Soybeans Today January 1998
Aerial Seeding May Have Some Potential On Clay
By Rich Maples
Heres the situation. You want to plant an early maturing variety in April so you
can get your plants up and going before drought can take its toll. The problem is,
youre busy plant-ing rice and its been raining too much to get conventional
equipment in your clay field.
Aerial seeding could be the solution, according to Dr. Lanny Ashlock, soybean
agronomist for the Cooperative Extension Service, U of A Division of Agriculture.
Ashlock says, "Because of all the clay soils and frequent spring rains in
Arkansas, its often been difficult for farmers to implement the Early Soybean
Production System, which couples a very early maturing variety, an indeterminate Group IV,
with a very early planting date, in April.
"In Mississippi and Louisiana, they use the early production system more because
they dont have as much rice to deal with. They dont irrigate as much as we do,
so they plant their soybeans early to try to avoid drought."
To help Arkansas farmers overcome the problems that can occur in April, Ashlock has
begun a study of aerial seeding on clay. The project is funded by the Arkansas Soybean
Promotion Board and is being conducted at the University of Arkansas Southeast
Branch Station at Rohwer.
Why clay? Ashlock says soils such as Sharkey and Perry clay hold moisture longer and
become so "plastic" when wet that the seeds embed themselves on impact.
Ashlock said the station superintendent, Larry Earnest, prepared a field for aerial
seeding during the fall of 1996. "He had the ground floated so it was nice and
smooth, and he constructed levees to catch and hold rainfall. The flood helped control
winter weeds and guaranteed that we would have a saturated field when it came time to fly
on the seed.
"The only negative thing was that we had ducks congregating in parts of the
flooded field. Their paddling roughed up the soil a little, but it wasnt a major
problem."
On April 9, the field was drained, and 24 hours later the seed was flown on. To prevent
plant disease, the seed was treated with a mixture of Apron, Vitavax 200 and sodium
molybdate.
Half of the 40-acre field was seeded at a rate of 60 pounds per acre, and the other
half was seeded at 90 pounds an acre.
"We were shooting for 120,000 to 130,000 plants per acre," said Ashlock.
"We applied the 90-pound rate because we werent sure how much seed it would
take. It didnt seem to matter which rate we used.
"Where the field was primarily clay, we got beautiful stands. The seed buried
itself in the clay, leaving only about a fourth of the seed showing.
"Where there was a mixture of clay and silt loam, the seed didnt embed
itself as deeply and we werent as successful getting a stand. The silt loam was also
in the higher part of the field and it dried out quicker."
Ashlock noted that the plot field was not precision leveled. "There were low areas
where we had 2 inches of standing water. The water absorbed the impact of the seed.
Instead of being embedded in the clay, the seed sunk down and sat on the clay.
"One of the problems farmers may have with this system is getting all the water
off the field and still leaving the soil wet. A little standing water in low areas
wont hurt, but you cant have over an inch."
Ashlock said Arkansas farmers who have aerial seeded in the past have usually done so
as a last resort. "Generally, its been raining a lot in June, its
approaching July and the farmers still have a lot of acreage to plant. As soon as it
clears up, they have to have the seed flown on.
"That time of the year, its so hot and the days are so long that by the time
plants sprout, if they dont get a timely rain, they die. A farmer might be
successful one year out of three.
"If you can fly on the seed in early April, when its cool and the days are
relatively short, theres a good chance of getting some rain every week.
"You can greatly increase your chances of getting a good stand of soybeans on clay
soils."
The 1997 project field was not irrigated. It averaged about 25 bushels per acre.
Beginning in 1998, the aerial seeding study will include both irrigated and dryland
fields.
Clay soils hold moisture and become so "plastic" when wet that seeds embed
themselves on impact.
Soybeans Today January 1998
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