Planting Date and Seeding Rate Effects on the Yield of Winter and Spring Wheat Varieties – Results from the 2005-2006 Cropping Year

The economic viability of Oregon wheat production depends on highly productive varieties and cost-effective sustainable management practices. Growers are continuing to adopt newly released varieties; however there are few available data on how to best incorporate these varieties into individual production systems. Growers are also exploring new management practices such as fall seeding of spring wheat varieties to take advantage of market opportunities. Clearly, information on these newer varieties and management practices is needed. Therefore, a study was initiated in the fall of 2005 to evaluate the performance of four newer Oregon winter wheat varieties compared to ‘Stephens ’ and ‘Madsen’. Two study sites were established at Pendleton and Moro, Oregon. The study evaluated variety performance across four planting dates and three seeding rates. The study found that planting date had the greatest effect on yield. Delayed plantings reduced yields by up to 24 percent. Further analysis found that there was no variety by seeding rate interaction, indicating that all varieties performed similarly across seeding rates. Among varieties, ‘Tubbs ’ yielded as well or better than ‘Stephens ’ across all planting dates. ‘ORCF-102 ’ was found to perform well in late plantings. The soon-to-be-released variety ‘ORH010920 ’ was found to have highly variable results due to its facultative nature, indicating that this variety is not as broadly adapted as hoped. We found that, among seeding rates, increased seeding rates can increase yield by up to 5 bu/acre in late plantings at Moro. However at Pendleton, it would not have been beneficial to increase seeding rates above 22 seed/ft2. A complementary study on spring wheat was also established in 2004. This study compared several spring wheat varieties to the winter wheat ‘Tubbs’. Three fall planting dates and a single spring planting date were evaluated. Our results indicate that the spring wheat varieties yielded as much as ‘Tubbs ’ in plantings after November 1