Possible Clues:

• Compound made from hot sap
• I appreciate that is found in luxury fertiliser
• Prize tree getting this fertiliser
• Salt used in fertilisers — hot spa (anag)
• Chemical compound used as fertiliser
• Salt container has broken
• Fertilizer container, for example, hot
• A more common term for potassium carbonate
• Fertiliser deriving from potassium
• Another name for potassium carbonate