Why is the treatment of phosphate rock with nitric acid important in the manufacture of fertilisers?

The treatment of phosphate rock with nitric acid is important because it converts insoluble phosphate into soluble forms, such as calcium nitrate, which plants can absorb. This process increases the availability of phosphorus, a key nutrient for plant growth.

A strong answer should directly address the approved learning objective to describe treatment of phosphate rock with nitric acid to produce soluble salts for fertilisers. (Chemistry only). This question belongs to Production and uses of NPK fertilisers within The Haber process and the use of NPK fertilisers, so the response should use that exact curriculum context rather than a generic statement. The answer is correct when it names the key idea, explains the link to chemistry only, and keeps the wording specific to AQA GCSE revision.