Secondary and Micro Elements中微量元素
Secondary elements are calcium, magnesium and sulphur — required in smaller amounts than nitrogen, phosphorus and potassium but in larger amounts than micro elements. Micro elements are copper, iron, manganese, zinc, boron and molybdenum: needed in very small quantities but indispensable. Both are generally present in fertilizers as additions and must be declared separately from the primary nutrients.
Key points
- Under GB 18382-2021, secondary elements below 2% and micro elements below 0.02% must not be declared on the package.
- Under GB/T 15063-2020, in compound fertilizers a single secondary element must reach at least 1.0% for available calcium, 1.0% for available magnesium and 2.0% for total sulphur; a single micro element must reach 0.02%, with molybdenum capped at 0.5%.
- Micro elements interact antagonistically: an excess of one can suppress uptake of another, so stacking every element into one product is not automatically better.
- Deficiency diagnosis should combine soil testing with plant symptoms; judging from leaf appearance alone is easily confused with disease or phytotoxicity.
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- Category：Fertilizer classification
- Definition basis：GB/T 15063-2020 Compound fertilizers
Updated：Oct 19, 2026