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Why Too Much and Too Little Water Hurts Your Crops

If you swear that wet springs
that foul your planting plans are worsening, you may be right.

Jerry Hatfield, director of
the USDA-ARS National Laboratory for Agriculture and the Environment at Ames, Iowa, reported
on spring precipitation in the Ames area at this week’s American Seed Trade Association
Seed Expo in Chicago.

in spring precipitation at Ames have decreased the number of workable field
days in April through mid-May by 3.5 days from 1995 to 2010, compared to a
1979-to-1994 time frame.

stress that puts on producers with less
workable days is tremendous, he says.

Rainstorms also are becoming
more intense. A measurement of Des Moines, Iowa, precipitation shows that from
1900 to 1960, just two years had more than 8 days with rainfall amounts
tallying 1.25 inches or more. From 1960 up until now, there have been seven
years with more than 8 days tallying 1.25 inches of precipitation and above
threshold. That’s a 350% increase.

Increased spring
precipitation and more intense rainfall fuel other maladies.

“Soils become more anaerobic,
so seedling diseases are much more prevalent,” Hatfield says. “You also get
more soil erosion with all the runoff from the field.”

This erosion can reduce soil
organic matter, which in turn reduces the water-holding capacity of soils. When
the weather turns dry—as it still inevitably will—less water exists in the soil
profile for the plant to tap.

Shifting patterns like more
variable precipitation will fuel variation in yields, says Hatfield.

Not surprisingly, an analysis
of yield variability in Nebraska showed much of it was removed due to

For dryland farmers, that
shows one way to combat yield variability is through soil management that
increases water availability to the crop.

Soybeans are more impacted by
stress and climate change than corn, says Hatfield. The news isn’t all bad, though,
since Hatfield says there is opportunity to help soybeans better roll with the
weather punches.

For example, Tommy Carter,
a plant geneticist at the USDA-ARS Soybean and Nitrogen Fixation Research
Laboratory in Raleigh, North Carolina, has discovered exotic drought-tolerant
germplasm that can help soybeans better tolerate drouth. Some of the germplasm creates
cultivars that are slow wilters. This can help soybeans better conserve and use existing soil water.

Some of these soybean lines
have unexpected benefits. One soybean line from Sweden, Fiskeby
III, not only was cold and stress tolerant, but also tolerated salty soils and
those soils prone to iron chlorosis, says Carter. Industry breeders can use
lines like this to develop high-yielding soybean varieties that better endure


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