Salinity and sodicity are two different conditions that have many characteristics in common and are closely related. However, they have significant differences that require unique strategies for each condition with respect to use and management. In general, saline conditions occur when the amount of soluble salt present in the soil water is high enough to have detrimental impacts on biotic systems. There are many types of salts and the environmental chemistry of salts can be quite complicated. Salts are a chemical combination of a positively charged (cation) and a negatively charged (anion). The solubility of a salt is defined as the amount that can be dissolved in water without crystallization or precipitation. Solubility is determined by the chemical composition of cations and anions. Salts such as sodium chloride (table salt) have high solubility compared to salts like calcium carbonate (lime) with low solubility. High amounts of soluble salt in soil water are detrimental to biotic systems, because they increase the osmotic pressure. This decreases the ability of biotic cells to extract water. Cations in soil water are adsorbed by soil clay particles. When 15% or more of the adsorbed cations are sodium ions, a physical effect occurs known as clay particle dispersion. Dispersed clay particles form dense soil layers with low porosity, which limits the plant root's ability to extract water and other nutrients. Both salinity and sodicity result in droughty conditions with respect to plant growth, but are quite different with respect to the cause.
The natural processes that contribute to the formation of saline and sodic soils are related to hydrologic conditions that allow movement of water and salts to concentrate at certain locations on the landscape. As a result, saline and sodic soils are often found together on the landscape. In fact, in many situations soils have formed that exhibit both saline and sodic properties. Because the chemical and physical mechanics of these two conditions are quite different, strategies employed for use and management are also quite different. The same strategy for suppressing salinity problems may have the opposite effect with regard to sodicity. The fact that these soils often occur as inseparable areas on the landscape further complicates attempts to apply effective management techniques. Before the expense of various management schemes are applied on saline and/or sodic soils, it is critical that the distribution of soil properties is adequately identified. Practices to manage soils affected by salts vary depending on the soil characteristics at each site. Some of the things that need to be ascertained before a management strategy can be formulated include: the distribution of the amount and type of salt; the geologic source of the salt; the site hydrology; and other soil properties that affect water and salt flow.
A major focus of my career has been on soil salinity/sodicity and its effects on use and management. I began academic research on this topic in the 1970s. I conducted field investigations on saline seeps in Divide Co., ND and sodic soils in Foster Co., ND. I have authored several professional publications based on these projects. During the years that I participated in soil survey projects, identification and characterization of saline and sodic soils was a regular activity. Later in my career as a water quality specialist in the upper Great Plains, salinity continued to be a topic that required attention.
Salts are manifested in may different ways in the soils of the Northern Great Plains. I outlined the range of soil properties that constitute saline and/or sodic conditions in NDSU Extension Bulletin 57 "Salinity and Sodicity in North Dakota Soils" http://www.ag.ndsu.edu/pubs/plantsci/soilfert/eb57-1.htm. In order to apply effective methods of use and management to these soils, two basic areas of knowledge need to be well understood: 1) salt chemistry; and 2) soil hydrology. I have published and presented results of scientific study that describe specifically the integrated nature of water and salt movement on and through the landscape, in the following:
Seelig, B. D. 1994. Weathering zones in coarse-loamy till related to pedogenesis of sodic soils. Abstract, 86th Annual meetings American Society of Agronomy, Seattle, WA.
Richardson, J. L., N. J. Lunde, and B. D. Seelig. 1991. Pedogenetic effects of groundwater recharge on solodic soils in North Dakota. Abstract, 83rd Annual meetings American Society of Agronomy, Denver, Colorado.
Seelig, B. D. and J. L. Richardson. 1991. Soil genesis of a sodic soil toposequence in central North Dakota. Abstract, 83rd Annual meetings American Society of Agronomy, Denver, Colorado.
Seelig, B. D., J. L. Richardson, and R. E. Knighton. 1991. Comparison of statistical and standard techniques to classify and delineate sodic soils. Soil Sci. Soc. Am. J. 55:1042-1048. https://www.soils.org/publications/sssaj
Richardson, J. L., D. G. Hopkins, B. D. Seelig, and M. D. Sweeney. 1990. Salinity causes. Proceedings Red River barley day, American Malting Barley Assoc., 9 Nov. 1989, East Grand Forks, MN.
Seelig, B. D. and J. L. Richardson. 1989. Soil profile characteristics on a sodium affected landscape in central North Dakota. Proceedings, 32nd Annual meetings Manitoba Society of Soil Science. Soil Sci. Dept., University of Manitoba, Winnipeg.
Richardson, J. L., D. G. Hopkins, B. D. Seelig, and M. D. Sweeney. 1989. Salinity development, recognition, and management in North Dakota soils. Proceedings, 6th International Soil Correlation Meeting: Correlation, Characterization, Classification, and Utilization of Cold Aridisols and Vertisols.
Seelig, B. D., J. L. Richardson, and W. T. Barker. 1989. Characteristics and taxonomy of sodic soils as a function of landform position. Soil Sci. Soc. Am. J. 54:1690-1697. https://www.soils.org/publications/sssaj
Seelig, B. D. and J. L. Richardson. 1988. Problems in classification of natric soils in North Dakota. Abstract, 80th Annual meetings American Society of Agronomy. Anaheim, California.
Seelig, B. D., R. Carcoana, A. Maianu. 1987. Identification of critical depth and critical salinity of the groundwater on North Dakota high water table cropland. Technical Completion Report, ND-03. North Dakota Water Resources Research Institute, North Dakota State University, Fargo.
Worcester, B. K., L. J. Brun, and B. D. Seelig. 1976. Application of seismology to the study of saline seeps. Proceedings, Regional Saline Seep Control Symposium. Montana Cooperative Extension Service Bulletin 1132. Montana State University, Bozeman, MT.
The use and management of saline and sodic soils in this region is an important issue considering that a significant percentage of the land area is affected. Data from the Natural Resources Conservation Service (NRCS) show that the extent of soils affected by salt and/or sodium is at least 10% of the land area in North Dakota. The affected soils in specific counties of North Dakota ranges from 5% to greater than 15% of the land area. Salinity and sodicity impact a wide range of uses including: 1) crop production on both dryland and irrigated land; 2) soil restoration on mine land, landfills, pipelines, oil well sites, and construction sites; 3) wetland condition; 4) septic system suitability; and 4) water quality. As a result, a majority of the consulting projects that I conducted required knowledge of soil salinity and sodicity to fully understand the soil management issues. Surveys for suitable plant growth materials (SPGM) often become saline/sodic soil field studies because of the large extent of soluble salts and sodium (e.g. the Grand Forks Landfill Permit Area Soil Resoures Studies and the Oil Well Pad Studies for Summit Resources, LTD in the Projects subsection). In other studies such as, Elstad vs ND State Water Commission, salinity/sodicity impacts were the main focus from the beginning.
The evaluation for degradation and eventual restoration of soils depends on an understanding of the soil's ability to perform a variety of functions perceived as beneficial. This requires a knowledge of soil properties prior to disturbance and techniques required to reestablish a level of beneficial function. I began working with these concepts as applied to energy transmission and production projects when employed by the ND Public Service Commission. My soil survey experience with the USDA Soil Conservation Service (SCS) provided me with intensive study and observation of soil properties and their relationship to beneficial landuse. Many of the consulting projects that I have worked on addressed soil degradation-restoration in tandem or separately. Generally these projects require knowledge of soil survey techniques to properly identify soil properties that relate to the loss of soil function and the application of restoration methods. In the Northern Plains "Soil degradation and restoration" Projectsare often closely tied to conditions described under "Soil salinity and sodicity" and require experience and knowledge of saline/sodic soils.
In North Dakota, the ND Public Service Commission Mineland Reclamation staff defined the criteria for "suitable plant growth material" (SPGM) in the early 1970s (refer to "Soil degradation and remediation" Technical Links subsection). It is a simple criteria that basically defines the acceptable range of of salinity, sodicity, and organic matter in topsoil and subsoil materials as they relate to plant growth. The SPGM criteria has been expanded for use in other areas other than just mineland reclamation, such as landfill cover projects as regulated by the ND State Health Dept. I have applied the concepts of SPGM to a variety of consulting projects including mineland, landfills, and oil well drilling pads.
Principles of soil degradation and restoration have much broader implications than just for land stripping activities. Wetland function depends to a large extent on soil properties. Activities that impact wetland soils require study to either avoid them or to reconstruct them to their original function. I have conducted wetland soil identification on many projects throughout the state for these purposes.
Soil erosion is one of the main processes that reduces soil function through the removal of excessive amounts of topsoil. It also results in deposition of transported soil materials that may reduce the function and productivity of the receiving soils. Topsoil differs substantially from lower soil horizons with respect to its organic carbon content, nutrient content, and soil structure that affects the movement and storage of fluids. Topsoil characteristics inherited by soils vary with landscape position and other soil forming factors. The interpretation of soil data collected depends on the knowledge of the landscape relationships between the process of erosion and topsoil properties. I have utilized the concepts of soil erosion to interpret soil-landscape data observations on mineland, landfill, wetland, and soil degradation projects. In the Topp Soil Erosion Study (described in the "Soil degradation and restoration" Projects subsection), I combined soil field investigations with soil data from laboratory analyses to determine damages related to nutrient losses from wind and water erosion.
In the past, wet soils have been viewed as non-productive areas that are a nuisance to normal farming practices. At best they can be farmed only irregularly, because of either continuous or intermittent saturation and often inundation. These areas were subject to extensive drainage efforts, which has substantially altered the landscape and hydrology in most agricultural areas. The obvious loss in wildlife habitat created a philosophical standoff between the agricultural and wildlife protection proponents ("food versus ducks"). In recent years, research has shown that wetlands actually provide many other beneficial functions including flood control, groundwater flow control, and processing of chemicals.
Soil scientists long ago recognized the connection between landuse and soils with different degrees of wetness. Soil surveys conducted by USDA agencies include an estimate of internal drainage for all soils delineated within a given project area. Soil surveyors use seven different categories that range from excessive to very poorly drained to describe the internal drainage of each soil delineation. As soil survey knowledge advanced, a classification system was derived that further refined soil wetness observations. Soils that were wet enough throughout the year to cause complete depletion of oxygen were defined as having an "aquic" soil moisture regime. Soils with the aquic soil moisture regime were unofficially recognized as wetland soils. When the US Army Corps of Engineers (USACE) became the regulators of wetland drainage, they developed the definition of "hydric" to describe wetland soils. Although the aquic and hydric soil definitions are similar, they are not exactly the same. The USDA and USACE have worked together to develop a working definition of hydric soils (refer to "Wetland soils" Technical Links subsection) to assist with the delineation of wetlands. However, the USDA still retains the definition for the aquic soil moisture regime for delineation of soils in its soil surveys. Regardless of the aquic or hydric soil definitions, soil classifiers or surveyors have been the group of scientific professionals most intimately involved in describing and delineating wetland soils. In fact, some states such as North Dakota require by law (refer to "Professional" Technical Links subsection) that a soil classifier be involved in any private consulting projects that produce wetland delineations.
My experience with wetlands includes eight years of soil survey work in Iowa and North Dakota. As a water quality specialist, wetland issues required continual attention because of their environmental influence on the quality of both surface and groundwater resources. In 2006 I published NDSU Extension WQ-1313 "Water quality and wetland function in the Northern Prairie Pothole Region" http://www.ag.ndsu.edu/pubs/h2oqual/watgrnd/wq1313.pdf. Many consulting projects that I've conducted have required hydric soil identification as a subordinate component of soil survey activities or a primary component of wetland delineations. I have worked on highway, pipeline, electrical transmission, and wind turbine corridors specifically to identify wetland location for the purpose of avoidance or replacement. I have also worked on wetland delineation projects that involved landowner and agency disputes or agreements related to damage and/or restoration.
The proper application of water for agricultural management depends on knowledge of the soil properties that exist in the irrigated field. There are two distinctly different aspects to this issue. The first deals with the determination of soil compatibility for irrigation with water of a known quality. The second deals with the day to day agronomic management of an irrigated field. In this case, knowedge of the soil properties must be combined with knowledge of the water requirements for a given crop. I co-authored two publications that relate to irrigation and soils: 1) NDSU Extension Bulletin 68 "Compatibility of North Dakota soils for irrigation" http://www.ag.ndsu.edu/pubs/plantsci/soilfert/eb68w.htm and 2) NDSU Extension Bulletin 66 "Soil, water and plant characteristics important to irrigation" http://www.ag.ndsu.edu/pubs/ageng/irrigate/eb66w.htm.
Not all soils can be successfully irrigated due to a variety of reasons such as steep slopes, excessive internal drainage, the presence of a shallow water table, very slow percolation, the presence of salts/sodium. Under these circumstances, the application of irrigation water is not economically feasible and in many cases will eventually result in soil degradation. These conditions need to be evaluated within the proposed area for irrigation to estimate their extent and likely impact on the success of the project. The principles of soil compatibility to irrigation are outlined in several publications (refer to the "Irrigation compatibility" Technical Links") I have applied these criteria to projects found under the "Irrigation compatibility" Projects subsection.
As discussed above under "Soil salinity and sodicity", an understanding of water and salt translocation through soils is critical to the determination of irrigation compatibility. The application of poor quality water to soils with slow percolation rates will eventually lead to the concentration of salts and sodium in the soil profile. This may also be considered a soil degradation-restoration issue.
Septic filtration fields are needed in many areas where centralized sewage collection and treatment facilities are not available. These filtration fields depend on the natural processes of organic chemical decomposition to effectively treat the sewage pumped into them. Adequate internal drainage is necessary to ensure that the filtration field will function properly given a certain rate of sewage inflow. Soil properties such as texture and depth to water table need to be determined to help design the size of the filtration field needed to absorb the volume of sewage to be applied. I have provided suitability assessments for many proposed septic filtration fields in both eastern and western North Dakota. These projects have ranged in size from single household units to larger housing developments with several household units.
Water quality and soils are intertwined in environmental processes that often defy adequate understanding without considerable application of instrumentation and data interpretation. However, as natural resource research and survey results have become available, we now have a much more comprehensive database to help predict water quality impacts and management strategies that may help reduce these impacts. The advent of GIS and GPS has helped to accurately locate critical factors related to groundwater and watershed dynamics that correlate with water quality parameters.
As a water quality specialist for seventeen years, I dealt with a broad spectrum of water resource issues. Water quality issues condense into two major areas: 1) data acquisition and analysis; and 2) water resource management. It is critical that objective scientific methods be applied in both of these areas to successfully maintain or improve the quality of our water resources. My experience in this arena suggests that the consistent application of scientific protocol to this issue to be the greatest challenge of all. I conducted educational programs that provided audiences with an objective view of water quality issues. These educational programs included an array of media tools such as radio and television interviews, meeting presentations, data analysis algorithms, and various types of publications (listed below).
A major focus of the water quality program that I built, was development of analytic tools for the determination of water resource vulnerability to agricultural chemicals. I utilized existing natural resource databases, such as the NRCS Order 2 soil survey, to develop a systematic approach for determining the potential for water resource contamination as outlined in NDSU Extension Report 18 "An assessment system for potential groundwater contamination from agricultural pesticide use in North Dakota - Technical guideline"http://library.ndsu.edu/repository/handle/10365/16363/browse?type=titleand NDSU Extension Bulletin 63 "An assessment system for groundwater potential contamination from agricultural pesticide use in North Dakota" http://library.ndsu.edu/repository/handle/10365/16363/browse?type=title. These publications provided the scientific algorithm to be combined with GIS to produce the on-line assessment systems utilized by the NDSU Ag & Biosystems Dept. http://www.ageng.ndsu.nodak.edu/pest/ and the ND Dept. of Agriculture.
I also developed algorithms to determine the potential for pesticide contamination to surface water, nitrate contamination to groundwater and surface water, and phosphorus contamination to surface water. In addition to the assistance provided to the ND Dept. of Agriculture, I worked with a variety of other water resource protection programs in other counties (Dickey, Golden Valley, McIntosh, Ramsey, Sheridan, Sioux, Towner, Wells, and Williams). These projects were conducted in cooperation with tribal agencies, county commissioners, county extension service, and 319 watershed projects. One of the last projects that I conducted was a cooperative effort with the US Fish and Wild Service as described in the book chapter "Application of GIS to integrated pesticide management on US Fish and Wildlife land" http://library.ndsu.edu/repository/handle/10365/16363/browse?type=title. The intent of all of these projects was to provide information that would assist land managers in focussing their attention on areas most likely to be problematic with respect to water quality protection.
I worked on USDA county soil survey projects for eight years in Iowa (Delaware and Sioux Counties) and North Dakota (Kidder and Foster Counties). During this time, I mapped approximately 220,000 acres and supervised soil survey activities in the two North Dakota counties. I coauthored the USDA, SCS "Kidder County Soil Survey Report"http://library.ndsu.edu/repository/handle/10365/16363/browse?type=title and published NDSU Extension Bulletin 60 "Soil Survey: The foundation for productive natural resource management" http://www.ag.ndsu.edu/pubs/plantsci/soilfert/eb60w.htm. I am well versed in the USDA publications "Soil Taxonomy", "Keys to Soil Taxonomy", "Soil Survey Manual", "Soil Survey Handbook", and the "Fieldbook for describing and sampling soils" (Refer to "Soil survey" Technical Linkssubsection). I apply the same standards set forth in these manuals to consulting projects and have integrated GIS and GPS (refer to "GIS and GPS" Technical Links subsection) into the survey methods. When conducting hydric soil inventory on wetland delineation projects, I follow guidelines set forth in the USACE "Wetland Delineation Manual" and the NRCS "Field Indicators of Hydric Soils" (Refer to "Wetland soils" Technical Linkssubsection).
Many of the consulting projects that have I have done required determination of the extent and location of soil properties. This has been accomplished using standard soil survey techniques. Soil survey work on most consulting projects is done at the Order 1 level or at scales equivalent to 8 inches to the mile or greater. This level of soil survey provides resolution of less than one acre for delineations compared to 5 acres for standard county soil surveys mapped at the Order 2 scale (about 3 inches to the mile). I have applied Order 1 soil survey techniques to mineland, landfill, oil well pad, and septic system suitability projects.