In 1963 and 1964, experiments were conducted in western Minnesota, eastern South Dakota, and southeastern North Dakota to study the effect of corn stand on yield, evapotranspiration, and water-use efficiency atdifferent stages of plant grow. the Five corn populations, within the limits of 6,000 to 24,000 plants per acre, were planted in a Latin square design at 7 and 10 locations during 1963 and 1964, respectively.
Under adequate moisture conditions in 1963, yields ranged from 60 to 134 bushels per acre at optimum stands of 14,000 to 22,000 plants, whereas, yields of 1 to 75 bushels at stands of 6,000 to 12,000 plants per acre were produced under the limited moisture conditions in 1964.
Evapotranspiration from planting to maturity ranged from 13.5 to 20.6 inches and from 9.4 to 17.1 inches for 1963 and 1964, respectively. Except at 2 of the 17 locations, evapotranspiration was not affected significantly by stand at any growth stage during the 2-year period.
Water-use efficiency increased as corn yield increased and reached a maximum of 454 pounds (8.1 bushels) corn per inch of evapotranspiration. No definite relation of water-use efficiency to stand was found for grain yields since optimum corn stands were related to growing seasons. Forage production and water-use efficiency generally increased with higher plant populations, so there was a dose relationship between them during the 2-year period.