In a broad sense, slow-release fertilizer refers to a fertilizer with a slow release rate of fertilizer nutrients, a long release period, and a crop growth requirement throughout the growing season of the crop. However, in the narrow sense, there are different definitions for slow release fertilizer and controlled release fertilizer. Slow-release fertilizers (SRFs), also known as long-acting fertilizers, mainly refer to fertilizers that are converted to effective nutrients in plants after being applied to the soil at a slower rate than ordinary fertilizers.

The release rate, mode and duration are not well controlled and are greatly affected by the fertilization method and environmental conditions. The advanced form of slow release fertilizer is controlled release fertilizer (CAFS), which means that the release mode of fertilizer in the crop growing season is pre-set through various mechanism measures, so that the nutrient release law is basically synchronized with the crop nutrient absorption, thereby achieving the purpose of improving fertilizer efficiency. a type of fertilizer.

Slow-release fertilizer is a commonly used fertilizer, but due to the complexity of the market, there are often many counterfeit products mixed in, how to distinguish between true and false fertilizers? Here is a brief introduction to the method of slow-release fertilizer. .

Slow and controlled release fertilizer true and false identification method

Broadly speaking, controlled release fertilizer refers to a fertilizer with a slow release rate of fertilizer nutrients, a long release period, and a crop growth requirement throughout the growing season of the crop. The advantage of this fertilizer is that it can be fertilized once without using top dressing, which can greatly save manpower input and reduce the amount of fertilizer used, which has great ecological benefits. In the process of purchasing, how should farmers identify true and false controlled release fertilizer? Zhang Min, a professor at the College of Resources and Environment of Shandong Agricultural University, suggested that the controlled release fertilizer can be identified from several aspects.

Slow-release fertilizers generally control the release rate of nutrients through the bread film outside the fertilizer granules, thereby achieving the purpose of slowing the release rate of nutrients. Therefore, the outer membrane of the controlled release fertilizer is often colored. At present, most of the slow-release fertilizers sold in the market are blended with common fertilizers, so that nutrients are provided by ordinary fertilizers in the early stage of crop growth, and nutrients are mainly provided by slow-release fertilizers in the middle and late growth stages.

Zhang Min therefore suggested that after opening the package of slow-release fertilizer, 100 capsules of fertilizer can be taken at random, and the number of colored fertilizers can be counted. If the number of particles with color exceeds 15, the content of controlled release fertilizer reaches 15%. , is a qualified product. If it does not reach, it will not be qualified.

In view of the fact that there are bad manufacturers who use the ordinary fertilizer to deliberately dye and prematurely control the fertilization, Zhang Min suggested that the fertilizer can be put into the water to soak, usually the dye will fade in the water, and the qualified slow-release fertilizer coating will not fade. .

"Different crops have different growth periods and fertilizer requirements, and the development direction of slow-release fertilizers is specialization. For the slow-release fertilizers of corn, cotton, rice and other crops, the release cycle is two or three months." Say.

In order to further identify the quality of slow-release fertilizer, Zhang Min suggested that you can cook slow-release fertilizer in boiling water. If the release cycle is controlled release fertilizer in two or three months, it will be released within half an hour, indicating that the quality of the controlled release is normal; if only a part is released, the quality can be.

"If time permits, you can also put the slow-release fertilizer in the cold water for a week or two to see the release. If the release cycle is delayed release fertilizer in two months, release about 1/4 in half a month, it is qualified. Product." Zhang Min said.

When farmers purchase slow-release fertilizers, they must ask for the corresponding purchase vouchers in addition to purchasing and selecting the products of large enterprises in regular stores.

At present, the area of ​​summer corn with slow and controlled release fertilizer for seed fertilization is increasing. Many farmers believe that if there is more rainfall in July and August, it will lead to early release of controlled release fertilizer and loss of sustained release. Zhang Min said that this is also a misunderstanding. He said that a large number of experiments have shown that the release rate of nutrients after the capsule is almost the same, whether it is in soil with moderate water content or soil with excessive moisture.

It rains more, and the reason why it affects fertilizer efficiency is that the nutrients have not been absorbed by the crops, and they flow with the water, or they are infiltrated into the ground. "The two main factors affecting the release of nutrients from slow-release fertilizers are temperature and moisture. In corn fields, as long as the soil is not particularly dry, it will not affect the release rate.

Recommended reading: the difference between controlled release fertilizer and controlled release fertilizer

The difference between slow release fertilizer and controlled release fertilizer

concept

Slow release fertilizers are new types of fertilizers that delay or control the rate of nutrient release. Compared with quick-acting fertilizer, there are some advantages:

1. The solubility in water is small, the release of nutrients in the soil is slow, and the loss of nutrients is reduced.

2. The fertilizer effect is long-term and stable, and the energy source continuously supplies the demand for nutrients of the plant throughout the production period.

3. Due to the slow release of fertilizer, a large amount of application will not cause the soil salt to be too high and "burn seedlings".

4. Reduce the number and frequency of fertilization and save costs.

Slow release fertilizers in a broad sense include two types of slow release fertilizers and controlled release fertilizers.

Characteristics

Slow release fertilizer: The release rate of nutrients in fertilizers is slowed by chemical and biological factors. Mainly slow-acting nitrogen fertilizer, also known as long-acting nitrogen fertilizer, generally has little solubility in water. After being applied to the soil, under the influence of chemical and biological factors, the fertilizer gradually decomposes and the nitrogen is slowly released to meet the nitrogen demand of the crop throughout the growing season.

Controlled Release Fertilizer: The water-soluble fertilizer is wrapped in the membrane by means of the outer coating to release the nutrients slowly. When the coated fertilizer granules are in contact with the moist soil, the moisture in the soil penetrates into the interior through the envelope, so that part of the fertilizer is dissolved.

This part of the water-soluble nutrient is slowly diffused outward through the micropores on the envelope.

The rate at which the fertilizer is released depends on the temperature of the soil and the thickness of the membrane. The higher the temperature, the faster the rate of dissolution of the fertilizer and the speed across the membrane; the thinner the membrane, the faster the penetration.

According to different film-forming substances, it is divided into non-organic coated fertilizer, organic polymer coated fertilizer and thermal resin coated fertilizer. Among them, organic polymer coated fertilizer is the most studied and controlled release fertilizer.

Slow release fertilizers and controlled release fertilizers are fertilizers that have longer fertilizer efficiency than quick-acting fertilizers. In this sense, there is no strict distinction between slow release fertilizers and controlled release fertilizers. However, from the mechanism and effect of controlling the rate of nutrient release, slow release fertilizer and controlled release fertilizer are different.

Slow release fertilizer is affected by many external factors such as soil pH, microbial activity, soil moisture content, soil type and irrigation water volume during release. Fertilizer release is uneven, nutrient release rate and crop nutrient demand are not necessarily completely synchronized; Most of them are single fertilizers, mainly nitrogen fertilizer.

The controlled release fertilizer is mostly NPK compound fertilizer or total nutrient fertilizer supplemented with trace elements. After being applied to the soil, its release rate is only affected by soil temperature. However, soil temperature has a great influence on the growth rate of plants. In a relatively large temperature range, the soil temperature increases, the release rate of controlled release fertilizers accelerates, and the growth rate of plants increases, and the demand for fertilizers also increases.

Therefore, the rate of release of nutrients by controlled release fertilizers is in line with the rate of demand for nutrients by plants, thus meeting the nutrient requirements of crops at different stages of growth.

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