Water-soluble fertilizers can be categorized into major-element water-soluble fertilizers, trace-element water-soluble fertilizers, humic acid-containing water-soluble fertilizers, amino acid-containing water-soluble fertilizers, and others. China's agricultural industry standards establish clear requirements regarding the quality of these fertilizers.
**Major-Element Water-Soluble Fertilizers**
These are liquid or solid water-soluble fertilizers primarily composed of the major elements—nitrogen (N), phosphorus (P), and potassium (K)—and supplemented, in proportions suitable for plant growth, with trace elements (copper, iron, manganese, zinc, boron, and molybdenum) or secondary elements (calcium and magnesium). The product standard is NY 1107-2010. This standard stipulates that for solid products, the content of major elements must be ≥ 50%, and the content of trace elements must range from ≥ 0.2% to 3.0%; for liquid products, the content of major elements must be ≥ 500 g/L, and the content of trace elements must range from ≥ 2 g/L to 30 g/L.
**Secondary-Element Water-Soluble Fertilizers**
These are liquid or solid water-soluble fertilizers composed of the secondary elements—calcium (Ca) and magnesium (Mg)—in proportions suitable for plant growth, optionally supplemented with appropriate amounts of trace elements (copper, iron, manganese, zinc, boron, and molybdenum). The product standard is NY 2266-2012. The technical specifications for these products are as follows: for liquid products, Ca ≥ 100 g/L, or Mg ≥ 100 g/L, or Ca + Mg ≥ 100 g/L; for solid products, Ca ≥ 10.0%, or Mg ≥ 10.0%, or Ca + Mg ≥ 10.0%.
**Trace-Element Water-Soluble Fertilizers**
These are liquid or solid water-soluble fertilizers composed of trace elements—copper, iron, manganese, zinc, boron, and molybdenum—in proportions suitable for plant growth. The product standard is NY 1428-2010. This standard stipulates that for solid products, the content of trace elements must be ≥ 10%; for liquid products, the content of trace elements must be ≥ 100 g/L.
**Amino Acid-Containing Water-Soluble Fertilizers**
These are liquid or solid water-soluble fertilizers based primarily on free amino acids, supplemented—in proportions suitable for plant growth—with trace elements (copper, iron, manganese, zinc, boron, and molybdenum) or secondary elements (calcium and magnesium). These products are classified into two types: the trace-element type and the calcium-element type. The applicable product standard is NY1429-2010. For amino acid-containing water-soluble fertilizers of the trace element type, the free amino acid content must be no less than 10% for solid products and 100 g/L for liquid products; furthermore, the total content of at least two specific trace elements must be no less than 2.0% for solid products and 20 g/L for liquid products. Amino acid-containing water-soluble fertilizers of the calcium type are also available in both solid and liquid forms; while all other specifications remain identical to the trace element type, the calcium content specifically must be no less than 3.0% for solid products and 30 g/L for liquid products.
**Humic Acid-Containing Water-Soluble Fertilizers**
Humic acid-containing water-soluble fertilizers are a class of water-soluble fertilizers that incorporate humic substances. These fertilizers—produced in either liquid or solid form—are formulated by combining humic acid (in proportions optimized for plant growth) with appropriate amounts of macronutrients (nitrogen, phosphorus, and potassium) or trace elements (copper, iron, manganese, zinc, boron, and molybdenum). Humic acids are a group of natural high-molecular-weight organic compounds formed through the microbial decomposition and geochemical transformation of organic matter, such as plant and animal residues. Typically extracted from peat, lignite, or weathered coal, these substances serve to stimulate plant growth, improve soil structure and fertility, and enhance both nutrient availability and crop resistance to environmental stress. The applicable product standard is the Agricultural Industry Standard NY1106—2010. This standard stipulates that, for macronutrient-type solid products, the humic acid content must be no less than 3%, while the total macronutrient content must be no less than 20%; for macronutrient-type liquid products, the humic acid content must be no less than 30 g/L, and the total macronutrient content no less than 200 g/L; finally, for trace element-type solid products containing humic acid, the humic acid content must be no less than 3%, and the total trace element content no less than 6%.
**Other Water-Soluble Fertilizers**
This category encompasses other water-soluble fertilizers that possess fertilizing efficacy but fall outside the scope of the five specific types listed above; these products are governed by their respective enterprise standards. This category predominantly consists of organic water-soluble fertilizers, including varieties formulated using extracts such as alginic acid, chitin, or chito-oligosaccharides as their core raw materials.
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