Corn and Soybean Irrigation Guidelines

As we traveled through Tunica county today we noticed a few growers received a shower or two recently.  Elsewhere across the Delta, a shower would be a welcomed Memorial Day event. Over the last couple of days we have received numerous questions  regarding irrigation initiation for corn and soybeans.  A couple of tables below detail general guidelines for corn and soybeans in soils ranging from silt loams to heavy clays.  Center pivot irrigation field thresholds are approximately 15-20 centibars less than the values presented in the charts.  Information on calculating average soil moisture can be found here, Watermark Sensors, Calculating Soil Moisture.  Remember, evaluation of sensor readings at different depths should reveal the active rooting zone.  If over a period of a few days a sensor has little or no movement, remaining in the 0 to 20cb range, most likely the roots have not developed to that depth. On the other hand, if the sensors are progressively moving upward 10-15cb per day, most likely roots are developed and utilizing moisture at that depth.