Delayed planting opportunities with winter wheat in the central Great Plains

Winter wheat (Triticum aestivum L.) in the Great Plains is not always planted at the optimum time for a variety of reasons. In order to identify wheat yield and related responses to delayed establishment, sequential monthly plantings from 1 October to 1 April were undertaken during 7 yr, 1985 to 1991, at Garden City, KS. 'TAM 107' was seeded at a constant heavy rate in bordered drill-strip plots in a randomized complete block design. Although considerable variability occurred among years, relative grain yield declined with progressive planting dates as follows: 1 October = 100%, 1 November = 77%, 1 December - 59%, 1 January = 57%, 1 February = 41%, 1 March = 16%, 1 April = 0%. Wheat planted on 1 April did not joint or form heads due to lack of a 6 wk period with temperatures below 51 degrees F as required for vernalization. Relative to the optimum planting date on 1 October, the wheat planted on 1 March was the last to produce heads and grain and the lowest yielding; had the most delay in heading (26 d later); was the latest to ripen (17 d later) and the shortest statured (5 in. less); produced the smallest seed weight (43% less) and the lowest test weight (21% less); produced the fewest heads per plant (58% fewer), the fewest kernels per head (33% fewer), and the fewest kernels per plant (73% fewer); and had the shortest grain-filling period (9 fewer d). Little variation in stand emergence or number of spikelets per head occurred through the range of planting-opportunity dates. These results provide quantitative criteria to help make cropping decisions relative to delayed planting situations for winter wheat in the Central Great Plains.