It helps your plants grow
When using fertilizers, check the package to see which kind of nitrogen you're getting. The "N" number of the "N-P-K" formula will tell you the percentage of nitrogen, by weight, in the mix. A "quick release" fertilizer will contain nitrates so your plant can use them right away. "Slow release" indicates the ammonium form of nitrogen. Ammonium nitrate is actually a half-and-half mix of nitric oxygen (quick release) and ammonium nitrogen (slow release).
The best organic sources for nitrogen are alfalfa meal, blood meal, fish emulsion, and guano. Budget-conscious gardeners can try the following trick. The next time you have fish for dinner, save the heads and the bones. Place these in the bottom of a windowbox or large planter before putting in the potting soil. The fish bones will act as slow release nitrogen fertilizers for your plants. Sound gross? Try collecting seagull turds (guano).
When fertilizing, remember that too much nitrogen can be as bad as too little. Plants can suffer nitrogen burn or grow so much foliage that they never flower.