Weekly in-season Updates
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INFORMATION |
August 19, 2007 Talkin’ Cotton
I was planning to write about timing of the final irrigation on cotton, but tropical storm Erin changed the emphasis back to management of dryland cotton. A good mid to late season rainfall is usually a yield maker in dryland cotton. Our cotton was starting to stress some due to a root system that is not as deep as usual, but this general rain is what we need to finish out the crop. In some areas, I’ve heard reports of extremely high rainfall amounts, which probably caused enough runoff to make the field rough for harvesting, and if heavy winds accompanied the rainfall the cotton could have lodged. When large green bolls are on the plant, their weight will usually keep the cotton plant on the ground and make harvesting difficult. Many times a cotton crop that is well into fruiting will have a large fruit shed following a rain. This is not caused by the rainfall but by a decrease in carbohydrates feeding the bolls. Cotton that is fruiting heavily has a high carbohydrate demand, and any slight decrease in the supply will cause it to shed the small bolls that have formed just after blooming. Usually rainfall is accompanied by cloudy weather and cooler temperatures. This slows the nutrient production by the plant and the plant reacts by shedding fruit. If a dryland crop has been under water stress, fruit abscission layers have already been formed on some small bolls, and they may go ahead and drop following the rainfall. In either case, if sunshine and warmer weather follows the rainfall, the plant will make up for the loss of bolls by holding onto bolls higher on the plant. The cotton should be cutting out or blooming out the top in late August. Normally, a bloom made after September 1 will not remain on the crop, so our crop has just about set it’s yield at this time. With a warm fall, I expect to see high (maybe a record) yields on our Oklahoma cotton crop.
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