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Date Submitted: 04/25/2012 07:04 AM
CROP INSIGHTS
Post Flood and Fallow Syndrome Examined
by Daniel Wiersma and Paul Carter
deficiencies occur even though soil testing often indicates
more available P after flooding than in nonflooded fields.
Summary
• Flooding destroys many acres of cropland each year,
leaving fields dead or unplanted for up to a year.
• Crops often exhibit purpling, light green color and poor
vigor when planted in fields that have been fallowed for
a year or more.
• Mutually beneficial fungi called vesicular-arbuscular
mycorrhizae (VAM) enhance nutrient uptake in plants,
especially phosphorus.
Post flood syndrome, or fallow syndrome, refer to the
same phenomenon – crops grown in fields flooded or
fallow the previous year that show symptoms of P and zinc
(Zn) deficiency, severe stunting, purple or light green
color and poorly developed roots. In addition to early
season growth symptoms, yields losses can be dramatic in
some instances, especially in corn.
• Fallowed fields have reduced levels of VAM and may
delay nutrient uptake and plant growth.
• This Crop Insights reviews post-flood and fallow syndrome, its causes, and possible agronomic management
options to prevent it.
Post Flood or Fallow Syndrome Defined
Flooding in North America is common and can affect large
regions of cropland in any given year. Large areas of the
Midwest and Great Plains were inundated with water in
1993, as was Georgia in 1994 and the Midwest again in
1996.
Fallow syndrome has been reported in other countries, as
well as the United States. In the Darling Downs area of
Australia, both P and Zn deficiency symptoms were
observed in fields left fallow for long periods (Thompson,
1987). In South Dakota, researchers found that P levels
were low in corn plants grown on land that was not
cropped the preceding year. In the 1960s, University of
Minnesota researchers conducted a study to evaluate
summer fallow vs. cover crops as options for land enrolled
in federal...