I have an idea. Both the field (plot_field_temp.xml) and the wheat (farming_wheat_harvest_a / farming_wheat_harvest_b) have extra materials. Maybe @LordGood know more of what he wanted to achive.
plot_field_temp.xml
spec
normal
diffuse
material (basic_trans.xml) required textures:
diffuse
farming_wheat_harvest_a
spec (props/yellow.png)
diffuse(gaia/farming_barley_harvest_a.png)
material (basic_trans_wind.xml) required textures
diffuse
So my uneducated guess @vladislavbelov, @wraitii would be that the game is somehow having fun swapping those unused textures because one shader still calls them. It usually uses the one it finds around like the palisade here.