The first growing season of a garden is the most work. Now that you've made the beds, turned over tough turf, and amended the soil, every season thereafter is about maintenance. If the borders are sturdy, the bed itself will remain intact for a few years. The main work in a garden, after the initial setup, is to restore the vitality of the soil.
Remove spent plants when the harvest is over, and add them to the compost. Try to take every piece of the plants, including the roots. Leaving them in the garden could make it easier for the the pests that feed on them to overwinter more comfortably and explode in population the next year. This is why if you have enough room, try not to plant the same type of crop in the same place within four years.
Compost can get hot enough to kill insect eggs and larvae, as well as fungus, so chop up the old plants and mix them well, and often. The bacteria that make the most heat need air.
Putting Beds to "Bed"
Cover the beds with as many leaves as possible--a foot high isn't too much. Water them to keep them from blowing away and to facilitate breaking them down. Leaf mold has amazing water and nitrogen-holding capacity, adds vital trace elements to the soil and increases all-important biomass to keep the dirt loose and workable. All winter long, soil organisms will incorporate the leaves into the bed, greatly reducing the work you'll have to do in the spring.
Fertility for the Next Season
Now it's time to amend the soil with nitrogen. Plants need this element more than any other nutrient. Even though 80% of what we breathe is nitrogen, it's very volatile and therefore difficult to hold into the ground, where plants can use it. Nurseries sell fertilizer, but finished compost and well-rotted manure can do the job, too. Some gardeners plant a fast-growing "green manure," crop, like alfalfa or legumes. Once the seeds germinate, they grow for a few weeks, before gardeners turn them into the soil before they can flower. After a few weeks, the green manure has rotted enough to release its nitrogen, and the soil is ready for vegetable crops.
Sun and water are more or less constants in the garden, but soil is always changing. As plants deplete the nutrients and change the structure of the dirt, gardeners need to be diligent in maintaining a healthy balance. Good soil ensures a good harvest.