I amend my soil with compost and manure usually once a year. I have a clay soil so if I let it go too long it turns into concrete. I mostly move the tomatoes to a different location when I grow green beans so the beans are not being shaded by them. I grew some corn this year also. I grew garlic last winter and it was a great success, ended up with 60 heads of garlic. Turnips also grow well here in the winter. I put in red clover once for a green compost and to fortify the soil. I haven't tried any other winter crops yet.