Impact of Soil pH and Aluminum on Winter Canola Cultivars in the Southern Great Plains.

Winter canola is a valuable crop in southern Great Plains agricultural systems. Not only does it help control problematic grasses in wheat production systems but typically results in a 10-15% increase in successive crop. While the benefits are known, the challenge for producers in the region have been to fit the crop into these traditional production systems. Soil acidity is a constant challenge for growers in the southern Great Plains and other crops that are typically grown in rotation with canola, i.e. wheat and grain sorghum, can produce adequately at moderately low soil pH. However, it is currently unknown on the sensitivity on winter canola, especially when using different cultivars grown in the region. Therefore, a study was developed to determine the influence of soil acidity on winter canola cultivars. Trials were established in Stillwater and Chickasha in 2015-2016 and Stillwater and Perkins in 2016-2017. Trials were established on a previously established pH gradient at all locations. Four different winter canola cultivars were tested that are common winter canola cultivars in the state. Stand counts were conducted both prior to winter and following the last frost in the spring. At harvest, plot grain weight was determined and utilized to estimate grain yield. Subsamples were collected from each plot and oil content was determined using a near infrared analyzer.  In 2015, yields generally declined as soil pH declined. However, yield decline was more drastic at the Stillwater location. Soil samples suggested that this was due to the lower concentration of soluble Al at the Chickasha location compared to Stillwater. Oil content followed the same general trend as grain yields. Cultivar played a significant role in winter canola survival. Both DKW 45-25 and 46-15 maintained at least 50% optimum yield when pH dropped below 5.5, while DKW 41-10 and 44-10 resulted in less than 25% yields below 5.5. This study emphasizes that soil pH needs to be corrected prior to winter canola production but soil test reports should not only look at soil pH but also soluble Al concentrations. Additionally, winter canola cultivars can be used to help manage acidic soil conditions. However, yield declines must be expected.