Would acid or alkaline soil benefit from rock phosphate?

Question

Which type of soil would benefit more from the addition of rock phosphate: acidic or alkaline soil?

Is one type of soil usually lacking in nutrients that rock phosphate contains?

Or does the acidic soil react with the rock phosphate to create a soluble form of phosphor? (that plants can more easily absorb)

They're my two theories, I'd appreciate it if someone could give me a definitive answer.

Answer 1

Alkaline soils would tend to have high concentrations of Ca2+ and/or Mg2+ ions present.  The phosphates of these metals are fairly insoluble and so difficult for plants to absorb.

From another angle phosphate ions produce quite basic solutions and so would help neutralise unwanted acidity in the soil.

Answer 2

I believe you are on the right track.

Acidic soil (low soil pH) would benefit more from the addition of rock phosphate.  Studies have shown that crops can utilize phosphates (convert them from inorganic phosphates to organic phosphates) best at a pH of around 6.0 and lower.

The organic sulphates are nutrients required for plant growth that the plant cannot produce itself and therefore must absorb from the soil.  

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