Effects of planting date on the development and yield of spring wheat: Simulation of field data

Much of the work on planting-date effects has been carried out with old cultivars and over a relatively few years. This study was conducted to use data from a recent study to determine whether a simulation model (Cropsim-wheat) could be used to examine the response of modern cultivars to planting date over an extended run of years. Field data for four spring wheat (Triticum aestivum L.) cultivars seeded at 12 planting dates, ranging from 29 April to 12 June, at 4-d intervals at Crookston, Minnesota, in 1992 were used. For all genotypes, crop duration was shortened as planting was delayed from 29 April to 23 May. Further delay in planting lengthened this duration. Simulation outputs for developmental aspects closely matched the field data. The early plantings yielded less than those established somewhat later, with the highest grain yields resulting from mid-May plantings. Cultivar Marshall planted on 7 May produced the highest yield (5.5 t ha(-1)) of any cultivar. Late plantings decreased grain yield. Grain number appeared to be the major component affecting grain yield. Simulation outputs from the basic model, which computed grain number as a function of biomass shortly after anthesis, did not match well the field data for early and late plantings. The inclusion of functions that related grain number to solar radiation and maximum temperature around anthesis and to biomass improved the predictions for plantings early and later in the season. The inclusion of these functions in wheat simulation models may be necessary for application to situations that result in differences in environmental conditions around anthesis.