Seed Bed Utilization Strategies: Lowering Salt Index in Canola Seed Row
Canola growers face a double-edged sword when applying common seed placed phosphorus fertilizers.
Canola demands ample plant-available phosphorus to thrive. Since phosphorus is not very mobile in the soil, you need to get it as close to the seed as possible so it can be utilized. However, the high salt index of MAP and other P fertilizers can desiccate the seed (this is largely due to the nitrogen component).
| DAP | MAP | |
| Salt Index | 29 | 28 |
When using a one pass system for fertilizer and canola seed, fertilizer must be applied in a side band or mid-row band to avoid seed damage/mortality. (To learn more on seed and fertilizer placement in canola, check out this great article on the Canola Council website.)
The most commonly recommended practice for reducing the risk of seed injury is to increase seed bed utilization (SBU) using a narrow row width and a higher spread opener. Yet from a practical standpoint, many growers don’t want to go through the time and cost to switch openers. What they would really appreciate is a solution that allows them to switch to a better product rather than changing equipment.
Some promising work is being done to find ways to reduce salt index by blending MAP (which has a salt index of 27) and alternative phosphorus products with up to 28% available P and a significantly lower salt index – potentially as low as one-quarter that of a MAP product. (View research results on low salt index fertilizer from 2016 Manitoba Canola Trials.)
A blend with 75% MAP and a 25% inclusion of a low salt index phosphorus product opens the door to several possibilities. The resulting mixture applied at current recommended levels would decrease seed injury, reduce hot spots in the field and provide a more site-active solution.
Reducing the amount of MAP would also give growers the ability to exceed the recommended safe rate (40 lb./ac. MAP, or 20 lb./ac. of actual phosphorus). Research is being done to examine this in greater detail.
As low salt-index sources of plant-usable phosphorus can be more expensive than MAP products, the ability to blend as an inclusion would also help keep input costs manageable while improving safe availability of phosphorus.
At Taurus we are passionate about solid agronomy and all aspects of it, from soil to seeding, to in-crop management-seed safety plays a big part in growing a successful crop.
