Canola planting is right around the corner. While last season’s canola crop had mixed results with many growers not achieving the yields they expected, there are several things growers can do prior to planting that can pay off later in the season and promote crop productivity and success.
Weed control is vital for canola production. Successful use of herbicides can help control problematic grassy weeds, which is one of the primary benefits of integrating canola in Oklahoma production systems. Within the canola production season, most canola yield losses associated with weed competition is early in the growing season. Once the crop is established, it can typically outcompete most weeds. However, this is only true if the crop was maintained weed-free up until this point. Therefore, preplant herbicide programs are essential to make sure the crop established into weed-free conditions. While there are a limited number of herbicide active ingredients that are labeled for preplant use in canola, those labeled are typically quite effective at managing weeds within the crop. Most growers would benefit from a preplant program that integrated a residual herbicide to delay in-season applications until the crop has been established. This is why one of the better preplant herbicides options is Trifluralin. Trifluralin can help manage most fall weed species as long as the seedbed is relatively clean and the herbicide is incorporated into the soil within 24-hours of application. This is why Trifluralin is a good option for producers that integrate tillage practices, as tillage can both clean the seedbed and incorporate the herbicide after application.
Fewer options are available for no-till canola producers. Glyphosate is really the primary option for pre-plant herbicide application, since incorporation cannot be done. Glyphosate can still be used with using conventional canola cultivars, as long as the application is made prior to emergence. Additionally, glyphosate can only control weeds that have already emerged and does not have any residual control. This results in the need for further applications in-season. Oklahoma State University is currently evaluating several other preplant herbicide options but as of this time these are all off label and considered illegal applications.
Soil nutrient management is also a practice that can help canola establish and achieve good early season growth. While we are very close to planting, soil testing and fertilizer applications are still a management practice growers can do to help the crop. Soil test results should help guide fertilizer applications but enough P and K are needed at planting and early in the fall. However, higher rates of both P and K are frequently associated with products that contain relatively high amounts of N. While canola does need N in the fall, too high of N fertilizer applications can lead to excessive fall growth and in-turn potentially higher winterkills. Enough N should be applied to ensure the crop does not stress but limit fall growth. Most growers should be able to utilize the 1/3 and 2/3 method, where only up to a third of the N is applied in the fall and higher rates are applied at green-up in the spring.
One application that has shown benefit in canola has been an application of N and P with the seed at planting. While these applications do not always translate to increased crop yields, especially if fields are not low pH or low STP, but can promote early season growth and increased root growth. These applications can either be applied in-furrow or beside the row. However, it must be cautioned that, due to the salt sensitivity of winter canola, in-furrow fertilizer applications cannot be made at rates as high as in wheat crop. This application provides both N and P to the canola crop early in the crop cycle and allows it to achieve good growth early in the season.
Probably the most important management considerations are the decisions grower make around planting. While other practices discussed can alter early season growth, these considerations will directly influence the growth of the crop.
There are several cultivars that are well adapted to Oklahoma systems. These include both conventional and glyphosate-tolerant cultivars. While there is a good amount of flexibility in the glyphosate-resistant cultivars, as they can utilize glyphosate to clean up weedy spots in the fields, yields from the conventional varieties have been competitive if not slightly higher when compared side-by-side in the Oklahoma State Variety trials. Challenges with conventional cultivars, i.e. limited broadleaf weed control, can typically be overcome with adequate early season weed control and adequate plant populations. These conventional varieties have value when growers will double-crop, especially soybean, behind canola as the conventional canola cultivars can be easily controlled with glyphosate. However, with increasing glyphosate-resistant summer weeds and the availability of auxin resistant summer crops, these glyphosate resistant canola cultivars can be a viable option in double crop systems.
Traditional planting dates range from September 10th through October 10th. However, optimum planting usually is during the last 10 days of September for the northern part of the state and the end of September through the first of October for the southern part of the state. When planting early, many producers just want to ensure that enough growth has been achieved before the first killing freeze to store enough reserves in the plant and rooting system to survive the winter. This is a good thought to always have during planting but canola only needs around 6 weeks of growth to increase the likelihood of winter survival. Planting on September 6th would result in 8 weeks before the first average light frost (November 2nd, NOAA), 10 weeks before the first freeze (28F, November 14th, NOAA), and 12 weeks before the first killing freeze (24F, November 25th, NOAA). If a large amount of growth was the only factor in achieving high winter survival and good stands in the spring, then planting into good conditions as early as possible would be the best practices. However, with increased vegetative material, high amount of water and nutrients will be needed to sustain the plant in later winter and early spring. This increased stress can result in diminished winter survival and spring stands. Pushing these planting dates back into late-September into early October can greatly increase winter survival chances in most years.
Several factors go into a successful canola crop. While many of these factors are associated with environmental conditions, proper management of planting will help with early season growth and over-winter survival, allowing growers their best chance at a successful crop in both good and poorer years.
We at Oklahoma State University wish all producers a safe and productive planting time. If any further guidance is needed regarding planting issues feel free to contract your local county extension office, regional agronomist, or myself.