Trouble spots take money from farmers’ pockets
Trouble spots in fields can take serious dollars from farmers. With inputs for planting corn around $500 an acre, those attending last week’s Saline and Sodic Soil Management Workshop and Field Tour in Pierpont were eager to learn ways to handle acres where the ground has turned white or crops won’t grow.
The workshop offered advice from farmers who have tried some alternatives as well as experts from government agencies showcasing soil pits and test plots. Based on a soil analysis, 7.6 million acres in South Dakota could be affected by high sodium content.
David Gillen, a farmer from White Lake, said, “There are not many other things in our operation that will give us as big of a return on our investment as cleaning up the salts.”
Gillen said that the market is telling farmers not to plant so much corn and suggested that maybe now is the time to fix some of the problem spots in fields. With the high dollar expense of inputs and corresponding land prices, farmers can’t afford to ignore the problem.
“The two things I’m doing are tiling plus adding gypsum and planting tall wheat grass to those problem areas,” he said about areas high in sodium.
Gillen said he’s tiled most of the salt areas where there is an outlet. In areas where he can’t tile, planting salt-tolerant crops is another way to fix the problem.
“If you depend on tile alone, it won’t release the sodium in the soil,” Gillen said. “If you only use gypsum, that won’t take care of the water problem. You have to use both.”
Seeding a salt tolerant crop such as tall wheat grass within a salinity pocket may be effective in lowering the water table. Cover crops seeded in the fall may be used to reduce the water table. That can provide the opportunity for salts to leach.
Gillen said this is the third year he’s planted tall wheat grass. He said they put in dormant seed after Thanksgiving. Drilling the seed into frozen ground works the best in wet areas.
“It works good around borders of the wet land,” Gillen said. “If the salt area is too concentrated, the partial stand will fill in over time.” As the roots reach into the soil, that improves the environment for biological activity, increasing organic matter and will help with future fertility.
As long as the price for corn is around $3, Gillen urged farmers to fix salt areas now. Those areas can be planted in corn when prices are better. After 3 years of tall wheat grass, the difference is evident. He’s certain it will be even better after 4 or 5 years.
“You can’t keep doing the same things and get better results,” Gillen said. “You are losing dollars on these spots.”
Why the problem?
In South Dakota, both saline and sodic soil are serious problems, according to Dr. Gregg Carlson of SDSU. Carlson noted that significant precipitation has caused problems with soil and water movement in some soils.
Factors contributing to salt soils include: 1) road construction, which hinders water movement, 2) adoption of management practices that conserve soil water, and 3) higher rainfall.
The James River valley shows high salinity, with layers where nothing will move in the soil. With a water table that rises and falls, those salt problems increase as precipitation increases.
Carlson said that farmers have adopted good farming practices to conserve moisture. Scientists are seeing that those great practices may result in problems with the electrical conductivity (EC) of the soil.
Carlson told farmers that they have to know the difference between sodic and saline soils.
If soil is white, there is likely a problem. They should collect a soil sample and send it to a lab to determine the electrical conductivity, which can be measured in the soil. Saline soils have high salts, sodic soils have high sodium.
Saline soils contain enough soluble salts to injure plants. Saline soils usually have an EC of more than 4 deciSiemens per meter (dS/m).
Sodic soils are low in soluble salts but relatively high in exchangeable sodium. These high sodium levels disrupt both the chemical and physical composition of soil clays. As a result, the soil surface has low permeability to air, rain and irrigation water. The loss of permeability due to less pore space can severely restrict water movement into the root zone resulting in plant stress from lack of water. The soil is sticky when wet but forms hard clods and crusts upon drying.
Project at Pierpont
Cheryl Reese, from the Department of Plant Science at SDSU, provided an overview of the soils and salt research project at Pierpont, focusing on the test plots and soil pits.
“The reason we started this project is that we know we have sodium,” Reese said. “If tile drainage is installed, that will moved the calcium out, changing the problem from saline to a sodic problem.”
Reese noted that salts are indigenous to the area. With climate change, charts showed precipitation changes from 1951 to now. The Pierpont area now gets on average 8 more inches of rain than it used to get. The shallower groundwater table has allowed for salt accumulation in the rooting zone and reduced productivity of crops that are not very tolerant of salts. When the water reaches the surface, the water evaporates and salts remain on the surface, often producing a white patch.
Crops such as wheat and soybeans don’t use as much water as the bluestem and switch grasses of the prairie. This results in bringing the water table up with more soil salts evident. Plants have different salt tolerances. Sugar beet, crested wheat grass, tall wheatgrass and barley are the most tolerant while corn, flax, potatoes, alfalfa can’t handle the salts.
Soil high in sodium looks like concrete, and water will not flow into the soil profile. So, when an area gets 2 to 3 inches of rain at a time, water comes off fast and causes extensive erosion.
Drainage is needed for improved soil health, but tiling alone won’t fix the problem, Reese said. If producers use tiling, they will need to add amendments to the soil. Adding gypsum, lime, elemental sulfur or sulfuric acid can help displace the sodium in order for it to be leached into the soil.
Reese suggested that farmers test for Sodium Adjustment Ratio (SAR) as well as electrical conductivity to find out if soil is saline or sodic.
Solutions in the field
In the soil pit, Doug Malo of SDSU noted that it was easy to see the white spots, indicating gypsum, sodium or threads of salts. The salts occur naturally from the ancient seabed.
The 7-foot-deep pit showed how the water table is moving up and bringing more salts to the surface. Malo described the topsoil as tight, showing a need to increase the structural aggregates of the soil.
“You have to fix the top layer with a combination of things, and that will lower the water table,” Malo said. “You want to bring salts below 3 1/2 to 4 feet. By lowering that level, natural rainfall can leach the salts. By planting [salt tolerant] crops around the rims [of problem areas], less water will be going down into those areas.”
Reese showed plots where amendments had been added to the soil. Results were promising.
“You have to get something done to take care of the problem,” Reese said. “At least get some cover on the ground, or it will be going into a reverse direction. Think about options.”
One of the farmers involved in the project was pleased to see some alternatives.
“We worked closely with Bruce Kunze, soil scientist from Flandreau. He taught us a lot already,” Grant Rix of Groton said. “Dad and I are on the local watershed district. We’re trying to stay attuned to what needs to happen and doing our own little studies. We hear from people that ‘you need to use drain tile.’ I refuse to believe that paying $900 an acre for tile will make my highly productive soil good again. I’d rather use this stuff they are showing here, to plant something to get the salts down. Soil amendments are a lot easier to put in the soil than drain tile.”
His dad, Roger Rix, felt the workshop offered farmers a lot of information.
“This is what I wanted to see,” Rix said. “The most interesting solution is the kind where you can correct the problem. We have a lot of sodic soils. We know the water can’t move through the profile. We don’t have big areas, but they start at the size of a car, and now are the size of two gyms. Maybe we’ll start by doing some planting in the headlands, maybe some wheat grass. That intrigues me.”
The workshop was sponsored by the S.D. Corn Growers, USDA Natural Resources Conservation Service (NRCS) and South Dakota State University (SDSU). Gillen noted that the South Dakota Corn Growers is dedicated to bringing together the education to move farming forward with crop production. With a great turnout, it appears that it was very helpful for producers.
As they drove away from the soil pits, Nathan and Elroy Johnson of Pierpont pointed out a field that has areas that are always non-productive on their farm.
“A few years back, I put some sugar beet seed down, but then we didn’t get any rain,” Nathan said. “I’m really thinking of trying some of things from the workshop.”