Drought, Stand Top ’03 Yield Limiting Factors
Tuesday, December 9, 2003
filed under: Optimizing Plant Development/Yields
Drought and poor stand establishment were two of the most significant sunflower production problems evident this year, according to a pre-harvest survey of sunflower fields across the U.S. sunflower production area, conducted in September. Drought and poor stand establishment were the top two yield limiting factors in last year’s survey as well.
Coordinated by the National Sunflower Association, the 2003 survey evaluated 181 sunflower fields across the plains, 118 in North Dakota, where most of the nation’s sunflower is grown. Most fields surveyed were oil-type, except Minnesota and Kansas, where the majority of fields surveyed were confection. About one-third of sunflower fields surveyed in Colorado and over one half in Kansas were irrigated. The preliminary results at press-time did not include outstanding data from three fields surveyed in Colorado and 12 fields surveyed in Texas.
A number of factors were surveyed and sampled in each field, including plant population, row spacing, tillage practice, pest and disease problems, lodging, top yield limiting factors, and yield potential. The NSA’s pre-harvest yield estimate for N.D. (which did not take abandoned or harvested acreage into account) was 1,434 lbs/ac; the USDA’s estimate for N.D. released on October 1 was forecast at 1,200 pounds per acre.
Larry Kleingartner, executive director of the NSA, says that the U.S. sunflower survey data allows the industry to get a sense of new crop quality and size, as well as production challenges. Results from the survey are used to develop sunflower research priorities, and help the NSA assess pest treatments and the need for new pest products. “We appreciate the cooperation of sunflower producers whose fields were included in the survey,” he says.
Kleingartner points out that while the survey indicates problems here and there, most of those problems are minor. Oil contents of seed entering the crush plants will be at the high end of the five year average. While confection seed size will be smaller this year, confection processors report seed with excellent color and very little seed damage from disease or insects.
“It really was a pretty good year overall,” he says. “Drought was the major yield limiting factor in many areas, and that cannot be controlled. Levels of disease were very low this year. The stem weevil complex was present, but not as significant as the previous year.”
Yield and Plant Population
There was a fairly close correlation between plant population and yield potential; the better the stand, the better the yield potential. Drought obviously impacted emergence, but poor seed to soil contact and early insect damage such as cutworms and wire worms may have contributed to stand problems.
Row Spacing, Tillage
Sunflower in most states was planted at a row spacing greater than 20 inches, with some exceptions such as western and central N.D., where solid seeding is more common. No-till sunflower was most predominant in fields in South Dakota, followed by Colorado and Kansas. Surveyors classified mechanical soil disturbance, including one-pass planting systems that incorporate sweeps, as minimum till, which was most predominant in fields surveyed in Kansas. Conventional tillage was most prevalent in Minnesota and the eastern half of N.D.
Certain weeds, not surprisingly, were more predominant in some states than others. The worst weeds in Colorado were kochia and red root pigweed, followed by puncture vine, lance leaf sage, and devils claw. In Kansas, palmer amaranth and puncture vine were most prevalent in sunflower fields surveyed, followed by red root pigweed, field sandbur, devils claw, barnyard grass and green foxtail. Kochia and green foxtail were the most prevalent weeds in North Dakota sunflower fields surveyed, followed by marshelder, wild mustard, and red root pigweed. Green foxtail, kochia, and red root pigweed were common weeds found in South Dakota sunflower fields.
Disease incidence was low overall, but there were hot spots. For example, some head rot was found in sunflower fields in central S.D. and some mid stalk rot in northeast N.D. (in each case, about 5% of plants infected). More significantly, wilt was evident in almost 20% of plants surveyed in northwest N.D., and verticillium could be found in about 25% of plants surveyed in fields in east central N.D. Phomopsis incidence was about 12% of fields surveyed in Colorado, and rhizopus incidence was about 19% in Kansas.
While disease incidence does not reflect disease severity and may not result in yield loss, areas where disease was detected should be monitored and managed with crop rotation and hybrid selection. Verticillium, for example, is a soil-borne fungus and can carry over to the next growing season, notes USDA-ARS plant pathologist Tom Gulya.
Bird damage was low overall, though damage was approximately 30% in fields
surveyed in north central S.D. Bird damage incidence was nearly 10% in northeast and east central N.D. Bird damage occurring after fields were surveyed in September would not be reflected in these figures.
Even though blackbird damage appears small in the overall average, damage to specific fields is often considerable. “It is important to note that surveyors choose just one small spot in the field that is surveyed, and bird damage may be on the other end of the field next to a wetland. The concern about blackbird damage is one of the major acreage limiting factors in the Dakotas and Minnesota that is a high priority for the sunflower industry,” notes Kleingartner.
The NSA field survey results indicate that the incidence of spotted stem weevil increased in North Dakota but decreased in the other states when compared to last year. Longhorn beetle incidence (also called the soybean stem borer or Dectes stem borer) increased in South Dakota but declined sharply in Kansas. Sunflower midge damage was very small this year with only Minnesota fields showing minor incidence. Minor seed weevil damage could be found in some fields in the Dakotas and Colorado, but declined slightly from last year, as did the banded moth. Ground lodging was minor but most evident in fields surveyed in South Dakota, which is almost entirely attributed to stem weevil infestation. – Tracy Sayler