Objectives
The overall project objectives were to demonstrate the ability of contrasting phosphorus (P) fertilizer formulations and biological inoculants to improve P uptake in flax. More specifically, we wished to explore whether flax P uptake and the corresponding seed yields might vary with the specific fertilizer formulation and whether biological inoculants intended to enhance P solubility and/or uptake were utilized. Additional questions we wished to address were whether the responses differed with environment and whether the combination of novel P fertilizer forms and biological inoculants might increase flax P uptake and seed yield beyond what could be achieved with either of these inputs applied alone.
Project Description
Field trials with flax were established at three Saskatchewan locations (Indian Head, Melfort, and Yorkton) in the spring of 2025. The objective was to demonstrate options for improving phosphorus (P) uptake in flax production and the treatments were a factorial combination of three biological and four P fertilizer treatments. The biological treatments were an untreated control (UTC), granular Penicillium bilaiae (PB), and granular arbuscular mycorrhizal fungi (AMF) inoculants. The P treatments were a control with no P fertilizer (0P), monoammonium phosphate (MAP; 11-52-0), MicroEssentials® S15 (13-33-0-15), and Smart NutritionTM MAP + MST (9-43-0-16). Where applicable, the P rate was 40 kg P2O5/ha, and all fertilizer was side-banded. Inoculant products were placed in-furrow. Data collection included residual soil qualities, emergence, early-season biomass yields, tissue P, P-uptake, seed yield, and test weights. While environment affected essentially all response variables, only seed yield and test weight were affected by the biological or P treatments. The seed yield response was unexpected, revealing a 4.5% reduction with AMF inoculant relative to UTC when averaged across locations and P treatments. Test weight was also highest in the UTC biological treatment; however, interactions revealed that this was inconsistent across P treatments and mostly driven by high and potentially random variability at Yorkton.
Grower Benefits
Overall, the results from this project did not demonstrate any significant responses to phosphorus (P) fertilizer application, regardless of the formulation. In terms of the lack of a P response, past research has shown flax to be a good scavenger of soil P and relatively unresponsive to fertilizer; however, more extensive trials have shown that modest yield gains can be expected with this crop when averaged over fields and years. Furthermore, an important goal of P fertilization is to maintain or build residual soil fertility; therefore, applying some P will be recommended under most circumstances to ensure optimum yields in the current flax crop while achieving longer-term soil fertility objectives. With no differences between formulations in terms of crop response, the most economical P fertilizer option would be that which is the least expensive, most likely monoammonium phosphate (MAP; 11-52-0); however, MicroEssentials® S15 and Smart NutritionTM MAP + MST may still be attractive to farmers seeking alternatives to ammonium sulfate as an S source. Regarding responses to biological inoculant products, our results were not necessarily inconsistent with past work since significant responses to both Penicillium bilaiae and mycorrhizal (AMF) inoculants have been rather elusive under field conditions in western Canada. While the observed seed yield reduction with AMF can potentially be rationalized, it was unexpected and conducting this work over additional years and/or locations is recommended to see if is repeatable or simply disappears with a larger data set. That said, our control treatments always performed at least as well as the treated plots; therefore, neither of these inoculant products would specifically be recommended for no-till, dryland flax production based on the current results.
