By making the best use of water, irrigation managers can free-up both water and equipment for use on other crops or other land.

Seed-producing crops respond more to irrigations during one particular stage of development than during other stages. Some of those crops include corn, barley, sunflowers, wheat and beans. Yields of storage and forage crops sugarbeets, potatoes, alfalfa and grasses are more directly related to climatic demand and cumulative water use during the season than to stress during any particular growth stage.

Sugarbeets are quite drought tolerant. They can withstand extended periods without rainfall or irrigation water by using water stored in the soil. Limited water can even increase the efficiency of sucrose production. Sucrose yield per unit of water use can be increased above that where maximum water use is allowed, simply by cutting off irrigations three to four weeks before harvest operations. Sugarbeets are only moderately sensitive to plant stress, except during the early growth stages. Afternoon leaf wilting during hot, dry, windy conditions has negligible effects on total sugar production. Water can be used more efficiently on sugarbeets by applying one last major irrigation to recharge the entire soil profile at the onset of the major stress period.

Sugarbeets adapt to limited irrigations by using deeply stored soil water and quickly recovering, when water is made available following major stress periods. Normal irrigations of sugarbeets could be reduced after the middle of July. Sucrose yield is likely to be reduced very little when such a practice is used and a final heavy irrigation is applied in early August.

Corn is very sensitive to drought stress, especially during the flowering and reproductive stages. Stress during the early vegetative stage is not nearly as serious as stress during flowering, pollination and early seed filling. Grain corn is most sensitive to drought stress between the 12-leaf and blister kernel stages; this period includes flowering, pollination and initial seed filling.

Stress during any part of the cropping season limits grain corn production. To maximize water use efficiency in grain corn, it is best to limit irrigations during the vegetative stage. The period from emergence to 12-leaf was lease sensitive to stress.

Barley responds to drought stress much like corn and other cereal crops. Yield is likely to be reduced very little when drought stress occurs during the vegetative period. However, a major disadvantage of early drought stress is the tendency for plants to tiller more than usual.

Although the increased tillering is desirable, often the tillers never produce grain-yielding heads. Barley is most sensitive to stress during jointing, booting and heading. Considering drought stress before, during and after heading, yield is reduced the most by drought before heading. Flowering and pollination appear to be the most sensitive periods.

Several studies have been conducted with spring wheat and winter wheat to evaluate the effect of limited irrigations on crop quality and production. Stress was most critical during and after heading. This response is similar to that for barley. There is little or no measurable benefit from irrigating spring grains before the boot stage, unless moisture stress is evident. Stress is likely to occur when the plants appear wilted and the leaves curl.

The period between grain filling and maturity is critical. Yield is reduced the most when stress starts during soft dough or during or following heading. Stress during the maturing process results in about a 10 percent lower yield. Moderate stress during the early vegetative period has essentially no effect on yield.