| Urea is one of the most important of all solid nitrogen fertilizers. The total world urea production capacity exceeds 4.2 10{dollar}sp6{dollar} mT per year. The application of urea to soil, however, may result in a significant loss of ammonia to the atmosphere. Laboratory and field experiments were therefore conducted to test the effect of different forms of urea and KCl mixtures on improving the nitrogen efficiency of urea fertilization. Urea, urea + KCl granular, urea + KCl in solution, and urea coated with KCl powder were compared to ammonium nitrate in field experiments in two different soils. The coated urea and the solution forms exhibited the best nitrogen efficiency. Efficiency was approximately equal to that obtained with ammonium nitrate and usually better than urea alone. Corn yield increased up to 22.5% when KCl was mixed with urea. Field study results were supported by lab studies which indicated that the lowest ammonia volatilization was obtained from KCl-coated urea and urea + KCl in solution, while the highest rate of ammonia volatilization occurred with urea alone. Highest soil pH values were obtained when urea only was applied to the soil, although soil pH readings were lower in all treatments as a result of nitrification. These results demonstrate that coating urea with KCl may offer a significant advantage over uncoated urea, especially in potassium deficient soils. |
