Why Does My Grass Turn Yellow?

A common problem during the summer months on a great number of laws in Austin County is the leaf blades turn yellow.  Despite the amount of rain, irrigation or fertilizer homeowners place on their yards, their once jalapeno green grass still turns to pale green or yellow.  This condition is known as Iron Chlorosis. Iron Chlorosis results when green chlorophyll in leaf tissue fails to develop. Iron Chlorosis first develops in new growth and appears as yellowish-green leaves, usually as an interveinal yellowing, giving the leaf a striped appearance. As the condition worsens leaves appear yellow to almost white.

Management practices can also contribute to iron deficiencies. Well aerated soil is needed for plants to take up iron. Excessive irrigation and soil compaction result in poorly aerated soils and reduced iron uptake. A common remedy for controlling Iron Chlorosis is the use of kelated iron.  In a recent study, 6 iron products were evaluated on St. Augustine grass.  Each product was applied at the lowest recommended rate and at 2, 3, 4 and 5 times that rate. For this study Ironite was applied at 10, 20, 30, 40 and 50 pounds per 1,000 sq. ft.

In general, application rates of 3 and 4 times the lowest recommended rate of application were required to produce the greenest color and a higher color rating.  At the 2x rate of application, which is the highest recommended rate for most products, 4 or 5 weeks were required to achieve a highly desirable color response. As a homeowner, I would be disappointed to see no response from products where I followed the label directions.  The bottom line is this, the problem can be corrected with kelated iron products, but cultural practices such as aeration to reduce compaction and following soil test recommendations will go a long way in helping to avoid the problem in the first place.

Yellow Grass

For more information on Iron Chlorosis or on Lawn and Turf Grass management, contact the Texas A&M AgriLife Extension Service of Austin County at (979) 865-2072, or click on the “ASK THE AGENTS” tab.

Prepared by Philip Shackelford, PhD
County Extension Agent for Agriculture & Natural Resources
Texas A&M AgriLife Extension Service of Austin County
The information given herein is for educational purposes only.  References to commercial products or trade names are made with the understanding that no discrimination is intended and no endorsement by Texas A&M AgriLife Extension Service personnel is implied.

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