Evaluation of Damage to Polymer Coated Urea Prills During Handling.

Use of polymer coated urea in crop production has increased in recent years as a potential practice to increase nitrogen use efficiency.  During the handling process, however, the polymer is susceptible to fracturing or cracking, which can significantly increase the rate of urea release from the coated prill.  We developed a 24 hour test to evaluate damage that can occur during handling during a typical application of ESN (Agrium, Inc.) with an air-boom spreader to potato fields.  For this test, 3.000 to 4.000 grams of ESN were placed in a beaker to which 400 mL deionized water were added.  The mixture was gently stirred with a glass stirring rod for about 15 seconds.  After 24 hours, the prills (and empty casings) were screened out and allowed to dry in a forced air oven set at 40 C until a constant weight was achieved.  The weight loss after 24 hours is assumed to be due to urea leaking out of the coated prill.  Samples of ESN were collected from a delivery truck, after transfer to a hopper of an air-boom spreader, and then from each of 24 boom deflector plates during a simulated application.  The amount of prill damage increased with each stage of handling.  The weight loss after 24 hours was 6.9% from delivery truck samples, 9.5% from spreader hopper samples, and 28.8% from deflector plate samples.  The weight loss from deflector plate samples ranged from 11.8 to 56.6% with the greatest loss occurring from deflector plates near the middle to end of the boom.  Samples from the deflector plates were hand mixed into one large sample. The effects of coating damage on potato crop response and in situ N release were evaluated during the 2010 growing season and will be presented.