I want to say that I am really enjoying this game, and in particular I appreciate the level of realism that has been put into the design of the crop system. It is by far the best one I have ever seen in any game of this kind.
As one additional shot of realism, I would suggest that you consider adding a fall planting of grain crops such as wheat and rye. In the Middle Ages, the system of fall planting was first described in records, according to which a grain was planted in late summer, after which point it established itself and then went dormant during the winter and was harvested in late spring.
There is no absolute need for such a system – what’s there now works fine. But having gone this far down the road of realism, adding this to the options would take the game that much further.