What it Means to Fertilize

Seasoned gardeners know the secret of lush, healthy plants lies in the soil Almost any species grows well in a fertile loam, the rich, dark crumbly soil that gardeners aspire. When soil conditions are less than ideal, however, fertilizers help to fill the gap. In essence, fertilizers provide the nutrients plants need when the soil cannot supply those nutrients.

Synthetic fertilizers, made in factories from various petroleum products and chemical reagents, can provide any needed nutrient in a form that plants easily assimilate. Organic fertilizers, on the other hand, originate from plant and animal sources as well as minerals mined from Earth, and they do not always produce instant results when applied to soil. Organic fertilizers, however, have relatively few health, safety and environmental problems associated with their use compared to the synthetic forms.

The three numbers listed on most fertilizer products reflect the percentage of, in order, nitrogen, phosphorus and potassium they contain. Nitrogen stimulates vegetative growth in plants while phosphorus has a greater effect on root growth and the formation of flowers and fruits. Potassium has various roles in the lives of plants, helping to maintain overall health and resistance to disease. The numbers 10-10-10 are for a common, all-purpose, synthetic fertilizer containing all the major nutrients -- nitrogen, phosphorus and potassium -- in a balanced proportion. Plants require small quantities of many other nutrients, however, which many organic fertilizers contain in trace amounts.

Fertilizer is needed only during the period of active plant growth in spring and summer. Hand-crank or push spreaders distribute granular fertilizers evenly over an existing lawn or area of bare soil in preparation for planting. Otherwise, granular fertilizers need to be spread by hand over the soil around existing plants to avoid contact with the plants' foliage. The same method is used for fertilizers in a powder form. Liquid fertilizers have the advantage of being applied with irrigation water, ensuring even distribution.

Lawns and vegetable gardens have greater fertilizer needs than perennials, shrubs and trees because large portions of plant material -- grass clippings and vegetables -- are constantly removed, taking nutrients with them. Composting plant waste returns some of the nutrients lost and maintains the natural process of nutrient cycling in the soil. Compared to a bag of 10-10-10 fertilizer, compost is very low in readily available nutrients, but it stimulates overall soil fertility in a balanced and long-lasting way.