As area producers struggle through though drought conditions, most seek to maximize returns from limited irrigation capacity. Because our aquifer is not refilling nearly as quickly as we are pumping, careful management practices to conserve water are becoming even more pressing. Many producers are making use of Low Energy Precision Application pivots, (LEPA) and similar pivot systems to maximize their irrigation efficiency. When on the proper setting, these types of systems use lower pressure regulated nozzles hanging fairly close to the ground to limit evaporation waist and causes by limiting air exposure, crop overspray, and heavily wetting a smaller area of soil surface. The nozzles of a LEPA type pivot have three settings; bubble, spray, and chemigate. This allows the LEPA type systems some flexibility and practicality in use.
When irrigating a crop for a stand, most producers set their LEPA nozzles to spray mode. This setting wets the entire soil seed bed and better ensures a profitable stand of young seedlings that cannot search very far through the soil for water on their own, but acts similarly to a conventional sprinkler in water use efficiency. An older style conventional sprinkler system loses about 20 to 25% of the water pumped to wind and low humidity while it irrigates in normal operating conditions. LEPA style systems only lose about 2 to 3% while in bubble mode in similar situations. During very high and sustained winds, something most area producers are all too familiar with, both systems do lose some efficacy but the volume of water lost by conventional pivots is staggering. In those situations, up to 94% of irrigation water applied can be lost. The timing for producers to change the settings on their LEPA type systems to bubble mode quickly becomes very important as we face water (and money) loss issues. To maximize irrigation efficiency, this switch to bubble needs to happen as early in the growing season as possible.
Cotton, our most pertinent area crop, first becomes capable of searching for its best water source with its tap root system at match-head square stage. Cotton at younger stages benefits more from the spray mode since it hasn’t developed the root system needed to take advantage of the bubble setting yet. Producers who make the change to bubble too soon often experience serious stand and or yield reduction without the help of rainfall, which has been severely limited lately. As cotton plants start getting bigger, they start developing their fruit set and water use increases drastically. Producers waiting too long to change to bubble mode risk notable yield loss through fruit set, not to mention the painful waist of precious water.
Our area’s cotton fields are ranging from 1st true leaf to pinhead square stage. For several fields, match head stage is only a few days away. For this reason we urge producers and consultants to keep close tabs on the stage of their cotton fields.
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