The NDSU Langdon Research Extension Center (LREC) has been a constant in studying soil health and how producers can reduce damage or even improve the quality of their cropland.
By Melissa Anderson
One of the methods that has been discussed at length at the LREC by resident soil health expert Naeem Kalwar is the use of cover crops to make “sour soil” productive again. NDSU Extension also has the expertise of Kevin Sedivec. He shared that another way a producer can encourage more productive soil is through the use of cattle grazing.
“The challenge is that we have areas where we plant our annual crops; we spend all that money. Either the seed doesn’t germinate or we get poor stand so we lose money. Then nothing is growing there; white salt crust shows up. Most of the time we go back and till it. That’s an added expense. That increases evaporation and creates high salt levels because water wicks up,” Kalwar explained.
Salinity in soil is related to water soluble salt issues which are a combination of chemical ions. Sodicity, on the other hand, is the sodium that is attracted to soil particles. Both types of “salt” can cause very large problems for crops. Soluble salts compete with plant roots for water while sodium leads to tight or dense soil layers making it hard for roots to grow.
“Sample and test these areas for salts and sodicity. That’s the number one step. Once we get all our bumpers, then we know what to do if there is a sodicity issue. We may need to apply soil amendments like gypsum or beet lime,” Kalwar explained. “Then we should establish buffer strips along the headlands or lower areas, and we should plant something that will grow there.”
For Kalwar, the past several years have been spent working to find the perfect mix of cover crop grasses that are salt tolerant but also valuable to the producer who chooses to plant them. Kalwar explained that when producers can no longer grow an annual crop, such as barley which has the highest salt tolerance, on valuable acres due to salinity or sodicity, the producer still has options.
“The grass mix I recommend is very salt-tolerant and palatable as hay, however, it’s not top quality hay. It is a happy medium,” Kalwar said. ”I have come up with this mix after consulting Kevin Sedivec and other NDSU people several times.”
The mix that Kalwar has created grows well in the commonly called “sour soil” areas and can provide producers with additional income either through haying or allowing grazing. Kalwar’s research into the grass mix has also led to a happy breakthrough in which the salt tolerant grasses can eventually decrease the salt and sodicity to allow alfalfa to grow, improving the quality of the hay or grazing area.
“The success of alfalfa with these grasses though is kind of like a breakthrough as it may take alfalfa 2-3 years, however, that can increase the quality of hay dramatically. So I would like to stick with the following mix for areas that do not even support salt-tolerant crops like barley or oats,” Kalwar shared.
The current mix recommended by Kalwar is: Tall Wheatgrass, Slender Wheatgrass, Western Wheatgrass, Green Wheatgrass (AC Saltlander), Russian Wild Rye and one to two pounds of a winter-hardy alfalfa like 6272A. Kalwar does caution producers about including Green Wheatgrass (AC Saltlander) as it can be invasive.
Admittedly, it will take years for the grasses to do their work of correcting the soil’s salinity/sodicity issue, but in the mean time, the land can be productive through haying or grazing. Sedivec points out that while haying is a good option there is an additional benefit to having cows graze on these areas.
“When I look at cover crops, I look at it as a feed source. It’s a great way to feed the cows and still have biology for the cover crop. The cows put back into the system through manure and urea,” Sedivec said.
By having cattle graze on the areas with salinity/sodicity areas, producers increase organic matter. With the increase in organic matter, the added benefit will lead to better water holding capacity in the topsoil along with improvements in many other soil functions. Kalwar explained that capillary water movement happens from “wet to dry areas”. For dry, saline, barren soil surfaces, groundwater water will start wicking up towards the topsoil. With it, it will also bring water soluble salts.
“Increased organic matter in the topsoil will lead to more moisture in the topsoil which will minimize the wicking up of groundwater. So, yes, organic matter will help reduce salinity,” Kalwar said.
With soil with sodicity issues, it is not quite clear what benefit it gets from organic matter. Because sodicity is caused when excess sodium is attracted to the negative charges of soil clay and humus particles, amendments are usually needed to correct the issue. By appling amendments like gypsum, calcium is added back to the soil to make up for the lower calcium level versus sodium.
“Increasing organic matter may not help greatly with that. Having said that, sodicity leads to the breaking down of soil aggregates, and organic matter also helps build aggregates. So, yes, the addition of organic matter will help reduce the effects of sodicity, however, in order to change soil chemistry by increasing calcium levels versus sodium, we probably will require amendments,” Sedived noted.
The cycle that Sedivec refers to is that the cover crop provides feed to the cattle who in turn provide manure which contains nutrients that future crops can use. Some producers have expressed concern that the grazing cattle may increase the bulk density of the soil below.
“We looked at compaction or bulk density, and we found that we actually reduced bulk density where we grazed these cows by 10 to 20 percent in that 2 to 3 inch zone,” Sedivec said of trial results.
For those interested in planting the salt-tolerant grass mix, the specific mix mentioned should be available through the following companies. The companies can also mix different grass types before shipping them. Prices, however, may vary so Kalwar generally encourages producers to call around for the best deal.
• Rivard’s Turf and Forage, Grand Forks – 800-731-5765
• Agassiz Seed & Supply, West Fargo – 701-282-8118)
• Pulse USA Bismarck – 701-530-0734
For questions or more information on this topic, please contact Naeem Kalwar at NDSU Langdon Research Extension Center 701-256-2582.