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Protect Corn Crop from Fallow Syndrome

March 11, 2020

The weather issues of 2019 may bring new challenges in 2020. Last year’s wet conditions led to flooded ground and millions of prevent plant acres. Fallow syndrome is generally found in fields that had no crop growing in them the previous year, and is a condition to watch for this growing season.


Impacted corn plants will show the following symptoms:

  • Phosphorus and zinc deficiency.
  • Severely stunted plants with short internodes.
  • Purple, yellow or light green color leaves.

Root growth can also be affected, and depending on the severity of the symptoms, can cause yield loss.

This agronomic image shows corn affected by fallow syndrome This agronomic image shows healthy corn

Fallow syndrome symptoms on corn in a field in north-central MO (left); Corn planted in the same field in north-central MO, but soybeans were planted the previous season (right). Source – Syngenta

The picture on the left shows the short, stunted plants and purple leaves associated with phosphorus deficiency as a result of this field only having turnips sowed later the previous summer. The picture on the right is from the same field; however, this portion of the field had soybeans planted the previous year, which is why they appear greener, healthier and taller.

What Causes Fallow Syndrome in Corn?

Fallow corn syndrome is a result of reduced beneficial fungi in the soil due to flooding, weed control and previously unplanted fields. The fungi, called Vesicular arbuscular mycorrhizae (VAM), have a symbiotic relationship with corn and wheat, and they will invade root systems and move between cells. They serve as an extension of the corn root, expanding the root’s surface area to assist in the uptake of water and nutrients, especially phosphorus and zinc. In exchange, the fungi receive nutrients from the roots, allowing them to continue to grow and develop and assist the corn plant with nutrient uptake.

When there is no plant growth for an extended period of time, populations of VAM are reduced. These fungi need actively growing roots to survive, including most root tissues and weed species.

Fallow Syndrome Management

The corn to the left was prevent plant that had a cover crop of turnips planted in late summer; the corn to the right is where soybeans were planted.  Source – Syngenta

While not a lot that can be done to correct fallow syndrome in-season, affected corn fields will eventually recover as summer progresses and populations of VAM increase. Yield losses, if any, can vary depending on the severity and length of crop symptoms.

There are preventive measures that can be taken in case of flooding or previously unplanted fields. An application of phosphorus in a band may reduce symptoms, even in fields where levels are high. The phosphorus must be placed in a band close to the small, developing roots, as broadcast applications will not help.

If fields are affected by flooding or are not able to be planted, planting a cover crop can help alleviate symptoms of fallow corn syndrome by providing VAM with rooting tissues to complete their lifecycle and keep populations high. Not all cover crops are beneficial hosts for VAM, however. Brassicas, like turnips and radishes, are poor hosts and do not help maintain adequate VAM levels in the soil.

If faced with prevent plant situations in the future, plant soybeans as long as possible into the season or plant a cover crop. Visit with your local NK® agronomist or NK sales representative for more information on managing fallow syndrome and fallow acres.

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