General Calcium Standards to be Revised

Recently, the reporter learned from the National Chemical Fertilizer Quality Supervision and Inspection Center (Shanghai) that the National Standard for Superphosphate, which was promulgated and implemented since 2006, is about to be revised. The new national standard will put forward a clear requirement for the water-soluble phosphorus content of superphosphate for the first time. To eliminate the blind spot of market supervision caused by the absence of a water-soluble phosphorus index set by the original standard.

The National Fertilizer Quality Supervision and Inspection Center (Shanghai) and the chief drafter of the National Standard for Superphosphate, Zhang Xiaoxuan, told this reporter that the current revision work has already started, and the specific indicators of water-soluble phosphorus need to be further collected from related parties. The new standard is expected to be introduced in one year.

Zhang Xiaozhen introduced that one of the important backgrounds that contributed to the revision was the fact that the phenomenon of oversupply of calcium phosphate by white fat has become more intense. White manure is actually a kind of chemical fertilizer. Its scientific name is fertilizer-grade dicalcium phosphate. As a byproduct of feed-grade dicalcium phosphate, white fertilizer has a higher phosphorus content and a lower cost. It is often used by some companies through the incorporation of phosphogypsum and even directly Act as calcium superphosphate sales. According to experts, the phosphorus content of white manure is cadmium-soluble phosphorus, and almost no water-soluble phosphorus. Phosphorus-soluble phosphorus can only be absorbed by crops in acidic soils or when it meets the crop's release of root acids. Therefore, the effect of application in saline-alkali soil is very poor. Calcium superphosphate is mainly composed of water-soluble phosphorus, and the proportion of water-soluble phosphorus is generally above 70%. It is suitable for use in soils with any pH, and it has an improved effect on saline-alkali land. This is currently not replaceable by other fertilizers.

However, the problem is that according to the current "Superphosphate" national standard, it cannot be determined that these white fertilizers with the appearance of superphosphate are unqualified products. The reason is that the national standard being implemented only requires the total available phosphorus content of superphosphate. The available phosphorus includes water-soluble phosphorus and cesium-soluble phosphorus. The standard does not distinguish this further. Therefore, as long as the phosphorus content meets the standard, it can be determined as qualified. White fertilizer thus avoids supervision.

However, although the national standard does not require further requirements for the form of phosphorus nutrient, the general manager of Yunnan Phosphate Fertilizer Co-marketing Co., Ltd. and Yunnan Pu-Calcium Consortium Zhang Weixin believes that these may be determined according to other provisions of the current standard. The calcium phosphate white fertilizer is a fake fertilizer. He explained that according to the national standard, the definition of superphosphate should be the product after reaction with phosphate rock, its main component is Ca(H2PO4)2·H2O (monohydrogen phosphate monocalcium phosphate), and white fertilizer is The by-product of feed-grade calcium hydrogen phosphate is mainly CaHPO4·2H2O, which are two different substances. Therefore, as long as it does not meet the definition of superphosphate specified in the national standard, it can be characterized as a counterfeit product.

For this revision of the standard, Xu Xiucheng, an expert in the field of phosphate and compound fertilizers and professor of Zhengzhou University, thinks it is necessary to strengthen the protection of superphosphate. At the same time, he also pointed out that calcium superphosphate is a good fertilizer, rich in calcium, * and other beneficial elements, is conducive to the full use of low-grade phosphate rock. Based on this, he proposed that the standard revision should also consider the following issues: for example, whether the elements such as calcium and * can be marked on the packaging, and whether the available phosphorus content can be appropriately reduced.