1.Observing the release period of nutrient
For the package of normal qualified slow controlled release fertilizer, it supposed to indicate the nutrients type and content of controlled release fertilizer, and the initial and cumulative nutrients release rate should also be marked on the font or back side of package. The initial release rate from slow release fertilizer and controlled release fertilizer should be 15% and 12%, and the cumulative release rate should be 80% and 75% respectively. The quality is questionable if the index from label is different from test value.
2.Checking the granules
At present, there were many factories will make the fertilizer granules into multicolored types, but never think that multicolored granules is slow and controlled release fertilizer.
In order to meet that shallow understand from farmers households, Many fake factories will make the fertilizer granules into different colors by adding chemical pigment, and pretend to selling those fertilizer. The buyer should look for formal manufacturer, in case of be tricked. Generally speaking, there were a complete thin and can be striped layer on the surface of coated slow and controlled release fertilizer, If it is difficult to peel, it can be removed with a knife. But if the particles is damaged severely or the coating is incomplete, we treat it as Inferior fertilizer.
3.Trying the solubility.
The difference from instant fertilizer is that Slow-release particles will not melt immediately in water. Some coated slow and controlled release fertilizer will expand when absorbing moisture, and speed up the release when add hot water, but its still slower than the common fertilizer. When cooling to the normal temperature, try to pinch fertilizer, if most of them is soft, then it is controlled release fertilizer. If its not soft or a pinch is broken, then that isn’t controlled release fertilizer.