Fall is a great time to feed perennials and trees. It's also the perfect time to prepare you spring grow plots. I see the farmer around me work his land after the harvest. He spreads manure and tills it under in the Fall and this makes ready for his spring planting. Not only does this get these chores out of the way but it helps replenish the nutrients and have them more available for the new seedlings. The same actions can benefit the outdoor cannabis grower. Feeding and loosening the soil now will make the nutrients more available and we can go about planting easier and quicker, which would less likely to attract attention. Also the usual varmints would not be as likely to dig in the freshly dug earth and disturb out seedlings.
Preparing a hole or plot for plants is a bit of work. But it pays off! A single plant can use a cubic meter sized hole and produce some significant weight. Nutrients can include humus, manure, alfalfa, ash, lime, just about anything you'd add in the spring. Also, if you can get a soil sample to your state farm extension service they will test it and advise what you may need to grow cannabis (or you can say vegetables).
Some locations it is not too late to plant nitrogen fixing crops like winter rye, alfalfa, soy bean or any beans you have available really. Optionally, you can mulch the area to hide the plot and keep early weeds down.
So, get out there, make a plan and start digging or turning over your area for next season.