Managing Salinity with Cover Crops: A Whole System Response

Managing Salinity with Cover Crops: A Whole System Response2018-10-04T12:17:22+00:00

In 2017, we initiated a study to see if we can use a cereal rye cover crop to improve corn and soybean production on saline soils. Soil salinity is a common cause of poor crop yield throughout North Dakota, and we need effective strategies for improving the soil health and productivity of salty soils. Cover crops have a lot of soil health benefits, and we think they can help improve productivity in saline soils, but they might also compete with the cash crop or encourage pests.

Our goals for this research:

  • Understand the differences in soils, plant growth, and insects in moderately saline soils (soils with an electrical conductivity between 2 -4 dS/m).
  • Test if a cereal rye cover crop in a soybean-corn rotation can improve soil health and crop productivity without introducing too many risks.

We established cover crop trials on four farms that all have patches of salty soil (in Aneta, Jamestown, and Northwood). We surveyed the fields for salts and interseeded cereal rye (40 lbs/ac) in strips across each field so that we have sampling points with and without cover crop and with and without salts (See Figure 2). In the first year of the study, we collected baseline soil data, measured yield, and surveyed insects. Two of the fields were planted to corn, and two were planted to soybean. We’ll continue to measure these for three more years, or two full rounds of a corn-soybean rotation, since it takes time for the soil to change.

In 2017, crops on the saline soils had lower yields, and the cereal rye did not further reduce yields. Saline soils often occur in landscape depressions, so they are also consistently wetter throughout the growing season; the cover crops did not necessarily dry out the soil in the fall. Since there is less plant growth and more water in saline soils, there’s a chance that the saline patches contain unused nutrients (like nitrogen and phosphorus). The difference in soil water and nutrient contents between saline and non-saline soils indicates that saline soils provide different habitat conditions for soil microbes—these patches aren’t just different because of salts. We don’t yet know how that might be important to crop production, pest occurrence, or cover crop health. We are still processing insect specimens from the field collections. All of these biological properties will be examined in much closer detail during the 2018 growing season, and in years to come.

In the next few years of the project, we’ll be measuring the different organisms that live in the soil and in the plant canopy, to see if they are good or bad, and if they change in the areas that have cereal rye. We’ll also be taking a close look at how much water the cereal rye uses, and if it is robbing water and nutrients from the cash crops. It is difficult to move salts from the rooting zone, but we expect that the cereal rye will provide some soil health benefits and help manage soil water, which is the best approach for reducing effects of salts.

We still have a lot to learn about cereal rye as a tool for managing soil salinity. In addition to understanding the basic nature and management of salty soil, this research will also help us understand the uses and limitations of cereal rye for improving soil health and crop yield.