March 1998 - Volume V, Issue 3

Iron Applications for Turf

David M. Kopec, Extension Turfgrass Specialist

Last month's issue showed you what caused iron chlorosis conditions and how to identify the difference between an iron and/or nitrogen deficient turf. This issue deals with correction of the iron chlorosis (iron deficiency) problem.

Iron is an actual component of the plant and is part of the chlorophyll (green cell) component of the plant. When conditions occur that cause an internal plant deficiency it's time to apply supplemental iron.

Iron applications (to correct deficiencies) are usually in the form of a liquid spray. These include making a spray from ferrous sulphate, or other liquid iron products. Most of the concentrated liquid iron products are chelates. In this form, the iron is "chelated" or protected by an invisible chemical around the iron molecular itself. Chelates also appear in concentrated powder forms, as well. Note that not all powders are chelates and that not all liquids are chelates.

Granular fertilizers sometimes contain small amounts of iron. They are not necessarily in the form readily available to plants.

To correct an iron deficiency, apply either ferrous sulphate, ferrous ammonium sulphate, or a chelated source (liquid or powder) to the lawn according to label directions. Usually 2-4 ounces of product per 1000 ft2 of lawn areas will correct the problem.

Mix the product with enough water to apply 1-3 gallons of water per 1000 ft2 of lawn area as a final solution. Shake the sprayer well and again periodically during the application. Spray the lawn at ten o'clock in the morning and let the spray dry on the leaves all day long. Water the lawn that night, or before the next time you mow the lawn. The remaining iron not taken up by the leaves will be taken up by the roots, or be stored in the soil.

Ferrous sulphate is stored in the soil shortly after application by a combining with high pH elements in our native soils. Thus, the iron becomes unavailable. This is why repeat applications of ferrous sulphate are required when deficiency symptoms occur and especially on sandy soils which have very little capacity to store nutrients. The "chelated" iron products, when sprayed on the turf, have the advantage of lasting much longer in the soil than ferrous sulphate alone. This is because the "chelating compound" which surrounds the iron itself, protects the iron from being changed into plant unavailable forms (especially under high soil pH conditions which feature caliche). Also, on occasion, iron deficiencies may occur after an application of phosphorous fertilizer. However, chelates would not be affected by this.

Iron products can temporarily stain sidewalks, driveways and paths. Within days, the turf should respond to the iron applications and turn darker green in color. Naturally, ferrous sulphate costs less than chelates, but you have to apply them more often and the effect is not as long lasting as the chelated form. 

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