Frequently Asked Phosphate Questions

What Happens to Phosphate Fertilizer?
Plant utilization of phosphate fertilizer is relatively inefficient. When banded into moist soil, phosphate fertilizer dissolves in soil water. However, it is quickly tied up, making it less plant available.

Most crops only recover 10 to 30% of applied phosphate fertilizer in the year of application. Over the long term, crops recover between 30 to 75% of the phosphate fertilizer applied. That is a long-term loss of at least 25%.

What is “Fixed” Phosphate?
Fixed phosphate is bound to soil particles or other elements in the soil. There are usually large amounts of fixed phosphate in soils, which is not available for plant growth.

What is “Soluble” Phosphate?
Soluble phosphate is phosphate that is dissolved in the soil solution (water) and is available for plant use. It is usually present in much lower levels than fixed phosphate.

Photo #1 Photo #2 Photo #3 The bonds that tie The base jar in photo #1 contains a calcium rich solution representing most prairie soils. When phosphate fertilizer is added (shown in photos 1 & 2), a precipitate forms from calcium binding with phosphate. The 3rd photo shows the bound phosphate after 24 hours. This is how phosphate fertilizer gets tied up in calcium rich soils making it unavailable for plant use.

Why do Plants Need Phosphate?
Phosphate is a major plant nutrient that plays an important role in:

• Root growth and development
• Crop maturity
• Yield
• Seed quality
• Tolerance to stress
• Improved nitrogen fixation in legumes

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