Wheat planting season is here, along with summer row crop harvest. As with any year, there will likely be delays due to weather in getting some wheat fields planted on time. If this happens, what is the cost in planting wheat later than normal and can increasing the seeding rate increase yield to compensate for losses due to delayed planting?
To answer these questions, a four-year study was initiated in 2009 at the Northwest Research-Extension Center in Colby and completed in 2012. The results in 2011 were not used due to the dry spring conditions that reduced yields across all treatments. TAM 111 was seeded at four rates (60, 90, 120, and 150 lbs/acre) and at the four planting dates of September 26, October 9, October 28, and November 7. The actual planting date for a particular year was within three days of these planned planting dates. For the Colby area, September 26 would be considered an optimal planting date in most years, and October 10 would be to the latter end of optimal timeframe. October 28 is late for this area while November 7 is very late.
The following chart shows the four-year average yields for each treatment in the study.
The following conclusions can be made from this study:
* When planting dates were later than optimal, increasing the seeding rate improved yields significantly. However, the higher seeding rates did not compensate for the effect of delayed planting on yield losses compared to the yields at the optimal planting dates. At these later planting dates, the plants do not tiller as much as at the optimal planting dates, and they do not have as much time to develop before cold weather begins. Increasing the seeding rate at late planting dates has the potential to compensate for the decreased tillering potential of wheat planted late, and increase yields compared to the lower seeding rates – although the yields will not increase to the level observed from wheat planted during the optimal planting time.
Brian Olson, Adjunct Professor, former Northwest Area Crops and Soils Specialist
Rob Aiken, Cropping Systems Agronomist, Northwest Research-Extension Center