Principle of Starter Fertilizer Fermentation

Introduction

• Composting, an ancient and simple method of processing organic waste and making fertilizers, has attracted much attention in various countries with the deepening of research and improvement of methods, because it has good ecological significance and also brings great benefits to agricultural production.
• To benefit. There are many reports that using well-rotted compost to prepare seed beds can suppress soil-borne diseases. And the antagonistic bacteria that follow after the high temperature stage of the composting process can make the bacterial count reach a very high level; during the composting process, under the action of microorganisms, each organic matter reaches a state that is difficult to decompose, stable, and easy for crops to absorb; at the same time, the action of microorganisms Reduce the toxic effects of heavy metals within a certain range.
• It can be seen that composting is a simple and effective method of making bio-starter fertilizer, which is beneficial to the development of ecological agriculture.
  

  Most starter fertilizer products in my country only compost and ferment for 15-20 days. Such products can only meet harmless standards. The compost fermentation process of high-quality starter fertilizer generally takes 45-60 days.

  
  
• This is because harmful microorganisms such as plant pathogenic bacteria, insect eggs, and weed seeds will be killed during the warming and high-temperature stages in the early stages of composting. However, the main role of microorganisms in this process is metabolism and reproduction, and only a small amount of microorganisms are produced. metabolites, and these metabolites are unstable and difficult to be absorbed by plants.
• In the later cooling period, microorganisms will humify organic matter and produce a large number of metabolites that are beneficial to plant growth and absorption in the process. This process takes 45-60 days. Composting through this process can achieve three purposes: first, harmlessness; second, humification; third, a large number of microbial metabolites such as various antibiotics, protein substances, etc.

1. Transformation of organic matter during composting

The organic matter in compost undergoes complex transformation under the action of microorganisms. This transformation can be summarized into two processes: one is the mineralization process of organic matter, which decomposes complex organic matter into simple substances, and finally generates carbon dioxide, water and mineral nutrients. etc.; the other is the humification process of organic matter, that is, organic matter is decomposed and then synthesized to generate more complex special organic matter – humus. The two processes are carried out at the same time, but in opposite directions. Under different conditions, there are obvious differences in the intensity of each process.

2. mineralization of organic matter

• Decomposition of nitrogen-free organic matter Polysaccharide compounds (starch, cellulose, hemicellulose) are first hydrolyzed into simple sugars under the action of hydrolases secreted by microorganisms. Glucose decomposes rapidly under well-ventilated conditions, and intermediate products such as alcohol, acetic acid, and oxalic acid are not easy to accumulate, eventually forming CO2 and H2O, while releasing a large amount of heat energy.
• If ventilation is poor, monosaccharides will be decomposed slowly under the action of anaerobic microorganisms, producing less heat and accumulating some intermediate products – organic acids. Under extremely anaerobic microbial conditions, reduced substances such as CH4 and H2 will also be generated.
• Decomposition of nitrogen-containing organic matter Nitrogen-containing organic matter in compost includes protein, amino acids, alkaloids, humus, etc. Except for humus, most of it is easily decomposed.
• For example, proteins are degraded step by step under the action of proteases secreted by microorganisms to produce various amino acids, and then undergo ammonification and nitrification to form ammonium salts and nitrates respectively, which can be absorbed and utilized by plants.
• Conversion of phosphorus-containing organic compounds. The phosphorus-containing organic compounds in compost, under the action of a variety of saprophytic microorganisms, form phosphoric acid, which becomes a nutrient that plants can absorb and utilize.
• Conversion of sulfur-containing organic matter. The sulfur-containing organic matter in compost generates hydrogen sulfide through the action of microorganisms. Hydrogen sulfide easily accumulates in anaerobic environments and is toxic to plants and microorganisms. However, under good ventilation conditions, hydrogen sulfide is oxidized into sulfuric acid under the action of sulfur bacteria, and interacts with the salt base in the compost to form sulfate, which not only eliminates the poison of hydrogen sulfide, but also becomes sulfur nutrients that plants can absorb.
• In the case of poor ventilation, desulfurization occurs, causing sulfuric acid to be converted into H2S and lost, which is toxic to plants. During the compost fermentation process, regular turning measures can be used to improve the aeration of the compost and eliminate the desulfurization effect.
• Conversion of lipids and aromatic organic matter. Tannins, resins, etc. have complex structures and slow decomposition, and their final products are also CO2 and water; lignin is a particularly stable organic compound in compost containing plant raw materials (such as bark, sawdust, etc.) The compound has a complex structure, contains an aromatic core, and exists in a polymeric form in plant tissues, making it extremely difficult to decompose.
• Under well-ventilated conditions, it is slowly decomposed mainly through the action of fungi and actinomycetes, and its aromatic core can be converted into quinone compounds, which are one of the raw materials for the resynthesis of humus. Of course, these substances will continue to be decomposed under certain conditions.

3. humification process of organic matter

• There are many opinions on the formation process of humus, which can be roughly divided into two stages: In the first stage, organic residues decompose to form the original materials that make up humus molecules, such as polyphenols, nitrogen-containing organic matter.
• In the second stage, the polyphenol oxidase secreted by microorganisms first oxidizes polyphenols into quinones, and then the quinones condense with amino acids or peptides to form humic monomers. Since there are many types of phenols, quinones and amino acids, and the ways of condensation with each other are also different, the humus monomers formed are also diverse. Under different conditions, these monomers further condense to form molecules of varying sizes.

4. Transformation of heavy metals during composting

• Urban sludge is rich in various nutrients and organic matter required for crop growth, and is one of the best raw materials for compost fermentation. However, urban sludge often contains heavy metals, which generally refer to mercury, chromium, cadmium, lead, arsenic, etc. Microorganisms, especially bacteria and fungi, play an important role in the biological transformation of heavy metals.
• Although some microorganisms can change the presence of heavy metals in the environment, increase the toxicity of chemicals and cause serious environmental problems, or concentrate heavy metals and accumulate them through the food chain. However, there are also some microorganisms that can remove heavy metals from the environment through direct and indirect effects, helping to improve the environment.
• For example, mercury, the heavy metal that caused environmental pollution that attracted the earliest attention, microbial transformation of mercury includes three aspects: methylation of inorganic mercury (Hg2+), reduction of inorganic mercury (Hg2+) to Hg0, and cracking and decomposition of methylmercury and other organic mercury compounds. Reduced to Hg0. These microorganisms that can convert inorganic and organic mercury into elemental mercury are called mercury-resistant microorganisms.
• Although microorganisms cannot degrade heavy metals, they can reduce toxicity by converting heavy metals and controlling their transformation pathways.

5. Compost fermentation process

• Composting is actually a form of waste stabilization, but it requires special humidity, aeration and microorganisms to produce the right temperature. It is generally believed that this temperature should be higher than 45°C. Maintaining this high temperature can inactivate pathogenic bacteria and kill weed seeds. The organic matter remaining after proper composting has a low decomposition rate, is relatively stable, and is easily absorbed by plants. The odor can be greatly reduced after composting.
• Many different types of microorganisms are involved in the composting process. Due to changes in raw materials and conditions, the numbers of various microorganisms are constantly changing, so no one microorganism always dominates the composting process. Each environment has its own specific microbial flora, and the diversity of microorganisms allows compost to avoid system collapse even when external conditions change.
• The composting process mainly relies on the action of microorganisms, which are the main body of compost fermentation. The microorganisms involved in composting come from two sources: one is the large number of original microorganisms in the organic waste; the other is the artificially added microbial inoculants. These strains have strong ability to decompose certain organic wastes under certain conditions.
• They have the characteristics of strong activity, fast reproduction, and rapid decomposition of organic matter. They can accelerate the process of composting reaction and shorten the time of composting reaction.