W3188: Soil, Water, and Environmental Physics Across Scales

(Multistate Research Project)

Status: Active

W3188: Soil, Water, and Environmental Physics Across Scales

Duration: 10/01/2014 to 09/30/2019

Administrative Advisor(s):

NIFA Reps:

Statement of Issues and Justification

Soil is the most crucial component in supporting life on Earths terrestrial surface. Soils transform and supply water, energy, nutrients, and organic materials and moderate release of water, nutrient and chemical needs for plants. Soil is where biological and chemical transformations occur, and it is the domain that sustains all flora and fauna ecosystem cycles. Although public awareness of the role of soils is meager, upholding and sustaining soil functions ought to be among the highest priorities of our society. Meanwhile, changing societal food and energy demands, land use and climatic conditions are imposing ever greater stresses on soil. The protection and stewardship of this crucial resource can be only assured through a better understanding of soil processes at different space and time scales.

Soil physics plays a critical role in understanding soil resources, and it has made outstanding progress in recent years considering soil as a homogeneous porous medium composed of various primary and secondary particle sizes. Storage, redistribution, transport and transformation processes of water, heat and chemicals are understood for relatively small-scale systems. However, Nielsen (1997) stated with regard to the vadose zone, it is there but nobody cares. Since then, much has been learned and documented in the Vadose Zone Journal among other esteemed outlets. Despite considerable scientific advances, knowledge gaps still remain in measurement and modeling, transfer across spatio-temporal scales, and multidisciplinary integration of results.

This project seeks to fill these gaps by developing new technologies for measuring transport, transfer, rate and state variables using comprehensive experimental designs that will yield appropriate scaling approaches. We will develop new measurement tools and process statistical structures for both measurements and processes essential for investigating soil ecosystem processes. We will improve conceptual and numerical modeling approaches that couple interdependent processes and improve our ability to transfer measurement and model information between scales. Finally, we will use our skills as soil physicists and soil scientists to advise and participate in national and international multidisciplinary projects to impart the importance of soil resources and the knowledge we have gained through decades of studying this critical zone.

We will achieve this by participating in activities such as establishing national research site observatories and measuring the spatial distribution of soil moisture across our Nation. The collaborations created and fostered through the multistate research program have spanned generations of soil physicists and hydrologists, and it is the collective opinion of the participants that multi-institutional and multi-PI collaborations have been significantly enhanced because of the multistate program. Indeed, maintaining the focus of such a large group would not be possible without this multistate program. The state-to-state networking/communication/collaboration is stimulated through the list-serve maintained at NDSU, Soil Physics division meetings at ACS and AGU, and W2188 meeting; the active year round communication that occurs is evidence to support that this has been effective. Using these collaborations, significant benefits have been realized through understanding soil physics principles and applying them to environmental sustainability of soil resources, protecting ground and surface waters, and improving agricultural production, to name only a few areas.

This group has maintained a flexible organization of researchers and field sites, rather than on focused, yet restrictive, approaches like common field sites or identical experimental approaches at different locations. Members tend to form and re-form around new multi-investigator programs while addressing critical questions. This flexible and synergistic approach has been extremely productive and it encourages a rich pollination of ideas and solutions to complex problems. The multistate committee structure is a convenient and efficient platform for establishing national research collaborations, validating approaches and techniques, pooling data, creating rigorous peer reviews, sharing equipment and developing the next generation of highly-trained soil scientists, environmentalists, and engineers.

This proposal seeks to maintain the ties between this extremely productive and creative group that without the W-2188 committee would not be as focused on national needs research. The proposal also highlights our efforts to improve environmental monitoring, implement basic soil physics research, reach out to a broader scientific community, and educate and communicate to stakeholders and colleagues within and outside our traditional discipline. Information on the scientific advancements, research findings, and inter-institutional collaborations throughout the world will continue to be provided through the committee web site maintained at NDSU. This project will engage scientists and provide answers on short-term problems affecting US agriculture and environmental protection in the areas of salinity, water quality, solute transport, evapotranspiration, soil water and chemical transport properties and other areas, especially ecological processes. Our research will focus on long-term problems, such as identifying and characterizing the dominant processes affecting the transport of mass and energy through soils and other porous media at various management scales.

This project is unique among multistate committee efforts because, rather than collaboration on a single focused objective, many collaborative projects are conducted simultaneously by organized groups of participating members and others. These extensive collaborations are established and maintained through our organizational structure. This strategy is inevitable given the diversity of problems addressed, but is also highly desirable, as information gained from the specific collaborations are shared with global science communities. The breadth of research topical areas will lead to a diverse set of outcomes that will significantly improve our knowledge regarding mass and energy transport in near-surface environments.

Related, Current and Previous Work

Though other active multistate research projects examine related soil and water quality issues, none of them focus on the interactions and feedbacks between soil hydraulic properties, energy and mass balances, environmental impacts, and scaling issues. These projects include: " W1007: Benchmark Soilscapes to Predict Effects of Climatic change in the Western USA " W2045: Agrochemical Impacts on Human and Env. Health: Mechanisms and Mitigation " W2170: Chemistry, Bioavailability, and Toxicity of Constituents in Residuals and Residual-Treated Soils " W2190: Interfacing Technological, Economic, and Institutional Principles for Managing Inter-sector Mobilization of Water " W3147: Managing Plant Microbe Interactions in Soil to Promote Sustainable Agriculture Projects outside the western region, including NC1178, NC1179, NE1038, S1053, SERA006, and WERA102 evaluate soil management, and soil and water quality. Some consider the impacts of climate change (NC1179, WERA102) and C sequestration (NC1178).

Although some projects share subject matter, there is little or no duplication with past W2188 or proposed core activities. While W1007 shares some research areas, especially on the role of soil development on ecosystem functioning and energy balance, W1007 focuses more on pedologic development from a biogeosciences perspective, which is not the past or future focus of W2188.

Many of the participants of W1007 are fellow colleagues and collaborators; thus direct overlap between groups is already self-regulated (Appendix E reviews). The same can be said for NE1038, with their focus on hydropedology of hydromorphic soils. The results of the previous W2188 multistate project are extensive, timely and applicable to numerous agricultural and environmental issues.

With the national dialog further expanding to include impacts of climate change, links between population growth in the western US and land use change, and the importance of soil to moderate and control the water budget and important ecological systems, the general themes of W2188 are even more critical. There is consensus that the soil physics community can and should be open to collaborative efforts, so that our historical knowledge and skills can also be applied to sustainable agricultural and environmental practices, natural resource stewardship and the mitigation of global climate change.

The objectives of this multistate project have a broad scope and are consistent with USDA national program goals, including protecting surface and ground waters, developing new instrumental and analytical techniques, and supporting a secure and sustainable environment while maintaining efficient agricultural production.

The objectives are: 1). To improve our fundamental understanding of vadose zone physical properties and processes, and how they interact with other environmental and biogeochemical processes across various spatial and temporal scales, 2). To develop and evaluate new instruments and analytical methods to connect our understanding of mass and energy transport in soil at different scales to environmental transformations, and 3). To extend our knowledge of scale-appropriate methodologies to improve stakeholder-management of soil and water resources that benefit agricultural, natural resource and environmental sustainability.

Concepts and previous work related to the objectives of this proposal are presented in the following text.

1. To improve our fundamental understanding of vadose zone physical properties and processes, and how they interact with other environmental and biogeochemical processes across various spatial and temporal scales

1.1. Non-destructive imaging methods such as X-ray Computed Tomography (CT) yield high-resolution (2 microns), 3-D representations of soil pore space that can be used in conjunction with advanced simulation techniques such as smoothed particle hydrodynamics (SPH) or the lattice Boltzmann (LB) model to significantly advance our knowledge about fluid distribution, interfacial phenomena, and flow and transport processes in agricultural soils. Ongoing and future research areas include improving scanning procedures and developing image segmentation and pore-space analysis tools for quantitatively characterizing soil pore space. A number of CT systems are used today by multi-state researchers, ranging from benchtop scanners to synchrotron microtomographs. They primarily differ in X-ray source and energy, detector geometry, and sample manipulation capabilities. Comprehensive reviews about fundamentals of computed tomography are provided in Stock (1999), Ketcham and Carlson (2001), and Wildenschild et al. (2002). Some applications of CT in porous media research include pore space characterization with respect to variables such as bulk density (Rogasik et al., 1999), volumetric water content (Hopmans et al., 1992; Rogasik et al., 1999), phase distributions (Wildenschild et al., 2002), breakthrough of solutes in porous media (Clausnitzer and Hopmans, 2000; Perret et al., 2000), and pore-scale configuration of immiscible organic fluids in multiphase systems (Schnaar and Brusseau, 2005, 2006ab).

1.2. Soil hydraulic properties are key to quantitatively describing soil water flow and chemical transport. Hydraulic properties of natural soils are scale dependent, time dependent, and spatially variable. In agricultural soils, temporal changes in soil hydraulic properties are primarily caused by tillage (Or et al., 2000), clay content and clay mineralogy, and water and soil quality. Changes in soil volume and pore space induced by clay swell-shrink processes present a challenge to developing predictive models for flow and transport, in particular to develop constitutive hydraulic functions. Such functions are important not only for design of man-made hydraulic barriers such as clay liners constructed for waste isolation, but also for fluid flow predictions in porous media (Mitchell, 1993; Benson et al., 1994). Recent advances in pore-scale modeling of fluid flow and liquid distribution in rigid angular pores have been developed through our collaborations. These consider both capillarity and adsorption (Tuller et al., 1999; Or and Tuller, 1999; Masad et al., 2000; Tuller and Or, 2001; Tashman et al., 2003) and provide the basis for a proposed multiscale-modeling framework in soils. Other methods for deriving hydraulic properties include pore-scale network models (Vogel, 2000; Vogel et al., 2005; Li et al., 2005), percolation-based methods (Hunt and Ewing, 2009), and lattice-Boltzmann methods (Vogel et al., 2005; Zhang et al., 2005; Schaap et al., 2007). Simultaneous scaling of soil water retention and hydraulic conductivity functions provides an effective means to characterize the heterogeneity and spatial variability of soil hydraulic properties in a given study area. The statistical significance of this approach largely depends on the number of soil samples collected. Unfortunately, direct measurement of the soil hydraulic functions is tedious, expensive and time-consuming. CA is developing simple and cost-effective hybrid scaling approaches (Nasta et al., 2013) that combine the use of ancillary information (e.g. particle-size distribution and soil bulk density) with direct measurements of saturated soil water content and saturated hydraulic conductivity. Our results demonstrate that the presented approach requires far fewer laboratory measurements than conventional scaling methods to adequately capture the spatial variability of the soil hydraulic properties. The process of mass diffusion in porous media is important for understanding migration of volatile gas from contaminated sites, transport of gases through the root zone of vegetated soils, and the interaction of aqueous and gaseous chemical constituents with the solid soil matrix. Many methods have been developed for relating the mass diffusion coefficient to phase fractions (solid, liquid, gas) of porous media, most of which have been empirical in form. In recent years and especially in the last decade, the mass diffusion coefficient was related to porous media properties such as the water retention curve (Moldrup et al., 2000; Moldrup et al., 2005; Resurreccion et al., 2008). The dependence of mass diffusion on phase distribution at the pore scale has been examined with pore scale models (Steele and Nieber, 1994a, b), percolation theory (Hunt and Ewing, 2009), and lattice-Bolzmann models (Chau et al., 2005). Thermal properties of porous media are important in many environmental and industrial applications. For instance, the thermal conductivity and heat capacity of soils greatly affect the partitioning of solar radiation into components of soil heating, the transfer of long-wave radiation, and sensible and latent heat transfer. The method of DeVries (1963) is commonly used for predicting the thermal properties from texture and phase content of porous media. More recent methods have used pore-scale modeling methods to relate the core-scale thermal conductivity to phase distributions (Hu et al., 2001; Ewing and Horton, 2007).

1.3. A traditional soil physics approach for explaining environmental processes is to examine small scale (~1 m3 or smaller) behaviors and then apply those results to larger, basin-scales using statistical upscaling techniques. This approach has provided significant mechanistic understanding of mass and energy balances, but it has limitations when using the results to explain basin-scale processes (surface runoff, soil moisture estimates for regional scale atmospheric models, large-scale water budgets). A recent review of the current status and research opportunities (Harter and Hopmans, 2004) in this area implied a need to better link small-scale physics with larger-scale hydrology through upscaling and downscaling approaches, so that soil property variability and dominant factors influencing water exchange can be placed into the appropriate context. For example, Seyfried and Wilcox (1994) identified deterministic length scales that could be applied to scale-dependent influences on hydrologic processes and models. They showed that shrub effects were limited to about 10 m and soil depth became important at length scales from 10 m to 10,000 m (for elevations below 1300 m). This has implications for hydrological response units that are used in large-scale rainfall-runoff and other models. This research program provides an excellent venue for soil physicists to participate in upscaling research, which would provide opportunities to collaborate with climate modelers and hydrologists.

1.4. The design of spatial and temporal sampling schemes is based on several questions. How do we sense variation of a soil physical and related state variable or property? How do we separate measurement noise from signal? What are ways of transferring scale-specific soil physical information to different domains while maintaining important variance characteristics? Do the spatial or temporal covariance behavior manifest that our measurement design was adequate to solve the problem? Typically, measurements taken at the instrument scale are used for spatial or temporal processes at some larger domain (Ellsworth and Boast, 1996). For this purpose, a good average of the derived property is often applied with a local-scale model to make a large-scale prediction (Cahill et al., 1999). Averages can be misleading (Stockton and Warrick, 1971). For example, when averages fail to represent the horizontal variability structure (Nielsen et al., 1973), predictions over time may be fallacious when the local status deviates from the mean. Nielsen (1987) questioned, How can we integrate information from the measurement scale to our goal scales? Investigations of the spatial and temporal variability structure of relevant soil physical state variables (soil water content) and related soil hydraulic functional properties (Western et al., 2004; Comegna and Vitale, 1993; Ünlü et al., 1989; 1990; Shouse et al., 1995) reveal substantial changes of spatial correlation lengths of soil-water-related state variables with time and the magnitude of soil-water content (Roth, 1995; Wendroth et al., 1999; Vereecken et al., 2007, Green et al., 2007; 2009). Accordingly, the cross-correlation structure between soil water and related variables depends on the magnitude of soil water status (Nielsen et al., 1973; Greminger et al., 1985). Moreover, seasonal evolution of soil moisture variance and correlation length reoccurs during times of reoccurring water status (Western et al., 2004). These more recent investigations cause us to revisit the original question posed by Nielsen (1987): Why is understanding spatio-temporal variability of soil moisture and related transport and transformation coefficients so important? This question can be applied to many scale-dependent processes, including estimating soil water processes in space and time, classifying functional and eco-physical soil and landscapes, establishing scale hierarchy of soil physical properties and regionalization, and scale transferring soil water processes. Nielsens question and these applications highlight the need to estimate regional distributions of soil water status and related transport coefficients, fluxes, and transformation coefficients at different size domains with sufficiently fine resolution to capture management and soil impact on variable magnitude (Robinson et al., 2008a).

1.5. Although soil physics and biophysics have addressed soil-plant-climate continuum issues for many decades (Russell, 1960; Campbell, 1977; Wraith and Baker, 1991; Campbell and Norman, 1998; Kirkham, 2005), the mechanistic understanding of plant root response to changing soil environmental variables such as temperature, water/salinity and nutrient concentration is still limited. Whereas a conceptual modeling framework of root response was recently developed (Simunek and Hopmans, 2009), experimental studies need to be conducted to confirm the hypothesized root responses to water, temperature and nutrient stresses, especially to compensation and nutrient uptake mechanisms. Interdisciplinary research has created a growing need and desire within this multistate project to pursue greater collaboration with ecologists and plant scientists. A decade ago, the term ecohydrology was coined and predictions of major breakthroughs and intensive activity in understanding spatio-temporal soil-plant-climate interactions were made (Zalewski et al., 1997; Baird and Wilby, 1999; Rodriguez-Iturbe, 2000). Today ecohydrology is a thriving discipline with soil physics as a major constituent informing research across scales from soil-nutrient-root interactions to desertification (Wardle et al., 2004; Hopmans, 2006; Reynolds et al., 2007). Recent inroads have been made applying principles of soil physics to vegetation and soil patterns (Robinson et al., 2008b), desert ecosystems (Shafer et al., 2007; Wang et al., 2007), Pinion-Juniper woodlands (Lebron et al., 2007), soil microbial habitat (Or et al., 2007), soil biophysics (Smucker and Hopmans, 2007) and other topics. The ever-increasing need for food supply is driving the rapid expansion of irrigation-agriculture in semiarid regions to boost otherwise limited agricultural productivity. A serious consequence of this practice is soil degradation leading to critical soil wettability problems. This is exacerbated by the use of recycled water to stretch stressed supplies. Poor soil wettability typically results in decreased crop quality concurrent with increased water use to sustain productivity. In addition, there is increased fertilizer use, runoff and soil erosion, which degrades waterways, aquifers and long-term soil health (e.g., Doerr 2011). For example, in eastern Oregons Columbia Basin, at least 70,000 acres of farmland presently exhibits water repellency. In order to compensate, growers are obliged to apply up to 25% more water (and nutrients). Traditional forms of amelioration(e.g., addition of clays, use of surfactants and removal of organic coatings) have failed to improve soil moisture conditions. Changes in climatic patterns may further exacerbate the problem in semi-arid regions common to the western US. Even though considerable work has been done to characterize the properties of poorly-wettable soils, there is still insufficient understanding needed to prevent the problem. To guarantee the long-term viability of our agricultural soils, especially as climate patterns change and as water resources decrease and the use of poor quality waters for agriculture increases, it is necessary to develop a broader and more ecologically encompassing solution. This project will address this important issue.

1.6. Emerging contaminants, such as hormones and pharmaceuticals, are widespread in the environment (Kolpin et al., 2002). Pathogens, which include viruses, bacteria or other microorganisms, are also creating major challenges as water resources dwindle and wastewater is reused. These emerging contaminants, pathogens and metabolites present unique challenges in understanding their fate and transport in the soil-water environment. Many emerging contaminants are potent at very low concentrations and labile, associating strongly with soil solids and undergoing rapid and complex transformations. Specialized laboratory experiments together with modeling and field observations are required to fully understand their fate and transport in the vadose zone (Fan et al., 2007a, b). Often these compounds (pesticides, radionuclides, and metals) can strongly associate with soil colloid particles (d 10mm in size), which can significantly enhance the immobility and persistence (McGechan and Lewis, 2002; Bradford et al., 2003; Bradford and Torkzaban, 2008). Colloids can be mineral particles, organic entities, or small living organisms, like bacteria or viruses, and engineered nanoparticles. They are ubiquitous in soils, and play an important role in soil formation and contaminant fate and transport. Understanding colloidal processes in soils and sediments is important for environmental quality and human health. We need to understand the mechanisms of colloid retention at different interfaces to make accurate predictions of colloid transport, colloid-facilitated transport of contaminants, nutrients, and other colloid associated entities such as soil carbon. The improved understanding will allow design of effective management and remediation practices to prevent soil and water contamination.

2. To develop and evaluate new instruments and analytical methods to connect our understanding of mass and energy transport in soil at different scales to environmental transformations

2.1. Throughout large segments of the terrestrial sciences, including agriculture, ecology, and hydrology, there is a pressing need to improve instruments to better interrogate subsurface environments, especially those capable of providing data for multiple state variables, which affect water movement, nutrient dynamics, plant root behavior and temperature profiles. Recent publications highlight the improvements (Mori et al., 2003; Ren et al., 2003), and the broader importance of the technologies toward answering multi-disciplinary questions (Ferré and Kluitenburg, 2003; Jones and Shenai, 2007). These new multi-function probes will be field and laboratory tested. Nonetheless, many of these approaches are still under development and will be improved upon.

2.2. Net ecosystem production and net ecosystem exchange are closely tied to soil properties. Researchers have a significant opportunity to assist the agricultural and ecological communities by addressing the importance of soil properties and processes. Heitman et al. (2008) showed an approach that uses heat pulse probes as a means to estimate latent heat flux, a critical component of the energy budget. Upscaling these point-scale values to basin-scale (Zhu et al., 2006) would allow better assessments of regional-scale water status, yet advancement of instrumentation and analyses has lagged the potential societal applications. In particular, remote sensing tools are becoming more sophisticated, but ground truthing is needed.

2.3. Quantifying soil structure has been a challenge ever since soil structure has been recognized as an important part of a soils physical properties (Baver, 1940, Kubiëna, 1938). In recent years, non-destructive imaging techniques such as X-ray computed tomography (CT) (Duliu, 1999, Taina, Heck, et al., 2008), nuclear magnetic resonance imaging (NMR) (Hemminga and Buurman, 1997) and neutron radiography (NR) (Oswald, Menon, et al., 2008) have become available, and these allow the study of soil structure non-destructively and non-invasively. Despite this considerable progress form the imaging side, relating soil structure to physical properties remains a challenge (Logsdon et al., 2013). As a consequence, soil structure information is still missing in most pedo-transfer functions (PTF) (Schaap et al., 1998; 2001). Another deficiency is the lack of incorporating spatial covariance (Wendroth et al., 2006) although one of the main goals of PTFs is regionalization of soil hydraulic properties.

3. To extend our knowledge of scale-appropriate methodologies to improve stakeholder-management of soil and water resources that benefit agricultural, natural resource and environmental sustainability The scale-appropriateness of a methodology, whether measurement or model, is based on the methods ability to provide measurements or calculations (soil water content, matric potential, water flux, heat flux, etc.) that capture the continuity of a process in the spatial or temporal domain, or both. The continuity of a spatio-temporal process needs to be derived, not only for assuring spatial representativeness of observations, but also to transfer the process of one or several variables across scales. Much has been done to develop methodologies that will upscale measurements made at point scale to the larger scale. A review of the state-of-the-art of such methods as applied to soil moisture monitoring is presented by Oschner et al. (2013). Numerous examples also exist for methods to upscale pore-scale characterization of porous media to the core scale (Or and Tuller, 1999), and from core scale to field scale (Yeh et al., 1985; Zhu et al., 2006). Capabilities to model large scale systems have improved greatly over the past decades because of vast improvements in computer speed as well as vastly improved numerical algorithms. In 1970, R.A. Freeze (1970) reported the simulation of watershed hydrology using 30,000 grid cells. In a recent example Kollet et al. (2010) demonstrated the ability to efficiently model the subsurface flow driven with land surface processes in a hypothetical watershed discretized with 8 x 109 grid cells using up to 16,384 parallel processors. Rather than using models that treat processes at fine scale (Darcy scale for instance), as with the Freeze (1970) and the Kollet et al. (2010) applications, an alternative is to use upscaled equations that are appropriate for field or subwatershed scale. An application of this type is outlined by Reggiani and Shellekens (2003), which describes the Representative Elementary Watershed approach to modeling of mass and energy transport in watersheds.


  1. To improve our fundamental understanding of soil physical properties and processes, and how they interact with other environmental and biogeochemical processes across various spatial and temporal scales.
  2. To develop and evaluate new instruments and analytical methods to connect our understanding of mass and energy transport in soil at different scales to environmental transformations.
  3. To extend our knowledge of scale-appropriate methodologies to improve stakeholder-management of soil and water resources that benefit agricultural, natural resource and environmental sustainability.


The activities by each of the state participants are outlined by objective/sub-objective in the following: Objective 1.To improve our fundamental understanding of vadose zone physical properties and processes, and how they interact with other environmental and biogeochemical processes across various spatial and temporal scales. 1.1.Non-destructive imaging for understanding sub-visible scale processes. CA will design a two-dimensional split-root study, allowing for partial soil root zone water, nitrate, and temperature stresses, while measuring plant activity through total water use (ET). Innovative techniques to measure soil water and nutrient status will be neutron tomography and application of heat pulse probe. AZ, NV, and CA will continue ongoing collaborations on use of X-ray CT and neutron tomography. Our focus is on solving questions related to the basic understanding of how the soil fabric affects water flow and contaminant transport in subsurface environments. A regional consortium of instrumentation and intellectual resources will be formed for use by students, post-docs and others interested in micro-scale processes. WY, CO, ID and AZ will evaluate different electromagnetic techniques to measure soil variables such as water content, water potential, and bulk electrical conductivity in larger basins and watersheds. TX will continue working on insitu, air-borne, and space-borne sensors for understanding soil hydrologic processes and related parameterization across various space and time scales (Ines et al., 2013; Mohanty et al., 2013; Mohanty, 2013; Shin et al., 2012). 1.2 Characterization and description of physical properties of the vadose zone. TX will develop a comprehensive coupled water and heat transport numerical model including multi-domain unsaturated zone water flow and heat transport processes at continuum scale. This will further improve our capacity to better understand the water and energy cycle. NM will work on determination of the thermal properties of different soils irrigated with low and high salinity irrigation water and saline and sodic treated wastewater. The survival and growth of some desert plants on these irrigation soils will be quantified. The pore-clogging due to concentrate (waste) application will be studied using image processing technique, in collaboration with CA. UT, AZ, and CA will study relationships between soil and manure physical properties and greenhouse gas emissions and evaporation. New inverse estimation schemes with uncertainty will be developed in collaboration with, CA and AZ. These researchers will estimate effective soil hydraulic and thermal properties across the USA at different resolutions by assimilating soil moisture from ground, air, and space-borne sensors. IA, NV, KS and ND will analyze shallow soil temperature gradients and thermal properties in order to estimate soil water evaporation across scales as a function of depth and time. VA will characterize the structural and hydraulic properties of soil through the use of methods including stable isotope analysis. 1.3. Vadose zone role in quantifying basin-scale responses. CA will conduct studies to examine the effects of vapor flow, vegetation, bulk density and particle size distribution on plant water absorption and desorption, soil erodibility, sediment mobility and overall water uses by the giant tree forests in the southern Sierra Nevada critical zone areas. This study will be conducted along with biologists and ecologists at CSU to look at related biological and ecological effects (Liang et al., 2009). CA will also quantify field to basin scale transfer of nitrogen and salts in irrigated agricultural landscapes through soils as conduit between surface/landscape/atmospheric processes and groundwater reservoirs. VA will examine the basin-scale effects of land cover changes on soil properties and hydrological thresholds. 1.4. Multi-scale flow and transport including impacts from climate change. TX will evaluate the feasibility of using inexpensive ground-based radiometric observations of the crop canopy to augment soil water profile measurements for improved irrigation management. State-space models will be used to incorporate observational error and mechanistic water flux processes to upscale root zone soil water content measurements. CA will collaborate with local investigators, measuring core-scale soil hydraulic properties, and apply scaling techniques to the hillslope scale. Measurements of soil water tension and soil moisture, in concert with piezometer data will be coupled with HYDRUS to simulate hillslope-scale soil hydrology. CA will study the effects of climate change on stream flow in Californias southern Sierra watershed based on existing studies (e.g., He et al., 2013). CA will link plot, field, and basin-scale data collection efforts to determine mathematical or statistical upscaling relationships for nitrate and salt transport through the unsaturated zone; and estimate landuse effects on transport. VA will quantify temporal variability of soil hydraulic properties at the core and field-scale with an emphasis to understand the role of moisture-dependent preferential pathways in structured soils. TX will evaluate deficit irrigation strategies to evaluate how crop water stress influences root elongation and proliferation, and other aboveground morphological plant characteristics. TX will also apply technologies (e.g., satellite-based products, point scale sensors, etc.) to quantify regional-scale soil moisture balance and associated biogeochemical fluxes. Feedback mechanisms will also be measured (e.g., soil C storage). AZ will investigate fundamental pore-scale flow and transport phenomena by means of X-ray CT and fluid dynamics modeling. Collaboration with NV to study water use and redistribution by native desert plant communities by means of weighing lysimetry, followed by expanding results to the basin-scale (ecosystem) scale. MN will use methods (Reggiani and Schellekens, 2003) for representing the hydrologic balance of a selected landscape at different scales. CA will conduct numerical simulations of water flow and contaminant transport in overland flow and in variably saturated soils for a wide range of conditions (topography and soil heterogeneity). Results will be used to develop more appropriate upscaled exchange terms for regional scale models. KY will continue to monitor water content, soil temperature, C and nitrous gas emissions in two different land use systems (agricultural crop, pasture). Field studies have shown so far that soil temperature and soil water content strongly affect the temporal variation of soil respiration, while other processes also affect the variability. (Kreba et al., 2013). KY will continue on space-time fields of soil gas fluxes and spatial processes of the soil gas diffusivity behavior (Ds/D0) versus air-filled porosity. ND will evaluate soil hydraulic and thermal properties in partially-frozen cracking soils. Small scale measurements will be up-scaled to improve flood forecasting systems in the Red River Valley of the North. 1.5. Applications of soil physics and biophysics in ecology and agriculture. UT and ID will design and model plant growth systems for reduced gravity conditions based on porous medium physical properties and plant physiological characteristics. ND will quantify soil structural pore spaces, soil shrinking and swelling, and thermal properties and their relationships to microbial activity. ND will quantify soil hydraulic and thermal properties in rangelands. WY will quantify coupled water flow and heat transport in rangeland and forest soils and study the impact of disturbance on water, heat, carbon, and nitrogen fluxes. NV and CA will examine the impacts of root water uptake and root growth on local soil properties immediately adjacent to roots (rhizosphere). Root water uptake models and high resolution CT scan analysis will be used to test and improve models of soil/root feedback on water uptake and soil hydraulic properties within the rhizosphere. AZ, CA, and DW will conduct experimental and modeling studies to investigate the role of rhizosphere scale processes, including rhizodeposition and microbial EPS production, on mitigation of water and nutrient stresses. CA will investigate the role of association between native shrubs and crops in managing moisture and nutrient stresses. OR will investigate two key hypothesis under the umbrella that agro-ecosystem-stress drives the soil towards a deteriorated form that is expressed as poor wettability. The molecular state of soil organic matter (OM) determines this wettability, and the hypothesis is that agronomic practices drive OM towards conditions that favor soil water repellency. A multi-scale investigation will include cropping trials at the field scale for six 125-acre commercial agricultural circles (Columbia Basin, OR) under historically different crop and tillage practices. Laboratory and field scale studies will be conducted to quantify OM molecular state of soils at the experimental fields. 1.6. Transport and transformations of solutes, colloids, and emerging contaminants. WA, CA, DE, VA, AZ and ND will investigate interactions of colloids with interfaces, and fate and transport of potential agricultural and emerging contaminants by conducting a combination of laboratory column experiments, numerical modeling, greenhouse studies, and field scale research. Microscopic (electron and confocal microscopy, tensiometry) and macroscopic (goniometry, light scattering, column experiments) techniques will be used to investigate and quantify the interactive processes. The mechanisms controlling colloid fate and transport in the vadose zone will be incorporated into mathematical models (HYDRUS). ND and CA will also use laboratory methods, primarily column breakthrough curves, batch sorption experiments, soil microcosm batch studies to examine the processes which control bioactive chemical fate and transport. Controlled experiments and observations from the field using soil extracts, lysimetry, and wells will be used to identify field fate and transport mechanisms. CA, ND, DE and NV will focus on characterizing the fate and transport of trace organic compounds (endocrine disrupting compounds) originating from reclaimed wastewaters in soil and water through field, laboratory, and numerical experiments. AK with USDA-ARS will conduct experiments on the attenuation of herbicides in sub-arctic soils. DE will conduct laboratory experiments and collecting wetland water and soil samples to elucidate the mechanisms of colloid release under dynamic redox conditions and determine the role that colloids play in nutrient transport and carbon cycling. CO will develop a simulation model for methane fate and transport in soil. A critical task of this work will be characterizing the soil biology of methane producers and consumers, particularly in response to changing soil water content and temperature. Using controlled laboratory and field experiments, TX will focus on understanding the linked hydrologic and biogeochemical processes in the vadose zone (Hansen et al., 2011; Arora et al., 2013). The group will collaborate by sharing experimental equipment, co-organizing symposia at professional meetings, and by coordinating research activities among the different participants. Developed mathematical models will be shared and improved based on experimental and theoretical results obtained by the group participants. Objective 2.To develop and evaluate new instruments and analytical methods to connect our understanding of mass and energy transport in soil at different scales to environmental transformations. 2.1. Improved Multifunction Measurement Devices. CA will continue developing and evaluating instruments to measure soil water content, soil solution salinity and nitrate, and unsaturated soil water fluxes. This work is related to the BHPP (button heat pulse probe) (Kamai et al., 2008) and the fiber-optics soil solution analyzer by Tuli et al. (2009). The current BHPP will be adapted to include two electrodes, so that soil solution concentration can be measured in concert with soil moisture (in collaboration with KS). The in-situ soil solution sampler with fiber-optics technology will be adapted to measure soil solution organics, such as BTEXs and gasoline-derivatives to assist in bioremediation of contaminant plumes in ground water and vadose zone. IA and KS will develop a heat pulse sensor to determine shallow soil profile temperature, thermal properties and sensible and latent soil heat fluxes. TX and CO will continue collaboration on a new down-hole soil water sensor to address the problems of inaccuracy and spatial variability seen with current capacitance sensors (Baumhardt et al., 2000; Kelleners et al., 2004ab, 2005; Evett et al., 2006; Mazahrih et al., 2008). Electromagnetic (Schwank et al., 2006; Schwank and Green, 2007) and soil water dielectric (Wraith and Or, 1999; Schwartz et al., 2009ab; Casanova et al, 2012b) theory and testing Casanova et al., 2012a, 2013) will be used to continue the development and refinement of downhole sensors that act as waveguides rather than antennas and that are relatively insensitive to interferences from bound water and bulk electrical conductivity, including correction for these interferences. CA will conduct studies to improve the detection of clay content (<2 ?m) in soils using laser diffraction with a new lens attached to a LISST-Portable (Sequoia Scientific Inc.), the only portable particle size analyzers available. TX will continue evaluation of the Cosmic Ray Soil Moisture Observing System (COSMOS) in a 5-ha subsurface drip irrigated field with cotton and corn as alternating crops in successive years. The COSMOS system will be compared with networks of neutron probe and wireless electromagnetic (EM) soil water sensors to understand the sensitivity of COSMOS to: 1) irrigation water supplied by subsurface drip irrigation at 0.30-m depth, 2) water supplied at the surface by irrigation, and 3) water contained in green biomass. In later years, COSMOS ability to linearly integrate over space will be tested by inducing patchy soil water variability by applying various levels of full and deficit irrigation in the ten management zones in the field. 2.2. Quantifying near-surface processes with instruments and analyses. TX and ID will characterize the influence of tillage on stored soil water, infiltration, evaporation and distribution of soil water across the landscape in dryland cropping systems. TX will evaluate eddy covariance (EC) sensed ET versus ET determined by mass balance using large weighing lysimeters and networks of soil water sensors under a variety of plant cover conditions, including bare soil. The persistent underestimation of ET by EC systems will be studied in light of the components of the energy balance, system sensor capabilities and advective conditions. UT, ID and AZ will develop multi-functional measurements for soil property determination including physically-based approaches for predicting evaporation rates from thermal surface signatures. IA will measure heat and water fluxes in soil that experiences time changing bulk density. They will work to develop a novel, physically-based approach for predicting evaporation rates from thermal surface signatures. These rates will be tested (with NV) using thermal surface signatures and weighing lysimeters recently installed in NV. NV will continue to develop the use of fiber optic temperature sensing to measure spatially distributed near surface soil moisture (Tyler et al., 2008, Moffett et al., 2008). Such measurements are currently being made at the SMAP Validation in Oklahoma. NV and CA will expand its analysis of fiber optic temperature sensing to estimate daily water content changes in the upper 15-20 cm of soil profiles. KY will continue the implementation of active optical crop sensors (GreenSeeker) to improve nitrogen fertilizer application schemes. Moreover, a new FTIR-spectrometer will be used to quantify soil gas fluxes at the land surface. NM will examine the soil moisture content using different sensors and soil temperature, and assess the usefulness of partial root zone drying techniques on water savings while maintaining crop yields, and mass and energy transport through the soil. Several meteorological, and soil and plant based measurements will be made inside the greenhouse. Numerical tools will be utilized to model soil water and solute dynamics through the vadose zone (Deb et al., 2013). CA, AZ, and MT will develop new measurement protocols, techniques, and instruments to measure soil water content and nutrient/salt fluxes under varying environmental conditions and atmospheric emissions of soil fumigants. CA and many of the other participants in this multistate program (USSL, UCD, WSU, DE, NDSU and DRI) will continue developing numerical tools, such as HYDRUS, to study and evaluate environmental processes and biogeochemical reactions across scales. CA will continue to develop deep vadose zone measurement techniques to assess water and associated nitrate leaching to the groundwater at the field-scale as well as to determine deep soil contributions to tree water requirements in a forested high-elevation watershed (CZO). 2.3. Quantifying Soil Structure. NV, AZ, KY and ND will examine soils of different texture with respect to soil structural indices to improve the indirect estimation of soil functional properties (hydraulic conductivity function). ND will also examine soils of different sodium absorption ratios and ionic strengths. This task is relevant for improving PTFs. Here, auxiliary variables in combination with PTFs and their spatial covariance structure will be investigated with respect to their support of capturing field scale spatial variability of soil hydraulic properties. Objective 3. To extend our knowledge of scale-appropriate methodologies to improve stakeholder-management of soil and water resources that benefit agricultural, natural resource and environmental sustainability. We will continue developing interdisciplinary meetings (joint session at the Ecological Society of America meeting, August 2008) and special publications (Young et al., 2007). Experimental methodologies and instruments (large-scale soil property determination) and sampling designs targeted at geostatistics (Isaaks and Srivastava, 1989) and applied statistical time series analyses (Shumway and Stoffer, 2000) will be adapted and developed for agricultural and ecological applications (Nielsen and Wendroth, 2003). NM will work on the temporal variability of thermal properties of soils irrigated with wastewater for different amounts of time. The geostatistical analysis of soil physical properties will be performed for arid area under different three geomorphic surfaces and eight soil mapping units. For the CA CZO site, deployment and monitoring of approximately 150 soil moisture sensors installed around a white fir will continue (Hopmans et al., 2012). The experiment is done in parallel with eco-physiological measurements to investigate how soil environmental stresses (water, temperature, nutrients) impact forest systems and to apply the results across the rainfall-to-snow-dominated transition zone. CA will further evolve computational methodologies to characterize high-resolution basin, continental, and global scale transfer processes of salts and nutrients between the cultural landscape and groundwater through the vadose zone, to improve our understanding of the role of soils vis-à-vis anthropogenic activities and the impact to long-term dynamics of groundwater quality and groundwater-dependent surface water systems. Across a network of micro-irrigated agricultural fields, with most to them in tree crops (almond, pistachio, citrus, walnut), CA will deploy state-of-the-art subsurface monitoring capabilities for soil moisture, soil nitrate, salinity, and leaching of water and nitrate. The main objective of this field-scale research is to develop improved irrigation management practices that minimize nitrate losses while maintaining crop production. Field measurements will be coupled with numerical modeling tools (HYDRUS) for the main purpose to evaluate best management practices. CA will continue examining the effects of global climate change on water resources availability in the Sierra Nevadas. A representative headwater basin near the headwaters of the San Joaquin River, with natural flow in the upper watershed, was selected for hydrologic simulations using the HSPF model and climate change scenarios. Field trials will also determine BMPs for irrigating with degraded waters and applying pesticides. ND and MN will study the vadosesaturated zone continuum to develop nutrient management methods that reduce loading to and degradation of ground water and subsurface tile drainage, while maintaining optimal economic benefits. Field observations will primarily originate from lysimeters, soil and plant samples, nutrient input records, and tile drainage measurements of water quantity and quality. MN and potentially CA will develop the ability to quantify the water fluxes across the surfaces of land masses of arbitrary size, providing the basis for developing new brands of hydrologic and transport models that can incorporate flux calculating procedures into SWAT or similar models. UT, AZ and ID will apply geophysical measurements for improved understanding of watershed and forest ecological processes. WY will combine monitoring data from a soil moisture sensing network with computer simulation modeling to improve drought prediction in Wyoming rangelands. OK will explore the potential to estimate groundwater recharge based on known soil hydraulic properties and daily soil moisture measurements at the >100 automated weather station sites comprising the Oklahoma Mesonet. Recently determined soil hydraulic conductivity functions (Scott et al. 2013) will be used, together with existing Mesonet sensors and unsaturated flow theory, to generate maps of groundwater recharge for the entire state of Oklahoma. NV will study native revegetation to examine how to reduce water demand for agricultural lands taken out of production in arid and semi-arid regions. WA, in collaboration with the USDA NSERL and US Forest Service Rocky Mountain Research Station, will continue to improve, test, and apply the WEPP (Water Erosion Prediction Project) model for watershed assessment and management. KY will continue to establish and expand an innovative field scale approach to studying water and solute transport processes. This approach is based on scale-dependent not random spatial distribution of treatments. This design allows studying important transport processes in heterogeneous field soils (Wendroth et al., 2013; Yang et al., 2013; Yang and Wendroth, 2014). TX will conduct remote- and field-based studies to assess impacts to landscapes (e.g., soil, water and ecosystem resources) from above-ground activities, including urbanization, energy development and land conversion. In addition, based on better understanding of physical controls of soil moisture at different scales (Gaur and Mohanty, 2013), TX will develop maps for soil moisture/soil hydraulic parameters at different scales (Ines et al., 2013, Shin and Mohanty, 2013) by using satellite remote sensing data for water resource management and decision support systems under changing climate scenarios.

Measurement of Progress and Results


  • Generating new information on mass and energy transport processes in soils at spatial and temporal scales appropriate for effective resource management.
  • Improved understanding of the role of scale in basin-scale processes, including evapotranspiration, water balance and ecological functions and services.
  • Generating new knowledge affecting the environmental impacts of soil, water and chemically-based agricultural practices and broader land uses.
  • Transference of results from non-destructive imaging into quantitative assessments of soil structure.
  • New instruments and analytical techniques for measuring water, chemical, and energy fluxes.
  • Output 6. New methodologies (computer and analytical models) that integrate knowledge of mass and energy transport, improving resource management. Output 7. New collaborations with ecologists, hydrologists, pedologists, and engineers who are predicting landscape responses from land use/land cover changes and climate variability. Output 8. Continued support of young faculty, post-docs and students, who are dedicated to studying the role of soil physics in environmental processes. Output 9. New graduate level, international course on soils in the global groundwater-agriculture interface.

Outcomes or Projected Impacts

  • New tools and capabilities to quantify and monitor movement of agricultural contamin
  • Develop new scientific knowledge and information about fundamental physical, chemical and biological processes affecting the transformation and transport of pesticides, pathogens, colloids, nutrients, salts, and trace elements.
  • Quantify the amount, fate and transport of bioactive compounds from commercial manure handling and disposal methods.
  • Improve understanding of processes that control behavior of trace organic compounds from grey water in soil/water systems, including mitigation practices.
  • Examine herbicide leaching to ground water versus metabolism in the soil and in plant in diverse climates.
  • Output/Impact 6. Develop plant growth media for reduced gravity environments of space. Output/Impact 7. Provide guidance to producers on the sustainability of drip irrigation in salt-affected soils with reduced quantity or marginal quality irrigation water. Output/Impact 8. Model sensitivity of drip irrigation management scenarios to assist farmers and managers as they adoption sustainable and efficient irrigation systems. Output/Impact 9. Develop simple and reliable soil water sensing systems to accurately quantify soil water balance and other hydrological processes. Output/Impact 10. Frequency-dependent dielectric measurements in soil to infer soil textural properties in addition to water content and electrical conductivity. Output/Impact 11. Improve measurement techniques to better characterize the relationships between soil, climate and geomorphic position at the landscape scale. Output/Impact 12. New thermal instruments and analytical methods for calculating sensible and latent heat fluxes. Output/Impact 13. Further develop fiber optic DTS as a reliable soil moisture sensor. Output/Impact 14. Evaluate and predict land-use changes on managed lands (impact of grazing on compaction, erodibility, plant communities). Output/Impact 15. Landscape-scale predictive capabilities for soil evaporation that can be implemented into large-scale climate models. Output/Impact 16. Improve protection of soil and water resources from energy production (i.e., coal and mineral extraction, in particular mine tailings. Output/Impact 17. Develop stronger connections between atmospheric measurements and soil physical and hydraulic properties, especially under climate change scenarios. Output/Impact 18. Solve the closure problem for various hydrologic fluxes, including heterogeneity adopted into lumped parameter models (i.e., SWAT). Output/Impact 19. Establish statistical structure between soil water, soil C storage and soil gas (C, N) emission fluxes in different land use systems before and after land use transition. Output/Impact 20. Develop new statistical methods to link crop yield and variability from sensor measurements. Output/Impact 21. Assessments, briefings, and legislative testimony in direct support of policy and decision-making bodies at the state and federal level. Output/Impact 22. Update versions of various numerical tools being developed: HYDRUS, HP1, CW2D module, the UNSATCHEM modules, the HYDRUS package for MODFLOW and others.


(2014): Complete research on delineating short-term influence of tillage on water storage and crop yield. Model testing of methane fate and transport in grassland soil. Complete drip-irrigation experiments in salt-affected soil. Conduct novel evaporation experiments using an environmentally-controlled laboratory lysimeter and large weighing lysimeters. Apply numerical modeling to evaluate optimal plant growth media for reduced gravity environments. Characterize and present ET estimates of montane vegetation from the Intermountain West.

(2015): Complete experiments to examine the impact of imposed soil water deficits on root elongation. Model testing of methane fate and transport in forest ecosystems. Conduct lysimeter studies to investigate water use and redistribution of plant communities in the desert. Improve segmentation and quantitative analysis methods for X-Ray CT images. Study greenhouse gas emissions from agricultural areas and management systems. Complete studies on the potential for water flow and contaminant transport from energy (coal) production. Apply REW concept to close water budget components at the basin scale for a select watershed in Minnesota.

(2016): Complete research on delineating short-term influence of tillage on water storage and crop yield. Model testing of methane fate and transport in desert ecosystems. Derive physically-based model that relates soil properties, topology, and atmospheric conditions to soil evaporation rates. Design soil surface preparation strategies for ag and environmental management, to reduce evaporation rates. Combine measurements of water content, water potential, and soil bulk electrical conductivity at the landscape scale. Distinguish herbicides that leach to ground water from those that metabolize in soil and plants. Couple landscape scale water balance modeling with meso-scale climate modeling.

(2017): Complete lysimeter measurements and analyses of nutrient movement toward ground water. Provide design criteria for vegetative covers of tailings impoundments and landfills in semiarid and arid environments. Code and distribute software package for segmenting and analyzing X-ray CT images. Complete experiments to examine temporal and spatial distribution of soil C and N dynamics and greenhouse gas emissions. Complete analyses of hydromechanical and hydraulic property impacts from expanding root structure in soils. Develop improved sensors for physical property and process determination.

(2018): Review soil water sensing systems for water balance determinations. Review and ensure effectiveness of commercialization efforts. Complete experiments to examine the impact of imposed soil water deficits on root elongation. Incorporate colloidal processes into workable numerical approaches. Quantify fate and transport of bioactive compounds from manure operators. Develop strategies to reduce greenhouse gas emissions from ag soils. Link atmospheric measurements and PTF-derived soil hydraulic properties to predict soil water resources .Incorporate new physically-based modeling methods for simulating watershed-scale processes. Develop a physically-based conceptual model of feedback mechanisms that affect C storage and release. Describe dynamic behavior of water and soil gas emission fluxes during and after land use transition. Strive to make sensors and algorithms developed by this group commercially available. Complete BMPs for irrigating with degraded water to reduce air contamination from ag pesticides. Prepare proposal for 5-year project renewal.

Projected Participation

View Appendix E: Participation

Outreach Plan

The project members comprise a group of dedicated soil, water and environmental scientists and engineers who excel in the communication of their research through different communications platforms, and who are active participants in soil and environmental research at universities and federal facilities throughout the country. They also lead in undergraduate and graduate instruction and mentoring, and by supervising post graduate, graduate and undergraduate research. Many of our members conduct workshops, short courses, and classes to train other scientists and the public, contribute to state, regional and federal agencies and publish their findings in top-tier, peer-reviewed journals, targeting both science and engineering communities.

W2188 members are active participants and presenters at many professional society international/ national/regional meetings (SSSA, AGU, ESA, EGU, ASABE, ASCE, GRA, GSA), and major workshops and symposia sponsored by these societies. Our members are frequent initiators of major workshops and symposia. They serve on journal editorial boards and as ad hoc manuscript reviewers, and therefore, enhance the overall quality of published research.

Members not only conduct research, but they serve the scientific community by their engagement in competitive grant review panels of federal and regional entities, and as peer reviewers for domestic and international grant proposals. Members frequently engage with legislators at the state and federal level, and with managers, directors, and personnel in local, regional, state, and national water management organizations (e.g., irrigation and water districts, state agencies, regional MOUs) to support scientifically-based policy development and technically sound decision-making. Through entrepreneurship, committee members have developed commercially available instruments, analytical tools, and textbooks. We fully expect this type of outreach to continue and thrive.

Results of our work will be available through the annual project report, the project website (http://nimss.umd.edu/homepages/home.cfm?trackID=6016), periodic joint meetings with related multistate research and/or coordinating groups, and through the international reputations and professional visibility of participants. All of the members at some time or another work with consulting firms, companies, government agencies, and/or farmers to adopt measurement and management technologies.


The current W2188 multistate committee consists of members representing SAESs, other Universities, the USDA-ARS, National Laboratories, and other research units. In addition, visiting scientists (U.S. and global) participate along with member hosts. Officers of W3188 will be the Chair and Secretary. As done for some time, the Secretary is elected each year at the annual meeting and advances to Chair the following year. The Chair may appoint members to serve on subcommittees as needed. Meetings will be approved by the AA. The current Secretary will be responsible for making local arrangements. Committee meetings typically have been held in Las Vegas, NV during early January, but this will evolve by choosing new locations at different host institutions (the 2009 meeting was held in Tucson, AZ, and the 2012 meeting was held in Hawaii). At each meeting, research accomplishments are reviewed, new opportunities and recommendations for multistate coordination/collaboration are discussed, and strategies for maximizing the impact of committee productivity are reviewed. In addition, we are now inviting scientists from different disciplines (geomorphology, land use planning, ecology), so that invitees can discuss new cutting-edge research directions that would engage areas of our expertise. In this way, fresh perspectives are injected into the committee, encouraging outward-looking and multi-disciplinary approaches toward pressing agricultural and environmental problems. The project committee and its precursors have had strong historical participation at the annual meetings (35-40 attendees), with new members inducted each year to ensure longevity and infusion of fresh perspectives. It should be mentioned however that in the very recent years the attendance has been down to about 25. Existing W2188 members have indicated a strong desire to continue participation, even if not able to attend the annual meeting. A priority for the committee leadership for the new project will be to evaluate ways to increase the active participation at the annual meeting.

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