Simultaneous pursuit of long accurate release control and high biodegradation rate is required as the membrane of control led-release devices in agriculture. The effect of the physical properties of poly(caprolactone) based polyurethanes as a polymer membrane on their biodegradation characteristics and the release profile was evaluated. The soil burial test at 28 degrees C resulted that the biodegradation rate of the polyurethanes increased as the number of average molecular weight (M-n) of poly(caprolactone) diol used increased from 500 to 1000, whereas it decreased as the M-n of poly(caprolactone) diol increased from 1200 to 2000. The biodegradation behavior was different when the M-n of poly(caprolactone) diols was used because of the recrystallization of long straight poly(caprolactone) chains. Poly(caprolactone) triol prevented recrystallization and led the high degradation ratio. The release rate of urea from the polyurethane-coated granules decreased as the M-n of poly(caprolactone) polyol decreased. These results indicated that the release profile was affected by the urethane content, and the biodegradation characteristic was affected by the glass transition temperature and the recrystallization of polyurethane membrane. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 246-253, 2009