Influence of planting date and seeding rate on winter wheat grain yield and yield components
Dahlke, B.J.; Oplinger, E.S.; Gaska, J.M.; Martinka, M.J.
Journal of Production Agriculture 6(3): 408-414
Winter wheat (Triticum aestivum L.) is commonly seeded over a 60-d period in the Midwest depending on crop rotation options, weather, and other farm operations. This study was conducted to determine whether winter wheat seeding rates should be altered depending on planting date and cultivar. Seeding date and planting rate responses of the cultivars, Merrimac an Cardinal, were evaluated at the University of Wisconsin Arlington Research Station during the 1988 to 1991 growing seasons. Eight planting dates ranged from 24 August to 3 November and seeding rates were 14, 28, 42, and 56 seeds/sq ft. Grain yield and yield components were influenced by all variables and specific interactions. Heads per square feet and kernel weight, two primary yield components, decreased as seeding was delayed after 12 September. Maximum grain yield occurred when planting Cardinal on 3 September using 28 seeds/sq ft. Delaying Cardinal planting to late September required a seeding rate of 42 to 56 seeds/sq ft to maximize yield. When planted in September and early October, Cardinal had higher yields than Merrimac due to heavier kernel weight. Changes in yield components allowed plants to adjust to varying conditions as planting was delayed. As grain yield decreased with a planting delay into October, kernel weight and heads per square feet continued to decrease for both cultivars. When planting was delayed past 3 October in 2 of the 4 yr, Merrimac had greater kernel weight, which translated into higher Merrimac grain yields than Cardinal. Grain yields of wheat planted in late October decreased due to yield component response to environment and to stage of plant development when growth ceased. These results can be used to improve establishment and yield of winter wheat, especially when planting at dates that are not always optimum.