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Slow release fertilizer overview
Slow release fertilizer (Slow release fertilizer), also known as slow-acting fertilizer, long-acting fertilizer, refers to the slow release of effective nutrients due to changes in the chemical composition of the fertilizer or surface coated with semi-permeable or impermeable substances. After being applied to the soil, it takes a short period of time for the solution to dissolve due to the difference in the compound or physical state. It can lastingly provide the nutrient elements necessary for plant growth. It combines the "quick effect" of chemical fertilizers, the flatness and long-lasting characteristics of farmhouses, and can reduce the loss of showering, which is generally 30% to 70% higher than the utilization rate of chemical fertilizers.
For the understanding of slow-release fertilizer and controlled-release fertilizer, many experts at home and abroad think the two are the same. For example, the American Crop Nutrition Association defines slow-release fertilizer as: Fertilizer containing more nutrients than quick-acting fertilizer. And there is no strict difference between slow-release fertilizer and controlled-release fertilizer. In fact, the two are different. Slow-release fertilizer refers to fertilizer that releases slower nutrients than ordinary fertilizers, but the release rate, mode, and duration of nutrients cannot be controlled. Controlled-release fertilizers, on the other hand, refer to fertilizers whose release rate, manner and duration are known and can be controlled during the preparation process.
According to the release of bioactive substances, people divide the release of nutrients from slow-release fertilizers into four types: diffusion, chemical decomposition, expansion, and infiltration.
Slow release fertilizer type
The slow-release nitrogen fertilizer nitrogen fertilizer has the largest amount of application in container cultivation, and the loss rate after application is much higher than other elements, with an average of 30% to 50%. Therefore, the study of the type of slow-release fertilizer is particularly significant. Common are: urea formaldehyde (UF) 38-0-0 (nitrogen content is usually between 32% and 40%), isobutene diurea (IBDU) 30-0-0. Both belong to the general category of low water-soluble organic nitrogen compounds, but the former are biodegradable compounds and the latter are chemically decomposable compounds. Sustained-release phosphate fertilizer single calcium superphosphate (Ca) H 2PO4 (2) 0-20-0, containing 12% of phosphorus and 18% of calcium; three materials of superphosphate (Ca) H2PO4 (2) 0-46- 0, containing 12% calcium; sintered phosphorus 0-50-0, a raw material that releases very slowly phosphorus; magnesium ammonium phosphate (Mg NH 4PO4) 7-40-6, which is a low water-soluble inorganic compound .
At present, the most widely used seedling container cultivation is Osmocote, which is a typical coated compound fertilizer. The outer layer of chemical fertilizer particles has a semipermeable membrane. When the Aofei fertilizer is applied to the soil, the water in the soil can slowly penetrate the membrane, and the chemical components in the membrane absorb water and generate pressure. When the pressure increases to a certain extent, the film will be squeezed and the nutrients released to achieve the purpose of sustained release. For this reason, according to different kinds or different growth stages of the plant's demand for nutrients, the green manure with different coating thickness will be distributed in the same batch of products according to a certain proportion. Therefore, in a certain sense, the Austrian green manure is a kind of controlled-release fertilizer, but the soil temperature and moisture content will greatly affect its release rate.
Application method
At present, more and more nurseries begin to use large-scale slow-release fertilizers. In general, slow-release fertilizers are applied in the following ways:
First, slow-release fertilizers are administered by metering (ie, applying the slow-release fertilizer to the surface of the container growth substrate). This method is currently widely used, it is convenient and quick, it is very suitable for dry or wet environment, and can create a gradual penetration of nutrient transfer system for container seedlings. However, this method also has disadvantages: 1. Fertilizing labor costs a lot; 2. If the container is tilted or even tipped over by wind, or if a lot of irrigation and rainfall occur, the fertilizer will overflow from the container, resulting in loss; 3. When the container is placed in full light, the rate of decomposition of the table fertilization may increase.
Second, in the deployment of the growth matrix, the slow-release fertilizer is mixed with the matrix in a container, which has the advantage of greatly saving labor costs and avoiding the need for multiple applications like the application of slow-release fertilizers. However, for the selection and determination of the optimum slow-release fertilizer dosage, it is necessary for the nursery industry to conduct the test in a small range in practice and then to promote it. The best practice is to apply slow-release fertilizers as a direct addition, and then add some slow-release fertilizers as appropriate to the growth of the container seedlings.
In addition, people also found in the research of holly container cultivation that placing the green manure fertilizer (17-7-12) directly at the bottom of the sowing hole can promote plant growth and improve plant quality compared to direct fertilization. But in general, this method works well in warm climate conditions.
Application of slow-release fertilizer in container cultivation
As we all know, one of the main problems in the container cultivation of seedlings is how to solve the nutrient supply and achieve optimal growth. At the same time, with the expansion of the container cultivation production scale, the environmental problems caused by the application of fertilizers have become increasingly serious. Increasing the use of fertilizers and reducing fertilizer pollution have become issues of concern to the world. Slow-release fertilizer uses slow-release technology. Once applied, it can basically meet the nutrient requirements of the whole growth period of the plant. It not only saves labor, saves fertilizer, but also has high fertilizer utilization rate, and can greatly reduce environmental pollution and ecological damage. For this reason, the use of slow-release fertilizers in container cultivation is of great significance.