Project : USDA ARS

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Research Project: Reducing the Environmental Footprint from Agricultural Systems through Managing Resources and Nutrient Inputs

Location: Soil, Water & Air Resources Research

2021 Annual Report

Objectives
Objective 1: Characterize and improve accounting of N emissions as N2O and NH3 losses from cropping systems. Subobjective 1.1: Quantify the soil and environmental factors contributing to N2O production by nitrifying and denitrifying bacteria. Subobjective 1.2: Assess the effect of cover crops on N2O production in the field. Subobjective 1.3: Assess manure injection/incorporation methods for impact on residue/surface cover, soil disturbance, and N emissions. Objective 2: Enhance process-level characterization of agrochemical emissions, fate and transport across spatial scales from micro-environments to regions. Subobjective 2.1: Determine the effect tillage practices have on agrochemical volatilization losses from agricultural fields. Subobjective 2.2: Improve measurement and modeling approaches to describe agrochemical emissions and transport from agricultural operations. Subobjective 2.3: Determine the emission flux of NH3 and other gases from cattle feedlot surfaces using flux-gradient technique. Subobjective 2.4: Compare particulate plume data measured with LiDaR to conventional model (ex. AERMOD) predictions to assess model accuracy for both near facility and downwind transport. Subobjective 2.5: Develop an improved physics-based model on the dispersion of herbicide droplets from mechanical sprayers by incorporating ambient turbulence conditions, the turbulent kinetic energy generated by the motion of the sprayer, and atmospheric stability. Objective 3: Develop strategies to manage the effects of manure properties and air flow on NH3 emissions. Subobjective 3.1: Manipulate swine diet formulations to improve N utilization, and reduce N excretion and NH3 emission along with other gaseous emission into the environment. Subobjective 3.2: Evaluate and develop ventilation practices for reducing NH3 and other air quality emissions.

Approach
This project will focus on knowledge gaps that exist in the loss of N and agrochemicals from cropping and animal systems. Three approaches will be pursued for addressing knowledge gaps: 1) quantify soil and environmental factors contributing to N2O and NH3 emissions in animal production and field cropping systems; 2) determine soil properties that drive volatile loss and transport of agrochemicals and N compounds, and 3) determine effectiveness of N control strategies for reducing NH3 emissions. In cropping systems, there are large gaps in our understanding of the N budget in soil including both mechanisms and magnitude of losses through emissions. Laboratory studies on N2O emissions will use stable isotopes to quantify both the effect of temperature and kinetics of denitrification under varying NH3 concentrations. Field studies using chambers will be used to quantify N2O emission for a range of soil and nitrogen management strategies. Assessing the effect residue/surface cover and soil disturbance have on N loss from manure application in cropping systems will be conducted during late fall and early spring. Whole field emissions loss of N will be quantified using both an open path laser system coupled with inverse dispersion modeling for NH3 and eddy covariance with a quantum cascade laser system for N2O emissions. Quantifying the transport parameters controlling volatile losses of pesticides from cropping systems based on tillage practices will use eddy covariance micrometeorology techniques to determine turbulent flux from whole fields. The relaxed eddy accumulation technique will be used to provide more accurate eddy diffusivities for pesticide vapor transport to improve agrochemical volatilization flux estimates. In addition, LiDaR will be used to develop dispersion models for droplets from mechanical sprayers for physics-based models on the loss of agrochemicals from fields due to spray drift. Quantifying the transport parameters controlling volatile losses of N compounds and particulates from animal production systems will involve LiDaR- to measure plume dynamics and produce a remote-sensing approach to quantify emissions and compare these results to conventional modeling approaches. In animal production systems, NH3 is the dominant form of N emissions, but gaps exist in effective N control/mitigation strategies that reduce N emissions. Reducing NH3 emissions from animal production will focus on improving N utilization in animal diets by use of feed additives and improving grind size of feed particles. Ventilation practices will be evaluating and optimized for reducing NH3 emissions. Knowledge gained through this research will provide producers and regulatory agencies scientific data to improve sustainability of agricultural production facilities in U.S. farming systems.

Progress Report
This is the final report for project 5030-11610-004-00D, terminating September 2021. Progress was made on all three objectives and their sub-objectives. Objective 1. Experiments were conducted to quantify the interactive relationship between nitrous oxide (N2O) production, temperature, and soil water content. The following results were found: 1) temperature response of short-term N2O production from water-saturated soil decreased when the atmosphere was made anaerobic; 2) N2O emissions had a dual control of temperature and soil water content; and 3) soil water content largely explained N2O emissions variability, but a significant portion of the variability was driven by diurnal soil temperature patterns. These results can improve ecosystem models estimation of temperature dependency of nitrous oxide emissions. We compiled and analyzed historical data (2012-2014) of N2O emissions under contrasting tillage and cover crop production practices in a corn soybean rotation (corn, soybean, corn). Treatments included chisel plow without a cover crop, chisel plow with oat cover crop, no-till management without a cover crop, no-till with rye cover crop and no-till receiving zero nitrogen (N) fertilizer. All treatments except the zero N treatment received the same fertilizer regime. Cover crop and tillage treatments did not influence N2O emissions over the three-year period, but the zero N fertilizer treatment led to 45-69% reduction in cumulative N2O emissions. These data highlight the limitations of traditional conservation management practices (cover crops and reduced tillage) to mitigate N2O emissions. A field monitoring study was conducted to quantify N2O emission under different fertilizer management and cropping system treatments. Treatments at the Upper Mississippi River Basin Long-Term Agroecosystem Research common experiment include: 1) fall chisel plow with spring-applied fertilizer (basic practice (BP); 2) no-tillage (NTNC), 3) no-till with winter rye cover crop (RC), 4) spring tillage with cover crop and winter camelina relay crop between corn and soybean (LTAR aspirational); and 5) a zero N fertilizer treatment that was otherwise managed as the NTNC (ZN). Nitrogen fertilizer applications in all treatments except the BP and ZN treatments correspond to ‘4R’ fertilizer management of right time, right amount, right place, and right formulation, with a split planting and sidedress N rate established by the late spring nitrate test. 4R N management led to an approximately 55% reduction in N2O emissions compared to the BP treatment. This decrease is attributed to fertilizer management and not tillage system, as tillage did not lead to increased emissions when fertilizer management was maintained (2012-2014 site years described above). Shifts in the management system to accommodate a winter camelina relay crop erased the N2O reductions that were gained from 4R management during the corn phase. The increase in N2O emissions appear to result from increased fertilizer application used to support the camelina crop and increased susceptibility to large fluxes during the spring thaw. The mechanism for increased emissions during the spring thaw are unclear, but these results point to the need for careful optimization of aspirational treatments to ensure environmental benefits are achieved. This study is currently in its sixth year and a manuscript will be prepared at the end of this year. A field method was developed for assessing NH3 loss from soil during manure field application. The field validation was developed over a two-year period from two field sites. Due to adverse weather conditions, coordination with growers, and a global pandemic over the last two years only three sites have been studied. Ammonia emission differences were seen between manure applicators using truck transport compared to growers using dragline manure transport with dragline transport being lower. More work needs to be done to confirm this observation. Future work is expanding the number of fields monitored and using an unmanned aerial vehicle for assessing field conditions. Objective 2. The long-term field monitoring of fluxes for two common pre-emergent herbicides, metolachlor and atrazine, continued for the 17th year and added volatilization losses from reduced tillage. The long-term database (15 years) for pesticide emissions was screened for emissions associated with daytime heating and high turbulence called “unstable air” and low turbulence associated with nighttime cooling called “stable air.” Four years have been identified as ideal candidates for developing model expressions of volatilization losses under stable nighttime conditions. However, travel and field activity restrictions in response to the COVID-19 pandemic has delayed the project 24 months. A Relaxed Eddy Accumulation (REA) instrument was designed and developed to improve the accuracy of pesticide volatilization loss estimates. Validation studies were developed for the REA instrument to accommodate high-precision, fast-acting solenoid valves of the REA instrument. Additional validation was required for a second season as the sampling protocol had to be further refined to accommodate new valves delaying the project by 12 months. However, travel and field activity restrictions in response to the COVID-19 pandemic further delayed the project 24 months. Light Detection and Ranging (Lidar) technology in conjunction with an array of turbulence and near surface meteorological measurements were used to detect particulate emission plumes from animal feeding operations, enabling a new remote sensing approach to estimate plume emissions. Landscape and facility structures all impacted transport processes. Transport processes often follow patterns of distribution involving gradual dispersion from areas of high concentration to areas of low concentrations called Gaussian. However, during conditions of summer heating, distribution patterns are more chaotic and follow non-Gaussian processes. These distribution patterns are strongly influenced by local meteorological conditions. New analysis techniques were being developed to differentiate when Gaussian and non-Gaussian processes prevail. However, loss of Lidar instrumentation and key collaborators ended the project prematurely. Lidar technology was used to determine whether spray drift model characterizations were accurate. Two-dimensional data from water vapor spray operations showed mechanical turbulence generated by large booms of agrochemical spray rigs that are used for multiple crop types. They lifted spray droplets close to 100 meters above the canopy, increasing the overall drift of droplets. This pilot study confirmed the need for a wider range of conditions to include stable and unstable conditions that establish drift loss potentials based on local meteorological conditions and the speed of the spray rig. However, the loss of Lidar instrumentation and key collaborators ended the project prematurely. Data from a two-year cattle feedlot were correlated and put into a database at the National Laboratory for Agriculture and the Environment. Ammonia concentrations collected from an open path laser and photoacoustic analyzer were synchronized with micrometeorology data. Ammonia emission flux from cattle feedlot surfaces was modeled using commercial software based on recommendations from the Environmental Protection Agency-USDA ammonia working group. Screening parameters were set up on turbulence data. Data from the study showed that the area associated with high animal activity (loading areas) had increased ammonia (NH3) emissions compared to holding pens and that extreme weather events with high winds led to emissions fluxes almost an order of magnitude higher than under typical conditions. Objective 3. A set of diet formulations were tested to quantify the impact that feed ingredients have on animal performance, manure and gas emissions. The diet formulations tested included: 1) crude protein level; 2) protein source; 3) antibiotics supplement; and 4) feed particle size. Lower crude protein (CP) diets reduced manure solids, pH, total N and sulfur (S), volatile fatty acids (VFA), and phenols, with NH3 levels in manure being reduced by 7.6% for each 1% reduction in CP. Ammonia emissions and odor emissions were reduced by 8.9% and 4.2%, respectively for each 1% reduction in CP. Animal retention increased by 7.0% for each 1% reduction in CP. Dietary protein sources affected manure solids, pH, and organic N and impacted manure retention of both carbon (C) and sulfur (S). Dietary fiber levels in protein sources reduced NH3 emissions, but dietary protein sources had no effect on odor emissions. Supplementing diets with antibiotics to increased performance had no impact on performance or gas emissions, but antibiotics in feed increased manure total solids, C and S. Reducing feed particle size increased animal daily gain while reducing manure solids, N, C, NH3, total VFA, total phenols and total indoles concentrations. Emissions of total VFAs and volatile organic compounds were lower from manures of animals fed smaller particle size diets, but NH3 emissions were higher. Greenhouse gas emissions were not impacted by any diet formulation. A study was conducted to determine the effectiveness of wet scrubber manure handling systems in swine finishing operations to control emissions of ammonia, particulate matter (PM), and odor. A commercial 2500 head swine finishing operation with a wet scrubber system was monitored for the control of air and PM emissions. Analysis of the air exiting the building showed concentrations of NH3 were initially reduced by 20-35% but as scrubber water solution aged differences became insignificant. Dust was controlled throughout. Additional research is being conducted to optimize the dosing solution of water for the wet scrubber system.

Accomplishments
1. Manure odor control and microbial community linkages. Manure management systems control odor through changes in the microbial community composition. ARS researchers in Ames, Iowa, and Florence, South Carolina, in collaboration with scientists from South Korea and Iowa State University compared the impacts of deep-pit manure management systems vs. those of pit-recharge manure management systems on odor control. Increasing the recharge rate (i.e., dilution rate) changed the dominant microorganisms in the manure, shifting them away from organisms that grow strictly in the absence of air to microorganisms that grow both in the presence and absence of air. Manure odor was lowest with manure management systems that diluted the manure. However, odor in air was not associated with any groups of microorganisms in manure. Information from this research will inform growers and engineers of limitations when designing manure management systems for the control of odor by microorganisms.

2. Dietary carbohydrate sources impact on manure characteristics and gas emissions. Livestock producers seeking to reduce the impacts of corn costs have turned to alternative feed grains and cheaper feed ingredients derived from industrial processing of food crops, commonly referred to as co-products. ARS researchers in Ames, Iowa, in collaboration with an Iowa State University researcher, conducted a swine feeding trial to evaluate the effects of carbohydrate source on animal performance, manure and gas emissions. Animals fed barley, an alternative feed grain, showed no difference in growth, manure composition, or gas profile compared to animals fed corn-based diets. Higher fiber supplemental diets based on co-products had no impact on swine performance, but the resulting manures tended to have higher levels of solids and nutrients than did animals fed corn or barley diets. Manures of animals fed the co-product diets had a 33% lower release from manure of NH3, an odorant and irritant gas. Dietary carbohydrate sources had no impact on total odor. Information from this research will be of value to researchers and growers looking for alternative feed ingredients to reduce diet cost or understand the environmental impact of animal diet source material.

3. Origins of swine foaming pits. Foam accumulation in swine manure has been linked to explosions and flash fires from sudden and unexpected release of flammable gases, including methane. ARS researchers in Ames, Iowa, in collaboration with scientists from Iowa State University and the University of Illinois conducted a field study to survey physical, chemical, and biological parameters that correlate to foam accumulation. The results showed that higher foaming rates were correlated with increased methane production, lower digestible feed ingredients, and a changing microbial community. Information in this report will be of value for growers, engineers, and scientists working on foaming issues associated with waste processing and potential mitigation measures to reduce methane production in swine manure.

U.S. DEPARTMENT OF AGRICULTURE

Soil, Water & Air Resources Research: Ames, IA