Location: Soil, Water & Air Resources Research2012 Annual Report
1a. Objectives (from AD-416):
Project objectives are: 1) Measure and model the impact of agricultural systems (animal and cropping) on air quality components to identify and develop potential mitigation strategies, 2) Measure and model the impact of agricultural systems on greenhouse gas emissions and develop and evaluate potential mitigation strategies, and 3) Measure and model soil and atmospheric factors limiting water, nitrogen, and light use efficiency of annual and perennial cropping systems to determine how they can become more resilient to climate change.
1b. Approach (from AD-416):
Studies across the soil-plant-atmosphere continuum in this project will develop new methods for quantifying emission and dispersion (particulates, NH3, VOC’s) from animal and cropping systems, improve methods for measuring different compounds in the air to provide increased quantitative capability to measure impacts of CAFO’s on air quality, determine greenhouse gas emissions (N2O, CH4, CO2) from cropping systems, and quantify effects of changing climate on water, light, and nitrogen use by crops. The initial development of a lidar-based approach to measure plume dynamics from animal facilities will be evaluated to produce a remote-sensing approach that will be used to guide sampling methods that use point-based samplers. These data will be collected over a range of facilities and throughout the day to capture the range of atmospheric stability conditions. Air sampling methods for volatile organic compounds will be accomplished with a range of methods from sorbent tubes and canisters. These will also be coupled with methods to measure the volatile organic compounds attached to particulates. These observations will be collected in different livestock facilities. Greenhouse gas emissions will be quantified using soil chambers for a range of soil management and nitrogen management studies to quantify the emissions throughout a year. Measures of water, nitrogen, carbon accumulation, and light use efficiency will use an integrated approach that blends micrometeorological with physiological measurements. These experiments will be conducted using field-scale environments and will integrate all efficiency factors into a combined assessment. The energy balance approach used in these studies blends the fast response of CO2 and H2O vapor signals with sonic anemometers, net radiation components, soil heat flux, and surface temperature along with remote sensing to obtain growth characteristics of the crop. Studies will be conducted in the rhizotron to assess the impact of rapidly induced temperature changes on crop physiological responses under a range of soil water conditions. Accomplishing these three objectives will result in the development of agricultural practices and mitigation strategies that reduce environmental impact, while maintaining or increasing productivity. Mitigation strategies to reduce GHG emissions will balance agricultural production efficiency and increased carbon capture and nitrogen use efficiency. Climate change and its impact on cropping systems raise additional concerns regarding resilience of current production practices and plant adaption to those changes. Methods are needed to quantify plant-climate interaction to link field observations with simulation models for corn, soybean, wheat, and native prairie systems. Developing a long-term program to quantify plant response to climate anomalies will also establish a database for developing more resilient crop production systems. This research will enhance scientific knowledge and provide information for producers and policymakers to maintain the viability of agricultural systems.
3. Progress Report:
Air sampling around livestock facilities is complex because of the rapid exchange processes created by the interactions of wind with the buildings. Under Objective 1, measurements of the three-dimensional wind structure near and around typical swine and poultry facilities combined with lidar particulate scans characterized the evolution and transport of particulate plumes. Particulate emissions from poultry and swine buildings do not possess Gaussian characteristics which form the basis of current emission model predictions. Additionally, analysis of high frequency turbulence data from a swine facility provided new insight on deployment of sampling instruments and appropriate sampling intervals for complex surfaces involving buildings and animals. Another study on gas exchanges over a feedlot (25,000 head) and dairy (2,000 head) focused on monitoring the emissions of ammonia, greenhouse gases, and select volatile organic compounds (VOCs). Key findings from the feedlot study were: 1) photo-acoustic infrared analyzers (PA-IR) are challenging to use due to cross interferences of gases and relatively low concentrations of methane, ammonia, and nitrous oxide; and 2) the diversity and concentrations of VOCs increased with temperature and showed vertical gradient with concentrations generally larger at the lower sampling height. Key findings for the dairy study were that major VOCs included alcohols, esters, volatile fatty acids, ketones, and carbonyl compounds and major sources for those compounds were silage piles and feedlot surface. Under Objective 2, volatilization of herbicides from soil has been evaluated for 14 seasons; however, until recently, no field investigations monitored both surface runoff and turbulent volatilization fluxes simultaneously. Herbicide volatilization exceeds herbicide runoff losses which contradicts the prevailing thought that surface runoff was the major off-site transport mechanism for herbicide. Under Objective 2, soil carbon dioxide (CO2) flux measurements for agricultural crops were completed monthly between crop harvest and planting and biweekly during the growing season. In addition to the survey CO2 flux measurements, continuous long-term chamber measurements were made on the mixed prairie and residue removal studies to develop temperature sensitivity relationships for CO2 evolution. To address Objective 2, nitrous oxide (N2O) flux measurements were added to estimate net greenhouse gas flux for each study. Initial laboratory testing of an eddy covariance system for N2O identified how temperatures affect data quality. Objective 3 has been addressed through research projects to evaluate the interactions of tillage systems and management inputs for corn-soybean production systems on water use, nitrogen use, and light capture efficiency. This is a multiple-year experiment for monitoring growth and vigor analysis and an evaluation was made of plant-to-plant variation throughout the growing season. Plant-to-plant variation ranged from 50 to 250% for all growth parameters and remained in this range throughout the growing season. These levels of variation were independent of tillage systems and management inputs.
1. Transport of dust and gases from livestock production facilities. Our ability to describe the processes affecting the movement of dust and gases away from a livestock facility has been limited by our lack of understanding of the wind flow patterns around facilities. The primary limitation in this effort has been the lack of our ability to measure the wind movement around these facilities while at the same time measuring dust and gas levels. ARS scientists in Ames, IA, along with collaborators at the University of Iowa and the Space Dynamics Laboratory at Utah State University, addressed this problem by using new tools which hadn’t previously been applied to livestock production facilities. One of these tools was a lidar system which can detect the movement of dust particles in the air as they move up and away from a facility, coupled with meteorological equipment designed to measure how rapidly air moves. These combined measurements demonstrated the presence of wind movement patterns opposite to what is currently believed about air movement, which now opens the door for much better models to describe how livestock facilities impact both the dust load and gas levels downwind of these operations. This approach was extended to measure dust emissions from agricultural field operations in California in order to compare conventional versus improved tillage management systems to determine if these improved systems reduced the dust load in the atmosphere. Studies from both livestock and tillage operations are important because of the increasing concern about the impact of dust emitted from agriculture on air quality.
2. Herbicide volatilization and runoff. Although numerous studies have been conducted on herbicide volatilization and herbicide runoff, there is a lack of understanding of how these two processes relate to one another during a field season. To better understand the impact of local meteorology, soils, and pesticide chemistry on herbicide off-site transport, an eight-year, field-scale experiment in Beltsville, MD, was conducted by ARS scientists in Ames, IA, and Beltsville, MD, where herbicide (atrazine and metolachlor) volatilization and surface runoff losses were simultaneously monitored and evaluated. This length of study was necessary to understand the differences among years and to provide a greater insight into the relationships between runoff and volatilization. Regardless of weather conditions, volatilization losses consistently exceeded surface runoff losses. It has always been assumed that herbicide runoff losses were the most prevalent form of loss from fields, however this study showed that herbicide volatilization losses were 25 times larger than surface runoff losses. These results show that both runoff losses and volatilization losses into the air have to be considered to develop environmentally sustainable practices. The research will infuence United States Department of Agriculture (USDA) and United States Environmental Protection Agency (USEPA) policy with regard to herbicide behavior and the information used to develop or improve pesticide behavior models.
3. Soil–plant–atmosphere coupling. Two case studies involving collaborations with researchers from Utah State University, University of Alabama, Iowa State University, University of Iowa, and ARS scientists in Ames, IA, combined remote sensing and surface meteorological measurements to understand the impact of advection (transport of warm dry air) to plant canopies and how this affects water use from the crop and warming temperatures caused by different conditions. The first case study looked at advection in a semi-arid region (Texas) and its effect on enhanced water evaporation and how it affects regional estimates of evaporation estimated from remotely sensed data. The second case study conducted as a cooperative project with Iowa State University and the National Center for Atmospheric Research involved a typical corn production landscape in central Iowa that contained a series of wind turbine lines throughout the landscape. There is an emerging question about the impact of wind turbines on wind movement over corn and soybean canopies located around the turbines and whether these impacts cause a positive or negative impact on crop production. This study is one of the first to quantify turbulence measurements in and outside of the crop production area affected by wind turbines. The initial results from this study documented that the wind movement over the crop is affected by the turbines and increases the turbulence over the crop leading to greater mixing of the air. Understanding these processes provides a foundation for better management of crops grown around wind turbine farms.
4. Climate impacts on agricultural crops. ARS scientists in Ames, IA, evaluated the impacts of changing climate on annual grain crops, specialty crops, and perennial crops. Long-term records of grain yields across the United States show that within season weather impacts during the period from the late 1950s to the early 1970s were relatively minimal, during the period from the early 1970s through the early 1990s there was large variation among years caused by more volatility in weather conditions, and followed by the period from the early 1990s through 2009 in which the weather impacts were diminished. There has been an increase in annual variation in crop yields across the United States since 2009 due to an increase in temperature and water stress. The analysis of Iowa corn and soybean production from 1950 through 2011 showed that 80% of the years had yield losses of less than 20% due to low rainfall, which could be offset through improved soil management to increase water availability to the crop. Results from 2012 demonstrate that soil management practices with enhanced soil water availability achieved through increased crop residue cover and soil organic matter content and coupled with nitrogen management show less impact of the drought (20% yield reduction) compared to conventional farming systems (40-50% yield reduction). These changes will help offset the impacts of projected changes in climate over the next 10-20 years to cope with increased weather variability.
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