The Effect of Tillage System and Proceeding Crop on Phosphorus Response of Flax

Flax is a major oilseed crop grown on the western Canadian prairies, with the majority of the production exported into the industrial oil market. Phosphorus (P) fertilization of flax is a challenge, as the crop is very sensitive to seed-placed starter P. Banding fertilizer P, either below or below and to the side of the seed row, is the preferred method of application with flax. In the absence of specialized seeding equipment, some farmers have resorted to increasing the P application in preceding crops, an attempt to supply residual P to the subsequent flax crop in rotation. Flax has been shown to have good association with vesicular arbuscular mycorrhizae (VAM) fungi, allowing it to expand its root absorptive surface area and potential P uptake. The objective of this research is to evaluate the role of preceding crop, tillage system, and P fertilization of the preceding crop in optimizing flax yield and quality.

Based on the preliminary results from this study, it appears that P nutrition of flax can be influenced by tillage system, preceding crop, residual P from fertilization of preceding crops, and side-banded P application. Therefore, it may be possible to select different P management strategies to optimize flax P nutrition and seed yield, depending on the cropping system, crop rotation used, and the equipment available. In 2001, mycorrhizal association in flax at five weeks was higher when the flax was grown after the mycorrhizal crop wheat rather than after the non-mycorrhizal crop canola. Association was also generally increased by using reduced tillage as compared to conventional tillage. Production of flax after canola appears to be a poor option, possibly because of the effect on mycorrhizal association and P nutrition. MB-11