Combines working in wet conditions to harvest crops have formed ruts in fields and likely compacted soils, but you shouldn't rush to correct compaction or rutting problems this fall.
"Using tillage to loosen the soil and relieve compaction requires soil to be dry enough so that soil shattering is effective," says Iowa State ag engineer Mark Hanna. "Because soil moisture has refilled the top 12 to 24 inches of the soil profile, deep tillage with a chisel plow or subsoiler this fall or next spring will use fuel and time — but is unlikely to loosen soil effectively between tillage shanks."
Hanna says the full soil moisture profile in upper layers will freeze and thaw over the winter and help loosen soil, depending on air temperatures and snow cover. He adds that entering the field this fall in wet moisture conditions for deep tilling or any type of tillage will be counterproductive by creating much deeper soil compaction.
Iowa State agronomist Madhi Al-Kaisi says compacted soil created beneath the rut may interfere with subsequent crop rooting and development. Ruts deeper than about 2 inches can also interfere with maintaining seed depth during planting operations next spring, unless they are leveled.
"Ruts deeper than planting depth will need to be leveled before planter operation," Al-Kaisi says. " A good strategy may be to wait until a week or two before planting next spring and use a light tillage pass, such as with a field cultivator, light disc, harrow or soil finisher. If only a portion of the field is rutted, consider tilling only that area to avoid recompacting subsoil in other parts of the field."
He says waiting until warmer weather next spring also allows for some potential drying of the top 2 or 3 inches of soil. It avoids further compaction of wet, plastic soil on the surface, which will happen with a tillage pass this fall.
Hanna adds that if compaction effects are observed during the 2010 growing season and soil is dry after harvest, tillage next fall may be considered deep enough to break through the compacted layer.