1998 Volume 69 Issue 6 Pages 555-560
The release of nitrogen from two types of resin-coated urea was studied in two saturated salt solutions at a constant temperature. From the water vapor pressure of the saturated salt solutions, the temperature of corresponding vapor pressure of pure water was calculated and this converted temperature was used in the simulation with our release model proposed previously. 1) The release rates in the saturated solution were proportional to the differences in water vapor pressure between inside and outside of the coatings. The rates of release were simulated satisfactorily with the proposed model by converting the temperature. 2) The cumulative nitrogen release did not reach 100% ; this fact suggesting the effect of osmotic pressure of the saturated salt solutions. 3) The coated urea swelled differently with different coatings and temperatures, and by correcting the gain in volume of the swollen fertilizer granules, the simulation of nitrogen release in saturated salt solutions agreed with actual release data.
