Immature cereals are harvested in some areas where it is not possible to grow maize for animal feed. Without going into details (you can find a nice explanation in this PDF), this script allows you to mow grain at the last green stage.
Normally, this type of crop is ensiled, but here it is necessary to mow them. Once cut, the ground crop is considered by Farming Simulator 19 to be fresh grass. You can squeeze it and wrap it to ferment it. Here is a fairly original script if it is not very realistic (mowing instead of silage) but which should satisfy some players who are fans of the immature cereal in real life.