattle feedlots under varying seasonal conditions; further work is identifying contributing factors.
Authors
Kenneth D. Casey, Associate Professor at Texas A&M AgriLife Research, Amarillo TX kdcasey@ag.tamu.edu
Heidi M. Waldrip, Research Soil Scientist at USDA ARS CPRL, Bushland TX; Richard W. Todd, Research Soil Scientist at USDA ARS CPRL, Bushland TX; and N. Andy Cole, Research Soil Scientist at USDA ARS CPRL, Bushland TX;
Additional information
For further information, contact Ken Casey, 806-677-5600
Acknowledgements
Research was partially funded from USDA NIFA Special Research Grants
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.
[Abstract] Subsurface manure application is theoretically susceptible to greater denitrification losses and nitrous oxide (N2O) emissions compared to surface application methods – primarily attributed to manure being placed in a more anaerobic environment. A review of field studies suggest N2O emissions typically range from 0.1% to 3% of total applied N from subsurface application methods, but there is considerable variation in emissions depending on pre- and post-application soil moisture conditions, readily-available carbon content in manure compared to background levels in soil, localized nitrogen form and oxygen concentration at the application site, and application depth. This paper will summarize peer-reviewed literature of field studies that quantify N2O emissions subsequent to subsurface manure application and identify the most prominent determining factors cited by authors.
Why Study Nitrous Oxide Emissions of Manure?
Ammonia abatement efficiencies of up to 90 percent have been documented with subsurface application and incorporation of animal manures compared to conventional surface application methods. While reducing ammonia emissions has positive implications for air and water quality, a portion of the nitrogen conserved may come at the expense of increased nitrous oxide emissions produced during denitrification and nitrification processes in the soil. As a greenhouse gas 300 times more potent than carbon dioxide at trapping heat, nitrous oxide has been linked to anthropogenic climate change and depletion of stratospheric ozone. Release of nitrous oxide from agriculturally-productive soils into the atmosphere also represents a loss of crop nutrients. Understanding the circumstances and manageable factors that contribute to nitrous oxide formation in soils subsequent to manure application is important for retaining crop nutrients and preventing greenhouse gas emissions.
What did we do?
A literature review was performed to investigate the factors that contribute to nitrous oxide emissions following subsurface application of animal manure to both grassland and arable land, compare results from different application techniques, and examine the conditions and circumstances that lead to nitrous oxide emissions.
What have we learned?
Several studies demonstrate significant increases in nitrous oxide emissions (from 0.1 to 3 percent) attributable to factors including increasing soil moisture content, high concentrations of readily-available carbon in manure substrate, increased nitrate concentration in soil, shallow application depth, high soil temperature, and ambient conditions during and immediately following application (table 1). Other studies show no difference in nitrous oxide emissions as compared to surface application methods. Reasons that subsurface application techniques will not necessarily result in greater nitrous oxide emissions were: 1) the length of the diffusion path from the site of denitrification to the soil surface may lead to a greater portion of denitrified nitrogen being emitted as nitrogen gas; 2) the soil moisture conditions and aeration level at the time of application may not be suitable for increased nitrous oxide production; 3) prior to manur e application, soils may already contain readily-metabolizable carbon and mineral nitrogen, thus any increase in nitrous oxide emission following application may not have a significant impact; and 4) weather events subsequent to manure application may effect soil moisture content and water-filled-pore-space, thereby affecting nitrous oxide emissions. Several studies document nitrous oxide emissions due to subsurface application methods (including manure incorporation and shallow injection) but research comparing nitrous oxide emissions from different subsurface application techniques and application depth is limited. Lack or absence of data in literature about manure chemistry, nitrogen application rates, application technique or method, as well as soil and atmospheric conditions during and after application made it more difficult to draw specific conclusions on factors affecting nitrous oxide emissions from subsurface-applied manure.
Further research is needed to determine the environmental and economic tradeoffs of implementing subsurface manure application methods for abatement of NH3 considering different future greenhouse gas emissions and market scenarios. Recent work suggests a link between denitrifier community density, organic C, and N2O emissions. Characterization of these biological mechanisms and identification of genetic markers for key enzymes should continue, particularly with respect to various subsurface manure application techniques, different manure types and N application rates, soil types, environmental conditions, and soil chemistry. Subsurface application depth plays an important role in determining the proportion of N2O to N2 emitted during denitrification; however, the number of field studies that examine the impact of application depth is limited. More research is needed to determine optimal manure application depth as influenced by soil type, soil chemistry, timing of application, and vegetative cover. Finally, future research on subsurface manure application will allow existing and future prediction models to improve estimation of annual N2O emissions at landscape scale and airshed levels. Refinement of greenhouse gas inventories, including N2O emissions from agricultural production systems, will assist agriculture producers, scientists, and policy makers in making informed decisions on greenhouse gas emission mitigation.
Future Plans
Future agricultural greenhouse gas regulations and/or carbon market incentives have potential implications for agricultural producers, including the method and timing of manure application. Controlled, replicated, and well-documented research on subsurface manure application and subsequent nitrous oxide release is critical for estimating the costs and benefits of different manure application techniques.
Authors
David W. Smith, Extension Program Specialist, Texas A&M AgriLife Extension DWSmith@ag.tamu.edu
Dr. Saqib Mukhtar, Professor and Associate Department Head for Extension, Texas A&M AgriLife Extension
Additional information
The publication ‘Estimation and Attribution of Nitrous Oxide Emissions Following Subsurface Application of Animal Manure: A Review’ has been accepted for publication in Transactions of the ASABE.
Acknowledgements
Funding for this effort provided by USDA-NIFA grant No. 2011-67003-30206.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.
Nitrous oxide emitted from cropland constitutes a significant component of the agricultural sector’s overall greenhouse gas footprint. In order to accurately evaluate mitigation strategies, predict impacts, and model system behavior under future climate scenarios, it is essential to have access to flux measurements collected under regionally relevant conditions of soil, weather, and management strategies. As part of the Climate Change Mitigation and Adaptation in Dairy Production Systems of the Great Lakes Region USDA Coordinated Agricultural Project, we are measuring nitrous oxide flux from a typical dairy forage rotation in south-central Wisconsin. The rotation consists of one year of corn and three years of alfalfa, receiving liquid dairy manure fertilization in corn and alfalfa establishment years. Fluxes have been tracked over two growing seasons, and comparisons are possible between years as well as between phases of the rotation. Ultimately this data will be used to calibrate models for use in footprinting and benchmarking efforts and in predicting future productivity and resilience of dairy-based systems.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.
We conducted a field study on corn to evaluate the effect of liquid dairy manure applied pre-plant (injection or surface broadcast with immediate or 3-day disk incorporation) or sidedressed at 6-leaf stage (injected or surface-applied) on emission of NH3 and N2O. Manure was applied at a rate of 6500 gal/acre, which supplied an average of 150 lb/acre of total N and 65 lb/acre of NH4-N. Ammonia emission was measured for 3 days after manure application using the dynamic chamber/equilibrium concentration technique, and N2O flux was quantified using the static chamber method at intervals of 3 to 14 days throughout the season. Ammonia-N losses were typically 30 to 50 lb/acre from pre-plant surface application, most of the loss occurring in the first 6 to 12 hours after application. Emission rates were reduced 60-80% by quick incorporation and over 90% by injection. Losses of N2O were relatively low (1 lb/acre or less annually), but pronounced peaks of N2O flux occurred from either pre-plant or sidedress injected manure in different years. Results show that NH3 emission from manure can be reduced substantially by injection or quick incorporation, but there may be some tradeoff with N2O flux from injection.
Why Study Land Application Emissions of Ammonia and Nitrous Oxide?
Figure 1. Injection equipment used for pre-plant application (top) and sidedress application (bottom) of liquid dairy manure.
Manure is a valuable source of nitrogen (N) for crop production, but gaseous losses of manure N as ammonia (NH3) and nitrous oxide (N2O) reduce the amount of N available to the crop and, therefore, its economic value as fertilizer. These N losses can also adversely affect air quality, contribute to eutrophication of surface waters via atmospheric deposition, and increase greenhouse gas emission. And the decreased available N in manure reduces the N:P ratio and can lead to a more rapid build-up of P in the soil for a given amount of available N. The most common approach to controlling NH3 volatilization from manure is to incorporate it into the soil with tillage or subsurface injection, which can reduce losses by 50 to over 90% compared to surface application (Jokela and Meisinger, 2008). Injecting into a growing corn crop at sidedress time offers another window of time for manure application (Ball-Coelho et al., 2006). While amounts of N lost as N2O are usually small compared to NH3, even low emissions can contribute to the greenhouse effect because N2O is about 300 times as potent as carbon dioxide in its effect on global warming (USEPA, 2010). We carried out a 4-year field experiment to evaluate the effect of dairy manure application method and timing and time of incorporation on a) corn yield, b) fertilizer N credits, c) ammonia losses, and) nitrous oxide emissions.
What Did We Do?
Figure 2. Average (2009-2011) NH3-N emission rates as affected by method and timing of manure application.
This field research was conducted at the Univ. of Wisconsin/USDA Agricultural Research Station in Marshfield, WI, on predominantly Withee silt loam (Aquic glossudalf), a somewhat poorly drained soil with 0 to 2% slope. Dairy manure was applied either at pre-plant (mid- to late May) or sidedress time (5-6-leaf stage). Pre-plant treatments were either injected with an S-tine injector (15-inch spacing; Fig. 1) or incorporated with a tandem disk immediately after manure application (< 1 hour), 1-day later, or 3 days later. All plots were chisel plowed 3 to 5 days after application. Sidedress manure applications were either injected with an S-tine injector (30-inch spacing) or surface applied (Fig. 1). Fertilizer N was applied to separate plots at pre-plant at rates of 0, 40, 80, 120, 160, and 200 lb/acre as urea and incorporated with a disk. Liquid dairy manure (average 14% solids) was applied at a target rate of 6,500 gal/acre. Manure supplied an average of 158 lb total N and 62 lb NH4-N per acre, but rates varied across years and application times.
Ammonia emission was measured following pre-plant and sidedress manure applications in 2009-2011 with the dynamic chamber/equilibrium concentration technique (Svensson, 1994). Measurement started immediately after manure application and continued through the third day. Ammonia measurement ended just before disking of the 3-day incorporation treatment, so the 3-day treatment represents surface-applied manure. Nitrous oxide was measured using the static, vented chamber technique following the GRACEnet protocol (Parkin and Venterea, 2010). Measurement began two days after pre-plant manure application and continued approximately weekly into October.
What Have We Learned?
Figure 3. Nitrous oxide (N2O) flux as affected by method and timing of dairy manure application from May to October of 2010 (A) and 2011 (B). Arrows show times of manure application. Note differences in scale for 2010 and 2011.
The 3-year average annual NH3 emission rate from surface applied (3-day incorporation) manure was relatively high immediately following application but declined rapidly after the first several hours to quite low levels (Fig. 2). Cumulative NH3-N loss over the full measurement period averaged over 40 lb/acre from surface application but was reduced by 75% with immediate disking and over 90% by injection. Ammonia losses varied somewhat by year, but patterns over time and reductions by incorporation were similar. The pattern of ammonia loss, 75% of the total loss in the first 6 to 12 hours, emphasizes the importance of prompt incorporation to reduce losses and conserve N for crop use.
Nitrous oxide flux was quite low for most manure treatments during most of the May to October period in both years (Fig. 3). However, there were some increases in N2O flux after manure application, and pronounced peaks of N2O emission from the injection treatment at either pre-plant (2010) or sidedress (2011) time. Greater emission from injection compared to other treatments may have occurred because injection of liquid manure places manure in a relatively concentrated band below the surface, creating anaerobic (lacking in oxygen) conditions. Nitrous oxide is produced by denitrification, a microbial process that is facilitated by anaerobic conditions. Reasons for the difference between 2010 and 2011 are not readily obvious, but are probably a result of different soil moisture and temperature conditions.
Figure 4. Annual (May-Oct.) loss of N2O as affected by method and timing of liquid dairy manure application. 2010 and 2011.
Based on these results, injection of liquid dairy manure resulted in opposite effects on NH3 and N2O emission, suggesting a trade-off between the two gaseous N loss pathways. However, the total annual N losses from N2O emissions (1 lb/acre or less; Fig. 4) were only a fraction of those from ammonia volatilization, so under the conditions of this study N2O emission is not an economically important loss. As noted earlier, however, N2O is a potent greenhouse gas, so even small amounts can contribute to the potential for global climate change. The dramatic reduction in NH3 loss from injection, though, may at least partially balance out the increased N2O because 1% of volatilized N is assumed to be converted to N2O (IPCC, 2010). Immediate disk incorporation was almost as effective as injection for controlling NH3 loss and, on average, resulted in less N2O emission than injection. But the separate field operation must be done promptly after manure application to be effective. A possible alternative is to use sweep injectors or other direct incorporation methods that place manure over a larger volume of soil and/or create more mixing with soil, thus creating conditions less conducive to denitrification and N2O loss.
Manure application timing and method/time to incorporation significantly affected grain yield in 2009, 2010, and 2012 and silage yield in 2012. Pre-plant injection produced greater yields than one or more of the broadcast treatments in 2009 (grain) and 2012 (grain and silage). Overall, yield effects of application and incorporation timing were variable from year to year, probably because of differences in weather and soil conditions and actual manure N rates applied. The fertilizer N equivalence of manure was calculated by comparing the yield achieved from each manure treatment to the yield response function from fertilizer N. Fertilizer N equivalence values were quite variable by year, but 4-year averages expressed as percent of total manure N applied were 52% for injection (pre-plant and sidedress), 37% for 1-hour or 1-day incorporation, and 34% for 3-day incorporation. So, when expressed as a percent of total manure N applied, N availability generally decreased as time to incorporation increased, which reflects the amounts of measured NH3 loss.
In summary, ammonia volatilization losses increased as the time to incorporation of manure increased. Injection of manure resulted in the lowest amount of NH3 volatilization, but higher N2O emissions. In this study, reducing the large NH3 losses by injecting manure provided more environmental benefit compared to the small increase in N2O emissions. In addition, injection or immediate incorporation resulted, on average, in higher fertilizer N value of manure for corn production. The decreased need for commercial fertilizer N could potentially result in greater profitability and a smaller carbon footprint.
Future Plans
We have started other research to evaluate yield response, N cycling, and emission of NH3 and N2O from various low-disturbance manure application methods in silage corn and perennial forage systems.
Authors
Bill Jokela, Research Soil Scientist, USDA-ARS, Dairy Forage Reserch Center, Marshfield, WI, bill.jokela@ars.usda.gov
Carrie Laboski, Assoc. Professor, Dept. of Soil Science, Univ. of Wisconsin
Todd Andraski, Researcher, Dept. of Soil Science, Univ. of Wisconsin
Additional Information
Ball Coelho, B.R., R.C. Roy, and A.J. Bruin. 2006. Nitrogen recovery and partitioning with different rates and methods of sidedressed manure. Soil Sci. Soc. Am. J. 70:464–473.
Intergovernmental Panel on Climate Change (IPCC). 2006 IPCC Guidelines for National Greenhouse Gas Inventories, vol. 4, Agriculture, Forestry and Other Land Use, edited by S. Eggleston et al., Inst. for Global Environ. Strategies, Hayama, Japan.
The authors gratefully acknowledge Matt Volenec and Ashley Braun for excellent technical assistance in conducting this research. Funding was provided, in part, by the USDA-Agricultural Research Service and the Wisconsin Corn Promotion Board.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.
A new method was used at the Ag 450 Farm Iowa State University (41.98N, 93.65W) from October 24, 2012 through December 14, 2012 to assess GHG emission from land-applied swine manure on crop land. Gas samples were collected daily from four static flux chambers. Gas method detection limits were 1.99 ppm, 170 ppb, and 20.7 ppb for CO2, CH4 and N2O, respectively. Measured gas concentrations were used to estimate flux using four different models, i.e., (1) linear regression, (2) non-linear regression, (3) non-equilibrium, and (4) revised Hutchinson & Mosier (HMR). Sixteen days of baseline measurements (before manure application) were followed by manure application with deep injection (at 41.2 m3/ha), and thirty seven days of measurements after manure application.
Static flux chamber (pictured) method was developed to measure greenhouse gas emissions from land-applied swine manure from a corn-on-corn system in central Iowa in the Fall of 2012. Gas samples were collected in vials and transported to the Air Quality Laboratory at Iowa State University campus.
Why Study Greenhouse Gases and Land Application of Swine Manure?
Assessment of greenhouse gas (GHG) emissions from land-applied swine manure is needed for improved process-based modeling of nitrogen and carbon cycles in animal-crop production systems.
What Did We Do?
We developed novel method for measurement and estimation of greenhouse gas (CO2, CH4, N2O) flux (mass/area/time) from land-applied swine manure. New method is based on gas emissions collection with static flux chambers (surface coverage area of 0.134 m^2 and a head space volume of 7 L) and gas analysis with a GC-FID-ECD.
Baseline (post tilling) greenhouse gas (GHGs) emissions monitoring was followed with swine manure application in the Fall of 2012 (pictured) and about 10 weeks of post-application monitoring of GHGs.
New method is also applicable to measure fluxes of GHGs from area sources involving crops and soils, agricultural waste management, municipal, and industrial waste. New method was used at the Ag 450 Farm Iowa State Univeristy (41.98 N, 93.65 W) from October 24, 2012 through December 14, 2012 to assess GHG emission from land-applied swine manure on crop (corn on corn) land. Gas samples were collected daily from four static flux chambers. Gas method detection limits were 1.99 ppm, 170 ppb, and 20.7 ppb for CO2, CH4, and N2O, respectively.
What Have We Learned?
Measured gas concentrations were used to estimate flux using four different mathematical models, i.e., (1) linear regression, (2) non-linear regression, (3) non-equilibrium, and (4) revised Hutchinson & Mosier (HMR). Sixteen days of baseline measurements (before manure application) were followed by manure application with deep injection (at 41.2 m3/ha), and thirty seven days of measurements after manure application. Preliminary net cumulative flux estimates ranged from 115,000 to 462,000 g/ha of CO2, -4.65 to 204 g/ha of CH4, and 860 to 2,720 g/ha N2O. These ranges are consistent with those reported in literature for similar climatic conditions and manure application method.
Greenhouse gases (GHGs) were analyzed in the Air Quality Laboratory (ISU) using dedicated GHGs gas chromatograph. The picture above shows an example of gas sample analysis for CO2, GH4 and N2O. Each ‘peak’ represents one of the tagget GHGs. Gas concentrations were used in a mathematical model to estimate GHG flux (mass emitted/area/time).
Future Plans
Spring 2013 measurements of GHG flux from land-applied swine manure are planned. The spring study will follow the protocols developed for the Fall 2012 season. Estimates of the Spring and Fall GHG flux will be used to develop GHG emission factors for emissions from swine manure in Midwestern corn-on-corn systems. Emission factors will be compared with literature data.
Authors
Dr. Jacek Koziel, Associate Professor, Iowa State University Department of Agricultural and Biosystems Engineering koziel@iastate.edu
Devin Maurer, Research Associate, Iowa State University Department of Agricultural and Biosystems Engineering
Kelsey Bruning, Undergraduate Research Assistant, Iowa State University Department of Civil, Construction and Environmental Engineering
Tanner Lewis, Undergraduate Research Assistant, Iowa State University Department of Agricultural and Biosystems Engineering
Danica Tamaye, Undergraduate Research Assistant, University of Hawaii College of Agriculture, Forestry, and Natural Resource Management
William Salas, Applied Geosolutions
Acknowledgements
We would like to thank the National Pork Board for supporting this research.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.
