By Harry Brook
So far, I’ve mostly talked about nitrogen. Let’s not forget there are other nutrients needed by the crop. The graph below shows the amount of nutrient uptake cereal crops have taken from the soil and when. Canola and other oilseeds are much the same. The nutrients must be available early on or you risk reduced yields.
This same curve also applies to oilseeds and pulses. Once the crop starts flowering, all the nutrients in the plant have pretty much been taken up and seed filling and ripening is just a redistribution of nutrients in the plant.
There are tools online to help predict how much fertilizer should be applied to get a specific amount of crop. There is a nutrient use calculator, which gives you total nutrients used for a specific yield. Here is the link:
Another useful tool is AFFIRM, which predicts yield and can help in deciding how much fertilizer to apply. It takes into account the previous crop, moisture conditions, soil test results and fertilizer budgets. Here is the link:
The program was specifically designed for Alberta conditions.
Other than phosphorus, potassium and sulfur, are there any other nutrients that are essential? Calcium is another but, due to the calcareous nature of our soils, you should never need to add it. In the trace minerals, copper is the only one that has demonstrated signs of deficiency. This can occur in wheat crops, on sandy or high organic soils. In those soils it is a good idea to include some copper when growing wheat.
There are many other trace minerals being touted by fertilizer companies as essential and necessary. Boron in canola is a common one. However, the only known case of boron deficiency in canola occurred in northern Saskatchewan. It was a confluence of weather conditions and soil conditions that caused it. If you are interested in some of these hyped fertilizer products, by all means try them. However, make sure you mark out where they’re applied and measure the results at harvest. Prove it to yourself.
The Canola Council conducted many, cross-prairies trials using a number of trace minerals and special fertilizers, along with the macro nutrients. The only fertilizer treatment that regularly brought more yield than the costs was using 20% more nitrogen than the check. Think about that next time you’re tempted with another “miracle” fertilizer product.
See below for some links to useful videos on fertilizer use.