Grass bales and Silage
To create hay the grass must be dry enough to be able to use a tedder. If you see the “Wet Crops” icon in the top right corner, then you will not be able to create hay. Using a tedder when crops are wet or when it is raining, leaves wet grass, not dry grass. You will need to wait until the “Wet Crops” icon disappears and then use the tedder.
Swaths and heaps of grass will start to rot and disappear if not baled in time and left on the ground. Swaths and heaps of straw and hay will rot when it rains. To prevent loss of material, work field by field: mow, bale and wrap for grass, or mow and directly ted to turn it into hay. Hay is then safe until it rains, so be sure to bale before then.
Note that heaps and swaths are not protected by sheds. This is a game limitation. Be sure to always bale your materials.
Grass bales will gradually rot and disappear after two days, unless they are wrapped so that they become silage bales. Wrapped bales do not turn into silage immediately, but instead need some time to ferment. It takes one third of a season (1 transition) to fully ferment either a silage bale.
Hay and straw bales exposed to rain will start to rot so keep them inside sheds. These bales will only rot if the map has been prepared with a so called Seasons mask.
Chaff in bunkers will take one third of a season to ferment (same time as bales), and is not affected by weather.