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Options Growing With Short-Stature Hybrids

Wednesday, January 2, 2013
filed under: Hybrid Selection/Planting

For years, plot trials of short-stature (SS) sunflower have indicated good moisture efficiency, quicker canopy and better tolerance to stem insect damage. More recent data demonstrate that, in general, yields of SS sunflower are comparable to conventional height sunflowers.

Triumph Seeds, based in Texas, initially developed short-stature hybrids for use in Texas, Oklahoma, Kansas and Colorado where longer-season hybrids are used. Now that Dow AgroSciences is merging the development work between Mycogen Seeds and Triumph, more short-stature hybrids will be utilized in early maturing sunflower genetics.

Farmers in the High Plains have been growing SS hybrids for years with much success. Now that Mycogen Seeds will be developing some of the Triumph lines that have been popular in the south, might there be an opportunity for growers in the northern region to take advantage of the positive attributes that SS hybrids have to offer? This question may be answered sooner rather than later, as SS yield trials will be planted in the Dakotas in 2013.

These trials will also begin to answer the key question of whether the yields are comparable in the northern growing conditions. Yield trials and university research projects conducted in the High Plain states of Kansas and Texas point toward yield parity of SS and conventional height ’flowers, and southern growers agree based on experience.

Dow AgroSciences breeders are currently introgressing earlier-maturity, Clearfield®, Clearfield Plus®, downy mildew resistance and low saturated fat traits, as well as confection types, in their short-stature breeding populations.

What does this mean for the farmer? It means that the advantages offered with short ’flowers may soon be more readily available to growers in the Northern Plains states with new and improved traits. Most farmers are still going to select for yield and oil content; but when those parameters are comparable in a SS hybrid, it gives the grower a nice option.

Some Background on Short-Stature Hybrids

Certain seed companies currently offer new hybrids that they classify as “short-stature.” Some may not have been bred specifically as such, but are of shorter height than other hybrids. The very early SS hybrid releases (15-20 years ago) were very different than modern releases, which began in earnest about a dozen years ago.

Thanks to work by Triumph sunflower breeder Joseph Legako, the gene has been identified to enable existing germplasm to be converted to SS hybrids without impacting other characteristics. Modern SS hybrids carry beneficial attributes of disease resistance, high oil content and high yield. This is critical because in early SS hybrids there were some issues with head size, yield and oil content that made them inferior to conventional height varieties.

First off, just how short is short? There is no industry standard for this criterion. Early SS hybrids were very compact, with heights that were 36-42 inches tall under irrigation, whereas conventional height sunflower hybrids generally were about 24 inches taller — and sometimes more. By contrast, some of today’s SS hybrids are not that much shorter than many of the conventional height hybrids. It’s important to note that environment will determine how tall any sunflower gets, so the numbers are mere guidelines.

The desired height will ultimately depend on the growing conditions, which can vary greatly from year to year. More recently, some companies are listing some of their newer hybrids as “short stature” or “reduced height.” The key is for the grower to find the traits that fit a particular situation and growing environment.

Standability is the number-one advantage, says NSA board member and east central Kansas farmer Karl Esping, who has grown all different heights of sunflower hybrids. In fact, this year he grew some mid-height varieties just to try them out. But he clearly prefers the short-stature for three main reasons: standability, field management options and ease of harvest.

Esping’s top priority is standability. “Plain and simple, they don’t fall down. I don’t even look first at yield; I look at what I can get in the ground and get a good stand,” he says. “In a normal year, I like to see the ’flowers top out at about 36 inches. The stalk quality is excellent and able to withstand the wind and insect damage.”

Seed company agronomists echo Esping’s sentiment that resistance to root lodging seems to be one of the best advantages of SS hybrids. In years when there is very good rainfall, hybrids tend to get taller. Those taller hybrids are more susceptible to root lodging during severe rain and wind storms. The robust stalk of SS hybrids might also be less prone to lodging caused by tunneling by stem-infesting insects like the stem weevil and the long-horned beetle (Dectes).

Esping’s second reason for using SS hybrids is the ability to use ground spraying equipment. It’s cheaper and gives better control for critical time frames such as spraying for head moth. Esping also likes the ability to better control drift and target a specific part of the plant. Using a ground rig to apply bird repellent to the backs of the heads for better efficacy, for example, can be achieved on a short ’flower that’s starting to tilt.

Texas A&M University extension agronomist Calvin Trostle, who has worked with SS hybrid trials in Texas, says the same holds true for growers in the far Southern Plains looking for the opportunity for greater management options. “The compact growth habit of SS sunflower has shorter internodes between leaf axils while maintaining the same number of leaves,” he explains. “Though this leads to greater shading of lower leaves, producers have better field management options, such as mechanical cultivation and spraying for key insects, especially sunflower (head) moth here in Texas.”

The latter reason is the greater consideration. By using a ground rig, many growers believe they can get better head moth control because they can increase the gallonage to at least 10 gallons per acre (versus 3 gal/ac minimum recommended spray volume for aerial applications of common pyrethroids for sunflower head moth control). Plus, with ground application, farmers do not have to rely on a spray plane operator’s schedule when timing is especially critical.

Trostle explains that most of the sunflowers in the Lubbock, Texas, region are in 40-inch rows, making applications via ground rig very feasible. Producers on 30" rows find this more difficult though if they have a smaller ground spray rig like Spray Coupe, where the tires are much smaller than what are on large rigs that cover a 90-to 120-foot spray swath. You can't get between the rows quite as well on 40-inch rows, and certainly not on 30s.

The third main reason Esping and numerous others in the High Plains prefer the short-stature ’flowers is ease of harvest. “Less material going through the combine reduces my dust, which in turn reduces my risk of fire,” he explains.

Esping stresses that his reasons for growing SS hybrids are geared toward his particular situation. He is clear to note that the last two years in Kansas have not been typical. Severe drought took a toll on all dryland crops, including his sunflower.

Other Agronomic Attributes of SS Hybrids

There are additional agronomic considerations for growing the shorter ’flowers. When it comes to some attributes, the choice is clear between short-stature and conventional height. However, with other desired characteristics, the choice depends on the situation.

Water usage is one example. While SS sunflower grows as a much more compact plant, some hybrids have a shorter root system that may not be able to go as deep as required for needed moisture.

Rob Aiken, crops research scientist with the Kansas State University Northwest Research-Extension Center at Colby, has done extensive work with SS hybrids commonly grown in the High Plains. Aiken explains that the rooting depth affects how much of the soil profile that the plant can explore and extract water from. Sunflower has that obvious advantage of going deep. “We have soils in western Kansas that have high water-holding capacity. We have measured substantial water extraction below 10 feet in the soil, so that means sunflower is able to get water that other crops can’t even begin to touch,” Aiken notes. “This is a very important consideration for dryland conditions because sometimes that last 200 or so pounds of yield is gained from that crop being able to go down there and pull that water out. So if you’re in a growing environment where deep water extraction is important, the standard height sunflower would be the choice.”

Not a lot of information is available on rooting systems in short stature versus standard height. Both have a good root system about four to five feet down; but the standard height goes beyond that to extract water deep in the soil profile.

Another area that’s debatable is in weed control. A good weed control program is important no matter the hybrid, and the plants’ canopy formation plays a significant role. The leaf canopy forms quicker on short stature, but conversely, it may provide less late-season protection against weeds because of the short plant. In other words, the weeds could outgrow the canopy.

Aiken provides some insight based on his research. “Short-stature hybrids we worked with were quicker to form a canopy and seem to have an advantage for weed control with their huge leaves,” he reports. Aiken is interested in the size and shape of the canopy, and those topics are in current research. It’s also important to consider that ongoing development by Dow AgroSciences breeders working on introgressing Clearfield and Clearfield Plus traits into SS hybrids will impact this.

Above all, Aiken stresses that productivity potential is there with SS hybrids. The hybrids he worked with in projects during 2009 and 2010 (along with Freddie Lamm, who managed those trials) yielded 3,000 to 3,200 lbs/ac with about 17-20.5 inches of water use (compared to corn water use of 24-25 inches). In regions where water is scarce, every inch of moisture matters.

Short stature doesn’t mean they don’t yield, which is a common misconception with earlier hybrids. Again, performance trials speak for themselves. The hybrids commonly grown in the High Plains tend to rank in the upper one-fourth in trials when it comes to yield.

Will the same hold true for the trials in the Northern Plains? Even when all evidence would point toward parity between short-stature and commercial height ’flowers, there’s still a ways to go to bringing them into production in the Northern Plains states. Eventually, the data will tell the story whether growers in that region will have more options when choosing the right hybrid for them.

— Sonia Mullally
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