Popularization of Science on Slow and Controlled Release Fertilizer

Slow and controlled release fertilizer is the general term of a kind of fertilizer with property of delaying the release of nutrient, namely the slow release fertilizer (SRF) and controlled release fertilizer (CRF) conceptually.

Slow release fertilizer refers to the fertilizer (GB／T23348-2009) that can slowly release the effective nutrient for crops by fertilizer’s chemical compounding action or physical process. Its release rate of nutrient is far below the rate of normal release in soil, so that the nutrient can be transformed effectively slowly. By means of technical measures, this kind of fertilizer limits the release process of nutrient, so as to make the release rate of the nutrient of chemical form much lower than that of natural release. However, the release process is uncontrollable and is affected by fertilizer character and environmental conditions. The fertilizer mainly refers to combined urea formaldehyde and inorganic coating fertilizer.

Controlled release fertilizer is the fertilizer that makes its nutrient release consistent with fertilizer requirement law of crops by the way of setting in advance the fertilizer release mode (release time and rate) In the growing season of crops through various adjustment mechanisms. The intension is to enable the release rate of nutrient in chemical form through processing and control to meet the given release mode, which can correspond with the law of the nutrient absorption of certain plants. The fertilizer mainly means the polymer coated fertilizer.

At present, the fertilizer coating and reaction by urea and organic matters are the two main ways to develop slow and controlled release fertilizer, including polymer coating fertilizer, sulphur coating fertilizer, ground phosphate rock coating fertilizer, urea formaldehyde and IBDU. In practical use, the polymer coating fertilizer with excellent performance on controlled release is often called controlled release fertilizer, and that with poor effect on controlled release is named slow release fertilizer.

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