Selecting the optimal fertilizer requires a deep dive into nutrient composition (NPK ratios) and solubility. For high-value crops, prioritize water-soluble flakes that ensure rapid absorption. You must verify the purity levels to prevent soil toxicity; high-quality shiny flakes should have a low heavy metal content (Lead, Arsenic, Cadmium) compliant with international standards like ISO 19830. Additionally, consider the release profile—whether you need immediate nutrient availability or controlled-release technology to reduce leaching and improve long-term soil health.