The soil compaction caused by combines, grain carts and trucks last fall could significantly reduce yields for several years in the future, warns Ron Gelderman, South Dakota State University Extension soils specialist.
"In one Minnesota study, yield loss from subsoil compaction was as much as 50% the year following a pass with equipment that has a 20-ton-per-axle weight," Gelderman says. "In the study, crop yields were reduced for 12 years. In another Minnesota trial, yields averaged 5% to 6% less for 5 years after only a single pass of a 20-ton axle load."
There are several solutions to the problem, Gelderman says.
One is to fill in the ruts to lessen the impact of poor seed-to-soil contact and resulting poor stands. However, filling ruts will not alleviate subsoil compaction deeper than 6 to 8 inches.
Deep ripping is an option, he says. However, results have been inconsistent. He recommends waiting until next fall when soils may be drier to deep rip.
"With dry soils, the ripper tends to fracture soils and may alleviate compaction, whereas with moist soils, the implement will only form a deep groove and can make the situation much worse," Gelderman says.
Some research work has indicated tillage needs to be done 50% lower than the compaction zone, but that other studies indicate that tillage 2 to 3 inches below the zone will help.
"In any case, ripping 18 to 20 inches deep will probably not reduce subsoil compaction below 15 inches," Gelderman says.
He says you may have to accept the yield reduction and let nature take its course.
"Mother Nature can slowly alleviate the problem with freeze-thaw and wet-dry cycles," Gelderman says.
One of the best ways to limit the problem is to avoid working or harvesting when soils are too wet.
"This is easier said than done, but if producers are facing wet conditions, they can limit axle weights and use recommended tire pressures to reduce compaction," Gelderman says. "Limiting harvest traffic to less than 20% to 30% of the field by designating traffic lanes also will help, and restricting heavy grain carts to headlands or lanes will help manage compaction."
In addition, Gelderman says unloading combines or grain carts when only half-full will reduce compaction under wet soil conditions and establishing controlled-traffic rows will permit good root growth while allowing field operations to continue.
Consider planting cover crops with deep, primary rooting systems, such as oilseed radishes, turnips or sugar beets, he says.
"These crops can work very well following short-season crops such as small grains and pulse crops where there is enough remaining growing season for roots to develop," Gelderman says.
He adds you might want to strongly consider no-till, because no-till fields are more resistant to soil compaction.
"Surface soils in no-till fields tend to be firmer with more soil strength and therefore they resist some compaction," Gelderman says. "No-till fields also tend to have well-developed soil structure containing macropores from old root channels and earthworm activity that will drain excess water."