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Issue No. 2, Article 10/April 8, 2011

Tillage: Think Seedbed and Rooting Zone

The official NASS estimate indicates that 4 percent of the Illinois corn crop was planted by April 10. That's a good start--equal to the one in 2004, when we had our highest yield ever in Illinois (180 bushels per acre). The only year in the last decade that we had a faster start was 2005, when 14 percent of the crop was planted by April 10. But it didn't rain much the rest of the season in some places that year, and we ended up with a yield of only 143 bushels per acre. With some rain in most areas within the last week, we hope that this year will look more like 2004 than 2005.

Almost all reports this spring are of great soil conditions, whether for applying ammonia and doing secondary tillage to prepare for planting or for planting itself. The large amount of tillage done last fall and the good soil conditions even where no fall tillage was done raise questions of how much tillage is needed this spring. While many producers have "voted from the tractor seat" and are doing spring tillage as usual, others are thinking that this may be the spring to do less tillage.

There are two fundamental reasons to do (or not do) tillage. First, you want to produce or retain very good conditions in the top few inches of soil so that seed can be placed into friable soil, with good seed-to-soil contact. In the right soil conditions and with the right equipment, no tillage at all may be needed to accomplish this. Where it is needed, try to create a place where the soil not only is in good condition for the seed, but also retains its soil-to-soil connections with the underlying soil, to keep it from drying out before the seed can germinate and emerge.

The other reason to do (or not do) tillage is to create a favorable place for roots to grow. This means having no distinctive physical barrier, such as that created by compacted soil, either unrelieved from previous compaction or created by tillage or planting operations. It also means having good soil-to-soil connections with the deeper soil in order to keep water moving to the surface as the plant starts to take up water. Deep ripping when soils are dry enough and not driving on soils when they're still wet can do a great deal to help create these conditions. But no-till can also help preserve these conditions when they exist.

One issue raised last fall with the large amount of tillage, in some cases followed by a leveling trip, was whether "stale seedbed" planting might be feasible this spring. Planting this way has the advantage of preserving soil moisture, and of course it means no tillage trip or cost in the spring (though it may be more accurate to say that "spring" tillage costs were shifted to last fall). Fall tillage tends to reduce the number and size of winter annual weeds, so burndown plus residual herbicides should be effective in stale-seedbed plantings. Planting depth may need to be adjusted to keep from planting seeds too deep. While we haven't done or seen enough stale seedbed planting to recommend it, the unusually good seedbed conditions this spring may make it worth trying, at least in a field or in some strips.

Though there aren't many fields going to corn that weren't tilled last fall, current soil conditions should also make no-till easier to do well this spring. One option that may allow fields--especially corn following corn--to be counted as no-till is "vertical tillage." This is accomplished using a wide variety of equipment types and brands, with the common theme being fast, shallow disturbance of the soil with little residue incorporation. Many of these implements also have attachments that help break corn residue into smaller pieces but leave most of it on top, thus helping seed placement while preserving cover.

An additional benefit that is claimed (and is probably the origin of the "vertical" term in the name) is that, unlike the field cultivator, disk harrow, or soil finisher, implements for vertical tillage do not till to a uniform depth, so they do not create a distinct layer several inches down, with loose soil on top and more consolidated soil beneath that can harden when it dries and prevent easy root penetration. Vertical tillage should generally be considered only in fields that were not tilled since the last harvest. Whether it is necessary or helpful depends a great deal on the conditions in the upper few inches of the soil. If seed can be placed well without using a vertical tillage implement, there would seem to be little reason to use it. In a 6-year study conducted by Eric Adee at Monmouth, vertical tillage done using an Aerway produced the same yield as no-till in corn following soybean.

Because rooting conditions following this past fall and winter should already be good, the emphasis this spring should be on minimizing compaction damage to the soil of the rooting zone. This means driving on fields as little as possible, staying out until soils are dry enough, and doing what you can to reduce compaction when tilling or planting. Controlling traffic--keeping wheel tracks confined to the same between-row positions as much as possible--will help.--Emerson Nafziger

Emerson Nafziger

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