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The results from a two-year field study indicate that the corn growers of western Kansas may not have to irrigate until black layer formation, as is the current practice. With the decline of Ogallala aquifer groundwater level and rising fuel cost any reduction of pumping makes economic sense. The first irrigation ending date was on August 10-15, corresponding to denting and starch layer formation of to towards the germ layer resulted in yield that averaged 7 bushels per acre less than the second ending date on August 21-22, which corresponds to starch layer at to towards the germ layer. However, continuing irrigation until September 1, corresponding to the start of black layer formation, improved yield by only 2 bushels per acre. A statistical analysis over the two years of data indicates that the first ending date is different from the last ending date, but the second ending date is not different from either first or last ending dates. Economic sensitivity tests show that irrigating until the formation of starch layer at to towards germ layer is feasible with a corn price of $2 per bushel and $6 per inch pumping costs. However, irrigating past this stage of grain development is not feasible even with $2.75 / bushel of corn and pumping costs as low as $2 / inch.