After a wet fall and spring, corn and soybean farmers must decide what field tillage operations are essential before planting the 2009 crop.
"Where I think things are a little bit different in 2009 compared to a normal spring is that there was less tillage done last fall than what may have typically been the case, because the conditions last fall were fairly wet," says Tony Vyn, Purdue University agronomist. "In this situation, farmers have a few alternatives to consider."
In Indiana, up to 70% of soybeans and 30% of corn are no-till.
"The first option in the spring is to not do any tillage at all," Vyn says. "Based on the experiences of the past 10 years in Indiana, it's fairly common for soybeans to be no-till seeded, typically into corn stover from last year. Some corn is also no-till seeded, typically into soybean stubble and sometimes into corn stubble."
While no-till seeding may be the solution for some producers, others may need to consider their options. One of those options is strip tillage.
"Strip tillage is essentially the disturbance of relatively narrow, 10-in. bands in fields where corn will be seeded into 30-in. rows," Vyn says. "This option has been increasing dramatically in Indiana – and although strip tillage is normally most effective if completed in the fall, spring strip tillage can be a viable option after wet falls like the one we had in 2008.
“However, the overall recommendation with spring strip tillage – and especially when it is close to the planting date – is for farmers to wait until soil conditions at the 4-5-in. depth allow you to strip till without creating large clods of soil that may become excessively hard. Tillage depth should also be limited to no more than 5 in."
For farmers who completed primary tillage operations in the fall but feel a secondary operation is necessary this spring, Vyn recommends keeping tillage shallow and limiting the number of passes to one.
"I think it's critical that the depth of tillage be limited, but also the number of tillage passes be limited to one," he says. "Should two or three tillage operations be considered essential for leveling fields or achieving weed control, it's our recommendation that the second, and if absolutely necessary the third, operation be done as shallow as possible. Generally speaking, there is no inherent need to do spring tillage to depths of any deeper than 3 in."
A final option for spring field preparation is vertical tillage – an operation in which producers use tools with straight coulters, harrows and rolling baskets in order to fluff up remaining surface crop residue with shallow soil penetration, without actually inverting the soil.
"Vertical tillage tools have the advantage of leaving more residue cover than a field cultivator or a disk, but less residue cover than an undisturbed no-till operation," Vyn says. "This operation is best suited for fields that are poorly drained or have high clay content and therefore dry more slowly in the spring."
Vyn says that whatever tillage operation is chosen, it's of utmost importance to wait for dry enough soil conditions and to keep all operations shallow.
"If we continue to deal with wet spring conditions, soil moisture will increase very quickly with depth, which means that deep tillage operations in spring could cause smearing and compaction," he says. "The combination of smearing and compaction is always going to be more of an issue when the soil conditions are reasonably wet at the time of tillage, and when dry, warm conditions persist after doing the operation.
"The worst possible combination would be tilling when the soil is wet and having that followed by a hot, dry spring. So a big part of tillage is trying to make sure you limit soil damage and creation of any root-restricting layers. That way, you give the maximum potential for unimpeded root development after tillage and planting."