Fertilizer Basics For Home Grounds

	ENVIRONMENTAL EDUCATION SERIES ENVIRONMENTAL QUALITY Agriculture & Natural Resources
EXTENSION ENVIRONMENTAL EDUCATION, AUBURN UNIVERSITY, AL 36849-5647

Fertilizer Basics For Home Grounds

ANR-744, 1992. By Dave Williams, Extension Horticulturist, Horticulture, Auburn University

Individual lawns and planting beds are small, but the total area of lawns and planting beds in urban environments is significant and may require significant amounts of fertilizer. Proper fertilization will enhance plant growth without polluting the environment. However, misuse of fertilizer can harm the environment and injure landscape plants by causing fertilizer burn to leaves and/or roots.

Nutrients That Affect Water Quality
Nutrients essential for plant growth may be present in a form or an overabundant supply that cannot be used by plants. Excess nutrients that enter the surface or groundwater may reduce water quality. Phosphorus is an important nutrient necessary for plant growth. When phosphorus is applied as a fertilizer, it is quickly bound to soil particles or taken up by the plant. Therefore, the major sources of phosphorus runoff into surface water are phosphorus bound to eroding soil particles or clippings and leaves that are left in streets and gutters.

Nitrogen is the nutrient that produces the greatest growth response in plants. Nitrogen is usually present in the soil as nitrate ions. Nitrate ions are soluble and not held by soil particles. Excess nitrate not taken up by plants will leach downward with percolating water and may enter the groundwater supply. Nitrogen is particularly dangerous to the very young. Nitrogen contamination is most commonly caused by over-application of nitrogen fertilizers and animal manures.

To avoid phosphorus and nitrogen loss to surface and groundwater:

Remove clippings and leaves from streets and gutters.
Cover the soil with healthy plants or mulch to reduce soil erosion.
Apply the proper amount of fertilizer.

Soil Testing
Begin your safe fertilization practices by taking a soil test. Soil testing is a service provided by Auburn University at a low cost. Soil test cartons can be obtained at your county Extension office. A soil test will tell you the levels of available phosphorus and potassium in the soil as well as the soil pH. To take a soil sample, follow the directions that come with your soil test carton. A fertilizer recommendation will be included with your soil test results. If levels of phosphorus and potassium are sufficient, there is no need to apply those nutrients. Because nitrogen is so soluble, it is not useful to test for the level of nitrogen.

Take a soil test to determine levels of phosphorus and potassium present in the soil.
Maintain pH between 5.5 and 6.5 for most trees, shrubs, and turf.

Fertilizer Types
Fertilizer can be purchased as "single ingredient" fertilizers, such as ammonium nitrate and urea for nitrogen, triple super phosphate for phosphorus, or muriate of potash for potassium. Combination fertilizers, such as 10-10-10 or 5-10-10, include all three nutrients. The three figures of the fertilizer analysis represent the percentage of each element in the fertilizer. For example, a 5-10-10 fertilizer contains 5 percent nitrogen, 10 percent phosphorus (as P205) and 10 percent potassium (as K20). An 8-16-16 fertilizer is a 1-2-2 ratio, but it contains a greater percentage of each of the fertilizer elements. Smaller amounts of the 8-16-16 should be used in place of the 5-10-10.

. Fertilizers can also be classified by their solubility. Soluble fertilizers release their nutrients rapidly; whereas, organic and slow-release fertilizers release nutrients over a period of time. The fertilizer in the slow-release formulation is released by water penetration, weathering, or microbial action, depending on the type of slow-release fertilizer. With one application of soluble fertilizer, plants may not be able to take up all the available fertilizer, and some nitrogen may leach below the plant rooting depth with percolating water. Slow-release fertilizers are designed to release at a rate more consistent with plant needs. Slow-release fertilizers are usually more expensive than soluble fertilizers. The choice of soluble or slow-release nitrogen depends on the reason for fertilization. Soluble fertilizers may be required when a quick response is desired, and slow-release fertilizers are excellent for regular maintenance. Fertilizers are also formulated with a combination of soluble and slow-release nitrogen. Fertilizer is available in dry and liquid forms. There is no difference in uptake from these forms. Both require irrigation or rainfall to distribute nutrients in the soil water solution so they are available for uptake.

Learn to read the fertilizer analysis. A 5-10-10 fertilizer contains 5 percent nitrogen, 10 percent phosphorus, and 10 percent potassium.
Use soluble fertilizers for a quick response.
Use slow-release fertilizers for regular maintenance.

Alternative Nutrient Sources
Many organic materials provide excellent sources of nutrients. Release of the nutrients from organic materials applied in proper quantities is usually slow, so little nitrogen is leached from the soil (although some "raw manure" sources, such as poultry manure, are "fast-release"). Composted sewage sludge, poultry manure, cow manure, composted leaves and other vegetation, peat moss, sea weed, and fish emulsion are all organic sources of nutrients. Prepared organic fertilizers include cotton seed meal (7-2-1).

The problem with using organic materials as sources of nutrients is that the content of available nitrogen and other nutrients is often unknown. If you purchase packaged manure or composted sewage sludge at a garden supply store, the "total" fertilizer analysis should be on the package. This does not mean that all those nutrients will be "available" to the plants. The level of nutrients in unprocessed organic materials, bulk sources, or organic material produced at home is anyone's guess. You may not apply enough fertilizer to get the desired result, or you may over-fertilize, causing nitrate leaching, salt toxicities, or excessive vegetative growth to occur. It is a common misconception that using organic fertilizer is beneficial to the environment and "safe." Organic fertilizers are safe if used properly, but over-application can be just as detrimental as over-application of inorganic fertilizers.

Organic materials can be excellent sources of nutrients.
Be careful applying organic materials when the fertilizer analysis is unknown.
Remember that organic fertilizers are not necessarily beneficial to the environment and "safe."

Purchasing Fertilizer
In order to make a decision about which fertilizer to purchase and how much to apply, it is important to know why you are fertilizing. For shade trees, you may want to promote rapid growth so that young trees quickly become large and functional. Or you may want to maintain the health and appearance of a mature tree. An additional reason for fertilization is to rescue a declining tree. Different amounts of fertilizer are required to fulfill each of these goals.

For more information, call your county Extension office. Look in your telephone directory under your county's name to find the number.

Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, and other related acts, in cooperation with the U.S. Department of Agriculture. The Alabama Cooperative Extension System (Alabama A&M University and Auburn University) offers educational programs, materials, and equal opportunity employment to all people without regard to race, color, national origin, religion, sex, age, veteran status, or disability.

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