Achieving Consistent Emergence
Sunday, April 1, 2001
filed under: Planting Systems
Getting Consistent Sunflower Emergence
Identifying the cause of poor or patchy stand establishment can be tricky
If you’re puzzled why you sometimes don’t get a good sunflower stand—even under planting conditions in which you should—don’t feel bad. Sometimes uneven stand establishment can baffle the agronomists too.
Two years ago, Ron Meyer, Colorado State University area extension agronomist, planted sunflower into what he describes as “the best soil moisture ever.” Nevertheless, he says the research trials resulted in poor stands. Under significantly drier soil conditions last year, however, the sunflower he planted got off to a much better start.
“I don’t know why that is. Stand establishment is getting to be a real concern of ours down here,” says Meyer, Burlington, CO. “You can shoot for a confection stand of 15,000 plants per acre and sometimes end up with much less than that.”
Looking for clues, crop scientists in the High Plains area have gone back into fields with uneven emergence, even retesting the germination of seed planted in affected fields. But the exact cause isn’t often clear.
Generally, oil sunflower tends to emerge with better stands than confection sunflower. The reason why, Meyer surmises, is that the size of confection seed is usually larger, and may require more moisture to start the germination process.
Bryce Brobst, agronomic research manager with Monsanto, Minneapolis, KS, says the seed shell is an emergence challenge that sunflower has which other crops do not. “Moisture needs to get through that seed coat first, then the seed. If you don’t have good seed to soil contact with moisture, then you’re going to have uneven emergence.”
Make sure the soil slice is closed and pressed firmly against the seed at planting, he advises. “And don’t put starter fertilizer (with nitrogen and potassium) in the furrow. Put it off to the side. Any salt in that slice, sunflower is very sensitive to,” says Brobst.
In no-till sunflower, Clair Stymiest, South Dakota State University extension agronomist, Rapid City, SD, says anything you can do to get residue out of the way of the seed path will help too. To that end, he says some producers and researchers are experimenting with using strip-till for better emergence in sunflower. (For more details on the field practice, see article on strip-till in the December 2000 issue of The Sunflower, which can be found online at the National Sunflower Association’s web site, http://www.sunflowernsa.com. Click on “The Sunflower Magazine,” then “The Archives”).
David Baltensperger, professor of agronomy and alternative crops specialist at the University of Nebraska Panhandle Research and Extension Center, Scottsbluff, hopes to zero in on the causes of poor stand establishment in the High Plains in a study on the problem. “We can have area wide differentiation. It can be too wet or too dry, but that doesn’t explain all the reasons why we sometimes don’t get good stands,” he says.
In researching the causes of poor stand establishment, Baltensperger is paying particular attention to wireworms, which seem to have increased in the High Plains. The insect might be infesting crops such as corn or winter wheat, then carrying over as a problem in sunflower.
“I have a hunch that wireworms are a bigger problem than we would give them credit for,” says Baltensperger. “Part of the reason I’m interested in them is that you can hardly find anything in sunflower research literature on wireworms and how to avoid them, and yet there’s hardly anybody in the High Plains selling seed that doesn’t recommend treating for wireworms. Untreated fields can be a disaster. So I’m trying to quantify it as a problem.”
To help his research on poor stands, Baltensperger encourages producers in the High Plains to contact him at the first sign of poor stand establishment. “We’ll try to find an agronomist to get over to your area to help identify what the cause might be,” he says. Baltensperger can be reached by phone at 308-632-1261, and by email: firstname.lastname@example.org.
Causes of Uneven Emergence
Following are potential causes of uneven sunflower emergence, according to Duane Berglund, extension agronomist at North Dakota State University, Fargo:
Seed germination or seedling vigor. If seed is in question and
happens to be carryover seed from the previous year, then a germ test
and vigor test are in order. Sample the seed lots and send to the
North Dakota State Seed Department Lab (or applicable testing lab in your own state) for analysis. Usually new seed sold by reputable companies have a current seed analysis attached to the bag.
Seeding into soil that’s too wet or too dry. Be mindful that “mudding” a crop in can cause uneven stands, and that preplant herbicide incorporation can cause excessive soil moisture losses.
The kind of planter you’re using. A row crop planter usually will result in better seed placement and firmer seed-to-soil contact. Boost your plant population by 4,000 to 5,000 if using an air seeder and narrow row plant spacings.
Planting depth. Ideal planting depth is 1.5 to 2.5 inches. Shallow plantings are best when planting smaller seed in cold, wet or fine-textured soils. Sunflower seedlings can emerge from planting depths of 3 inches or more in warm, sandy soil but emergence can be delayed. Soil temperature at deeper seeding depths should be at a minimum of 45 F for planting (A temperature greater than 50 F is needed for optimal sunflower germination.)
Speed. Driving too fast at planting can result in erratic stands.
Soils that are tilled too loose, than planted too deep. This may particularly be a problem on hillsides.
Early-season cutworms. Most damage by cutworms occurs when plants are at the cotyledon to two-leaf stage. Damage consists of young plants chewed off slightly below or at ground level. Cutworms feed primarily at night. When checking fields for cutworms during the day, dig down into the soil an inch or two around recently damaged plants, where you can find the gray to gray-brown larva.
Early-season wireworms. Currently the only insecticide registered for wireworm in sunflower is Lindane as a seed treatment. In corn, wireworms are most likely to be problems when the crop follows pasture or grassland. Continuous corn is also more susceptible. Infestations often are found in coarse textured soils (sandy loam) where moisture is abundant, perhaps in low spots of fields.
Soil crusting. This may be a problem in some soils. A rotary hoe can be used to help break the crust and allow sunflower seedlings to emerge.—Tracy Sayler