Last week Extension Turfgrass Specialist Dr. Jim McAfee was working in the Kingsville area.

One of the issues that he addressed with local turfgrass managers was iron cholorosis.

This yellowing of St. Augustine turf is a problem that generates numerous calls to the Extension Office each year.

Dr. McAfee indicated that an iron cholorosis problem may be the result of several factors or conditions.

However, he was quick to point out that proper management of turf often limits issues related to iron cholorosis.

Over watering can cause a reduction of iron uptake in some turfgrass species, resulting in iron cholorosis.

Excessive fertilization, leading to a phosphorus buildup, will cause the problem as well.

It is important to point out that excessive fertilization applications resulting in a buildup of phosphorus can and does occur with both organic and inorganic fertilizers.

Often times homeowners develop a false sense of well being if they are utilizing organic products.

In addition to wet conditions and excessive phosphorus, a cholorotic look can also be due to compacted soils and soils with high pH.

These 2 problems are certainly seen quite often in the Kingsville area.

Iron cholorosis results when green chlorophyll in leaf tissue fails to develop.

Although iron is not part of the chlorophyll molecule, it is one of the nutrients essential for chlorophyll synthesis.

When iron cholorosis first appears turfgrass leaves are yellowish-green in color, giving the leaf a striped appearance. This striping is due to an interveinal yellowing.

As the condition worsens leaves appear almost white in color.

Regardless of the cause, iron cholorosis can be corrected by applying iron sulfate or iron chelates.

These products can be obtained wherever lawn and garden supplies are sold.

In alkaline soils, foliar applications are more effective since soil-applied iron is tied up quite rapidly and its availability to the plant is limited.

Follow up applications may be required to restore a bright healthy green color.

Caution should be used when spraying iron solutions.

Any over-spray may leave rust stains on sidewalks, bricks, and clothing.

Improving management practices

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will help limit future iron cholorosis problems brought about by improper irrigation strategies, excessive fertilization applications, or by soil compaction.

Utilizing a soil test to determine the type and the amount of fertilizer needed insures that phosphorus is not allowed to build up to problem levels.

Aerating compacted soils can strengthen lawns and improve grass vigor, since compaction prevents adequate gas exchange, moisture penetration and nutrient movement.