"Autumn" planting is species dependent. Any plant that withers before it's ripe for harvest sprouts anew the next spring (possibly while still covered by snow and with the ground still frozen), but once the time for withering sets in it's too late to sow that plant. Withering time varies significantly between plants, and some have a fairly short window between harvest and withering. The Wiki describes when plants can be sown, sprout, harvested (assuming planted early enough), and wither (as well as flowering for some plants).
The current imperfect model has you prepare the field once and it will then be usable throughout your character's life with no degradation. Real life slash-and-burn farming depletes the soil in a few years (3-5?), at which time the field is abandoned and a new field is prepared. Continued use of the field results in gradually decreasing yields. Also, I expect real life usage to require some kind of soil preparation annually, although that process would differ from the initial one. On top of that, I expect you'd also have to remove weeds during the growing season.