Forage and Seed Yields and Forage Qualities of Biennial Canola Following Peas in the Pacific Northwest.

When planted as double- or multi-purpose crop, canola can play a significant role in renewable energy, food and feed production in the Northwest. The green pea-canola cropping system can provide new opportunities for growers in the region through: i) providing additional annual farm income with the production of green pea and canola forage, ii) protecting the soil from wind erosion through vulnerable periods (late summer through spring) with crop coverage, and iii) producing canola seed in the subsequent year for oil (biofuel or food) and high-protein meal (animal feed). The objectives of the current study were to assess the effect of pea precursor crop, canola purposes, and N and S fertilizers on biennial canola forage and seed yields. The experiment was conducted in a split-plot design with four replications in 2012/13 and 2013/14 cropping seasons. The main plots were biennial canola purposes (dual or single). The dual-purpose biennial canola treatment was cut for forage in fall, allowed to regrow, and harvested for seed the following year. The single-purpose biennial canola was grown only for seed. Subplots were 3 x 3 factorial combinations of N (0, 112, and 224 kg/ha) and S (0, 33 and 66 kg/ha) fertilizer rates in a randomized complete block design. In 2012/13, the main plots were 55 m wide by 15 m long, whereas subplots measured 6 m wide by 15 m long. In 2013/14 subplot sizes were 4.6 m wide and 7.5 m long. Sixteen-percent moisture adjusted biennial canola dry matter yield from growth stage 28–29 (BBCH scale) was 2183 and 1285 kg/ha in 2012/13 and 2013/14, respectively. Poor establishment reduced the forage yield in 2013/14. In 2012/13, there were no significant differences in forage yield between plots that received N and the check. No trend was observed for forage yield with an increase in N rate. The lack of difference to applied N in 2012/13 compared to the check indicated that N mineralized from pea residue was presumably adequate for vegetative growth. In 2012/13, the inorganic N in the soil prior to pea planting was approximately 2.2 kg/ha in the first 15 cm of the soil, much lower than what was documented before biennial canola planting (24.6 kg/ha). Unlike 2012, in 2013, biennial canola forage yield increased with an increase in N rate. This is not surprising, considering the poor pea stand we had before the biennial canola crop.  In both years, no response to S fertilizer was observed for biennial canola forage. In 2012/13, biennial canola seed yield was 2514 and 2679 kg/ha for the dual- and single-purpose biennial canola, respectively. Yield was not significantly different, suggesting the removal of biennial canola forage in the fall for hay might not reduce the seed yield. Both N and S had no significant effect on biennial canola seed yield at p<0.05. This could be due to the same reason indicated above for forage yield; i.e., N contribution from pea possibly reduced the yield penalty in the check plot and did not dramatically change due to high rates of N. These preliminary results suggest that biennial canola can be a potential alternative crop in the cereal dominated farming systems of Northwest.