Urea Hydrolysis in Loblolly Pine Needles: Effects of Urea Concentration and Temperature.

In the United States, about 600,000 ha of pine trees are fertilized with urea, a fertilizer that is hydrolyzed by the urease enzyme to release ammonium. Part of the released ammonium can be lost as ammonia, depending in part on the rate of urea hydrolysis. This study was conducted to evaluate the effects of urea concentration and temperature on the rate of urea hydrolysis in pine needles. To evaluate the effect of urea concentration, samples of new needles were incubated at 37^oC for 24 hours with urea concentration ranging from 0.1 to 10 M. To evaluate the effect of temperature, samples of new needles and old needles were incubated for 24 hours with 0.1 M urea at 5, 15, 25, and 35^oC. The rate of urea hydrolysis increased with urea concentration and followed Michaelis-Menten kinetics. Similarly, the rate of urea hydrolysis increased with temperature and could be described with an Arrhenius equation.