Location: Soil, Water & Air Resources Research2011 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. Measurements of the three-dimensional wind structure near and around typical swine and poultry facilities were combined with the lidar particulate scans to characterize the evolution and transport of particulate plumes. Particulate emissions from near 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. 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 thought to be the major off-site transport mechanism for herbicide. For agricultural crops, soil carbon dioxide (CO2) flux measurements were completed approximately monthly between crop harvest and planting and completed 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. 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 issues with temperatures affect the quality of the N2O. Research projects to evaluate the interactions of tillage systems and management inputs were implemented for a corn-soybean production system on water use, nitrogen use, and light capture efficiency. This is a multiple year experiment for monitoring growth and vigor analysis and during the first year 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. We addressed this problem by using some 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 and this instrument was coupled with meteorological equipment designed to measure how rapidly air moves. These measurement systems were integrated together by Agricultural Research Service (ARS) researchers in Ames, IA, along with collaborators at the University of Iowa and the Space Dynamics Laboratory at Utah State University. These combined measurements demonstrated the presence of wind movement patterns opposite to what is currently believed about air movement. This information now opens the door for much better models which can be used 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 Agricultural Research Service (ARS) researchers from 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. In this study, regardless of weather conditions, volatilization losses consistently exceeded surface runoff losses. Surprisingly, herbicide volatilization losses were 25 times larger than herbicide surface runoff losses because it has always been assumed that runoff losses were the most prevalent form of loss from fields. Understanding these processes shows that to enhance environmental quality both runoff losses and volatilization losses into the air have to be considered. The research will affect U.S. Department of Agriculture (USDA) and U.S. Environmental Protection Agency (USEPA) policy with regard to herbicide behavior and the information used to develop or improve pesticide behavior models.
3. Climate impacts on agricultural crops. Climate change will impact agricultural crops; however, there has not been a comprehensive analysis of the overall impacts of changing temperature, precipitation, and CO2 on agricultural crops. The potential implications of climate change have been summarized in two review articles by a combination of Agricultural Research Service (ARS) researchers at Ames, IA, Beltsville, MD, Fort Collins, CO, Urbana, IL, Maricopa, AZ, Temple, TX, and university researchers. These reviews showed that the impact of high temperature stresses on plants will negatively affect both vegetative growth and crop yield. One of the most susceptible stages of plant development to temperature stress is during pollination and the rising nighttime temperatures affect the rate of grain-filling leading to reduced grain yields and reduced grain and fiber quality in cotton. Rising temperatures, coupled with the more variable precipitation, is creating a situation in which crop stress will be more prevalent. These reviews provide a reference baseline on the state of current information on climate impacts on grain crops, pastures, and rangeland plant systems which is valuable in assessing the potential strategies for adapting to climate change.
Hernandez-Santana, V., Asbjornsen, H., Sauer, T.J., Isenhart, T., Schilling, K., Schultz, R. 2011. Enhanced transpiration by riparian buffer trees in response to advection in a humid temperate agricultural landscape. Agricultural and Forest Meteorology. 261:1415-1427.