Following Soybeans with Sunflower
The more acres planted to soybeans in the Northern Plains, the more challenges to the crop rotation, especially when economics is prompting more growers to cut back on their wheat acres.
It is still preferable to follow a broadleaf crop like sunflower or soybean with a grass crop like wheat or corn. However, sunflower can follow soybeans, but keep field history in mind, advises Terry Gregoire, North Dakota State University area extension agronomist, Devils Lake. Gregoire does not advise beans following sunflower, or sunflower following beans, on fields where Sclerotinia was a severe problem, such as 2004.
Sclerotinia produces the hard, black resting bodies called Sclerotia which can survive in the soil for a number of years (five or more) which can infect susceptible broadleaf crops is subsequent years, if weather is conducive to the formation of Sclerotinia (referred to as white mold in canola, dry edible beans, and soybeans).
Gregoire says sunflower planted on soybean ground is less of a risk than soybeans planted on sunflower ground. In the latter situation, he advises planting soybeans in wider rows to open up the plant canopy and allow for better dry-down of plants in the event of prolonged wet weather at flowering, when soybeans are most susceptible to white mold.
NDSU extension agronomist Duane Berglund agrees that sunflower following soybeans is preferable to beans on sunflower ground, although the research data of sunflower following soybeans is limited. “Now dry beans or canola following any of those two (sunflower or soybeans), that would be an absolute no-no,” he says. Weed pressure, including Canada thistle, should be greatly reduced following Roundup-Ready soybeans. As well, Berglund says sunflower would also take advantage of a 40-lb/ac nitrogen credit following soybeans.
If planting sunflower on last year’s soybean ground, grow one of the more disease resistant hybrids available, he advises.
A change in federal crop insurance rules several years ago allows sunflower (both oil and non-oil) to be grown on fields planted to soybeans, dry peas and lentils the previous year, without affecting federal crop insurance coverage.
Rotation restrictions remain when the previous year’s crop is canola, crambe, dry beans, mustard, rapeseed or safflower. Sunflower planted on acreage where any of these crops were planted the previous year will not be eligible for federal crop insurance coverage.
The crop insurance change to allow sunflower following soybeans, dry peas, and lentils was made in recognition of the fact that Sclerotinia head rot is caused primarily by windborne ascospores. The biggest risk of Sclerotinia head rot in sunflower is when weather is conducive for the development and spread of these ascospores, which may be blown in and infect sunflower regardless of crop rotation.
“Decision driven by economics”
Mike Clemens of Wimbledon, N.D., had a lot of soybean ground available last year, and with the high sunflower prices, planted some sunflower following corn, and some sunflower following soybeans.
“It was a decision driven by economics,” he says. “The numbers weren’t there for wheat but the prices were attractive for sunflower, so we looked at other rotations to work the sunflower into.” Weather was ideal with no disease pressure, and yield and quality of the sunflower was excellent both on the soybean and the corn ground.
He planted a sunflower hybrid that performed well and ranked high for Sclerotinia tolerance, in trials at the nearby NDSU Research Extension Center in Carrington. “I figured that took some of the gamble out of my program, by using that research.”
Clemens, who is chairman of the National Sunflower Association, soil tested before planting and took the previous year’s nutrient credits into account before fertilizing his ‘flowers. “Looking at the fertilizer cost, we put down less N than what we normally would in the past, before it would be more like 80 to 90 lbs N but we ended up putting down closer to 40 to 60 lbs of N and it worked out well.”
Even though the previous crop was Roundup-Ready soybeans, Clemens put down a glyphosate burndown before planting sunflower on the bean ground to control early-germinating weeds, then followed up with an application of Spartan and then Select about four weeks after planting for grass control. A big wheel sprayer – 150 acres an hour – helps cover a lot of ground and thus minimize fuel application costs.
Clemens tries to minimize tillage, and plants sunflower into residue of the previous crop. One would think that soybean residue would be easier to plant into than corn residue, but that’s not necessarily the case.
“You have the corn stalks but the bean residue can be like clumps of barbed wire out there. The soybean residue seems to break down slower than the corn residue,” he says. “I think it’s important to have that planter set for residue management, with residue managers or trash whippers at the front of the planter and the proper closing wheels for higher residue situations to get a good stand.”
Clemens says he’ll likely grow some sunflower again this year on last year’s soybean ground, going by field history and soil moisture recharge, and again selecting the best hybrid for the situation. – Tracy Sayler
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