Know How Much Water, You’re Putting Out

 John Hester, Area Engineer for USDA’s Natural Resources Conservation Service in southeastern Missouri.

MidAmerica Farmer Grower

   John Hester, Area Engineer for USDA’s Natural Resources Conservation Service in southeastern Missouri, was paired with Dr. Gene Stevens, Cropping Systems Specialist, University of Missouri-Fisher Delta Research Center, to explain the value of using irrigation tools to schedule irrigation in cotton, during the recent Delta States Irrigation Conference.
   “Cotton is much more sensitive as far as moisture on crops,” he said.
   “Irrigation is really a step-by-step process,” While scheduling seems to be the last thing you think about when you consider irrigation, you have to do all the prep work before that.
   What you need to know is what’s happening down in the soil, “If you see a plant that’s already stressed, it’s too late.”
   “Earlier in my career I worked at an irrigation water quality office,” he noted. “That’s when we developed the PHAUCET program. Evapotranspiration (ET) scheduling and soil moisture sensors were not practical then for most producers. Today, these are simple and effective if used right.”
   Moisture storage in the soil, plus net irrigation water, plus rainfall has to be weighed against crop water use ET.
   He explained that spotty rains occur in the area and it’s not practical to have water gauges in every field.
   Hester recalled that he offered to handle the irrigation scheduling for a farmer as a means of gaining information for irrigation effectiveness and to ser how big a difference it could make.
   “We need to know how much water we are putting on the fields,” he said. “Most farmers can say how long they pump the water, but do not know how much water they are putting out. They need to know the net irrigation.”
   One other consideration then is storage in the soil, and that means knowing the type of soil as well.
   “We also need to know the effective root zone, whether it’s 12-inch, 14-inch or all the way down to 24- or 30-inch. It’s important to put that information in the program.
   He displayed a chart showing that nine different irrigations were needed for an 8-inch root zone, while only four were needed for the 16-inch zone and three for the 24-inch zone.
   The value of soil moisture sensors is that they will tell you how much moisture is in the soil. They need to be calibrated to some part of the field. 
   “Interpretation is a big deal with these soil moisture sensors.” He strongly applauded the University of Missouri’s Crop Water Use App which was developed from the Arkansas Irrigation Scheduler. Farmers have the option of entering rainfall amounts from their gauges or allow the program to automatically enter radar estimates from the National Weather Service. Evapotranspiration is calculated in the app from links to the Missouri Extension weather station network..
   “It’s easy to use, very accurate, and it’s free.” ∆
   BETTY VALLE GEGG-NAEGER: Senior Staff Writer, MidAmerica Farmer Grower
MidAmerica Farm Publications, Inc
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