Posted by Jeremy Boychyn, Agronomy Research Extension Specialist
Phosphorus (P2O5) is a different beast compared to nitrogen and because of that, it should be managed differently. Long term is the key phrase for phosphorus planning. Too many times have I seen phosphorus plans that extend only one season long. A more balanced approach would be to plan three to four years (or greater) P2O5 removal in advance while accounting for the previous three to four years actual removal. This allows you to understand if the previous three to four years have put you in a P2O5 deficit or surplus. From here, you can better plan for phosphorus application in the coming years. Below is an example plan.
In this example, the last four years your yields averaged higher than expected and you removed an additional 16lbs of P2O5 above what you applied over those four years (132lbs P2O5). To account for that 16lb deficit of P2O5, you should look at your rotation on that field over the next four years and determine where to make up for this deficit. In other words, if you were planning to apply 132lbs P2O5 over the next four years, instead plant to apply 148lbs. Revisit this plan every year and you will always be working with a long-term phosphorus plan.