Abstract: A field adjustable mattress system/method allowing a baseline mattress configuration to be ergonomically modified after initial installation is disclosed. The baseline system generally consists of an optional bottom mattress support (BMS) connected to a bottom mattress cover (BMC) that partially envelops a static mattress core (SMC) from the bottom. A top mattress cover (TMC) completes the encapsulation of the foam mattress core and is attached to the BMC using top/bottom mattress cover zippers (MCZ). Field adjustment of the mattress system is accomplished by inserting one or more mattress adjustment layers (MAL) between the top of the SMC and the TMC and inserting an adjustment border panel (ABP) via the MCZ between the TMC and the BMC. The MAL may comprise one or more layers and may be inserted using horizontally and/or split configurations to permit a variety of ergonomic combinations to be supported in a single mattress system.