As a veteran ag engineer for Iowa State University Extension, Mark Hanna is cautious about saying the current drought may still be holding on when strip-tillers need to get into fields after harvest to make strips, build berms and place fertilizer.

However, Hanna says it's not too early to consider some of the impacts of the drought. This is especially true for strip-tillers who may be going into fields where corn has been chopped for silage instead of combined for grain.

"For some farmers in Iowa and adjacent states, they’re more likely to chop silage this fall than in years past," Hanna says. "Because of the shorter corn crops, farmers may be going from having to wrestle with how to handle too much residue to recognizing they may not have enough residue to cover the soil.

“For some farmers, this may mean choosing to strip-till, if they've used conventional tillage in the past. For other farmers, they may want to consider no-tilling."

Strip-tillers who go back and make a strip in the old corn row instead of moving over and off the row to make new strips could encounter some resistance from corn that's chopped for silage. That’s because corn harvested for grain leaves taller stalks, Hanna notes.

"With the shorter stalks in corn silage, there could be a little more of a problem as these stalks are more apt to stand up than to bend over," he says. "That means the old root balls could bunch up in the strip-till rig. But strip-till rigs with row cleaners and coulters and strong shanks, as well as rigs with coulters instead of shanks, should be able to handle this."

Dry Soil Creates More Wear

Dry soil could create other problems, Hanna adds.


Mark Hanna

He expects there will be a bit more wear on knives, and that the drawbar pull or draft will increase some, too. Strip-tillers may need to increase down pressure because there will be more mechanical resistance in the soil.

"It's just like when you go out to dig a post hole," he says. "You would much rather dig it when the soil has a few inches of moisture in it vs. into dry, hard soil. The soil just digs easier when there's some moisture in it."

The dry soil, with increased resistance, could also affect how deep knives go into the soil and the depth that anhydrous ammonia is placed, Hanna says.

While it's difficult to predict in early August what conditions will be this fall — even when it’s bone dry — Hanna says he still expects that there will be a little more of a problem with the soil sealing the anhydrous.

“Even so, you don't need that much moisture in the soil for it to bind with anhydrous,” Hanna says. “Watch to see if there are little white puffs of vapor or if you smell it. These are indications that the soil is not sealing."

Poor sealing could result from knives not placing anhydrous as deep as strip-tillers intend it.

"If you see problems sealing, check to see if the knife is getting as deep at you want it to," Hanna says. "If not, then apply more down pressure on the springs. Another angle to help sealing anhydrous is to use covering discs.”

Knife-Track Sealing

Fortunately, it doesn’t take too much moisture for anhydrous ammonia to bind with soil particles, says Clarke McGrath, Iowa State University Extension agronomist in western Iowa.

“The bigger concern is how soil and moisture conditions impact the sealing of the knife track,” says McGrath, writing in last week’s Iowa Farmer Today CropWatch Blog.

“When soils are dry, sometimes big clods are just moved by the knife and not broken up, so it could leave big gaps where anhydrous could move quickly and escape into the air,” he says.

In theory, the loss could be bad, says McGrath, who sold tens of thousands of tons of anhydrous while working in agri-business. In his work in business and since then with ISU Extension, McGrath says he’s very rarely seen anhydrous escape. And when it’s happen, it has occurred in spots of hardpan.

“More often, we see vapor loss in wet soils, with gas escaping up the smeared knife track,” McGrath says. “If soil conditions and the toolbar setup help seal up the knife track with loose soil, the gas should stay put. In really dry soil, the gas may move about 4 to 5 inches — and maybe 6 inches in really coarse soil — from the point of injection. So, going about 7 to 8 inches deep would be good enough to hold on to that 4 to 5 inches of movement.”

Rougher Strips

Dennis Turnwald, product marketing manager for Unverferth Mfg. Co., Kalida, Ohio, offers several recommendations for strip-tilling in dry soils, which can leave a rougher textured strip.

“It may even warrant postponing strip-till operations until later in the fall, perhaps early next spring after moisture levels return to more normal conditions,” he says. “If strips end up too rough, make an easy follow-up trip with a soil conditioner. That will help break the clods but not disturb the residue between the rows.”

Surprisingly, even though spring soils are wetter, they can work better after several thorough soaking-freezing-thawing cycles through the winter, Turnwald says.

“Don’t compromise. Wait for the right condition before making strips,” he says. “With strip-till, you're preparing next year’s seedbed, so compromises this fall can lead to a mediocre crop in 2013. Don’t assume a lumpy fall strip will ‘weather over’ this winter and magically appear next spring in great condition.”

Whether strip-tillers knife in anhydrous ammonia or inject liquid fertilizers, the strips require good soil cover over the strip, Turnwald says.

“Talk to others who’ve been practicing strip-till to find out what works and doesn’t work,” he says. “They will be eager to help you, and why not learn from history?”