FERTILIZER AND TEMPERATURE EFFECTS ON UREA HYDROLYSIS IN UNDISTURBED SOIL

Few published studies have examined the effects of a continuous fertilizer application on urea hydrolysis. In the present study we investigated the effects of 9 years of continuous application of urea and P fertilizers on urea hydrolysis in undisturbed soil samples as affected by temperature (5-45-degrees-C). Undisturbed soil samples of surface horizons (0-7 cm) were obtained with cutting rings (50 cm3 from different fertilizer-treatment plots and inserted in polyethylene bottles (with cutting rings). Each soil sample (in the cutting ring) was treated with 10 ml urea solution (0.5 mmol urea N g-1 soil) and then brought to 90% field capacity. The samples were left to equilibrate for 30 min at a temperature of 4-degrees-C, then placed in an incubator at 37-degrees-C for 6 h. The results indicated that 9 years of continuous application of urea but not P had a significant effect on urea hydrolysis in soil. There was a good correlation between temperature and urea hydrolysis in soil. Q10 was between 1.97 and 2.08 in the temperature range 5-45-degrees-C.