Post Flood Syndrome

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...