Proper scheduling will improve irrigation water use efficiency

Monday, July 3, 2017

Recent rains have provided an opportunity for producers to reset their irrigation programs and implement proper irrigation scheduling. Most areas of the county have received enough rains over the past few days to eliminate moisture deficits from their fields. Scheduling irrigation events that are triggered/initiated based on EvapoTranspiration (E.T.) can allow producers to adequately meet the moisture demands of the crop without applying irrigation water too frequently.

Reducing crop stress is the main objective of almost all production practices, and irrigation plays an important role in that process.

According to Dr. Earl Vories with the USDA-ARS, “Irrigation should be managed to ensure that soil moisture isn’t the limiting factor to yield.” Lack of adequate soil moisture can reduce fertilizer use efficiency and result in crop stress. On the other hand, over applying irrigation water can also introduce crop stress by eliminating oxygen in the rooting zone and leaching nutrients out of the profile. The practice of irrigation should include the goals of supplementing the crop with moisture while conserving ground water resources. Vories says, “Irrigation programs that are timed properly can accomplish both goals.” He says that “even if our area doesn’t have the groundwater challenges faced by others, pumping only what the crop needs reduces your energy costs.”

On-farm demonstrations of gauges that estimate evapotranspiration (figure 1) from fields have helped producers improve irrigation timing. The gauge is set near field borders and provides a visual reference of moisture status of the field. The E.T.-Gauge functions to provide an estimate of evaporation and crop transpiration. These sources of water removal from a production field are affected by soil texture and crop developmental stage. Adjustments for the crops growth stage are also included in the set-up. Research has shown that plant available moisture is influenced by soil texture. Additionally, water requirements of the crop vary depending on growth stage. Combining the water holding capacity associated with a particular fields predominate soil texture and the moisture requirements of the crop at its current growth stage, provides information used to set an allowable moisture deficit mark to trigger irrigation events. Producers can see the water level in the gauge and time their irrigation once the allowable deficit is reached. On-farm demonstrations and tests have shown considerable efficiency improvements when irrigation is triggered based on E.T. thresholds.

Current soil moisture in fields across the county may be adequate, but things change quickly. Being prepared now can help producers avoid problems with improper irrigation timing during the season. I well remember a conversation I had with Mike Ellison a few years ago. During a particularly rainy period in the production season, I asked Mike if he was worried about all the rain. As he sipped his coffee and read the paper he said, “Nope, this is Mississippi County. I don’t care how wet the fields are now, we are never more than a week away from a drought.” So take this opportunity to work on an irrigation scheduling plan that will help improve irrigation water use efficiency.

For additional information on irrigation scheduling, or if you are interested in learning more about E.T. gauges, please contact the Mississippi County Extension Office at (870) 762-2075. You can also email me at

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