Plants grow best with adequate fertilizer. With a sandy soil, you control plant growth. Pour on the fertilizer, and you can have the greenest lawn in town, but expect to do lots of mowing. Too much fertilizer also can make shrubs lanky and keep tomato plants from fruiting. The trend is to give the plants just the fertilizer needed for good growth and no more.
Lawns require fertilizer when they begin spring growth and again in the fall.
During the rest of the year, you be the judge. Often during the summer when the lawn turns a little yellow, an iron application can re-green the turf without making extra mowings necessary. Once a shade tree is established, usually within three years, special feedings can be discontinued. For older trees, fertilizer applied to nearby lawns and shrubs can supply the nutrients needed. The extensive root systems easily absorb nutrients.