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Plant Stand: The Top Yield-Limiting Factor

Wednesday, December 1, 2010
filed under: Optimizing Plant Development/Yields

When it’s added up, millions of dollars are spent each year on sunflower research across the private sector, USDA, universities and farmers through their checkoff contributions, which are combined into the National Sunflower Association. Prioritizing where those dollars need to be spent is a job taken very seriously.

A huge part of the prioritization process includes the results of the annual national sunflower survey. The survey involves volunteers with agronomy backgrounds who spend as much as an hour in a randomly selected field looking at a variety of factors that may be inhibiting yield.

All volunteers use the same reporting format. The data are then compiled by survey coordinator Dr. Hans Kandel of North Dakota State University.

A total of 174 reports from the 2010 survey have been received as of this writing, with a few more expected. Surveyors are asked to designate two yield-limiting factors in each field. When totaling the top two factors, the category “no problem” was the most common response this year — which is very satisfying. Plant spacing/ plant population was easily the most common cause as a yield-limiting factor. That is not totally surprising since much of the sunflower acreage in the northern states was “mudded in” during the wet 2010 planting season. Farmers reported inconsistent stands early in the season due to the less-than-desirable planting conditions.

Regardless of the 2010 planting conditions, however, it should be noted that plant stands and plant spacing have been a consistent problem since the first survey was conducted in 2002.

Since that first survey, there have been improvements in seed treatments eliminating wire worm, flea beetle and, to some extent, cutworm. Great strides have been made in minimizing seedling diseases like downy mildew through seed treatments and genetic resistance. Planter technology has also improved seed placement accuracy.

But the issue continues to be a significant yield-limiting factor, and more attention needs to be placed on this at the research and producer level. An information generating format has been set up on the National Sunflower Association website ( where farmers and others can provide insight into stand establishment and plant spacing. We encourage our readers to participate in that.

The other significant yield-limiting factor in 2010 was disease. The majority of diseases found in the surveyed fields included Phomopsis and Sclerotinia (which includes basal stalk rot, mid-stalk and head infection). Rust was apparent in many fields but was found at low severity levels. The use of fungicides and genetic improvement appears to be managing this disease.

Each year’s weather presents particular disease issues. Phomopsis, a stalk disease, has been on the rise for the last three years. In 2010, approximately 40% of all of the fields surveyed had some evidence of this disease.

Extended warm and wet conditions foster the disease, which was typical of 2010. Phomopsis has been of most concern in Europe, where breeders have made great strides in developing genetic resistance. Breeders here are doing the same. Work is also being done on fungicides.

Traditionally, the disease has affected the U.S. crop later in the season, thus not impacting yield as greatly as in Europe. However, that was not the situation in all cases in 2010. This is a disease of concern — one that pathologists and plant breeders are taking seriously.

The weed situation has not changed much from last year. Canada thistle is the most common weed found in sunflower fields in Manitoba and North Dakota. Kochia is one of the most common weeds found in South Dakota, Manitoba and Colorado. Palmer amaranth and puncture vine are significant problems in Kansas. A majority of the surveyed fields had excellent weed control.

Minimum- and no-till dominate in all states with the exception of Minnesota and irrigated fields in Kansas and Colorado. Solid seeding with air drills is most common in North Dakota and Manitoba, with about 28% of the fields in rows less than 20 inches apart.

“Overall, it was a good crop,” says survey coordinator Kandel. “Yields were good to excellent in all areas. The surveyors take a very critical look at the field to determine what is limiting yield. With past years’ data, we are identifying trends and issues that need attention from the farmer and the researcher.”

Sunflower yields must increase consistently to remain competitive with other crops, and this survey is a good tool for directing research emphasis and funding. Survey summaries from previous years (going back to 2002) can be found on the NSA website under the “grower” section. — Larry Kleingartner

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