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Strategic Planting

Saturday, January 15, 2005
filed under: Planting Systems

You might consider it risky to grow sunflower next year if it’s too dry. Or you might consider it risky to grow sunflower if it’s too wet.

Then again, if you preferred to sidestep risk, you wouldn’t grow any crop – heck, you wouldn’t even be farming today.

“There’s risk in anything we grow,” says David Franzen, extension soils specialist at North Dakota State University. “We had to plow down a lot of corn this year north of Highway 200. Canola, you have things like white mold and flea beetles. Wheat, you can have scab and rust. Soybeans, there’s chlorosis, white mold, aphids, and rust.

“We don’t live in an area where you can count on the same weather every year,” he continues, “so diversifying your crops is one way that we can reduce production risk. There are years when people had trouble with sunflower or soybeans, but the small grains pulled them through. In years when small grains didn’t pull through, crops like soybeans and sunflower did well. So diversity within the farm is a wonderful thing. It’s something that has helped people stay in business, and more than that, be profitable.”

Roger Ashley, NDSU extension cropping specialist at the Dickinson Research Extension Center, agrees. “If you put everything into an early-season crop like wheat, you might actually be taking on more risk.”

Ashley says growers shouldn’t base their ’05 crop decisions on 2004’s unusual weather. It makes more sense, he says, to look at crops that offer the best economic return which have the best chance to perform well in your own particularly growing area, then play the weather odds. “I certainly wouldn’t rule out warm season crops like sunflower in 2005. No sense in farming last year all over gain,” he says. “We have an equal chance for dry conditions, wet conditions, and normal conditions. So if you’re an optimist you’ll play the odds, and here, that means you’ll be hoping for average to above-average precipitation.”

Ashley says sunflower performed poorly in some areas of western N.D., and well in others. Sunflower may be a particularly good fit on fields planted to successive small grain crops. “It would be more likely that sunflower could tap into subsoil moisture that hasn’t been utilized, compared to another crop of wheat.”

Steve Merrill, soil scientist at the USDA-ARS Northern Great Plains Research Lab, Mandan, N.D., says ‘flowers have benefits on wet ground too, improving what he calls “trafficability,” or the ability to draw soil moisture out of the ground. It is also a crop that can perform better in salty/saline soils better than other crops can.

Merrill and other researchers conducted a study at Mandan during a three-year period that offered a look at water use of different crops in what turned out to be three different water-use environments: better-than-average moisture (1999), near average (2000) and above average (2002).

Sunflower and safflower used the least amount of soil moisture, while dry peas and barley used the least amount. Soil water use is a function of both rooting depth and crop maturity, says Merrill. “For example, soybeans use more soil moisture than dry pea. Both are legumes, but the difference is that soybeans have a longer growing season than dry pea.”

The Mandan research group concluded that water use differences can help growers make dynamic or strategic cropping decisions: flexible choices of crop species and management inputs dependent upon changing soil and land, climactic, and economic conditions. For example, if soil water is relatively available, then the more deeply rooted oilseeds sunflower and safflower might be included, but if low water use is needed, dry pea or barley might be good choices.

Using available soil N

With fertilizer prices hovering between $350-$400/ton, many growers will find legume crops that fix their own nitrogen, such as soybeans, dry edible beans, and dry peas, as attractive crop choices.

There’s something to be said too about crops that can take advantage of residual soil N too deep to be taken up by other crops, and no crop does this better than sunflower.

University research validates the sunflower plant’s ability to nab soil N. A three-year Kansas State University study in the late 1980s demonstrated that sunflower roots extended into the soil about 9.9 ft deep, while grain sorghum rooted to about 8.3 ft deep, nearly a 2 ft difference.

K-State has observed further that in fields with irrigated corn over multiple years, it can be common to find 200 to 400 lbs/ac of nitrate below the corn root zone, typically three or more feet deep in the soil. Sunflower will root down and extract that residual N, provided there’s not a compaction zone to inhibit root growth, and if subsoil moisture is adequate to encourage root growth.

A study at the USDA-ARS Central Great Plains Research Station in Akron, Colo., in the late 1990’s further illustrated the ability of sunflower roots to find residual soil N. The Akron research group analyzed recovery of N fertilizer placed deep in the soil profile with different placement methods. They found that sunflower recovered half the fertilizer N placed two feet deep. They measured 23% recovery from fertilizer N placed four feet deep, and 12% recovery at five and a half feet deep.

Sunflower would take advantage of residual N left behind from crops that failed last year, including corn. “Corn ground could have sunflower on it very easily in lieu of soybeans. Sunflower should do fine there. Wheat and barley wouldn’t be advisable because of the increased risk of scab,” says Duane Berglund, NDSU extension agronomist.

Franzen anticipates that corn abandoned last fall because of frost, then cut and incorporated, would contribute roughly about 30 lbs of N per acre toward the subsequent crop. This estimate from a plowed-under nature-induced corn green manure crop comes from a study in Minnesota by John Lamb, where sugar beets followed sweet corn, harvested while the stalks and leaves are green, leaving green matter behind similar to that of failed immature field corn.

Additional breakdown of corn residue will be more gradual, some of which would be cycled into the soil as organic matter and some N that would become available to the following crop late next season as residue decomposition continues. Adequate credit for N contributed by the previous crop should be factored into fertility planning ahead of planting sunflower. While sunflower is adept at using residual soil N, too much N late in the season could result in lower oil content.

The only way to know for sure how much fertilizer your sunflower crop will need next spring is by soil testing. It’s generally recommended that you’ll need 50 pounds of soil N plus fertilizer N in the top 2 feet of soil for every 1,000 pounds of expected sunflower yield. – Tracy Sayler

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