Saline Seep Study at Williston Research Extension Center

Since June of 2016, Dr. Clair Keene, Area Extension Specialist in Cropping Systems, has been researching how to prevent saline seep formation and growth. Saline seeps are discharge areas on the soil surface that are caused by salt accumulation at low points in the landscape. When salty groundwater is within six feet of the soil surface, it is pulled to the soil surface, and the water evaporates and leaves behind dissolved salts, which then create a saline seep. They typically form at the bottom of hills and on the sides of slopes.

Some of the early signs of saline seep development is a flush crop growth combined with excellent crop yields, increasing moisture (causing inaccessibility), and abundant growth of Kochia and foxtail barley. The later signs are sparse germination of crop plants, declining crop yields, increasing numbers of salt-tolerant weeds, and salt crystals forming on the soil surface. " The saline seeps inhibit plant growth, resulting in reduced crop yields and loss of profit for the grower. Saline seeps are common in this area due to the long history of grain-fallow cropping systems," said Dr. Keene.

A saline seep at the Williston Research Center occupies one to two acres of a dryland field at the bottom of a slope. The seep has been around for approximately the past 20 years but began to increase in size within the last five years.

The Montana Salinity Control Association, a satellite organization of Montana's Soil Conservation Districts, has installed groundwater monitoring wells to define the recharge area for the seep. The recharge area is about 90 to 100 acres.

In June of 2016, Dr. Keene planted 40 acres of alfalfa and perennial grasses to decrease the water table and prevent further saline seep growth. Keene planted a variety trial with four alfalfa varieties, and two different types of perennial grasses in the saline seep to evaluate the salt tolerance of various forages. She harvested biomass from plots in September of 2016 and May and July of 2017. "I hope to keep collecting data from this research project for the next three to five years."

Some strategies to reduce saline seep formation are intensifying crop rotations, incorporating high water use crops, and planting perennial forages such as alfalfa and salt-tolerant grasses. These strategies will lead to decreased water tables and shrinking saline seeps.

Dr. Keene explained, "I have been very pleased with the first two years of the saline seep experiment. All four of the alfalfa varieties we are testing have established in the seep and are looking very good. The grass species are struggling a little bit but they are slower to get going. We were able to take two good cuttings this year and we might have been able to do a third if we had more help with the project. Two cuttings in a drought year is an amazing thing, and that is the kind of result we are looking for: instead of spending money in seed and fertilizer on ground that won't yield, why not plant it to a perennial crop that you don't have to spend money on each year and can give you forage?"