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August 2, 2019 - Understanding Boron - Will it benefit my crop?

The importance of boron, deficiency symptoms, and how to apply to your cotton crop

Driving through central and east Georgia in the last couple weeks of July, the word of the month has been isolated showers. I guess that is two words, but it has been consistent. Rainfall has been hit or miss with only portions of fields catching water. Not only are rapidly growing areas of dryland fields appearing very thirsty, irrigation scheduling and growth regulator management has become a challenge.

USDA Crop Progress Reports state 60% of cotton acres fall between good and excellent condition, down 15% from this point last year and down 10% over the last 5-year average. Over 90% of our crop is reported to be squaring with over 70% setting bolls. Yield potential is evident across the state, just needing rains to cooperate as we push towards maturity.

With droughty conditions in many areas, I've recently gotten a few questions on boron applications. Although boron (B) is a micronutrient, it is one of the most limiting nutrients for cotton including nitrogen (N), potassium (K), phosphorus (P), and sulfur (S). Although required in trace amounts, boron is needed for proper development of plant tissues because it transports carbohydrates from leaves to fruit.

While visual boron deficiency is rare, it can be described by classic dark rings on leaf petioles, shortened internodes, and deformed leaves and fruit. Deficiencies are typically noted in years following lime applications, as the nutrient becomes less available as pH increases. Boron may also leach through well drained soils with limited ability to hold the nutrient in the event of excessive moisture, but is also difficult for the plant to take up during droughty conditions. The image below shows the classic symptoms of rings on the petiole and leaf malformation I found near an old lime pile.

Cotton has the greatest demand for boron during boll development. Along with carbohydrate transportation, it plays an important role in translocation of nitrogen (N) and potassium (K) from leaves to bolls. University of Georgia Extension recommends 0.5 lb per acre of boron, applied in split applications of 0.25 lb per acre, although a single application of 0.5 lb per acre is possible. Foliar applications of boron are considered the most effective method. To understand precise need of the cotton plant, petiole or tissue sampling is required.



For more information about cotton production practices in your area, contact your state Extension cotton specialist. As always, your PhytoGen cotton development specialist also is available to discuss agronomic options.

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COTTON DEVELOPMENT SPECIALIST:

SHAWN BUTLER, PH.D.

Shawn Butler is the PhytoGen cotton development specialist for central and east Georgia. A native of Jackson, Tenn., Shawn holds a Ph.D. in Agronomy and Crop Science and a M.S. in Crop Pathology, both from the University of Tennessee, specializing in Application Technology, Precision Agriculture, and Remote Sensing. He enjoys helping cotton producers implement technology and find applied solutions to agronomic challenges. When Shawn isn’t scouting fields and visiting with growers, he enjoys following sports, playing golf, boating and home projects.