Effect of porogen on nutrient release from vegetable oil coated urea

Abstract: Adding porogen is often used as one of the key technologies regulating nutrient release from fertilizers. Adding porogen can artificially changes the coating porosity、pore diameter size、structure close degree, then adjusting the permeability of coating and controlling the nutrient release rate. , In this paper, we studied the effect of porogens on nutrient release of vegetable oil coated urea and potentials for applying this technology for the development of controlled release fertilizer. The vegetable oil coated urea was prepared using the best surface reaction coating technology of manufacturing controlled release fertilizer in China. The mixed vegetable oil consisted of tung oil、castor oil、peanut oil、soybean oil、cottonseed oil, the coating materials were then mixed with vegetable oil and curing agent through. lateral or base jet vortex fluidized bed., resulting six percent of urea. ST and SB were used as porogens in this experiment, ST is water soluble starch, SB is easy to swell in water. The experiments were performed under the still pure water dissolving incubation. We set up three temperature gradients with 25℃、30℃ and 35℃, respectively. The refractive index method was used for analyzing the urea content in the coated urea incubation solution, the nutrient release rate and longevity of vegetable oil coated urea were computed. The effects of adding porogen on nutrient release curves、temperature dependence and nutrient release activation energy of vegetable oil coated urea were analyzed, the relationship between nutrient release from vegetable oil coated urea and the amount of porogens was developed. The results showed that adding either ST or SB accelerated the nutrient release from vegetable oil coated urea, and shorted the longevity. If the amount of ST was added as 1%、3%、5%, the longevity of vegetable oil coated urea was shorten to 29.78、60.78、67.44 days, respectively. The longevity of vegetable oil coated urea was reduced with the increased proportion of ST. The nutrient release curves of coated urea with different proportion of SB was almost identical. The temperature dependence Q10 was reduced with increased ST. However, the temperature dependence Q10 was increased with increase of SB. In addition, nutrient release activation energy of vegetable oil coated urea was decreased by adding porogen.