Location: Rangeland and Pasture Research
Title: Forage quality of winter canola grown on the Southern Plains. Author
Submitted to: Agronomy Society of America, Crop Science Society of America, Soil Science Society of America Meeting
Publication Type: Abstract Only
Publication Acceptance Date: October 3, 2011
Publication Date: October 12, 2011
Citation: Goldman, J.J. 2011. Forage quality of winter canola grown on the Southern Plains. Proceedings of the Agronomy Society of America, Crop Science Society of America, and Soil Science Society of America International Annual Meetings, October 16-19, 2011, San Antonio, Texas. Poster #1314. Technical Abstract: Winter canola seed production is becoming a popular option for winter wheat producers in the Southern Plains. Using herbicide resistant canola varieties in a wheat rotation can improve wheat yields by clearing the field of weedy grasses that are difficult to control. Canola is grown for its oil. This oil, which is used for cooking and biodiesel, is obtained from the harvested mature seed. The ability to utilize winter canola as a dual-purpose forage, similar to winter wheat, should maximize economic returns for ranchers. In this system, cattle would graze the canola after stand establishment, in late fall and early winter. Cattle would then be removed before spring re-growth and seed production. There are at least two concerns with dual-purpose canola, significant reduction in seed production and toxic levels of nitrate accumulation in leaves and stems that poison cattle. To determine nitrate concentration in leaves and stems during the potential grazing period, winter canola was established at Woodward, Oklahoma in September 2010. The canola forage (leaf and stem) was harvested on November 19, January 4, and March 2, prior to spring re-growth, for nitrate and crude protein analysis. The first two harvests were separated into leaf and stem before analysis, while the last harvest was combined due to limited forage availability. Based on parts per million (ppm) nitrate concentration in the forage, forages containing 6500 ppm or less are considered safe to eat, from 6500 to 20,000 ppm, caution must be used when feeding and the forage should be diluted. Concentrations of nitrate greater than 20,000 should not be fed and are potentially toxic. On the November 19 harvest, before a hard freeze, the leaves contained 4,440 ppm nitrate and the stems 19,058 ppm nitrate. Harvests on January 4 and March 2 occurred after a hard freeze, which apparently reduced forage nitrate levels (January 4 leaf was 2,577 and stem 2515 ppm, March 2 leaf+stem was 2,483 ppm). These results indicate that before a hard freeze, canola stems may contain toxic concentrations of nitrate, however after a hard freeze, nitrate levels in canola appear to be safe for grazing. Based on these results, future experiments will be designed to determine the optimum grazing window and include animal performance measurements and subsequent seed yield data.