Controlled Release of Paraffin Wax/Rosin-Coated Fertilizers

For effective deliveries of nutrients to plant species, we have studied release profiles of KCl, NH 4 NO 3, KNO 3, (NH 4 ) 2 SO 4, and K 2 SO 4 as fertilizer substrates. The effect of coating the fertilizers with paraffin wax or a mixture of paraffin wax and rosin and the effect of temperature (25, 30, and 35 °C) were explored. The dissolution rate and ultimate amounts dissolved were in the order of KCl > NH 4 NO 3 > KNO 3 > (NH 4 ) 2 SO 4 > K 2 SO 4 . The order was unchanged whether the fertilizers were coated or not. Coating with paraffin wax exhibited ultimate amounts dissolved lower than those of uncoated samples. Wax/rosin-coated samples attained dissolutions similar to those of uncoated samples but at slower rate. The results showed wax/rosin coating to be more effective than wax-only coating, but the difference diminished for low dissolving fertilizer such as K 2 SO 4 . When wax-coated samples were tested at 25, 30, and 35 °C, the rate of dissolution increased but the order of the ultimate amount dissolved was unchanged. As the temperature was increased, the range of the ultimate amounts dissolved between KCl and K 2 SO 4 narrowed. The ranges are 0.09, 0.07, and 0.06 mol/dm 3 for 25, 30, and 35 °C, respectively.