Improving the dissolution and releasing characteristics of potassiumnitrate and urea fertilizers by their coatingwith some organic and inorganicmaterials

Author(s): Ebtisam K.Heikal, Salah A.Khalil

This work describes the method of producing physically prepared slow – release fertilizers to provide an insoluble coating on granules of water – soluble fertilizers. The fertilizers chosen are potassium nitrate and urea. Stearic acid, calcium hydroxide, paraffin was, fatty acid and talk are the materials used to prepare four types of coating varying in their composition. These types of coating are referred to by a number of examples : Ex1, Ex2, Ex3 and Ex4. The granules of coated fertilizers were tested for their dissolution in water at 20 and 40 °C. It was found that coated potassium nitrate has lower dissolution than coated urea. As the temperature was raised from 20 to 40 °C, the dissolution rate increased for both fertilizers. The treatments Ex3 and Ex2 have the best (lowest) dissolution rate, respectively. The Ex4 treatment recorded the worst values due to that the strength of the granules was quite poor. Releasing rate of potassium nitrate and urea fertilizers in sandy soil at 25 and 50 °C and field capacity 20 and 40 % was tested. Increasing temperature increased the releasing rate. Moisture content had lower effect. Potassium nitrate fertilizer recorded lower values of releasing than urea. Among the treatments, coating of both fertilizers decreased their releasing rate in the following order, Ex3 > Ex2 > Ex1 > Ex4 and finally the uncoated treatment.

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