Every spring, people start showing up to buy new potting soil to replace the old stuff from last year. I can understand the desire once you look at the gray, dried block of peat moss sitting in the pot. But this can be an expensive proposition, especially if you are talking about large containers.
Make Old Potting Soil Like New. While it's not good for business, I always tell people to reuse their existing potting soil by simply mixing in fresh compost or compost-based potting soils. A mixture of 1/3 to 1/2 new material to existing material is enough to refresh your potting soil and make it look like new. That's it...problem solved, money saved! Just add a good fertilizer when you plant, and you won't notice any difference between your recycled potting soil and new potting soil...it may be better!
Not All Potting Soils Are The Same. Here's some other info that may help you with your potting/container garden soil. Almost all potting soils are made from Canadian peat moss. It is useful as a potting mix ingredient because it is light and inexpensive (even though it is brought from Canada - another government subsidy). This is also the material in the pot that remains after a growing season, dries out, and turns into a brick. Some believe that we are destroying the peat bogs but my research shows that these bogs are nearly infinite in supply. I don't like it because it unfairly competes with out local compost potting soil producers such as Lady Bug and Garden-Ville AND because it has no growth enhancement properties - ie., no fertilizer. If you want a high quality, long lasting potting soil, naturally pre-fertilized, try Garden-Ville's or Lady Bugs products. Made from compost, rock dusts (for trace mineral content), and natural fertilizers, you will see consistently excellent results.
Making Cheap Potting Soil Better. For some, the lure of $2 bags of potting soil are inescapable. You can make cheap potting soil much better simply by following the instructions above. Mix compost and/or a premium potting soil in with the cheaper stuff and you have a much better medium in which to grow your veggies and flowers.