Columbia, Missouri
March 31, 2008
Cool, wet soils can cause extra
hazards to soybean seed being planted this spring. Caution
should be taken at planting time to assure good stands, said a
University of Missouri
Extension agronomist.
“Bad things can happen to good seed,” said Bill Wiebold, MU
soybean specialist. “Worse things happen to poor-quality seed.”
Extra precautions may be needed this year to avoid a need for
replanting, Wiebold said. “With a short seed supply and high
demand for seed for increased soybean acreage, there may be a
short supply of elite seed available for replant.”
There may be a temptation to plant too early, Wiebold said.
“Problems increase if seed is planted in soils below 50˚F in
temperature and soils that are waterlogged.”
Poor conditions can slow plant growth. Seed in the ground begins
to expend stored reserves to cause cell expansion and division.
Under ideal conditions, the plants emerge quickly, reducing
risks to the seed.
Water is necessary for germination, Wiebold said. However, too
much water, which enters through cracks in the seed coating, can
lead to over-absorption. This becomes a bigger problem if
conditions are not right for rapid germination.
As seeds soak up water, they expand. “Water absorbed too quickly
can cause cell walls to rupture,” Wiebold said. “That can cause
cell death. An intact seed coat slows water absorption.”
Gentle handling of seed helps reduce cracks, chips and other
damage that can hurt germination. “Seeds not handled carefully
during harvest, storage and transport are likely to contain
cracks that are invisible to the human eye,” Wiebold said.
“Those cracks cause problems during germination.”
Every commercial seed supply contains a tag giving details on
seed quality. However, germination percentages obtained in the
lab may be higher than those achieved under field conditions.
While seed companies sell high-quality seed, there may be
pressure to lower standards to meet the demand, Wiebold said.
High water content in the soil can be associated with colder
temperatures but also lower oxygen levels in the soil. “Water in
soil pores excludes oxygen needed for seedling growth,” Wiebold
said. “Initial water absorption by seeds is not dependent on
oxygen. Even dead seeds can absorb water.
“Once water content exceeds 50 percent, continued absorption
depends on energy released by the seed respiration rate,” he
said. When growth starts, oxygen demand increases rapidly. That
oxygen must come from air in soil pores.
Delaying planting until conditions are suitable for quick
germination and growth will improve the success rate and help
avoid expense of replant.
There are added hazards awaiting slow-to-germinate seed.
When seeds germinate, the cells release sugars into the
surrounding soil. Pathogens in the soil can use energy from the
sugars to multiply and invade the seed. That leakage of sugars
is more likely with low-quality or cracked seed, Wiebold said.
“I don’t usually recommend treating seeds with fungicides,”
Wiebold said. “This may be a year to use seed treatments, both
fungicides and insecticides, to assure a better stand.”
Selecting high-quality seed, delaying planting until soils are
ready, treating the seed, and careful handling of seeds during
planting help ensure a good stand.
Every detail in the operation affects a successful planting.
Now, more than ever, careful attention can pay off.
For free weekly updates on crops, producers can subscribe to an
electronic newsletter, “Integrated Pest & Crop Management.” Go
to
http://ppp.missouri.edu/ipm and click on “Subscribe to
Newsletters” on the left side of the screen. A similar service
is provided for home gardeners. |
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