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1539 Eleventh Ave. Helena, MT 59601
Phone: (406) 444-2074 | Fax: (406) 444-2684
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Montana Salinity Control Association


Salinity Control in Montana

Saline seep causes a salt buildup that reduces productivity of the soil. Saline conditions also contaminate groundwater and surface water used for domestic purposes, livestock, and wildlife. Saline seep water, predominantly sodium and magnesium sulfate salts, is often nearly as salty as sea water.

How Do Saline Seeps Form?

Water in excess of what can be stored in the annual-crop rooting zone or used by growing crops dissolves salts in the soil and leaches down to build up a water table on top of the bedrock. The artificially created water table gradually rises until the water reaches the surface to evaporate, leaving a white crust of salts. (See Figures 1 and 2)

Plant growth eventually is reduced or eliminated. Saline areas spread gradually and affect thousands of acres, sometimes affecting major portions of a watershed. Salinity has taken more than 300,000 acres of cropland out of production in Montana.

What Causes Saline Seeps?

Saline conditions can be created by any change that converts native range or perennial forage to a land use less efficient in using precipitation or irrigation water. The predominant land use change in the Northern Great Plains has been to crop-fallow. Both the soil profile and underlying bedrock in central and eastern Montana have an elevated and highly soluble salt content. Most of the saline seeps have formed since the 1940s with the advent of large-scale crop production.

Salinity problems are generated by salts leaching from the soil into the groundwater. The recharge areas for the seepage are generally within 1 or 2 miles from the discharge area and often much closer. Groundwater does not recognize surface boundaries, so often the recharge area ownership is shared or controlled by other producers. The two most common barriers to land use changes are:

• the problem of making arrangements for haying equipment and marketing

• the lack of an assured yield in a flex-crop system

However, these problems are often perceived, rather than real. Producers generally find that the diversification of hay and alternative crops can improve their long-term productivity.

Solutions to Seeps

Montanans have three general solutions to address saline seeps. They may be used separately or in conjunction with each other.

• Saline seeps, developed with the advent of crop-fallow, can be reclaimed with a 5-to 10-year rotation from crop to perennial forage for haying/grazing in the recharge area. The deep-rooted crop most commonly used is alfalfa, but other legumes and grasses can be used. (See Figure 3)

• Perennial vegetation planted under the Conservation Reserve Program (CRP) mimics the water use by alfalfa hay when placed in the recharge area. (See Figure 4)

• Switching from the crop-fallow system to a flexible but more intensive annual cropping system can help prevent salinity problems. The flex-crop system should always follow the forage rotation and can include cereal grain, oilseed, and annual legume crops.


Saline seep is caused by a dynamic situation; it will recur eventually if the recharge area is returned to annual cropping. Therefore, the perennial forage will need to be rotated back every 10 to 20 years. Shallow monitoring wells installed in a groundwater investigation will help predict when the rotation is needed.

Where Do I Get Help?

Two organizations that can provide help are the Montana Salinity Control Association (MSCA) and your local conservation district. Each one will coordinate activities with the U.S. Department of Agriculture (USDA) and other agencies at your request to provide opportunities for financial and technical assistance.

The Montana Salinity Control Association provides a groundwater assessment and site-specific reclamation plan. MSCA does charge for the groundwater investigation; however, USDA cost-share is available. There is no charge for the initial site visit with the producer to see whether an in-depth investigation is needed or whether verbal recommendations are sufficient. Working with MSCA is voluntary, as is implementing any of the recommendations. MSCA can work with individual producers or small groups and on the watershed level.

Conservation districts grew from public concern for the condition of our natural resources in the early 1930s. Today, Montana's 58 conservation districts provide local citizens with an opportunity to shape resource planning in their areas. Conservation districts administer the Natural Streambed and Land Preservation Act of 1975 (310 law), provide guidance to local U.S. Natural Resources Conservation Service (NRCS) personnel by defining local resource priorities, act as project sponsors and facilitators, and promote understanding of resource issues through workshops, tours, and educational outreach. MSCA is a satellite organization of Montana's conservation districts.

 Application


Paul Brown Soil Moisture Probe: Easy, inexpensive method for determining soil moisture.

Theory

The Paul Brown Soil Moisture Probe is a penetrometer specially designed to assist in determining stored soil moisture.  In dryland crop areas, knowledge of stored soil water at seeding, in addition to expected precipitation for the growing season, is an important element of predicting crop yield.  In 1942, Shaw et al. reported that soil moisture was the dominant factor influencing the force required to push a soil penetrometer into the soil.  There was a rapid increase in resistance with decreasing moisture.  Thus, when soil water content falls significantly below field capacity, the penetrometer can no longer be pushed into the soil. 

Use

The Paul Brown Soil Moisture Probe is pushed into the soil, without turning, by the user applying his or her weight to the handle.  The probe will be stopped by dry soil.  Rocks and gravel may also stop the probe, but are easily detected.  Depth of moist soil is then measured on the probe shaft.  The quantity of water held by the moist soil is dependent on soil texture.  Estimates of the quantity of water held in the soil can be determined by converting depth of soil moisture into inches of plant available water with the following table:

Soil Texture

Plant Available Water per Foot of Moist Soil

 

Inches

Coarse  -  sand

0.5

Coarse  -  loamy fine sand, fine sands

1.25

Mod. Coarse  -  sandy loam, fine sandy loam

1.5

Medium  -  silt, silt loam, loam, very fine sandy loam

2

Mod. Fine  -  clay loam, sandy clay loam, silty clay loam

2.2

Fine  -  sandy clay, silty clay, clay

2

EXAMPLE:  Three feet of moist medium textured soil: 3 x 2.0” = 6.0” of plant available water.

Soil samples for determining texture at the depth of penetration can be obtained by turning the probe two or three times while applying pressure to the handle.  The probe is then pulled out of the soil without turning.  The auger will collect a small amount of soil for analysis.

We encourage all curious about the Paul Brown Soil Moisture Probe Dr. Paul Brown’s own publications which are the basis for nearly all the material on this website.  Dr. Brown’s publications include specific yield equations for many areas of the Northern Great Plains, and for numerous crops and cultivars.  Dr. Brown’s 1990 publication with Dr. Gregg Carlson includes a highly detailed appendix on Paul Brown Soil Moisture Probe use.  Dr. Brown’s most pertinent publications are available on this website under our Publications and Resources section. 

Then....

 
Dr. Paul Brown and an associate demonstrate use of the Brown Soil Moisture Probe in 1960

And now.....

 
Dr. Perry Miller demonstrates use of the Brown Soil Moisture Probe in 2005 

Contact

Montana Salinity Control Association

PO Box 909
Conrad, Montana 59425
406-278-3071
800-537-6717