Finer Points of Strip Tillage Explored

By Ron Johnson Dairy Editor
Thursday, August 21, 2008 8:00 AM CDT

Farmers from at least four states attended the Midwest Strip Tillage Expo last week at Arlington. They learned about some of the benefits of this alternate tillage method n potentially less soil erosion and possibly higher yields.

They also heard about some of the finer points of strip tillage from Tony Vyn, an agronomist at Purdue University, West Lafayette, Ind.

Just what is strip tillage? A commonly used definition is tillage that leaves narrow zones n or strips n of soil undisturbed. These strips are often 6 to 8 inches wide and 6 to 8 inches deep. These strips are approximately where the previous year’s crop rows ran.

Vyn began by talking about making “berms,” or low ridges in strip-tilled fields. Some farmers make berms while others do not.

These berms can range from 1 inch to 8 or 9 inches above the surface of the rest of the field, said Vyn. It’s in the berms where the corn or soybeans are planted.

Berms serve a couple of functions, according to the agronomist. First, they provide a planting area that drains and dries faster.

Second, soil in the berms warms faster than surrounding soil. This means that seeds can germinate faster and crops can grow larger and mature quicker.

Vyn said it’s better to build berms in the fall, if soil conditions permit. But they can be built in the spring, if the soil is not overly wet. He recommended berm building “at least a week or two before the actual planting.”

Farmers building berms in the fall should stay away from tillage tools that have rolling baskets, cautioned Vyn. He explained that the idea is not to make a seedbed at that time, but just to make a raised surface for planting later.

But farmers who have well-drained soil might not want to go with strip tillage at all, according to Vyn. They might be better off, he said, using no-till for their corn and soybeans.

Field slope can dictate whether or not strip tillage should be used, too. Vyn’s recommendation was to use no-till if a field has more of a slope than 5 or 6 percent.

One way to look at strip tillage is as a “compromise” between no-till and chisel plowing, Vyn said. Strip tillage leaves more residue than chisel plowing, but less than no-till.

He offered a few figures to back that up. A field measurement after planting corn in Indiana showed that a field that had been chisel plowed had only a 20 percent residue cover. For strip tillage it was 70 percent coverage, and for no till, 90 percent of the field contained old-crop residue.

What might a farmer expect from strip tillage? Vyn said the corn should be taller than with “conventional” tillage if both crops were planted side by side, on the same date. By “conventional,” he meant chisel plowing or moldboard plowing.

Yields might be higher with strip tillage, too. A comparison of strip-tilled corn and no-tilled on a loam soil in northern Indiana showed the strip-tilled corn winning the yield contest. It came in at 192 bushels per acre, versus 180 for the no-tilled crop.

Auto guidance

Some farmers are using automatic guidance systems to help them get perfectly straight berms and to plant into the berms. Planting exactly in the center of the berm gives the seed the highest soil temperature.

One study found that the temperature in the center of a berm reached 73 degrees, noted Vyn. But move 7 inches off center and the temperature got to just 71 degrees.

Yield measurements support planting right in the middle of the berm. Vyn said one count had corn planted using an auto guidance system yielding 216 bushels per acre. By contrast, corn that was planted “visually” yielded 209 bushels per acre, presumably because the seed was not deposited precisely in the center of the berms.

Fertilizer placement

Vyn offered a couple of thoughts on fertilizer placement. He warned that there’s a “big risk associated with placing a high rate (100 pounds per acre or more) of nitrogen in the center of the strip.”

That’s because doing so requires rain “right after planting,” Vyn explained. He said he has seen corn stands reduced by up to 50 percent if adequate rain did not come soon enough.

Farmers who still want to apply large amounts of preplant nitrogen should make sure it’s placed about 4 inches deep, Vyn added.

What about using less fertilizer for strip-tilled corn ground? Vyn said there’s “probably not” more latitude to trim the amount of phosphorus and potassium being applied when strip tillage is used.

Instead, it might be a good idea to make sure the corn rows get moved across the field from one year to the next. That way, the fertilizer will also be moved across the field.

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