Simple idea, add a compost bin where rotten food is stored that will eventually turn into compost after a few days.
In order for the compost to have an effect it the soil must be dug again and the compost mixed in. The effect will boost the growth of the plants for a set number of days before compost must be applied to the soil again.
Idk if someone thought of this but to add to it. How about a % base as well where so much of your food goes to composting. But of course rotten food goes first.
This will be a part of the rework of the farming system in the future, if i remember correctly? 
if so, I must have missed it, I do think I have suggested this before tho, but I didn’t find my old post about it
edit:
actually I talked about it here but I forgot to make the thread for it on its own. problem solved I guess
This sounds like a good idea. It will create better food where it may take a little longer for the food to spoil because the crops are better. For instance the corn will be a better quality. (ex. amazing corn basket)
The questions I have in mind are: 
What level of farmer will this hearthling utilize this mechanic?
Will it work with the quality of food that the hearthling produces? If so How will this be implimented?
Do we make it where it works like a stockpile where hearthlings take food to this compost stockpile and when it becomes ready they carry it to the designated area to be mixed into the farm zone terrain? 
if you wanted it to be realistic this would require water as water is needed to regulate the temperature of the compost more water = more heat = faster decay it can be quite a bit more complicated but as I understand it thats basically how it works
This is so true. 
Hope this gets implemented when the devs revamp the farmer job.