If Northampton zoning laws were as they should be, if I noticed a decline in soil fertility, I’d just go into the next yard, cut down all the trees and grass then wait for the dry season (based on this year, that would be the winter). I’d burn the slash then start my crops the next year. The ashes would help fertilize the soil.
Unfortunately my neighbors might object. Worse, if my other neighbors did this in my yard, they’d find played out dirt (I’ve got no trees). I guess that’s a good reason not to practice slash and burn agriculture in urban areas.
When I lived in Worcester I had a neighbor who planted all of his crops in the same spots each year (he did not use beds like his hippy next-door neighbor); he liked where the tomatoes grew, so he was sticking to it. He fertilized with good ‘ol 10-10-10 from the Home Despot and applied pesticides and fungicides with wanton abandon. He suggested that any success I enjoyed probably came because he was killing all the bugs for me: testosterone based gardening competition (my carrots were bigger FTW).
There is a middle way. To travel this middle way, it helps to practice good crop rotation. Right before you put a seed in the ground be sure to rotate it four times perpendicular to the ground.
Not really. Ideally crop rotation involves a planned series of different crops on any plot of ground. For instance planting corn the first year, winter squash the second and soy the third. The fourth would see a return to corn. This works OK on field scale, but in the small garden we’re usually trying to grow lots of different plants in several different families.
My habit is to try to avoid planting the same family in a particular plot within three years. I have enough beds to do this, and if I were really organized, it would work. In practice, I dig an extra bed many years.
The basic families most of us grow are brassicas (broccoli family), nightshades (tomatoes, potatoes, and peppers), legumes (beans and peas), alliums (onions, garlic and leeks), umbels (carrots, dill, parsnips), cucurbits (cucumbers and squashes), and other (lettuce, basil, sweet potato, etc.). I keep a record of where I plant things each year then try to avoid planting the same family for three years. I’m particularly careful of the nightshades and the brassicas since they seem to pick up the soil borne diseases easily. This then brings us to why you should rotate crops. First diseases, both fungal and bacterial lurk in the soil over the winter waiting for their juicy hosts to show up. Second, different crops have different nutritional needs, and rotation can take advantage of this.
Of course, if you use compost that hasn’t fully decomposed, or if you move soil from one place to another in your garden, you’re negating much of the good of crop rotation. The only way to handle this is to pull the plants out, roots and all, spin them three times counter-clockwise then place them back in the soil. They’ll be good and rotated then.