Could a Coat 'Warm Up' Interest in Small Seed
Five might be the magic number on the basketball court; but when it comes to hybrid sunflower seed, five is not the preferred size for most producers.
That’s not because the small seeds don’t have adequate genetic potential. Rather, the aversion to #5 seed is largely due to the difficulty most standard row-crop planters have with accurate singulation of the smaller seeds. Doubles or triples often occur, resulting in excessively close plants. That in turn means more competition for nutrients, moisture and sunlight; smaller plant heads and harvested seed size; and generally lower yields than would be obtained with uniform in-row seed placement.
Some growers using air drills to solid-seed their sunflower find #5 seed quite acceptable. But because it’s the least-popular size overall, hybrid seed companies often find themselves with leftover quantities which are either sold into the birdseed market or simply discarded. While the bird market provides some value, neither alternative is an economically desirable one for the hybrid supplier.
Trevor Bailie believes he may have an answer for that situation. Bailie is general manager of Canadian Seed Coaters, which operates facilities in Saskatchewan and Arizona under the name Precision Seed Coaters, Inc. As the name implies, Canadian Seed Coaters applies coatings to seeds such as clover, alfalfa and grasses. But its biggest market is in canola, where coatings containing insecticides and fungicides are commonly applied to the seed for both crop protection and grower safety.
More recently, Canadian Seed Coaters has been exploring the coating of sunflower seed. While the inclusion of fungicides or insecticides may one day be part of the process, interest to date has focused on improving planting accuracy with #5 seeds.
“Our objective is to take the small #5s and build them into a ‘#4’ so they are physically acceptable to the grower,” Bailie explains. That effort basically involves the application of a lime or talc coating to the seed. The shape of the seed does not change; it simply “bulks up” and, as far as one’s mechanical planter is concerned, has been transformed into a #4. By weight, this coating process adds about 50 percent to the seed; so if the coating company receives 100 pounds of “naked” seed, it sends back 200 pounds of coated seed.
After running a number of sunflower trials on its own, Canadian Seed Coaters asked North Dakota State University to conduct tests to evaluate the performance of coated #5 and #4 seed in comparison with uncoated #5s and #4s. This research was carried out in 1996 by NDSU extension agricultural engineer Vern Hofman and extension agronomist Duane Berglund.
Hofman and Berglund had three basic objectives in their study: (1) to evaluate the accuracy of seed placement of several row-crop planter seed metering mechanisms, in the laboratory, with coated and uncoated seed at three different travel speeds; (2) to compile planter index numbers that could be used to compare the seeding accuracy of the various planters; and (3) to conduct a dryland field study of sunflower emergence of coated versus uncoated seed at the two seed sizes and three planting depths.
The hybrid used in the NDSU tests had respective seed counts of 8,772 (#4) and 10,000 (#5) per pound. The #4 uncoated seed was used as the “baseline satisfactory value” for sunflower stands (meaning the #5 seed would need an index value equal to or better than the #4 uncoated if it was to be judged adequate for planting).
Two different types of coated seed were used in the NDSU tests. One coating was a lime-based material, the other a talc.
In the seed placement segment of their study, the NDSU researchers looked at four commonly used planters: the John Deere 7200 MaxEmerge; Kinze 2000; John Deere 71 Flexi planter; and the White air planter. All planters were tested using the manufacturer’s recommended disk, plate or finger. Planter meters were set up to drop seeds on a moving greased belt, causing the seeds to stick exactly where they fell for measuring purposes. Field speeds of three, five and seven miles per hour were duplicated, with 10 replications of each test. The metering systems were set to drop 22,000 seeds per acre, which, when based on 30-inch rows, should result in one seed every 9.5 inches.
What did Hofman and Berglund find? With only one exception (the Kinze planter at seven mph), the planting accuracy index values for the #5 talc-coated seed were better than those for the #4 uncoated seed. For the most part, the planters also were able to travel at the faster speeds with the coated seed without sacrificing placement accuracy.
The JD 71 Flexi planter did the best job of seed placement, at slower speeds, with both coated and uncoated seed. “With plate planters, seed must be sized uniformly; [otherwise] the seeds won’t fit the plate cells, and typically the planting accuracy drops off significantly when travel speeds exceed about five mph,” the NDSU researchers note. “In these tests, the seed was all of a uniform size — and especially so with the coated seed.”
The White planter had the lowest values of the four units in the tests, mainly because of a significant number of skips and doubles. The use of coated seed did result in a better performance, but that “was due to the more-uniform seed size, which is extremely important for this planter.”
The field test portion of the NDSU study looked at differences in seedling emergence between coated and uncoated seed; also, at the effect of different planting depths on emergence.
The test area was seeded on June 4 with a JD MaxEmerge II at 22,000 plants per acre (30-inch rows). Planting speed was 3.5 mph, with the three planting depths being 1.5, 2.5 and 3.5 inches. Each treatment was replicated four times. Data were collected on (1) days to first emergence, (2) days to 100-percent emergence, (3) number of plants per acre emerged, and (4) number of sunflower doubles/triples per 10 feet of row.
The NDSU researchers found that full emergence was actually earlier from the 2.5- and 3.5-inch planting depths due to many of the 1.5-inch depth seeds having been planted into dry soil in need of rainfall. “Seeding depth had a much greater effect than coating” on emergence, they report.
Plant populations were highest above the desired 22,000 with the uncoated #4 and #5 seeds; but “the coated seed was found to be more consistent due to the even uniformity,” the researchers indicate. “The #5 talc-coated seed was the best, followed by the #4 talc-coated seed, the #5 lime-coated and the #4 lime-coated seed.” The lime-coated did have a higher population at all depths for both the #4 and #5 seed as compared to the talc-coated.
The coated seeds also had fewer doubles or triples than did the uncoated seeds. “The #5 uncoated seed had slightly more doubles and triples than #4 — which was due to the smaller seed size,” Hofman and Berglund observe. “The #5 talc-coated seed, overall for all seeding depths, produced the lowest number of doubles/triples — but only slightly better than the #4 talc-coated.” There were more doubles/triples among the lime-coated seed versus the talc-coated, which probably accounted for the higher plant populations of the lime-coated. They also report some flaking of the lime coating.
What do Hofman and Berglund conclude regarding their 1996 tests?
First, the coated seed clearly did provide better seed placement as compared to uncoated seed. Second, the seed coating did not appear to hinder seed germination or emergence. “Planting depth was the overriding factor — especially when seed was placed into dry soil,” they note.
These test results were favorable and deemed quite reliable, Hofman says, and NDSU currently has no plans to conduct further studies on sunflower seed coatings.
Berglund says that if hybrid sunflower seed companies do eventually decide to offer coated #5 (or even #4) seed to their customers, the costs of the coating likely would have to be absorbed by the seed company. Another area where coating could be viable for the companies would be in the planting of parent seed stocks in hybrid production fields, as many of those seeds are quite small and skinny — though obviously of substantial value.
“A secondary advantage of coated seed is that a coloring agent can be added, thus making it easy to check seeding depth and accuracy,” Berglund observes. “Finding black sunflower seeds in dark soil can be difficult.”
Bruce Hovland, general manager of Interstate Payco Seed Company, says his company has been investigating the feasibility of coated #5 seeds and will be conducting field tests in 1997 in cooperation with Canadian Seed Coaters. “However, this is a project so in its infancy that we’ve not yet determined costs,” Hovland relates. “We’ve just tried to get it to the point where we’re very satisfied with (1) the plantability scores and (2) germination and emergence.” He says it’s too early to predict whether — or how soon — coated sunflower seeds could be available to the interested grower.
Trevor Bailie obviously hopes such an option will one day be a reality — and perhaps expand to where fungicides (e.g., Apron) and/or insecticides would be mixed into the sunflower coating as well. In the meantime, he says, the use of the coatings simply to enlarge #5 sunflower seed shows promise of making these smaller cousins a more “plantable” — and economic — option. — Don Lilleboe
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