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Hardpan blocks roots from deep nutrients and moisture

When Scott Steinberger starts talking about a 350-plus bushel per acre barley yield, or a 135-bushel canola yield, a lot of producers think he is either full of baloney or he has been smoking some kind of “special” crop. The 24-year-old North Dakota farmer is quick to point out that those exceptional yields were just blips on his yield monitor. But the point to be made, says Steinberger, is there can be great yield potential locked away in your soils.

“When I tell people we had barley yields that exceeded 300 bushels per acre, they think I am making it up,” says Steinberger, who farms 3,000 acres with his father, John, and an uncle Dan Steinberger at Kenmare, North Dakota, just south of the Saskatchewan-Manitoba border. “But the yield monitor doesn’t lie. In one spot the yield actually reached 366 bushels per acre. The field average is no where near that, but it does give you some sense of yield potential.”

To be specific, those exceptionally high yields were on just one-third to one-half of an acre out a 307-acre barley field. The average overall yield for the field was about 100 bushels per acre. About four per cent of the same field — that’s less than 15 acres — produced between 175 and 250 bushels per acre.

Similarly, canola averaged about 50 bushels per acre, but there were a few spots where yields peaked to an amazing 140-plus bushels per acre.

So what happened on those few acres to produce such high yields? Steinberger has been looking at yield-improving research over the past few years, and one treatment he believes does make a difference is deep tilling — or subsoiling. Over the past 10 years, he has used two different

Lee Hart is field editor of Grainews, based in Calgary. Contact him at 403-592-1964 or by email at [email protected]

tillage tools to break a hardpan layer that materializes about 12 inches below the soil surface on their farm, which is mostly clay loam soil.

“This year on those couple sites, the roots reached below that hardpan layer where there was a good reserve of nutrients. Parts of that field are also subirrigated,” he says. “All factors considered, the crop had exceptional nutrients and with subirrigation, it was like growing a crop under a conventional irrigation system.”

Overall, however, he’s expecting the subsoiling will increase yield by about 20 bushels per acre. As roots grow below that hardpan layer, the crop can make use of nutrients and moisture. “In some of our soil testing we found on two quarter sections that we had as much as 200 pounds of nitrogen below that hard pan layer. Those are nutrients the crop can’t reach. The roots go down, but as soon as they hit that hardpan they grow sideways.”

That’s another aspect of the exceptionally high yield story. Because soil tests had shown high levels of nutrient carryover below the hardpan level, Steinberger only applied 30 pounds of nitrogen at time of seeding. “There was this great reserve of nitrogen in the soil the crop couldn’t reach until we subsoiled,” he says. “We applied 30 pounds of N but the crop actually used 140 pounds of N.”

Steinberger says the roots of a wheat crop can grow seven feet deep, while the roots of some native grasses can grow as much as 30 feet deep.

The Steinbergers were surprised to find that a hardpan layer had developed under their crop land. There is no exceptional amount of equipment traffic on their fields. Every year they do some chisel plowing, and each spring they make one pass with a cultivator before seeding.

They made the first subsoil treatment as part of an on-farm trial back 1999. The goal wasn’t to deal with a hardpan layer. It was more an attempt to get certain crop nutrients deeper into the soil. Research at Purdue University had shown there was a yield benefit in corn by placing nutrients such as phosphorous, sulphur, and potatssium about 12 inches below the soil surface.

“I thought if that treatment improved corn yields it might be good for grains and oilseeds, too,” says Steinberger.

The subsoiler

They bought a DMI subsoiler with a parabolic curved shank and modified it to place the nutrient blend about 12 inches deep. They got the nutrients down, but they didn’t see any real difference in yield related to nutrient placement. What they did see was a difference in yield related to the subsoiling. In areas where they did not subsoil, yields were lower.

The Steinbergers didn’t particularly like the performance of the DMI subsoiler, so a few years later they bought a Miskin v-ripper with 20 inch shank spacing. They treated more of their cropland with this tillage tool.

“With two treatments, in 1999 and again in 2004, using the two types of deep tillage tools we have treated the whole farm,” says Steinberger. “In some areas that hardpan layer was four to six inches thick. Until we did that first subsoiling back in 1999 we didn’t think there was a hardpan layer. We figured if there was any compaction, frost action would take care of it. We could dig in our fields and the soil was fluffy and loose down to about nine inches. But then you get down another few inches and it is like hitting cement.”

While Steinberger is convinced that subsoiling is a necessary treatment every few years, to break up the hardpan layer, he still wasn’t completely satisfied with the performance of the two deep tillage tools he had.

After reading about the Australian built Agroplow deep tillage tool in a Grainews article in early 2008, Steinberger was interested in learning more. He came to the AgroPlow Canadian headquarters at Crossfield, Alta., north of Calgary, for a better look.

One downfall, in his view, of both the DMI and the Miskin deep tillage tools is that they caused too much soil disturbance and actually turn the soil over. “With deep tillage I want the hard pan layer to be shattered but I don’t want the soil mixing,” says Steinberger. “I want the various soil horizons to remain in the same order.”

That was an important feature of the Agroplow deep tillage tool. The digging blade works below the hardpan layer, lifting upwards and breaking the soil sideways without soil inversion or mixing.

Steinberger bought a 22-foot wide Agroplow deep tillage tool with 13-inch spacing. He only got about 80 acres of his farm treated this fall before winter set in. He pulls the plow with a Challenger 85D 370-horsepower tracked tractor. “I plan to work the subsoiling into a rotation so we are treating fields every three to four years,” he says. “We hope to make it a fall treatment ahead of the canola rotation.”

Steinberger was so impressed with the Agroplow tool, he also agreed to serve as the company’s first U. S. based product sales rep and consultant. He can be reached at 701-848-6741 or by email at [email protected]Contact the Agroplow Canadian office at 403-946-5300 or visit the company website at www.agroplow.com.

Grainews will have more on subsoiling in the January 12 issue.

About the author

Field Editor

Lee Hart

Lee Hart is editor of Cattleman’s Corner based in Calgary.

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