Since you don't have a huge area to feed, consider staying with natural fertilizers and the mulch program from above. The three main nutrients are
Nitorgen,
Pphosphorous, &
K (Potassium) . If you use traditional fertilizers, they are most often all water soluble. After a few big rain falls, most of it washes away from the roots and can't be used buy the plant. The salt, not "table salt" but usually a sulphur salt, will remain in the root zone which is not good for helping the transfer of nutrients into the roots. High orgaic matter in the soil from compost or mulch helps prevent most of this. It's very important to keep the pH right for your plant's requirement. pH effects how well the roots absorb needed nutrients. Tomatoes love Phosphorous. If your leaves look purpulish it needs more P.
- Test your soil and know what your plant needs..
- Adjust the pH down with lime only as needed, acidic oak leaf mulch or compost to raise it.
- Add neutral pH compost anytime by side dressing. A good mulch program will help accomplish this too, just watch how what you mulch with effects the soil pH.
- Nitrogen: try dry blood, cotton seed meal ...
- Phosphorous: steamed bone meal ...
- K is Potassium, a little wood ash will do but watch-it lowers pH. Cotton seed meal has some too i think.
This is basic organic gardening and you'll see your garden get better year by year. The NPK additives above will bild in the soil because only a small part of each is imediately water soluble and available to the plant. The muclh and compost will be the main source of plant food. When the soil pH is correct, the remaining insolubale neutrients in the root zone will convert to usable forms (becuse it didn't wash away) and be taken up by the plant. You'll be amazed at how many earthworms you'll have too.