Giving crops an extra boost of fertilizer is called side-dressing. Good side-dressing helps crops grow evenly and smoothly and helps deliver better harvests.
If you've mixed plenty of organic matter into your soil over the years and grow green manure corps like peas, beans and buckwheat, chances are your soil is pretty rich in nutrients. If your soil is fertile and you have added a little fertilizer to the soil before planting, your crops probably will do very well without side-dressing. Two exceptions are corn and onions which are heavy feeders and almost always require regular side-dressing.
If you've just started to improve your soil by adding organic matter, side-dressings are important. This is especially true in a sandy soil with little organic matter. Plant foods drain down through a sandy soil and away from the roots of your crops. To keep crops growing smoothly, you'll probably need to side-dress.
Not all crops need side-dressings. Peas and beans, greens and root crops grow fine when fertilized only at planting time. Carrots, beets and turnips need only a little extra bonemeal at planting time to provide phosphorus for the roots.
Side Dressings are usually applied by either circling the plants or banding.
Circle the Plants With tomatoes, peppers, broccoli and other transplanted crops, dig a shallow circular furrow around each plant. Sprinkle the fertilizer in evenly and cover it. Put this circle of plant food about 5-6 inches away from the plant stems. If the plant is quite large, put the circle of fertilizer around the outer leaves or "drip line" of the plant.
Banding With the corner of a hoe, open a furrow 1-2 inches deep in a straight line next to a row of plants. Keep the furrow about 5-6 inches from the line of plants. Put the fertilizer in the furrow and cover with soil. Covering the fertilizer is important because a heavy rain may splash it onto the leaves causing burns.