In addition to considering tillage in fields on a corn-corn rotation, Vyn recommends farmers consider limited fall tillage for fields with a history of compaction, high clay content, lack of systematic drainage or fields with very slow-drying soils.
He also advises farmers to consider the risks of fall tillage on their fields, especially in sloped areas. They should consider the amount of topsoil that could be lost, and the future yield loss in those eroded areas, if they bury residue that could be left to provide protection from runoff.
"Tillage has a permanent effect that can forever change soil water-holding capability on slopes," Vyn adds.
Normally, the protective residue cover and greatly reduced soil disturbance associated with no-till mean less evaporation loss and higher soil water availability to roots. But this year, no-till fields did not provide as much protection against the drought as expected.
The early-season onset of high temperatures and lack of rain limited both root growth and shoot growth in 2012. Corn and soybean varieties differ in their relative rooting ability under stress conditions, but rooting in all varieties after the early seedling stage depends on energy reserves coming from shoot growth.
"The near-surface soil was so dry, lack of tillage meant more resistance to root penetration, meaning corn or soybean plants in those fields sometimes experienced more drought stress before flowering than other tilled fields, despite the crop residue cover," Vyn says. "But we may never see such a severe, early drought occur with that combination of timing and high temperatures again. A later-season drought occurring after deep early root establishment would have favored no-till more."
If farmers decide to practice fall tillage, they can choose from several management techniques. Standard primary tillage procedures include using a disk, chisel plow, deep ripper, moldboard plow or strip tiller.
Vyn says agronomists favor strip tillage because it allows for minimal soil mixing and residue incorporation while preparing fields for earlier seeding of spring crops, and it can be combined with fertilizer application.
"It's a proven, versatile tillage practice that creates a warmer, drier zone of soil in the spring that ensures timely seed placement in both corn-soybean and corn-corn rotations," Vyn adds. "Precision automatic guidance systems have also simplified crop row placement in the center of the loosened strips."