Berks County Cooperative Extension -

TURFGRASS - FERTILIZATION

Investment opportunity.

Dollar for dollar, proper fertilization will enhance lawn health more than any other management technique. Dense, inviting stands of turfgrass result from application of the appropriate fertilizer at prescribed intervals. Seizing this investment opportunity begins with a soil test to determine pH. Soil test kits are available from private sources or may be obtained at nominal cost from Penn State Cooperative Extension - Berks County. Easy-to-follow instructions are included with the kit. After the soil is analyzed by Penn State's Agricultural and Analytical Services Laboratory, the results, including fertilizer recommendations, are sent to the address on the mailing label. Without the results of a soil test in hand, it is not feasible to begin an effective fertilization program. It is important to recognize that insufficient fertilization may result in lawn deterioration, while excessive amounts of fertilizer may burn the grass, encourage the development of certain diseases and promote formation of thatch.

Necessary nutrients.

Turfgrass requires certain nutrients that are not adequately supplied by soil. While a soil test may on occasion suggest adding calcium or magnesium to the soil, the following three nutrients are considered essential:

Nitrogen (N). Nitrogen is necessary for vegetative growth and desirable plant color. Types of nitrogen are discussed below.
Phosphorus (P). Phosphorus is necessary for root development and other vital plant processes.
Potassium (K). Potassium is necessary to enable certain plant process. It also enhances disease resistance and winter hardiness in turfgrasses.

Purchasing fertilizer.

Price and bag size should not be the primary considerations when buying fertilizer. The total amount of nutrients and the sources or kinds of nitrogen are the true measures of value. There are two broad classes of nitrogen: quick release and slow release. A quality turf grass fertilizer should contain at least 10% nitrogen with approximately 30% or more or the total nitrogen as water-insoluble or controlled-release nitrogen. Consider the following example of the guaranteed analysis of 16-4-8 turf fertilizer:

Total nitrogen (N) 16%.

1% Ammoniacal Nitrogen.
10.3% Urea Nitrogen.
4.7 % Water-Insoluble Nitrogen.

Phosphoric Acid 4%.
Soluble Potash 8%.

In this example, the percentage of nitrogen (16%) is more than ample to qualify as an acceptable turfgrass fertilizer. The amount of fast-release nitrogen as a percentage of total nitrogen is 70.63% (10.3 + 1 X 100 divided by 16). The amount of slow-release nitrogen as a percentage of total nitrogen is calculated by multiplying 4.7 X 100 and dividing the result by 16 (percentage of total nitrogen). The result in this example is 29.37%.

Frequency of application.

An effective fertilizing regimen must start with a soil test that includes fertilizer recommendations. To facilitate implemetation of the recommendations, Penn State Cooperative Extension - Berks County offers a brochure entitled, Designing A Lawn Fertilization Program that takes the guesswork out of selecting the appropriate fertilizer. In the absence of a soil test, frequency of application is determined by consideration of nitrogen sources. The following are general guidelines that may be used where a soil test has not been conducted:

Nitrogen Source	Number of Applications	Time
30% or more of total nitrogen as water-insoluble or controlled-release nitrogen	Two	1. Mid to late spring 2. Late summer - early fall
15 to 30% of total nitrogen as water-insoluble or controlled-release nitrogen	Three	1. Mid to late spring 2. Late summer 3. Late fall (before ground freezes)

Miscellaneous considerations.

Using a mulching mower to return nitrogen rich grass clippings to the lawn can significantly reduce the amount of fertilizer necessary to maintain a healthy lawn. For more information about this environmentally compatible practice, contact Berks County Cooperative Extension and request the Recycling Turfgrass Clippings Penn State fact sheet.

The late-summer/early-fall application of fertilizer is the most critical since it assists the grass in its recovery from heat or drought stress and stimulates root development. Strong roots prepare grass for the rigors of winter and pave the way for a healthy lawn in spring.

If an application of fertilizer is made in mid- to late-spring, care should be taken to avoid overfertilizing. Excessive amounts of nitrogen applied at this time foster vegetative growth at the expense of root development and may result in the appearance of diseases later in the summer.

Sources: Sources: The Penn State Master Gardener Manual
Designing A Lawn Fertilization Program (McNitt and Landschoot, Penn State University)
Document created: 15 December 1999; Revised: 3 March 2001