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Plant Spacing Again on Survey Agenda for 2014

Friday, February 7, 2014
filed under: Research and Development

Usually the purpose of research is to provide answers to questions. But the 2013 spring and fall sunflower surveys have left agronomist Max Dietrich with more questions than answers. He and colleague Dwain Barondeau have a list of questions nearly as long as their list of survey data — some collected in 2013, and some collected in previous years.

Dietrich has been collecting and analyzing sunflower data since 2001, the first year of the National Sunflower Association’s annual fall survey. The survey is conducted in oil and confection sunflower fields in Minnesota, North Dakota, South Dakota, Kansas, Colorado, Nebraska, Texas and Manitoba. Among the most yield-limiting factors identified in surveys have been plant spacing, plant population and plants that don’t contribute to yield.

In 2013, Dietrich & Barondeau surveyed 15 fields in the western Dakotas — once in the fall and once in the middle of the growing season. The idea was to not only provide data to help growers make better management decisions, but also for the second set of data to help answer questions about uneven plant spacing, low plant populations and plants that contribute to yield compared to seeds planted.

Barondeau lined up growers who planted their sunflower with a row planter and filled out a form with each grower’s management information and the location of the sunflower field. The two surveyors would analyze two 30-inch rows, 25 feet long, recording total population, skips (spaces wider than 18 inches) and doubles (plants less than 4.0 inches apart). Then the surveyors dug up the furrow for every skip to see if they could determine what happened to the seeds (e.g., birds, rodents, insects, disease or germination issues). They then repeated the same procedure 50 feet farther into the field.

What Dietrich and Barondeau found was that 25% of the seeds planted did not contribute to yield. Also, 18% of the seeds didn’t produce a sunflower plant. And 1% of the plants were lost over the summer and 6% of the plants did not contribute to yield. That was 10 to 15% more loss than what is generally considered acceptable.

By digging up the furrow for the 75 skips they saw, the surveyors found that 3% of seed issue was due to germination problems, 33% was because of insects, 16% was from bird, rodent or deer activity, and 0% was attributable to diseases. On about half (48%) of occasions, no seed was found or no reason could be determined.

Then the surveyors dug up five consecutive plants, measured planting depth and counted the number of leaves. In the 15 fields that Dietrich & Barondeau surveyed in the summer of 2013, the average seeding depth was 1.81 inches. Seeds planted at 2.0 inches averaged 15 leaves per plant. Those planted more shallow averaged fewer than 12 leaves per plant. Seeds planted deeper than 2.0 inches averaged almost 16 leaves

They were surprised that seeds planted deeper tended to emerge faster than seeds planted shallower — especially given the cool, wet spring experienced in the region last year.

Dietrich and Barondeau next compared the fields with the most skips versus those with the least; also, most doubles versus least, and most skips and doubles versus least. They found no significant differences in those comparisons.

Dietrich still has questions. Do skips and doubles really affect yield? Does plant population affect yield? Is seeding depth important, or is it more important to have every seed at the same depth?

The best way to find those answers is to do another survey. While the National Sunflower Association Board of Directors has decided not to underwrite a planting survey in 2014, Dietrich will conduct his own survey as part of his work with Pioneer. This year, he and Barondeau will modify the survey slightly, hoping to get some answers.

The idea is to follow the same plant through the entire season. In 2013, surveyors returned to the same fields, but not necessarily to the same plants; they simply evaluated plants 100 feet into the field, and then another group 50 feet further into the interior.

Dietrich plans to return to the exact spot this year. He’ll use flags and GPS coordinates to make sure he checks the same plants. “We need to be more specific. In the past, we’ve just dug up five plants at random. I’d like to dig up 10 plants. That will provide some exact results, rather than the averages that were used in the past,” he says. “I’d also like to look at 20 fields instead of 15. We’ll do three in South Dakota and 17 in western North Dakota.”

Dietrich hopes this meticulous survey work will pay off in the form of more answers to his numerous questions. “I have questions about seeding depth. I want to understand why seeds that were planted at 1.0 inch took longer to come up,” he observes. “I’ve always said I thought a 2.0-inch seeding depth was ideal. Anything shallower than 2.0 inches seems to cause problems, even skips. I think the planter just gets going too fast, the seeds don’t get deep enough, then they don’t come up.”

He also has questions about plant population and seed spacing for which he wants better answers: How does plant population affect incidence of disease? Does plant population cause sunflower to dry down faster? Does plant population affect oil content? How could technology help with spacing?

They are valid questions — questions for which Max Dietrich is determined to find better answers in 2014. He and Barondeau plan to start this season’s survey around mid-June, depending on how the spring planting season plays out. — Jody Kerzman

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