Growing Power

By Tim Torres

February 15, 2008 5 min read


Fertilizers help give gardens necessary nutrients

By Tim Torres

Copley News Service

How green does your garden grow? That depends on your fertilizer.

Fertilizer is any material that supplies nutrients to plants, according to the Cooperative Extension Office of the University of Alabama.

Fertilizers can be classified into one of two categories: organic or inorganic.

Organic fertilizers are derived from living or once-living material. These materials include animal wastes, crop residues, compost and numerous other byproducts of living organisms. Inorganic fertilizers are derived from nonliving sources and include most of our man-made, commercial chemical fertilizers.

Before you decide on a fertilizer, you need to consider the nutritional needs of your garden or lawn. After you know what is available in the soil and what you need, you can determine the amendments. You may need to use two or more fertilizers because one type may not satisfy everything.

To evaluate your soil makeup, follow the instructions provided by the Los Angeles Division of Agriculture and Natural Resources, through the University of California Cooperative Extension.

Put about one cup of your soil into a clear straight-sided quart jar with a lid and add about one tablespoon of Calgon bath beads. Fill the jar with water and shake for several minutes, then let it stand for a bit. After the soil separates, you can estimate the percentage of sand, silt and clay. Sand will be the bottom layer, silt the next, followed by clay. Organic matter with be floating at the top.

An idea soil should have equal amounts of clay, silt, sand and organic material. You can buy some of these materials at a garden shop to amend your soil.

Clay soils hold a lot of minerals but have poor drainage, while sandy soils have excellent drainage but have poor mineral holding capacity. It should be noted that compost - organic material - improves every type of soil.

To evaluate your soil's nutrients, you can use one of the many commercial soil analysis kits on the market. "They are really relatively easy to do," says Beverly Flather, a master gardener with the University of California at Davis Cooperative Extension Office.

Most $30 commercial kits will help you determine your soil's nutrients and acidity, measured by its pH. Soil pH should be between 5.5 and 7.5. It can be increased by applying granular or ground limestone, or decreased by adding sulfur.

As for organic verses inorganic types - both have their advantages and disadvantages. Inorganic types are easier to use and you have more control over their nutrients. Organic sources vary in nutrient content and we have very little control over this. However, organic sources can sometimes be obtained for little or no cost; they add valuable organic matter to the soil; and are slow in releasing their nutrients.

If you buy an inorganic fertilizer, it is best to use a standard, slow-release type. Plants need many nutrients, but mostly need nitrogen, phosphorous and potassium. You will see these three listed on fertilizer labels as N-P-K.

The numbers on any fertilizer bag refer to the percentage of the three primary nutrients. The first number represents the percentage of nitrogen. The second number indicates the percentage of phosphorous, and the last number, the percentage of potassium. The condition of your lawn or garden determines the nitrogen-to-potassium ratio you use. For instance, you would choose a fertilizer with a high potassium-to-nitrogen ratio if your soil has low potassium levels; your lawn undergoes periods of stress from heat, cold, drought or foot traffic; or your lawn has a history of disease.

Whatever fertilizer you buy, make sure you follow its directions. "Failure to read the label and apply the appropriate amount is the No. 1 mistake" home gardeners make, says Flather.

Another tip from the experts is to make sure you sweep up any inorganic fertilizer that lands on the sidewalk or driveway during its spreading. If it gets into your local waterways, it can harm the environment.

When to apply fertilizer is almost as important as the fertilizer itself. Most experts recommend applying nitrogen fertilizers in the spring and fall (for cool season grasses) and throughout the summer (for warm season grasses), since this is when the grass plant is actively growing.

If you need professional help determining what is going on in your soil, the place to start asking questions is your local garden center, or you can contact your local extension office by using the U.S. Department of Agriculture Extension Office Web site at

? Copley News Service

Visit Copley News Service at

Like it? Share it!

  • 0