AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335
Spring 1997, No. 2
SPRING APPLICATION OF CHLORIDE TO WINTER WHEAT
For the past several years, wheat response to chloride fertilization has been observed from Texas through Canada. The response is usually expressed in improved color, suppression of fungal diseases, and increased yield. Increases in wheat yield have been attributed to reduced injury from fungal diseases and classical nutrient response. Although chloride is classified as a micronutrient, plants may take-up as much chloride as secondary elements such as sulfur.
Chloride performs several functions in plants.
Chloride is an anion and is therefore mobile in the soil. In areas where rainfall is relatively high and internal soil drainage is good, chloride may be leached from the soil profile. Also, in areas where muriate of potash fertilizer has not been regularly applied, chloride deficiencies may occur. Atmospheric chloride deposition tends to be rather high along coastal regions and decreases inland. Chloride response in the Great Plains has been common because of low atmospheric deposition and the infrequent use of chloride-bearing fertilizer.
- It is essential for photosynthesis.
- Along with potassium, it is important in controlling the opening and closing of leaf stomata (pores). This function is critical in the maintenance of proper turgor, plant tissue strength and integrity, and improving drought tolerance.
- It influences the nitrogen nutrition of plants. Higher levels of soil chloride encourage the uptake of ammonium-nitrogen over nitrate-nitrogen. This has been linked to the suppression of wheat diseases.
- It advances plant maturity.
- It improves overall disease resistance and crop tolerance to disease.
Spring topdress applications of chloride have been associated with suppression of various fungal diseases and increased grain yield. In one Texas study, chloride at 40 pounds per acre applied in the spring increased wheat yield by 8 to 12 bushels per acre and significantly decreased leaf rust infection. The response to spring applications may be greater in years when rainfall is heavy since disease pressure will usually be greater. As previously mentioned, chloride tends to move with soil water. Therefore, under wet conditions it may be leached from the soil, increasing the likelihood of response to spring applications.
Response of wheat to chloride fertilization is common in the Great Plains. Preplant or topdress applications are generally effective in meeting chloride requirements, suppressing certain diseases, and increasing yield. Although time may be limited, it's not too late to benefit from spring topdressing of chloride. As always, balanced fertility assures the most profitable production scheme, and chloride is often an important part of a balanced winter wheat fertility program.
For more information, contact Dr. W.M. (Mike) Stewart, Great Plains Director, PPI, P.O. Box 6827, Lubbock, TX 79493. Phone (806) 795-3252.
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