AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335
Winter 1998, No. 7
Chloride is involved in several important roles in plants, including,
· Transport of other nutrients in the plant
· Stomatal activity
· Accelerated plant development
· Reduced lodging
Increases in wheat yield from chloride fertilization are usually associated with the correction of chloride deficient conditions or suppression of fungal diseases. Under low soil chloride conditions some varieties may exhibit chloride deficiency symptoms, sometimes referred to as physiological leaf spot syndrome. These symptoms are similar in appearance to tan spot or septoria but are not caused by a pathogen. The absence of leaf spotting does not always mean that chloride is not deficient since spotting is dependent upon wheat variety. Chloride has been shown to reduce the severity of several root and foliar diseases. In one Texas study leaf rust infection of the flag leaf was reduced from 68 to 27 percent by topdressing with 40 pounds of chloride per acre as muriate of potash.
Research has shown that where wheat responds to chloride fertilization the average response is just over 5 bushels per acre, although yield increases as high as 23 bu/A have been observed. Whether or not wheat will respond to chloride usually depends upon soil chloride level, disease pressure, plant chloride, and variety. Response to chloride is likely when soil chloride levels are less than 30 pounds per acre from 2-foot deep soil samples. The optimum level of soil chloride is at least 60 pounds per acre-2 feet. Continuing research has shown that some varieties consistently respond to chloride and some do not. For example, Kansas studies have shown that under low soil chloride conditions Karl 92, 2163, and Jagger consistently respond to chloride topdressing while Ogallala does not.
Chloride is not a "magic bullet". It is one of 17 nutrients essential for proper plant development and function. Where conditions such as low soil chloride levels or high disease pressure exist, chloride can be a profitable component of a wheat fertility management program.