Final Report for LNC96-102
[Note to online version: The report for this project includes tables and appendices that could not be included here. The regional SARE office will mail a hard copy of the entire report at your request. Just contact North Central SARE at (402) 472-7081 or email@example.com.]
Background. Saline seeps are an increasing concern in the dryland crop production areas of Kansas. Locally known as “alkalai spots” or “slick spots”, saline seeps are areas of bare soil or reduced crop production usually located on hillsides and ranging in size from a few square yards to tens of acres. Seep development in this region is probably related to the shift from native grass prairie to annually cropped winter wheat. Wheat uses less water than native grass. The water not used by the crop moves downward through the soil. In sites susceptible to saline seeps, the water typically encounters a soil layer that directs it to a surface seep downslope from where it entered the soil. In the seep, water evaporates and leaves behind salts that were picked up along the way. Saline seeps typically go unnoticed for many years until salt concentration in the topsoil decreases crop production, which in turn leads to soil erosion problems. Normal crop production is possible in reclaimed saline seeps. Farming practices and crops can be modified to use water productively before it moves below the root zone or toward the seep.
Basically, we need to shut off the faucet feeding the seep to allow it to heal. We can do this by growing crops that use more water but still give the farmers a comparable profit.
Objectives. (1) Demonstrate several practices for utilizing soil water while it is still a relatively non-saline resource in the seep recharge area. (2) Determine crops and management practices that can sustainably control seeps. (3) Educate farmers about causes and potential solutions.
1. Demonstration. Five demonstration sites in two counties were identified for this project through cooperation of K-State Extension, Natural Resources Conservation Service, and Soil and Water Conservation District personnel. A database of surface and profile soil salinity of both seep and recharge areas at each site was developed and analyzed using computer geographic information system software. Three of five sites implemented alfalfa or native grass. After just 2 years, there already was evidence of saline seeps receding at the one site that fully implemented project recommendations. By comparison, saline seep severity increased in the two sites that did not implement alternative high-water-use cropping systems and the two sites that had existing alfalfa or native grass but in the wrong location (i.e., not in the recharge area).
2. Research. A hydrologic model was developed to help farmers determine how much land must be converted from current wheat cropping to alfalfa in order to control and remediate the saline seep. We estimated that 14 to 32% of the upslope area should be converted to alfalfa on the five demonstration sites to cut seep recharge by 50%. If 100% of the recharge area were converted to alfalfa, 83 to 99% less water would enter the seep. Thus, we think at least one-third of the upslope recharge area should be converted to alfalfa; more should reclaim the seep faster.
The economic feasibility (net return per acre) of producing switchgrass (potential bioenergy crop) was compared to continuously cropped winter wheat and alfalfa. At this time, more favorable economics (larger acreages, higher competing energy prices) are needed for competitive production of bioenergy crops. However alfalfa, one of the better crops for saline seep reclamation, was an economically competitive cropping alternative to wheat in this area.
3. Education. More than a hundred farmers attended field tours in each county at project sites. In just the 2nd year after establishment, tour attendees witnessed greener alfalfa just upslope of one seep, supporting our claim that the alfalfa was using the seep water before it could reach the “alkali spot”. This provided a good preliminary indication that we were controlling saline seep expansion while reducing erosion and growing profitable crops!
The goal of this project was to demonstrate the feasibility of using deep-rooted, high water-use vegetation to return areas with saline seep damage to sustainable farm production. The specific project objectives were to:
1. Demonstrate that control of up-gradient subsurface flow using deep-rooted vegetation is a practical and effective method for arresting and controlling saline seep damage.
• Rationale: Bioremediation of this type has been applied to saline seeps in Australia as well as the Northern and Southern Great Plains. Research recommendations and farm experience is currently available, but must be applied to site-specific conditions in south-central Kansas, where hydro-geologic conditions that form saline seeps are common. Use of bioremediation methods could return large acreages to sustainable crop production.
2. Determine which management practices, crops, and rotations are suited for saline seep remediation.
• Rationale: Saline seeps were unknowingly initiated in south-central Kansas when native grass prairies were replaced by agricultural crops about a century ago. It is now known that the reduced water use of traditional crop production practices is directly responsible for current saline seep development. Remedy of this situation will require appropriate selection of crops and flexible management practices to provide farmers with practical, economic, and sustainable options for saline seep control. Experience from other regions must be applied to local climatic and hydro-geologic conditions in south-central Kansas.
3. Educate local farmers about the causes of saline seeps, and the solutions that are available to arrest saline seeps and return affected areas to production.
• Rationale: Currently there is a general misunderstanding in the farm community about both the causes and remedies for areas with high soil salinity from saline seeps. Though most farmers in these areas can readily identify the problem areas (commonly called alkali spots or slick spots), few know the source of the problem or an appropriate treatment. Recommendations range from doing nothing to the addition of gypsum. These demonstration sites serve to help local farmers correctly identify saline seeps, increase their recognition of conditions which lead to saline seeps, and educate them about management practices to remediate these sites.
4. Develop and demonstrate the electrical conductivity approach to identifying and mapping saline seeps and potential recharge areas.
• Rationale: Use of this method could greatly increase the effectiveness and reduce the cost of implementing a seep control treatment. A simple and inexpensive method has been developed for mapping salinity gradients in the soil profile. Recommendations based on experience with local soils and subsurface water conditions could allow future crop consultants or consulting engineers to more accurately assess the size of the saline seep area as well as the direction of saline recharge (which may not necessarily follow surface topography). This information is essential for sizing and locating bioremediation treatments.
Seep Control and Remediation
Two general methods have been used to remediate seep areas. Subsurface drains installed up-gradient from the seep can intercept the lateral water movement and reduce the salt loading to the seep area. One of the investigators on this project has used drainage and warm-season perennial grasses to reduce a 20+ ha seep in south-central Kansas to only a few square meters over 15 years. Further adoption of this control practice is limited by the high initial cost and identifying an acceptable outlet for the drainage discharge. Alternatively, agronomic practices can be modified to use the water before it percolates below the root zone. Use of the water by a crop in the recharge area while it is a relatively non-saline water resource is considered the better approach.
Normal crop production is feasible in reclaimed saline seeps. However, once the seep area has been controlled and reclaimed, a return to previous production practices would quickly reactivate the seep. Soil water in the recharge area will need to be continually managed to prevent recurrence of the seep and allow sustainable production on the land.
County Extension, Natural Resources Conservation Service (NRCS), and Soil and Water Conservation District personnel helped identify sites in each of two counties for this project. After initial site assessment, two to three demonstration sites were selected in each county (5 sites total). The location of the sites was determined in consideration of several factors: the establishment of a saline seep condition representative of the region, interest/ involvement of the farmer, and access and visibility within the local communities. All demonstration sites have both seep and recharge areas held by one land-owner or operator. In Rice County, three sites were selected: two owned and operated by Bill Oswalt (Rice 1 & Rice 3) and one by Bruce and Phil Ramage (Rice 2). In Harper County, two sites were selected: one owned and operated by Curt Hostetler (Harper 1) and one leased and operated by Darrin Cox (Harper 2).
For each site, surface and profile soil salinity of both seep and recharge areas were mapped on a planned grid within each field. Extracted soil cores at 0-6, 6-12, 12-24, and 24-48 in. were used to estimate saturation extract conductivity, texture, and total soil water content. In addition, these cores were used to identify the initial salinity profile. The seep area was mapped using lab measurements of soil saturation extracts from these cores as well as several other methods of estimating salinity. Maps of soil conductivity were used in conjunction with overlays of topography and soil water to estimate direction and extent of the recharge area. Soil and hydraulic properties were entered into a geographic information system (GIS) and mapping software for analysis purposes. This allowed identification and analysis of spatial variation and relationships among the various recharge and seep characteristics.
Two types of fixed-array, four-electrode meters were used. One fixed array was constructed using a soil and water conductivity unit as a current source/resistance meter along with an electrode spacing to give approximately 1 m (3 ft) effective measurement depth. Temperature, moisture content, and clay content were used to adjust the raw data, resulting in ECe-1 and ECe-2 as referenced below (see Results Section). A second fixed-array sensor, a prototype Veris Technologies mobile fixed-array unit, was tested on two of the three Rice County sites. A key feature of this unit was that the four electrodes were common field coulters set at a shallow depth pulled behind a four-wheel drive cart. Data from the four electrodes were sampled on a near-continuous basis as the coulters moved through the field, and were saved in an on-board computer along with GPS coordinates for the sample locations. The two readings taken at each sample point had quoted effective depths of 0.3 m (1 ft) and 1.0 m (3 ft). Veris Technologies (Salina, KS) is currently marketing this instrument for commercial agricultural mapping applications.
The electromagnetic induction meters used in this study were the EM38 and EM31, manufactured by Geonics Limited (Canada). The EM38 has an intercoil spacing of 3.2 ft, and theoretical observation depths of 2.5 and 5.0 ft in the horizontal and vertical dipole orientations, respectively (McNeill, 1986). The EM31 meter has an intercoil spacing of 12.7 ft, and theoretical observation depths of 10 and 20 ft in the horizontal and vertical dipole orientations, respectively (McNeill, 1980). Values of apparent conductivity are expressed in mmhos/cm (dS/m). Horizontal and vertical readings of the EM38 were taken on a 30 m (100 ft) grid spacing and EM31 readings were taken at 20 m (66 ft) grid spacing. Grid points were located using a Garmin 12-channel GPS unit with external, backpack-mounted satellite and FM antennae and Coast Guard differential signal correction. This portable unit was developed specifically for use on this project. Lateral accuracy was typically within about 2 m or less (given a 15 to 20 second stabilization period) when 6 to 8 satellites were visible and cloud cover was minimal.
A series of deep cores was taken to determine depth to any impermeable or highly permeable layer(s) that may control seep recharge. Five cores were made along transects directed through the seep and primary recharge areas at each site (except Rice 1, which was under terrace construction when coring equipment was available). Cores were extracted using a Giddings Probe to the impermeable layer depth, which varied by site from 8 to 22 ft. Soil was analyzed for texture, soil color, water content, and salinity of each soil horizon. These data were used to characterize the geology of each site, particularly those aspects related to seep development.
Sampling wells were installed into the five core holes at each site (except Rice 1). These were to be monitored for hydraulic gradients and water quality. However, this was not possible in practice. Each monitoring well was capped with a heavy metallic cap 12 to 14 inches below the ground surface, beneath the tillage layer to allow unimpeded farming operations. Metal caps were located at sampling time using a global positioning system (GPS) to narrow the location to within about 2 m and a metal detector to fine tune the location in which to dig for the well. However, cloud cover occasionally made the GPS unreadable at the time of field work and standing crops made use of the metal detector not feasible during large parts of the year. Thus, continuous piezometer well data were not collected.
Estimating Recharge Treatment Areas
An important part of each remediation effort is to find the amount of each farmer’s land that would need to be converted from the current wheat cropping to alfalfa in order to control and remediate the saline seep. A hydrologic model was developed to estimate the water balance in the saline seep recharge areas, and to estimate the effectiveness of various acreages of alfalfa treatments in reducing seep recharge.
The traditional farming system is continuous-wheat, with winter wheat planted in September-October and harvested in May-June. The summer period (with no crop) is intended to store water for the next wheat crop. However, 30% of annual precipitation typically occurs during the last two months of wheat production (May and June) and 45% occurs during the fallow period (between July and September) in south-central Kansas. It is this water that the alternative practices are intended to utilize.
Option 1. One alternative is to shift to a perennial system (e.g., alfalfa). Here, the entire up-gradient area would be planted to a high transpiration, perennial crop. This would maximize water use and allow close approximation of the native grass system while allowing profitable economic return from the land (see Economic Analysis Section).
Option 2. Another alternative is a “high intensity” cropping system. For example, winter wheat would be grown one season as normal. Then, if soil moisture is adequate (e.g., > 76 mm in upper root zone, as per Halvorson, 1988) and normal precipitation is expected, sorghum would be planted following wheat harvest. A short-season sorghum crop would utilize water during the summer period while still allowing an adequate water store for the upcoming wheat crop. This rotation would continue unless soil water stores are inadequate following wheat harvest; in this case, no summer crop would be grown, and wheat would be planted once again in fall. Other crops and timings are possible in this flexible rotation and would be determined by the farmer along with the assistance of county Extension agents or other knowledgeable consultants.
Option 3. Finally, a buffer strip or plantation of deep-rooted, high-transpiration trees could be installed up-gradient from the seep. This system could be used alone or in conjunction with one of the other methods described above. Depending on the species grown on the plantation, the crops and/or forest products produced could have profitable markets for biomass energy or other uses.
Salinity data collected at each site using several methods is summarized in Table 1 for one sampling time at the Rice County sites. Data was separated to compare samples taken within the saline seep and those take outside the seep area, where the seep area was roughly defined as the zone with poor or no crop growth. Within-seep means were significantly different from outside-seep means, as indicated by non-overlapping standard errors, except for two measurements at deeper levels (Rice 1: EM31-V; Rice 2: SE 24-48) and one shallow measurement (VER 0-36). This indicates that salinity was indeed higher beneath the plant-affected saline areas, and that all sensors had adequate precision and resolution to detect the increased salinity with the seep zone.
Besides being higher in the seep zone, salinity often exhibits an inversion with depth in saline seeps: salinity is higher near the surface than at depth. While no sites exhibited a clear inversion, at Rice 1, where the saline seep was the most clearly defined and well developed, the difference in salinity between seep and non-seep zones decreased with depth, as indicated by means of SE 0-6, 6-12, 12-24, and 24-48 (Table 1). The means also had the least variation (no significant differences) with depth at that site. By contrast, seeps at Rice 2 and Rice 3 were visually less distinctive and this was reflected in the data. Salinity increased significantly with depth within the seep at Rice 2 and Rice 3. It is also interesting to note that the outside-seep salinity levels indicated by saturation extract data showed very little variation among sites, often demonstrating no significant differences among data taken at the same depths at different sites.
A field-level GIS system (FIS) was used to correlate the various instruments with the saturation extract conductivities, considered to represent “actual” salinity, and with each other. FIS was also used to investigate correlations between individual sensors and weighted combinations of various depths of saturation extract conductivity. In almost every case, better correlations were found when considering more than a single layer. Correlations from FIS were corroborated by results from a multiple linear regression analysis. These analyses are all discussed in Mankin et al. (1997) (Appendix D).
Though many of the instruments yielded poor correlations with actual data at some sites, useful information was nonetheless extracted from maps generated with their data. A complete set of maps from FIS for the Rice 1 site is presented in Mankin et al. (1997) (Appendix D). All data is shown at the same horizontal scale, and data range grey-scales are the same for similar instruments to aid in comparisons between maps. North is toward the top of the page. Similar saline seep “hot spots” are seen in maps from all the sensors (Appendix D, Figs. 5-13), in agreement with saturation extract conductivity data (Appendix D, Figs. 1-4). All instruments were useful in delineating saline seep areas.
For remediation treatments to be located effectively, recharge direction for the seep must be clearly established. The deepest data, from the EM31-V (vertical dipole orientation) (Appendix. D, Fig. 13), appears to show not only the relative salinity hot spots in the same location as seen in shallower data, but also a “finger” of salinity from the bottom-center of the map to the upper left (north-west direction). A less-exaggerated finger also appears in the center of the map directed toward the west. These fingers may represent movement of higher salinity groundwater toward the seeps.
Soil Core Analysis
Soil from each deep core was analyzed for texture, soil color, water content, and salinity of each soil horizon (Appendix A). These data were analyzed by NRCS project cooperators. This analysis is summarized below.
Rice 2 (SE 21-19-6). Soils in the “recharge area” are in the Geary, Smolan, Longford Crete association (MLRA 75). These soils in this area typically consist of 2-3 meters of loess capping old paleoterrace alluvial deposits (notice the EC jump in Rice 2 point 1, at the contact @ 215″). Soils in the discharge area at this site are a combination of stratified clayey and loamy colluvial and more modern alluvial sediments (colluvium from hillslopes above, and Little Ark alluvium). The sandier alluvial sediments are the water bearing strata.
The saline-sodic soils in the discharge area most resemble the new Buhler series (established in Reno County soil survey update). Buhler soils are fine-silty mixed, superactive, mesic, Vertic Natrustolls. Sandier loamy alluvium are usually deeper than 60 inches in the Buhler series in Reno County. The De (Detroit) map units in this part of Rice County have a high percentage of saline-sodic soils and will need to be updated in the future. Also note that as water table nears the surface, maximum EC goes up.
Rice 3 (SE 7-19-6). Shale (of the Dakota Formation) underlies the recharge and discharge sites here. Soils in the recharge area are mapped as Lc (Lancaster loam), 3-7% slope, eroded. In actuality, it appeared that the recharge area soils were somewhat marginal to the Edalgo series (formed in residuum from shale vs. sandstone for Lancaster). Discharge site soils somewhat resembled the Buhler series. Soil data did not seem to show a very high salt content here. We would suspect that the SAR’s are high, however.
Though we did not test for SAR, we can almost guarantee that in this area as EC goes up so does SAR. These seeps are saline-sodic seeps. We have seen SAR’s of 50 to 90 and greater on several seeps we have sampled in the past. This means, however, that ultimate reclamation of these seep sites will likely require Ca additions (e.g., gypsum) once the salt bulge starts to leach back down.
Harper 1 (W2 36-31-8). Soils in the recharge area resemble the Farnum and Shellabarger series. These sediments in this part of Harper County are either old remnant paleoterrace deposits, or are pedisediment from the high paleoterraces to the north. Stratified loamy, clayey, and sandy sediments are common. The Harper formation underlies the old alluvium here probably within 15 feet of the surface (although we were not able to core to that depth, other cores we’ve taken in this landform position usually hit Harper sandstone within 15 feet).
The deeper lighter-textured stratified loamy and sandy sediments are the water bearing strata. Again, soil data looks good and follows water table depths.
Harper 2 (NE 15-33-8). Recharge-area soils are the Grant, Nashville, and Quinlan series (deep, moderately deep, and shallow soils formed in residuum from Harper sandstone and siltstone. The soft Permian bedrock itself is likely the ultimate salt source for most of these seeps in Harper County. Discharge area soils do not fit any series of which we are aware. They consist of stratified fine-silty and coarse-silty colluvial sediments from the upper hillslopes, and overlie Permian Harper formation at various depths.
The water table and salt profile appear to fit well here too. Again, previous results have indicated high SAR’s along with the high EC’s (saline-sodic seeps) in Harper County.
Estimating Recharge Treatment Areas
A hydrologic model was used to simulate daily deep percolation on each field for a 41-year period. A variety of wheat-alfalfa combinations were used to explore the effects of a range of potential remediation treatments. Average annual recharge to the saline seep, expressed as an average depth for the entire recharge area, decreased as the areal percentage of alfalfa increased (Figure 1). A similar trend was seen in the number of months that contributed deep percolation (Figure 1); as the percentage of alfalfa cropping area increased, the number of months contributing to recharge decreased.
The percentage of recharge area to be shifted from wheat to alfalfa was determined for a given target percentage reduction in total recharge. Our current general recommendation is to implement at least enough alfalfa acreage to reduce seep recharge by 50%. The simulation estimated that a 50% reduction in total recharge would require 14% (Rice 1), 24% (Rice 2), 32% (Rice 3), 22% (Harper 1), or 17% (Harper 2) of the recharge area to be converted to alfalfa production, depending on the site. If 100% of the recharge area were converted to alfalfa, average annual recharge volume would be reduced by values ranging from 83% for Harper 1 to 99% for Rice 2, also depending on the site. The major limitation in application of these results is that we do not know the percentage of seepage reduction needed to control the seep. This model, its development, and limitations are discussed in detail in separately published articles (Mankin and Koelliker, 1997, 2000).
The modeling approach was also utilized in two class projects for Hydrology students at Kansas State University (BAE 551: 1997 and 1998). Spreadsheets were used to model daily seep recharge using actual climatic data at various sites around Kansas, Nebraska, and Colorado. Results demonstrated the regional variability in seep potential. In all cases, alfalfa or poplar reduced seep recharge compared to corn or winter wheat. Less seepage was modeled for crops with higher ET and larger root zones, soils with larger available soil storage capacities, and climates with lower precipitation intensity and volume distributed more evenly throughout the year. Recharge was most likely in the spring, particularly when following a wet autumn.
Based on the initial mapping and modeling, the reclamation treatments were prescribed. Farmer involvement at this stage was critical to assure that treatments were suitable for local conditions and that any changes in management were practical and reasonable. At meetings with farmers verbal “buy-in” was felt to be strong. However, various reasons caused treatments to be established fully at only one (Harper 1) of five sites during the project period.
(a) Two sites (Rice 2 and 3) had either CRP grasses or alfalfa growing on-site, but in what was considered to be the “wrong” location in the field after preliminary analysis. There was an interest from both farmer and researcher perspectives to test the “wrong location” hypothesis before adopting alternative crops and management. Thus, although treatments were never established on these sites, they were considered to be good test cases for determining the importance of correct treatment location on the field.
(b) One farmer (Rice 1) had an opportunity to add terraces to the study field site, which diverted his attentions from the saline seep remediation project. Monitoring was continued on this site and considered to be a “control” to study the characteristics of untreated saline seeps in Rice County.
(c) A fourth site (Harper 2) was never developed due to a resistance to change during unsure economic times for the farmer in the context of the commodity markets. Monitoring was also continued on this site and considered to be a “control” to study the characteristics of untreated saline seeps in Harper County. It is hoped that all project sites will adopt the discussed recommendations in the near future.
Assessment of Saline Seep Dynamics
[Background for this section draws upon information presented in Doolittle (1997).]
Saline seeps are groundwater discharge sites in which concentrations of soluble salts tend to increase toward the upper part of the soil profile (Richardson and Williams, 1995). In areas of saline soils, 65 to 70% of the variance in apparent conductivity can be explained by changes in salinity alone (Williams and Baker, 1982). Salama et al. (1994) related apparent conductivity to recharge/discharge mechanisms within watersheds. They associated low values of apparent conductivity with low concentrations of total soluble salts and recharge areas.
Discharge areas were associated with high values of apparent conductivity and greater concentrations of soluble salts near the surface. Discharge areas had inverted salt profiles. Discharge areas and inverted salt profiles are associated with rising groundwater tables, increased groundwater flow and mobilization of soluble salts, and greater discharge at or near the surface.
Saline seep discharge areas in this study were identified using a modification of the EM discharge index used by Richardson and Williams (1995). The EM discharge index used in our study was determined by dividing the EM38 horizontal dipole measurement (shallow soil, up to approx. 0.75 m) by the EM 38 vertical dipole measurement (deeper soil, up to approx. 1.5 m). An EM index greater than 1.0 indicates an inverted salt profile (i.e., shallow soil more saline than deeper soil). The area at each site with EM index values of 0.8, 1.0, and 1.2 are plotted in Figure 2. These data indicate how the size of each saline seep zone changed during the study period. To provide more information about how the saline seep size changed at each site during the study, the relative area of each site at various EM indices was studied. The area at a given EM index (i.e., 0.8, 1.0, or 1.2) at each sampling time was divided by the area found during the initial sampling time at that site. This allows direct comparison among sites of the relative increase or decrease in saline seep area measured during the study. Relative-area EM index data for EM index vales of 0.8 and 1.0 are presented in Figure 3.
Harper 1 (proper treatment starting in Fall 1997) and 2 (no treatment) both demonstrate a decrease in acreage with EM index >0.8, but only Harper 1 also has a decrease in area at EM index >1.0 (Fig. 3). The EM index also confirms our visual assessment that Harper 2 sustains the largest severity of saline seep, having more than 3 acres with EM index >1.2, more than 7 acres with EM index >1.0, and more than 11 acres with EM index >0.8 (Fig. 2). Harper 1 was less severe but still had more than 3 acres with EM index >0.8 at the end of the sampling period (after 1½ years of treatment with alfalfa in the recharge area). This indicates that the reclamation of Harper 1, though underway, is not complete.
Rice 1 (no treatment) and Rice 2 and 3 (improper treatment location) all show increases in area with EM index >0.8 and >1.0 during the study (Fig. 3) (except Rice 3, which had no area with EM index >1.0 during the study). Rice 1 had a small but steadily increasing seep zone (Fig. 2). It is also interesting to note that seep acreage (EM index >0.8) of all Rice County sites increased between July 1997 and March 1998. A similar increasing trend was seen five of the seven times a site had measurements in both fall and the following spring. This indicates that the fall to spring period may be the time when the most seep recharge commonly occurs.
From these results, several conclusions can be drawn:
1. Harper 1, the only site with proper treatment implementation, was also the site with the most unambiguous decrease in saline seep area.
2. Based on Rice 1 and Harper 2, both sites with no treatment, saline seeps increase in size without applying some method of controlling seep recharge.
3. Based on Rice 2 and 3, both with high-water-use crops that existed prior to the beginning of the study but in the “wrong” locations with respect to the saline seep recharge area, correct location of high-water-use crop treatments are essential for remediating saline seeps.
4. The effects of proper remediation treatments can begin to be documented after only 18 months with periodic EM38 monitoring.
5. Natural fluctuations in saline seep area occur. This can mask trends in short term treatment responses.
6. The fall to spring period may be a critical time for saline seep recharge.
Saline seeps are not just individual farmer problems. Reduction in farmland decreases the Nation’s food supply, tax base, and security. Salty water from seeps can also pollute fresh-water streams and groundwater if not controlled. Farmers lose money by applying seed, fertilizer, and pesticides to unproductive seep areas since it is often unmanageable to farm around these parts of the field. But also, since seep areas have poor infiltration and potentially high runoff rates, topsoil and applied chemicals can easily be swept into streams and the water supply during runoff events. The goal of this project to remediate the saline seeps on thousands of acres of farmland in central and south-central Kansas has clear benefits.
In the not too distant future, NRCS probably will be dealing with some soil survey updates in Harper/Barber County, including a wide variety saline seep-lands. There may be some cooperative research efforts possible between NRCS and Kansas State University that could be of great help to both NRCS and K-State. Regardless of what these soils might be re-mapped or re-classified as, the farmers (our customers) need good advice on how to manage these seep areas. The information gained in this project could really help provide good management principles, rather than a perception that some agency (like NRCS) is telling them what to do.
In addition to traditional food and feed crops, several crops show potential for production on lands recharging or affected by saline seeps. For example, switchgrass has been demonstrated as a small-scale alternate energy source for schools, hospitals, and industrial processes. Use of such crops beyond their planned objective for saline seep control will increase the value of the reclamation process to the landowner. The economic feasibility (net return per acre) of producing switchgrass was compared to continuously cropped winter wheat and alfalfa. This analysis forecasts an annual net return per acre to the farmer for each of the above crops over a period of ten years beginning in 1998. Future supply figures for alfalfa hay and wheat as well as price per ton and bushel respectively were obtained from the Food and Agricultural Policy Research Institute (FAPRI).
The annual return numbers were used to estimate the net present value to the farmer over the ten-year period of time. In addition, a risk analysis was performed to be used in conjunction with the net present value figures to help determine the best possible course of action for the farmers.
In the case of using the lands for producing alfalfa hay or continuously cropped wheat, the net return per acre should be an adequate guide when determining which crop to plant over the next ten years. But the production of switchgrass for energy purposes means that it will be competing with a conventional energy source such as natural gas; the delivered price of this conventional energy source must also be taken into consideration when analyzing whether to grow switchgrass.
Total Cost Analysis
The total cost associated with using switchgrass as an alternative energy source is a function of the land, production, transport, and processing costs plus the amortized capital cost of the conversion system. Each of these costs needs to be converted into a cost per million Btu ($/MMBtu) in order to make a valid comparison with the delivered cost of natural gas. Further analysis in presented in Appendix F.
Production cost analysis. Since the lands affected by saline seep could readily be used to produce either alfalfa or continuously cropped winter wheat, the net present value of variable costs (NPVVC) associated with a range of yield scenarios for each crop was determined. For this study, three scenarios were used for each crop: 2.5, 3.5, or 4.5 tons per acre for alfalfa; and 25, 33, or 44 bushels per acre for continuously cropped winter wheat.
The NPVVC’s of each crop and yield scenario are presented in Table 2. Each NPVVC of alfalfa was compared to each NPVVC of continuously cropped winter wheat (nine different cases). The higher of the two NPVVC’s for each of the nine cases was chosen for use in setting the edge-of-field price per ton for switchgrass. This price was set as the price that equated the NPVVC of switchgrass to the higher NPVVC for either alfalfa or continuously cropped winter wheat production in each of the nine cases. These prices are given in Table 3. This was converted into $/MMBtu by dividing by 15.84 MMBtu/dry ton.
Delivered cost of energy. The delivered cost of energy ($/MMBtu) is the sum of the edge-of-field cost of production, transport, and processing costs, and an amortized conversion system capital cost. Table 4 presents a total cost analysis for the edge-of-field costs for each of the nine yield scenarios considered in addition to the delivered cost of energy from switchgrass ($/MMBtu). In all cases, the delivered cost of energy derived from switchgrass was higher than the competing conventional energy source, natural gas (about $3.50/MMBtu). Therefore, production of switchgrass as an alternative energy source on these lands for this particular application would be uneconomical and should not be pursued at this time.
The net return associated with a range of yield scenarios for each crop demonstrated the economic difficulty with farmers switching to biomass energy crop production. Further, the delivered cost of energy derived from the conversion of switchgrass was found to be significantly higher that the current energy source, natural gas. However, the economic analysis also indicated that alfalfa was a competitive cropping alternative to wheat in this area.
At this time, the analysis indicates that it will be highly unlikely that the current project lands will be used for producing switchgrass due to the small acreages at each site. This inevitably translates into a smaller scale-of-economy when the purchase of conversion equipment is taken into consideration. Of course, larger acreages and/or more favorable economics for energy crop production may alter this assessment.
Farmer cooperators provided access to the land with saline seep damage. They assisted in selection of crop species and management practices, and have implemented or will implement the treatment as mutually agreed upon. They provided current and, if possible, historical information on cropping and management near the saline seep location. Farmers helped present their experiences field days.
Final selection of specific crops and practices was dependent on farmer input and local soil and hydro-geologic conditions. Though it is not grown extensively in the region, alfalfa is crop with which farmers are familiar (most farmers seem to know someone who grows it). This makes it the least intimidating option for most farmers.
Through various programs, this project directly reached several hundred farmers, local leaders, Extension Educators, and locally based State and Federal agency personnel. The key impact of this project was an increased awareness within Rice, Harper, and surrounding counties about the causes of saline seeps and the potential solutions available.
As a result of this study, we have several messages and recommendations for farmers:
1. There is often water available in the soil that farmers are not using and that is contributing the their saline seep problem.
2. They can correct this situation by changing to a high water-use crop on a portion of the area upslope from the saline seep (at least one-third of the recharge area – the area upslope from the seep) or by increasing the cropping intensity by double cropping in average to wet years.
3. The economics of both these changes can actually be beneficial to the farmer.
4. Both choices also reduce soil erosion and improve stream water quality.
The primary thing not to do is ignore the saline seep problem since it will not go away by itself.
Educational & Outreach Activities
Various phases of the site assessment and remediation treatment design have been published and presented at an international conference. The technical gains from these aspects of the project are also being shared with the scientific and engineering community at large through future refereed journal submissions. Below is a list of these publications and brief summaries. The full articles are included in the appendices.
Mankin, K.R., K.L. Ewing, M.D. Schrock, G.J. Kluitenberg. 1997. Field Measurement and Mapping of Soil Salinity in Saline Seeps. Presented at the ASAE International Meeting, August 10-14, Minneapolis, Minnesota. Paper No. 97-3145. American Society of Agricultural Engineers, St. Joseph, MI. (see Appendix D)
Summary: A comparison of field measurements and resulting grid maps of soil electrical conductivity measured using several techniques is presented. Measurement techniques include: (1) a 4-electrode sensor using fixed-array configuration; (2) a mobile electrical conductivity sensor mounted on tillage tines; (3) EM38; (4) EM31; and (5) saturation extract conductivity from field soil samples. The various methods are compared for accuracy, reliability, and ease of use, particularly for field grid-type sampling for GIS applications. All methods adequately identified saline seep locations. EM31 apparently was able to determine seep recharge direction.
Mankin, K.R. and J.K. Koelliker. 2000. A hydrologic balance approach to saline seep remediation design. Applied Engineering in Agriculture, Manuscript #SW3451. (accepted) (see Appendix C)
Mankin, K.R. and J.K. Koelliker. 1997. Phytoremediation of Saline Seeps by Hydrologic Modification. In: Applications of Emerging Technologies in Hydrology. A.D. Ward and B.N. Wilson, eds. Special Proceedings of the ASAE International Meeting, August 10-14, Minneapolis, Minnesota. Paper No. 97-2013. American Society of Agricultural Engineers, St. Joseph, MI. (see Appendix E)
Abstract: Concern about saline seeps is increasing in the dryland production regions of Kansas and the North American Great Plains. To reclaim salt-affected seep areas, site hydrologic factors must be modified to reduce seep recharge. A simple method is needed to help design effective remediation treatments. A hydrologic balance model, POTYLDR (Potential Yield Model, Revised), was modified and used to estimate the water balance in a saline seep recharge area and to estimate the effectiveness of various acreages of alfalfa treatments in reducing seep recharge. This model uses readily available data, such as daily rainfall and temperature, NRCS runoff curve numbers, NRCS soil irrigation classes, Penman evapotranspiration parameters and Blaney-Criddle crop coefficients, to determine runoff, evapotranspiration, soil moisture, and percolation from the root zone. According to the assumed seep mechanism, deep percolation from the local recharge area was used to estimate seep recharge. Various percentages of the seep recharge area were shifted from the current wheat cropping to alfalfa to determine the reductions in total recharge and number of months contributing to recharge. A 50% reduction in total recharge required 14 to 32% alfalfa acreage depending upon site-specific factors of five targeted fields. A given alfalfa acreage reduced total recharge volume more effectively than it reduced the number of months contributing to recharge. The major limitation in application of these results is selection of the percentage seepage reduction needed to provide seep control. The modeling approach provides an important indication of a system’s responsiveness to changes in vegetation and quantifies this response in a way that is useful for designing bioremediation treatments that require control of seepage or shallow groundwater recharge.
Nelson, R.G. and K.R. Mankin. (in work). Economic Assessment of Conventional and Bioenergy Cropping Options for Saline Seep Remediation. To be submitted to Applied Engineering in Agriculture. (see Appendix F).
Mankin, K.R. (in work). Monitoring the effectiveness of saline seep remediation. To be submitted to Applied Engineering in Agriculture.
An informational sign (4 ft x 8 ft) was installed at each cooperator site (Appendix G). The sign identifies the farmer cooperator and other project cooperators, provides a pictorial diagram of a common cause of saline seeps, and advertises the name and phone number of the local county Extension agent for further information.
A wall-mount display discussing saline seeps and their remediation has been developed and installed in the Biological and Agricultural Engineering Department in Seaton Hall, Kansas State University. This display presented the basic local-recharge mechanism of saline seep development, a description of basic monitoring and modeling work, and a summary of preliminary results and recommendations.
The display was also presented to a broad audience of County Extension Agents at a poster break-out session in the Annual K-State Research and Extension Conference, at which all Agricultural Experiment Station and Cooperative Extension Service personnel in the state meet for 1 week annually. At the display, handouts of a Project Overview was available along with copies of the two project publications.
The display was also presented at a regional bioremediation conference (Beneficial Effects of Vegetation in Metals-Contaminated Soils) held at Kansas State University.
A K-State Extension bulletin on saline seeps, “Controlling Saline Seeps” (Appendix B), was published. It summarizes the concepts involved in saline seep development and provides a preliminary discussion of potential solutions. The first print-run of this publication was 2000 copies. This publication will be updated after longer term experience with saline seeps in Kansas.
Spring 1998. Presentations on “Controlling Saline Seeps” were made at two K-State Extension meetings on March 9, 1998 (Rice County, approx. 45 attended) and March 18, 1998 (Harper County, approx. 8 attended). Handouts were prepared that formed the basis for the later Extension publication.
Summer 1998. One field tour was held on a Rice County site (Rice 2, Bruce and Phil Ramage Farm) August 25, 1998. The tour was well-received by about 30 farmers in attendance. Several K-State Extension agents in attendance obtained copies of the draft Extension bulletin (about 60 copies distributed), and expressed interest and concern about saline seeps in their counties. Each receives many calls annually concerning this issue and knew of specific cases in which the farmer was seeking solutions. This reiterated to us that efforts to return saline seeps to production must be continued and expanded.
Summer 1999. A second field tour was held in conjunction with the Harper County Range-Forage-Livestock Tour on a Harper County Site (Harper 2, Curt Hostetler Farm) August 30, 1999. About 80 people attended and received the Extension bulletins produced from this project. Extra bulletins were provided to county resource people (NRCS, SWCS, and Extension). This site had planted alfalfa in the saline seep recharge area as recommended. The site was nearing the end of its second growing season. Attendees were able to see a saline seep, which supported no crop but only a collection of weeds, and an area of greener alfalfa growing just upslope from the saline seep location. The weeds and eroded soil in the seep clearly demonstrated the problem. And the lush alfalfa provided clear support of our claim that the alfalfa was using the seep water before it could reach the “alkali spot”. (It was interesting, and expected, to note that no one in the audience knew the term “saline seep” but everyone nodded in recognition of the term “alkali spot” or “slick spot” in reference to the saline seep problem locations common to the area.) This field tour demonstration provided a good preliminary indication that we were controlling saline seep recharge and expansion while reducing erosion and growing profitable crops!
Areas needing additional study
More information is needed to prove the effectiveness of vegetative treatments in remediating saline seeps. This project uses elementary instrumentation methods that are “noninvasive” and suitable for use in working farm fields. This will allow tracking of saline seep reclamation, but will not allow detailed monitoring and analysis of the mechanisms of seeps reclamation. An instrumented research saline seep site coupled with groundwater flow modeling analysis would allow a greatly improved understanding of the mechanisms of seep remediation. In turn, this would allow fine-tuning of recommendations for the type, amount and extent of cropping and management system changes needed to slow, cease, or reverse saline seep growth.
Further education is needed to assist farmers in this area with the transition from continuous winter wheat farm operations to alfalfa or intensive, flexible crop rotations. This project will provide one piece of information to support the use of alternative cropping rotations, particularly for those farms affected by saline seeps. The same practices also have broad application for diversifying overall production in this region, improving soil health, and reducing water quality impacts.
Doolittle, J. 1997. Electromagnetic Induction (EM) Assistance. Report to T. Domingues, USDA-NRCS, 14 April 1997. USDA-NRCS, Radnor, PA.
Halvorson, A.D. 1988. Role of cropping systems in environmental quality: Saline seep control. In Cropping Strategies for Efficient Use of Water and Nitrogen, W.L. Hargrove, et al., ed., pp. 179-191. ASA Spec. Publ. 51. ASA, CSSA, and SSSA, Madison, WI.
Mankin, K.R., K.L. Ewing, M.D. Schrock, G.J. Kluitenberg. 1997. Field Measurement and Mapping of Soil Salinity in Saline Seeps. Presented at the ASAE International Meeting, August 10-14, Minneapolis, Minnesota. Paper No. 97-3145. American Society of Agricultural Engineers, St. Joseph, MI.
Mankin, K.R. and J.K. Koelliker. 2000. A hydrologic balance approach to saline seep remediation design. Appl. Eng. in Agr., Manuscript #SW3451. (accepted)
Mankin, K.R. and J.K. Koelliker. 1997. Phytoremediation of Saline Seeps by Hydrologic Modification. In: Applications of Emerging Technologies in Hydrology. A.D. Ward and B.N. Wilson, eds. Special Proceedings of the ASAE International Meeting, August 10-14, Minneapolis, Minnesota. Paper No. 97-2013. American Society of Agricultural Engineers, St. Joseph, MI.
McNeill, J.D. 1980. Electromagnetic terrain conductivity measurement at low induction numbers. Technical Note TN-6. Geonics Ltd., Mississauga, Ontario. 15 pp.
McNeill, J.D. 1986. Geonics EM38 ground conductivity meter operating instructions and survey interpretation techniques. Technical Note TN-21. Geonics Ltd., Mississauga, Ontario. 16 pp.
Richardson, D.P. and B.G. Williams. 1995. Assessing discharge characteristics of upland landscapes using electromagnetic induction techniques. Division of Water Resources, Institute of Natural Resources and Environment, CSIRO, Canberra, Australia. Technical Memorandum 94/3. 33 pp.
Salama, R.B., G. Bartle, P. Farrington, and V. Wilson. 1994. Basin geomorphological controls on the mechanism of recharge and discharge and its effect on salt storage and mobilization – comparative study using geophysical surveys. J. of Hydrology, 155:1-26.
Williams, B.G. and G.C. Baker. 1982. An electromagnetic induction technique for reconnaissance surveys of soil salinity hazards. Australian J. of Soil Res., 20:107-118.