DETERMINATION OF THE RELEASE OF NUTRIENTS FROM COATED FERTILIZER GRANULES BY COLD WATER TEST (CWT)

Abstract

European Standard of EN 13266 points out a method for the determination of the release of the nutrients from coated release fertilizers (CRF). Principle of the method depends on elution of a test portion of a fertilizer with a specified volume of water. Determination of the concentration of the nutrients, that have been dissolved in definite time intervals. In this study, 16-10-17 fertilizer granules were coated with polymers with different thickness. After that, the release of N, P, and K nutrients were followed at definite time intervals by CWT method. The amounts of nutrients released at the end of each period were analyzed and these values were recorded. The coating provides a controlled release of nutrients and determination of ‘M’ value, means month, for each type of CRF as 2, 4, 6, 12 or 18 months etc. So, the effect of the coating on the nutrient release was investigated by CWT method. According to this study, 50 µm coating of polymer provides the release time of 2M. Similarly, when the coating thickness is increased to 100 µm and 180 µm, the release time reached to 4M and 6M, respectively. As a result, it was seen that the increment of coating ratio causes the reduction of release of nutrients. It means that release times of the nutrients can be controlled by coating thickness. Also, release period could be fixed by this method. This situation ensures using less fertilizer, with the benefit of leaching fewer nutrients, provides ease of use, reduce the application costs compared to water-soluble fertilizers