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, SDSU Extension soils specialists.
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. In the study, crop yields were reduced for 12 years. In another Minnesota trail, yields averaged 5-6% less for 5 years after only a single pass of a 20-ton axle load.
There are several solutions to the problem.
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 6-8 inches.
Deep ripping is an option. However, results have been inconsistent. Gelderman recommends waiting until next fall when soils may be dryer to do deep ripping.
"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."
Some research work has indicated tillage needs to be done 50% lower than the compaction zone, but that other studies indicate that tillage 2-3 inches below the zone will help.
"In any case, ripping 18-20 inches deep will probably not reduce subsoil compaction below 15 inches," Gelderman 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 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 20-30% 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, 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 oil seed radishes, turnips, or sugar beets.
"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."
You might want to consider no-till, Gelderman says, 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. 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."
For more information about addressing soil compaction issues, call Gelderman at 605-655-4770, e-mail him at Ronald.Gelderman@sdstate.edu, or refer to the recent Minnesota Extension publication available at this link: mn4h.com/distribution/cropsystems/M1271.html.