Buyers must prioritize the P2O5 (Phosphorus Pentoxide) concentration, typically ranging from 10% to 60% depending on the formulation (e.g., Ammonium Polyphosphate or Phosphoric Acid). It is crucial to verify the pH levels (usually 6.0-7.0 for foliar application) and solubility rates to ensure the product does not clog irrigation systems. Additionally, check for heavy metal content (Cadmium, Lead, Arsenic) to ensure they fall below the maximum allowable limits set by international agricultural standards.