A method and apparatus are provided for applying preservative to agricultural crops during baling. The method comprises at least one moisture sensor (64) and a preservative application system (50) for selectively applying preservative to the crop material (42) as it is being baled. An Electronic Control Unit (ECU) (40) receives data from the moisture sensor (64) and controls the preservative application system (50) according to a high moisture set point, a high moisture set point ratio an application rate/high moisture ratio (404, 504). When commencing a baling process (405, 505) a moisture content of the incoming crop material (42) is sensed and determined whether the sensed moisture content meets and exceeds the high moisture set point (406, 506)and/or the high moisture set point ratio (407, 507). The preservative application system (50) will be activated when both the high moisture set point and the high moisture set point ratio have been one of met and exceeded (408, 508)； wherein the rate of preservative application (409) to the application rate/high moisture ratio for the high moisture set-point ratio will be adjusted. Furthermore an agricultural baler (10) for operating with a respective method is disclosed.
