The so-called "release" refers to the process of nutrient transformation from chemical substances into effective form can be directly absorbed by the plants (such as dissolution, hydrolysis and degradation); "release" refers to the chemical nutrient release rate is far less than the instant of the fertilizer release rate of soil into plant available nutrients; controlled release "" refers to the regulatory mechanism of the nutrient release in accordance with the release mode set (release rate and release time) consistent with the crop nutrient absorption law. Therefore, under the action of organic nitrogen compounds in biological or chemical decomposition (such as urea formaldehyde fertilizer UFs) commonly known as slow-release fertilizer (SRFs), and the coated fertilizer is not sensitive to the biological and chemical factors are often called controlled-release fertilizer (CRFs).