OPTIMUM SEEDING DATE FOR WINTER-WHEAT IN SOUTHWESTERN SASKATCHEWAN

Winter wheat (Triticum aestivum L.) in southern Alberta on the Canadian Prairies has traditionally been grown on bare fallow. Recently, the improved winterhardy cultivar Norstar and improved management recommendations, such as seeding directly into stubble or into chemical fallow, have encouraged producers to adapt this crop to the colder climate of southern Saskatchewan. The objective of the experiments reported herein was to determine if the optimum time for seeding winter wheat on stubble and chemical fallow differed from that recommended for seeding on conventional fallow in southern Alberta. A 4-yr study of stubble-seeded wheat and 3-yr study of wheat seeded on chemical fallow were carried out on a medium-textured soil at Swift Current and on a coarse-textured soil at Cantuar (only the stubble treatment). The results for stubble-seeded wheat confirmed that both plant population and yields decreased sharply by 40 to 60% and 30 to 40%, respectively, as seeding was delayed after the first week of September until very late October. The decrease in plant population was less pronounced on the sandy loam soil (40%) than on the silt loam soil (56%). On chemical fallow, there was a gradual decrease in plant population but grain yield did not decrease until seeding was delayed to mid-October. Test weight was reduced (about 8%) by delayed seeding, and plants took 10 to 13 d longer to mature, which facilitated disease (e.g., rust) infestation. Grain protein concentration was not affected by time of seeding. For optimum results in southwestern Saskatchewan, winter wheat can be seeded into chemical fallow until early October but should be seeded in stubble by mid-September.