A grass management system comprising: a traveling vehicle (2A, 2D) configured to travel; a mower detachably connected to the traveling vehicle, the mower having a mowing device configured to cut grass; a roll baler detachably connected to the traveling vehicle, the roll baler having a baling device configured to bale the grass and discharge a baled material; a first physical quantity detecting device configured to detect first physical quantity information of the grass in a mowing operation performed by the mower; a first position-detecting device configured to detect a first machine position of the mower; a second physical quantity detecting device configured to detect a second physical quantity information of the grass in an operation where the roll baler collects and bales the grass already mowed; a second position-detecting device configured to detect a second machine position of the roll baler, and a database configured to store the first machine position and the first physical quantity information of the grass and to store the second machine position and the second physical quantity information of the grass, a first map creating circuit configured to create a first physical quantity map of the grass in an agricultural field based on the first machine position and the first physical quantity information of the grass; characterized by: a second map creating circuit configured to create a second physical quantity map of the grass in the agricultural field based on the second machine position and the second physical quantity information of the grass, the first physical quantity information of the grass being different from the second physical quantity information of the grass; and. a display device configured to display both of the first physical quantity map and the second physical quantity map on a screen. a traveling vehicle (2A, 2D) configured to travel; a mower detachably connected to the traveling vehicle, the mower having a mowing device configured to cut grass; a roll baler detachably connected to the traveling vehicle, the roll baler having a baling device configured to bale the grass and discharge a baled material; a first physical quantity detecting device configured to detect first physical quantity information of the grass in a mowing operation performed by the mower; a first position-detecting device configured to detect a first machine position of the mower; a second physical quantity detecting device configured to detect a second physical quantity information of the grass in an operation where the roll baler collects and bales the grass already mowed; a second position-detecting device configured to detect a second machine position of the roll baler, and a database configured to store the first machine position and the first physical quantity information of the grass and to store the second machine position and the second physical quantity information of the grass, a first map creating circuit configured to create a first physical quantity map of the grass in an agricultural field based on the first machine position and the first physical quantity information of the grass; characterized by: a second map creating circuit configured to create a second physical quantity map of the grass in the agricultural field based on the second machine position and the second physical quantity information of the grass, the first physical quantity information of the grass being different from the second physical quantity information of the grass; and. a display device configured to display both of the first physical quantity map and the second physical quantity map on a screen. a second map creating circuit configured to create a second physical quantity map of the grass in the agricultural field based on the second machine position and the second physical quantity information of the grass, the first physical quantity information of the grass being different from the second physical quantity information of the grass; and. a display device configured to display both of the first physical quantity map and the second physical quantity map on a screen.