An experiment involving six winter wheat (Triticum aestivumL.) cultivars, an early-April herbicide application on wheat and on four dates after wheat harvest, and the growth of a subsequently planted corn (Zea maysL.) crop was conducted at North Platte, NE. ‘Centurk 78’ suppressed barnyardgrass [Echinochloa crus-galli(L.) Beauv. # ECHCG] more than ‘Bennett’ and ‘Eagle’ in the growing wheat and after wheat harvest in July, but there were no differences in weed yield among cultivars in corn planted 11 months later. Herbicides applied to the tillering wheat in early April improved weed control in wheat and the subsequent corn crop. Also, herbicides were applied 5, 25, 45, and 300 days after wheat harvest. Weed growth increased and soil water decreased as spraying dates were delayed. Herbicides applied 5 days after harvest did not maintain adequate weed control in the corn planted 11 months after wheat harvest and low corn yield resulted. Plots receiving herbicides 300 days after wheat harvest had the least soil water in the fall after wheat harvest but the best weed control in corn and highest corn yields because of better weed control in corn.

Differences in weed interference among winter wheat (Triticum aestivumL.) cultivars have been observed in farmer fields. Identifying cultivars that are more competitive would be useful in weed control programs. Twenty cultivars of winter wheat were grown with spring germinating weeds during 1979 and 1980 and eight cultivars were grown in 1981 at North Platte, NE on a Typic Argiustoll soil. Cultivars included semi‐dwarf through normal statured types and were adapted to a wide geographic area of the Central Great Plains. ‘Lancota’ selections (NE 78939, NE 78906, NE 78895, NE 78892, and NE 78925) and sister lines NE 78742 and NE 78743 were good weed competitors. ‘Centurk 78’, ‘Buckskin’, ‘Vona’, and ‘Sage’ were intermediate, while ‘Homestead’ and several lines with Homestead germplasm were relatively poor annual weed competitors. Several cultivars that were 73 to 78 cm tall were poor competitors with weeds, while most cultivars that were 83 cm or taller were good competitors. NE 78742 (75 cm) and NE 78743 (72 cm) were among the shortest cultivars but were among the best in competitiveness with weeds. Cultivar selection can reduce summer annual weed growth in winter wheat