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  MG Manual Reference
Ch. 12, pp. 23 - 26

[Maintenance: irrigation | new lawn | fertilization | renovating | mowing | mowing heights
| dethatching | aeration | weed ]


New seedings and spriggings require intensive irrigation to ensure successful establishment. Seedings require light and frequent watering to ensure that the seed and surface of the soil are constantly moist. Plan to keep the soil moist for up to 30 days following planting. During hot days this may necessitate 3 or 4 light waterings during the day to provide adequate moisture for rapid and successful germination. If the soil dries out during the germination process, the seedling is likely to die. Areas sodded and plugged also require intensive irrigation. However, frequent light watering is only required until the sod or plug is rooted. Once sod or plugs are rooted, irrigate every second or third day.


Begin mowing the new lawn when the height of grass is 1/3 greater than the intended mowing height. Be sure that the lawn mower is sharp. A dull mower tends to pull grass seedlings out of the ground or causes leaf blade tips to be bleached or white. Try to minimize traffic on the new lawn until it is mature. Broadleaf weed control may be necessary. Do not apply broadleaf weed control to new lawns until they have been mowed two times. Begin a good, comprehensive fertilization program as outlined below.


A well planned (and simple) fertility program is essential to turf maintenance. Turfgrass requires 16 basic nutrients for growth. Most of these are available to turf from soil, but not in proper amounts for proper growth. Turfgrass fertilizers usually have some mixture of the most abundantly needed nutrients. The ones needed in the greatest amounts are N-P-K. Sulphur as a fertilizer component is sometimes included, since it is beneficial in lowering our high pH soils. See the appropriate lawn calendars and fertilization guidelines for fertilizer rates and application dates.
Fertilizer Terms for Lawns

Fertilizer Analysis or Grade:
The fertilizer analysis or grade is the percent by weight of the fertilizer product of the individual fertilizer element(s). The numerical contents on the label usually contain three values for the fertilizer analysis. These include the amounts of nitrogen (N), phosphorous (P), and potassium (K). If the fertilizer contains any one of these, it must include content values for the other element(s) as well. If they do not exist, then a "0" must appear on the label for that element. For example, a (21_7_14) fertilizer is 21% nitrogen, 7% phosphorous and 14% potassium, by weight. A (21_0_0) fertilizer is 21% nitrogen, but has no phosphorous and no potassium. A (16_20_0) fertilizer has 16% nitrogen, 20% phosphorous, and no potassium (by weight).
Some commonly used quick release fertilizers that are readily available commercially are: ammonium sulfate (21_0_0), ammonium phosphate (16_20_0), ammonium nitrate (34_0_0), potassium nitrate (13_0_44), calcium nitrate (19_0_0), superphosphate (0_27_0), triple_superphosphate (0_45_0), and potassium sulphate (0_0_45).
Other "brand name" fertilizers usually contain mixtures of these products as blended products. These can have any analysis or grade combinations. Examples include (21_7_14), (10_20_10), etc.
Fertilizer Ratio:
Fertilizer ratio is the relative amount of N to P to K in a fertilizer. The fertilizer ratio is easily calculated by dividing the lowest grade number into each of the other grade numbers on the label. For example, on a (21_7_14) fertilizer, divide the 7 into each grade value for N_P_K. This results in a 3_1_2 ratio fertilizer. Note that fertilizers with the same ratio do not have to have the same grade. A (30_10_20) fertilizer has a 3_1_2 ratio (just like the 21_7_14) but its analysis is much higher.
Many commercial lawn fertilizers are available in ratios of 3_1_2, 4_1_2, or 2_1_2. This is based on plant demands and general soil characteristics.
Complete Fertilizer:
A complete fertilizer includes some amounts of all three of the major elements of N_P_K. It does not say how much is present (analysis or grade). It does not say in what relative amounts (ratio). Examples of complete fertilizers include (20_15_5) and 34_10_6). Note that fertilizers such as (33_0_0) or (15_0_20) are not complete, because they lack having all three elements of N_P_K.
Starter Fertilizer:
A starter fertilizer is usually one which is high in phosphorous (P). It may or may not contain other elements as well. Usually, contents of 20% (P) or more are termed starter fertilizers. Superphosphate (0_27_0), triple_superphosphate (0_45_0), and ammonium phosphate (16_20_0) qualify as starter fertilizers.
Fertilizer Applications:
Generally, starter fertilizers should be applied to turfgrass soils before establishment, after overseeding, or during a renovation process.
Regular fertilization programs should include knowledge of the basic times of the year that the turf is growing, and secondly, some extreme soil conditions which may be present. On sandy based soils, it is usually wise to apply a complete fertilizer, since phosphorous and potassium may be lacking somewhat. On more heavily textured soils (loams, clays, silty soils, etc.), regular fertilizations can be made with high nitrogen fertilizers since P_K are usually available. One application per year should be of a complete fertilizer, on these soils as well.
Listed in the lawn maintenance calendars are suggested guidelines for popular Arizona turfgrasses.
Fast vs. Slow Release

Fast release fertilizers dissolve in water quickly and can be taken up readily by the turf. Since they dissolve quickly, they can burn the turf since the fertilizers are actually salts. Slow release fertilizers are those which exhibit "slow" chemical reactions in the soil in order to make the nutrient available over a larger period of time. There are other types of slow release fertilizers which have coatings which will break down slowly, or have small pores in the fertilizer pellets which "ooze" out the fertilizer over time. New technologies for slow release fertilizers are being developed. Slow release fertilizers should be used only during active growth periods. This is during summer for warm-season grasses and the spring and fall for cool-season grasses. Do not apply a full years fertilizer requirement in one application.
More emphasis is being placed on potassium or potash (K) fertilization. Some researchers believe that K should be applied in at least 50% of or equal to the amount of nitrogen. K is beneficial for food storage, root growth, and minimizing many plant stress factors.
Iron containing fertilizers are beneficial in promoting good turf color, without the excess growth sometimes experienced with nitrogen containing fertilizers. Ferrous sulphate is inexpensive, but may be short-lived in our high pH western soils. Cheleated irons are more effective but more expensive and are used on high profile turfs.

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