First of all, there are two types of potash fertilizers, one is simple potassium fertilizer and the other is compound fertilizer containing potassium.
The common simple potassium fertilizers include potassium chloride, potassium sulfate and potassium silicate. Potassium chloride: divided by the place of production, with red and white types; the appearance of a block, powder and irregular granular; potassium oxide content (in K2
O% indicates that imports are generally 60% and domestic production is 57% or 60%. Potassium sulfate: generally white crystalline particles or powders. Some products are slightly miscellaneous because of impurities. Domestic potassium sulphate, including Lop Nur or Taiwanese, generally contains K2
O is 50% and German production is 54%. Potassium silicate: dark gray powder, as an industrial by-product, can only confirm the content through laboratory tests, generally K2O is 10% to 14%, and is alkaline.
Common potassium compound fertilizer, potassium content of compound compound fertilizer can be seen from the packaging bag: N-P2O5-K2O. Binary compound fertilizer - Potassium nitrate: white crystalline particles, rare in the market.
Second, the identification of potash is really complicated, and it is ultimately necessary to rely on laboratory tests. The simple identification method of potash fertilizer described here is only a qualitative identification method, and the level of potassium cannot be identified, and the effect is limited.
One is the iron-burning method: The fertilizer particles (large or small) are burned on a red-hot piece of iron. Any non-melting, odorless, and heat-induced bouncing phenomenon can be roughly classified as potassium fertilizer. If the iron plate is tilted to directly subject the fertilizer to high temperature combustion, a colored flame will appear. The golden shiny flame is sodium, and the pale yellow entrained lavender flame is potassium. There is also a kind of powdered potassium fertilizer, the color can be brick red, light red or white, the identification method is also burning on the iron sheet, potassium fertilizer showed no melting, no odor; while the performance of phosphorus fertilizer is light gray, although Not melting, but odor. Note: If the iron pieces are melted by the high temperature and there is heavy smoke, all the ammonia odor is ammonia nitrogen fertilizer, and only the ammonia-free ones may be nitrate; if the fertilizer particles on the iron pieces do not melt and do not pulsate , but odor acid or bone odor may be phosphate fertilizer.
The second is to dip the saturated potassium fertilizer solution on the wire coil and burn it on the high-temperature flame to observe the color of the flame, but it is difficult to grasp the flame color difference between potassium and sodium. However, if poor quality potassium fertilizers other than conventional ones are encountered in the market, such as the use of unrefined potassium feldspar in small pieces or powders, the content of soluble potassium can only be measured by laboratory tests. Only the combustion method can only be qualitative, not quantitative, that is to say, can only distinguish between authenticity and inferior quality. Therefore, when farmers choose to purchase chemical fertilizers, they must go to regular sales outlets to avoid being deceived.
Author: Cao Yiping (China Agricultural University)