Phosphorus, Know Your Level

Posted over 4 years ago

Phosphorus (P) nutrient needs should be based on your soil analysis and the nutrient needs of your particular crop.


  • Apply phosphorus and potassium based on soil health needs identified by a soil sample analysis
  • Reduce runoff, which minimizes both phosphorus loss and environmental risk
  • Do not make broadcast surface applications on frozen ground
  • Restrict application to ideal conditions, ahead of planting or during crop growth

Phosphorus nutrient levels, unlike nitrogen, typically remain in the soil over much longer periods of time. The challenges with managing phosphorus nutrients are the long-term maintenance, build-up and cool down phases. Application of phosphorus can be done using a wide variety of sources and equipment, but timing should be based on plant growth stage needs. For instance if you’re applying pre-plant or when plants are small, starter fertilizers would be your ideal phosphorus application source, but for developed plants top-dressing would be most practical method.

When soil testing reveals that phosphorus levels exceed the nutrient response build-up threshold, you should not apply any more phosphorus. Applying additional phosphorus past the crop maintenance plateau level will not display additional crop response from those increased phosphorus nutrient levels and as a result, you could potentially be wasting valuable nutrient resources.1