We have brought many soil samples into the lab from our Vancouver area properties. We have never received a recommendation to add phosphorous to the soil, yet phosphorous is one of the big three in the NPK fertilizer formula: nitrogen, phosphorous, and potassium. Why do we have ample phosphorous in Vancouver?
Phosphorous breaks into water insoluble compounds in the soil. Typical chemical fertilizers require water to break down the fertilizer for the plant to feed from the nutrients. If the phosphorous is water insoluble, then the plants cannot feed off the chemical phosphorous, designed to be used with water.
This does not mean there is no phosphorous in the soil. This means the plants cannot take it up, and then show signs of phosphorous deficiency. The usual response? Add more phosphorous. Add to this Vancouver's excessive rainfall, and the result is soil high in phosphorous.
Organic forms of phosphorous are not bound in water-insoluble compounds, and plants can feed from them.
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