Analysis and determination of organic fertilizer components

Organic fertilizer: It mainly refers to fertilizers formed from various animals and plants after a period of fermentation and decomposition (this includes processed rapeseed cake, which has no unusual odor). Organic fertilizers contain large amounts of biological matter, plant and animal residues, excreta, and biological waste. Applying organic fertilizers not only provides crops with comprehensive nutrients but also offers long-lasting fertility benefits. They help increase and renew soil organic matter, promote the growth of microorganisms, and improve the physical and chemical properties as well as biological activity of the soil. They are thus a major source of nutrients for the production of green food. Compost is an organic fertilizer made by mixing various types of orange stalks, fallen leaves, grass, residues from plants and animals, as well as human and animal manure, with a small amount of soil. Ponded compost: The raw materials used for ponded compost are essentially the same as those for composting, but it is fermented under submerged conditions. Stable manure refers to the fertilizer made by composting the excreta of livestock and poultry such as pigs, cows, horses, sheep, chickens, and ducks, along with straw bedding. Biogas fertilizer is a by-product of the decomposition of organic matter in a sealed biogas digester to produce biogas, including biogas liquid and residues. Green manure: The use of cultivated or wild green plant bodies as fertilizer. Such as the legume species like mung beans, broad beans, shepherd’s purse, cowpeas, alfalfa, and vetch. Non-leguminous green manures include ryegrass, field radish, cockleburr, Azolla, water hyacinth, and duckweed. Crop straws are one of the important organic fertilizers; they contain essential nutrients for crops such as N, P, K, Ca, and S. Under suitable conditions, through the action of soil microorganisms, these elements are mineralized and returned to the soil for uptake by crops. Compostable cakes: rapeseed cake, cottonseed cake, soybean cake, sesame cake, castor seed cake, tea seed cake, etc. Clay fertilizer: Unpolluted river clay, pond clay, ditch clay, harbor clay, lake clay, etc. Now, with the continuous advancement of science and technology, through artificial pure culture techniques for beneficial microorganisms and scientific extraction methods, a variety of different types of bio-organic fertilizers can be produced. These fertilizers can improve soil quality, reduce environmental pollution, and enhance crop yield and efficiency. Bio-organic fertilizers will be the main trend in fertilizer use for agricultural production in the future.

The friend on the second floor didn’t read the question carefully; what the original poster was referring to wasn’t the types of organic fertilizers, but rather the testing of amino acids and humic acid in organic fertilizers. Let me explain the methods for analyzing amino acids; please feel free to point out any mistakes. Currently, the analysis and determination of amino acids are primarily carried out using instruments such as ion exchange chromatography (IC), high-performance liquid chromatography (HPLC), or gas chromatography (GC). The detectors used in these instruments include ultraviolet-visible spectroscopic absorption, fluorescence, chemiluminescence, and others. However, since the UV-Vis spectra of most amino acids exhibit very weak absorption and they lack fluorescence of their own, they cannot be detected directly. Derivatization is usually required to improve the sensitivity and selectivity of detection. Electrochemical methods are attracting increasing attention due to their simplicity, sensitivity, lack of radioactivity, and environmental friendliness.

Direct electrochemical analysis of amino acids: For amino acids with electrical activity such as cystine, cysteine, and tyrosine, direct electroanalytical methods are generally employed. The half-cysteine can be directly determined using cyclic voltammetry; in phosphate buffer solutions with a pH value of less than 7, an oxidation peak appears at 0.96 V on the gold electrode, while a reduction peak appears around -0.75 V. The peak currents of both the oxidation and reduction peaks are proportional to the concentration of cysteine. Studies have shown that it is possible to directly detect the concentrations of tryptophan and tyrosine without any derivatization steps. By placing a polyamide-modified carbon paste electrode in solutions of tryptophan and tyrosin, respectively, using 0.2 mol/L HCl–CH3COONa (pH=3.0) as the electrolyte, cyclic voltammetry scans were performed from 0.5 V to 1.50 V. Stable oxidation peaks appeared at 0.94 V for tryptophan and 0.92 V for tyrosine. As the number of scans increased, the peak currents for both compounds decreased. By employing 2nd-order differential techniques, the detection limits for tryptophan and tyrosine could be achieved at 0.024 mol/L and 0.034 mol/L, with relative standard deviations of 5.2% and 7%, respectively.

The humic acid in compound fertilizers refers mainly to active humic acid, which in turn includes fulvic acid, pectic acid, and yellow humic acid – all three of these acids are soluble in alkalis and ammonia. Common analytical methods for humic acid include gravimetric analysis, spectrophotometry, coulometric titration, and potassium dichromate volumetric method.

Currently, amino acids are mainly analyzed for their carbon content, from which the amount of amino acids can be determined

It seems that there are no **standards for organic fertilizers, as their components are not fixed like those of compound fertilizers, making them difficult to test. Organic fertilizers contain hundreds of different active ingredients, and many of these ingredients are still subject to debate....................

Humic acid is the residue of animals and plants. Humic acid is a natural organic substance used in the manufacture of, participation in, or improvement of fertilizers. It can produce organic fertilizers as well as organic-inorganic fertilizers. It can be used in the production of compound fertilizers or specialty fertilizers. It can improve chemical fertilizers through methods such as encapsulation, wrapping, and coating, and it can produce liquid fertilizers. It can be used as a carrier for microbial fertilizers. It can produce fertilizer twin products. For soil conditioners, regulators, amendments (including the improvement of saline-alkali soils), etc. This shows that humic acid is an essential and important member of the fertilizer family. Moreover, it has already played an important role in the adjustment of the fertilizer structure. In our country, humic acid has been used in fertilizer production for nearly forty years. But there is no unified standard for winning. It has severely restricted the healthy development of humic acid fertilizers. 2003. The Ministry of Agriculture has entrusted the **Fertilizer Quality Supervision, Inspection and Testing Center and the Guangdong Provincial Soil and Fertilizer Station with formulating standards for the determination of humic acid in fertilizers, giving hope that industry standards, which have remained unresolved for a long time, will finally be established. When establishing standards for the determination of fulvic acid, it is necessary to clarify in which fertilizers humic acid is present, and the standards should be formulated on this basis. The commonly used methods for analyzing humic acid nowadays include volumetric method, weight loss method, and acid extraction method.

Currently, the main methods for analyzing organic matter in fertilizers are the potassium dichromate titration method and the combustion method. Since many fertilizers decompose at high temperatures when measured using the combustion method, causing interference, the potassium dichromate titration method is generally used in various standards for determining organic matter. The main standards for testing organic matter in fertilizers are: Ministry of Agriculture of the People’s Republic of China NY525—2002 Standard for Organic Fertilizers ； Standard of the People’s Republic of China **GB 18877—2002: Standard for organic-inorganic compound fertilizers. For the determination of organic matter in both of these standards, the potassium dichromate titration method is used. The principle involves using a quantified solution of potassium dichromate and sulfuric acid to oxidize the organic carbon in organic fertilizers under heating conditions; any excess potassium dichromate is then determined using an iron sulfate solution, with a blank test also being conducted simultaneously. The organic carbon content is calculated based on the amount of oxidant consumed before and after oxidation, and this value is multiplied by the empirical constant of 1.724 to convert it into organic matter percentage. Both standards require that organic fertilizers must be those that have been decomposed and fermented, and the methods for testing organic matter are also the same ； The difference lies in the operational procedures and calculation formulas for organic matter testing under these two standards, which also results in differences in the test outcomes during actual analysis. It should be noted that organic fertilizers generally do not have specific requirements regarding the content or testing of humic acid and amino acids.........................

I have a question for the person upstairs: humic acid and amino acids are also important components that play a role in organic fertilizers. According to conventional testing methods, organic fertilizers and chemical fertilizers with similar effects have N, P, and K contents that are only half of those in chemical fertilizers; so how can I highlight the advantages of organic fertilizers? Is there any way to make the detection of humic acid and amino acids as clear and straightforward as that of N, P, and K?