GB/T 33804-2025 in English

The standard divides fertilizer-grade potassium humate into three types. The core differences are reflected in:

• Type I products: require soluble humic acid ≥60%, K₂O ≥12%, organic matter ≥70%, suitable for high-end economic crops
• Type II products: soluble humic acid ≥50%, K₂O ≥10%, organic matter ≥60%, meet the needs of field crops
• Type III products: The basic indicators are soluble humic acid ≥40%, K₂O ≥8%, suitable for soil improvement purposes

The newly added requirement of sodium content ≤2.0% (uniformly applicable to all types) can effectively prevent the risk of soil salinization.

Optimization of key testing items

1. Soluble humic acid: adopt HG/T 3278 acid precipitation method, and cancel the original Appendix A method
2. Potassium content determination: uniformly use GB/T 17767.3 tetraphenylborate potassium weight method
3. Toxic and harmful substances: strictly implement the limit requirements of GB38400-2019

The newly added particle size determination (GB/T 24891) provides a basis for quality control for granular products.

Precautions for manufacturers

• The product label must indicate the type (Type I/II/III) and the corresponding index value
• The error of the net content in packaging must be controlled within ±1%
• At least 1kg of sample should be retained for each batch of products

Agricultural application guidance

Classification according to the new standard:

• Type I: Recommended for facility agriculture and high-value economic crops
• Type II: Suitable for use as base fertilizer for field crops
• Type III: Mainly used for soil remediation projects such as saline-alkali land improvement