See the little dents in the kernel?  This means the corn has made, and is ripe.  You could water the field forever, at this point, and the plant would not take up anymore water.  Irrigation has now stopped on all three fields of corn.  Gradually the stalks will dry, turning a golden color.  We will wait to harvest until the moisture in the plant, the ear, and each kernel reaches a certain moisture point.  Summer is ending, harvest is upon us!