1. Sources and classification of humic acid (Some following parts are called HA.)
Humic acid is generally considered to be a complex mixture of hydroxybenzene carboxylic acids with non-uniform molecular weight. Lignite, peat and leonardite have high HA content and are the main sources of HA extraction. The extraction rate of HA was highest in leonardite, followed by lignite and peat.
According to the traditional method of soil science, humic acid can be divided into HA, fulvic acid and humin. HA is also divided into 3 categories: do not dissolve in alkaline solution, can dissolve in acidic solution called black HA; Only dissolved in alkaline solution, can not be dissolved in acidic solution is called brown HA; can be dissolved in both alkaline and acidic solutions called Fulvic acid.
2. Characteristics of humic acid
Humic acid is a kind of high molecular organic acid which is composed of aromatic group and many functional groups. It has good physiological activity, absorption, complexation, exchange and other functions.
- (1)Promote the formation of soil aggregates, enhance soil permeability, enhance soil water and fertilizer retention ability;
- (2)Stimulate the growth of plants, enhance their ability to resist drought, cold, diseases and pests;
- (3)Improve the quality of agricultural products;
- (4)Stimulate the activities of soil microorganisms,improve the sufficient carbon and nitrogen elements, improve the living environment of microorganisms, and increase the number of soil beneficial microorganisms and soil enzyme activity.
3、Classification of humic acid fertilizers
According to different techniques, HA fertilizers are generally divided into the following categories:
- — Humate (potassium, sodium, calcium, magnesium, ammonium, boron, etc.)
- — HA derivatives (nitro HA, nitro humate, HA complex, etc.)
- — HA- resin copolymer (HA super absorbent resin, HA soil improver)
- — Fulvic acid fertilizers (fulvic acid drought resistance agent, fulvic acid nutrient liquid fertilizer, fulvic acid granular compound fertilizer)
- –Controlled release HA single fertilizer (controlled release HA urea, controlled release HA phosphate fertilizer)
- — HA organic and inorganic compound fertilizer (various special fertilizers)According to different application modes, HA fertilizers can be divided into the following categories:
- — Fertilizer for seed dipping and root dipping (sodium humate, potassium humate, fulvic acid anti drought agent)
- — Foliar spraying or root flushing fertilization (sodium humate, potassium humate, fulvic acid drought resistance agent, fulvic acid nutrient liquid fertilizer, HA liquid fertilizer)
- — Field base fertilizer or topdressing fertilizer (humate, HA derivative, controlled release HA single fertilizer, HA organic and inorganic compound fertilizer, HA biological fertilizer)
- — Soil improvement fertilizer (humic acid super absorbent resin, humic acid soil conditioner)