Organic fertilizer refers to fertilizers formed from animal and plant residues, excrement, organic waste, etc. through natural fermentation or artificial treatment. Its core feature is the abundance of organic matter and various nutrients, which can improve soil structure, enhance soil fertility, and promote material cycling in the ecosystem. 1、 Types of organic fertilizers 1 Farm manure 1) Composting materials: straw, fallen leaves, animal and plant residues, human and animal manure, etc. Characteristics: Through aerobic fermentation and maturation, it is rich in organic acids, peptides, nitrogen, phosphorus, potassium and other elements, which can comprehensively supplement soil organic matter. Function: Improve soil particle structure, enhance water and fertilizer retention ability, and promote microbial reproduction. 2) Raw materials for composting: Similar to composting, but requires fermentation under flooded conditions. Characteristics: Long fermentation cycle, slow nutrient release, suitable for rainy areas in the south. Function: Improve sticky and heavy soil, reduce nutrient loss. 3) Raw materials for manure: mixing livestock manure and straw bedding for composting. Characteristics: Rich in organic matter and trace elements, long-lasting fertilizer effect. Function: Improve soil microbial activity, especially suitable for planting fruit trees and vegetables. 4) Source of biogas fertilizer: residue and liquid after fermentation in biogas digesters. Characteristics: Contains biogas slurry and sludge, rich in humic acid and amino acids. Function: It can be used as a base fertilizer or foliar fertilizer to promote crop growth and reduce diseases.

2. Definition of green manure: Fertilizer that is produced by planting leguminous or non leguminous plants and then plowing them into the soil. Function: Biological nitrogen fixation: Leguminous green manure can fix nitrogen in the air and reduce the use of chemical fertilizers. Improving soil: root exudates and residues decompose to increase soil organic matter and alleviate continuous cropping obstacles. 3. Raw materials for commercial organic fertilizers: weathered coal, peat, animal manure, etc., undergo high-temperature fermentation and deodorization treatment. Beneficial bacterial species such as Bacillus subtilis and amyloliquefaciens are also added to bio organic fertilizers. Features: Odorless, harmless, easy to use.

Function: Quickly replenish soil organic matter, suitable for large-scale planting; Beneficial bacteria inhibit the reproduction of pathogenic bacteria and reduce soil borne diseases. 4. Other organic fertilizers: 1) Crop straw raw materials: corn, wheat, rice and other straw. Function: Directly returning farmland can increase soil carbon sources, and it needs to be combined with nitrogen fertilizer to accelerate decomposition. 2) Cake and fertilizer ingredients: by-products of oil extraction such as rapeseed cake and soybean cake. Features: Rich in protein and oil, it needs to be decomposed before use. Function: Provides slow-release nitrogen, suitable for fertilizing fruit trees and flowers. 3) Raw materials for mud fertilizer: unpolluted sediments such as river mud and pond mud. Function: Supplement trace elements and improve soil viscosity.

2、 The core role of organic fertilizers

1. Provide comprehensive nutrients

Organic fertilizers contain various nutrients required for crop growth and development, such as nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and trace elements, which play an important role in balancing soil nutrients. In addition, the utilization rate of organic fertilizers is high. Taking straw returning as an example, 50% to 90% of potassium can be utilized by crops.

Organic fertilizers are rich in organic substances, including proteins, amino acids, enzymes, peptides, amides, alkaloids, and certain vitamins, auxin pigments, as well as urea, uric acid, and hippuric acid from animal excrement, and humic acid, fulvic acid, and humin from decomposed organic fertilizers.

The phosphorus containing organic compounds in organic fertilizers mainly include nucleoprotein, phospholipids, phytochemicals, adenosine phosphate, nucleic acids, and their degradation products. In addition, nutrients such as sulfur, calcium, magnesium, and trace elements are continuously released with the decomposition of organic fertilizers, becoming effective nutrients.

The nitrogen-containing compounds in organic fertilizers include water-soluble carbohydrates, starch, cellulose, hemicellulose, lignin, fatty resins, tannins, as well as organic acids, alcohols, aldehydes, and phenols. Among them, soluble sugars, phenols, organic acids, etc. are easily absorbed and utilized by crops. The remaining components can be degraded by microorganisms to produce carbon dioxide and water, providing carbon nutrients for crops.

2. Improve soil physical and chemical properties

1) Increase and update soil organic matter

According to statistics, in the soil of cultivated land in southern China, soil organic matter converted from organic fertilizers accounts for about 2/3 of the annual generation of soil organic matter. Organic fertilizers can increase soil organic carbon and regulate the C/N ratio. Organic fertilizers such as manure, straw, compost, and stubble can accumulate more soil organic matter when applied to the soil, while green manure, especially leguminous green manure, often plays a good role in supplying nutrients and renewing soil organic matter.

2) Increase soil humus

After organic fertilizer is applied to the soil, it is decomposed and condensed by microorganisms to form new humus, which is an important material basis for the formation of aggregate structure. It has strong composite ability with soil particles and can increase the degree of organic-inorganic composites. After the application of organic fertilizer, due to the presence of more oxygen-containing functional groups in humus colloids, the exchange with cations is increased.

3) Adjust soil acidity and alkalinity

Applying organic fertilizer can also regulate soil acidity and alkalinity. Applying organic fertilizer in acidic soil can neutralize acidity, while in alkaline soil, it can buffer salt.

3. Promote ecological cycle

Organic fertilizers can provide energy and nutrients for soil microorganisms, promoting their reproduction. Organic fertilizers contain a large amount of enzymes, which can enhance soil enzyme activity and improve the level of effective soil fertility. Organic fertilizer can also reduce pollution, replacing chemical fertilizers can reduce the risk of nitrate pollution in groundwater, and returning straw to the field can reduce incineration pollution.

4. Stimulate crop growth

Some types of organic fertilizers, such as humic acid fertilizers, can promote crop metabolism. Spraying eggplant fruit crops with sodium humate leaves can increase the sugar content of the fruit; Used to soak branches and promote rooting of cuttings. In addition, the rational use of organic fertilizers can eliminate the pollution of soil, water sources, and air caused by excrement from centralized livestock and poultry farming; Eliminate or reduce the toxicity of pesticides and heavy metals to crops.