(gardening) Practical Lawn Fertilization.pdf

PUBLICATION

8065

Practical Lawn Fertilization

J. MICHAEL HENRY, University of California Cooperative Extension Farm Advisor,

Environmental Horticulture, Riverside County; VICTOR A. GIBEAULT , University of

California Cooperative Extension Specialist, Environmental Horticulture, University of

California, Riverside; VINCENT F. LAZANEO , University of California Cooperative

Extension Farm Advisor, Environmental Horticulture, San Diego County

P roper maintenance is the prerequisite to having an attractive lawn. One of the major

requirements of proper maintenance is adequate fertilization to insure optimal

growth and development of leaves, roots, and the other parts of the plant. A well-

planned and executed maintenance program—which includes mowing, irrigation,

and thatch and soil compaction control as well as fertilization—will produce good-

looking, pleasingly green turfgrass that will quickly recover from wear, pest damage,

or mechanical injury.

UNIVERSITY OF

CALIFORNIA

Agriculture

and Natural Resources

http://anrcatalog.ucdavis.edu

WHAT IS FERTILIZER?

A fertilizer is any material containing at least one of the essential elements for plant

growth that is added to the soil for the purpose of supplementing the plant nutrient

supply. The elements essential for plant growth are shown in table 1 .

Most nutrients are normally available in plentiful amounts in soil, air, or water,

but some are needed by turfgrass in greater amounts than the soil can supply. All

lawns need nitrogen (N) fertilizer; in some areas, phosphorus (P), potassium (K), or

sometimes iron (Fe) may also be required. Check with your local Cooperative

Extension farm advisor or master gardener for possible nutrient deficiencies in your

particular area.

WHEN DOES YOUR LAWN NEED FERTILIZER?

There are two methods to determine when and which fertilizer elements are needed.

The most common method is to visually evaluate the appearance of a turfgrass

stand.

A nitrogen-deficient lawn has poor color (yellow-green to yellow), slow or

restricted growth, poor density with possible weed invasion (especially clovers), and

an obvious reduction in grass clippings after mowing. Iron deficiency also results in

yellowing of young turfgrass leaves, although there is no initial stunting of the

growth. Phosphorus is the third most common nutrient deficiency. A phosphorus-

deficient turfgrass stand has a dull, blue-green color, which progresses to individual

leaf blades, giving them a purple color along their margins and then a reddish tint

from leaf blade tip to base.

Visual evaluation of the lawn is often adequate for determining when to apply

more fertilizer. Irrigation deficiency or pest or disease problems may also cause yel-

lowing or reduced growth, but they cause more dead (brown) leaf blades, and symp-

toms are usually not as uniform throughout the grass stand as with nitrogen defi-

ciency. If you are interested to learn the exact levels of soil nutrients, submit a rep-

resentative soil sample to a commercial soil-testing laboratory. The sample should be

at least 1 pint (0.5 l) and should be derived from several sampling locations in the

lawn. Local University of California Cooperative Extension offices do not perform

this service, but they may be able to suggest private labs that do agricultural or hor-

ticultural soil testing for a fee.

ANR Publication 8065

Practical Lawn Fertilization

WHAT KIND OF FERTILIZER SHOULD

YOU USE?

Table 2 shows commercially available fertilizers

that supply the commonly needed elements. The

nutrient sources are listed on each fertilizer bag in

an analysis statement that gives the percentage of

each nutrient supplied by the product. For example,

16-8-8 is a turf fertilizer that contains 16 percent

nitrogen, 8 percent phosphorus (P 2 O 5 ) and 8 per-

cent potassium (K 2 O). A fertilizer containing nitro-

gen, phosphorus, and potassium is often referred

to as a complete fertilizer ( fig. 1 ) . Nitrogen is the

major element in a complete lawn-type fertilizer.

With all the different lawn fertilizers on the

market, one might wonder how they are different,

other than in percentages of nutrients. One of the

main differences is the way in which products

make their nitrogen available to grass roots. Fast-

release or soluble nitrogen products are usually

the least costly. They can provide a quick greening

response for a relatively small amount of product

applied. However, they can “burn” the lawn if

improperly applie d ( fig. 2 ), and they also are soon

used up, which means more frequent application

will be needed.

Natural organic materials, including biosolids

(sewage sludge), animal manures, compost, or

other by-products, also contain plant nutrients.

Although safer to use because they are not as apt

to burn turf, they are generally bulky due to their

low concentration of nutrients and are often more

T able 1. Essential turfgrass nutrients, in order of relative quantity

Nutrients needed in comparatively large amounts

Source

Nutrients

air and water

carbon (C)

hydrogen (H)

oxygen (O)

soil

nitrogen (N)*

phosphorus (P)†

potassium (K)‡

calcium (Ca)

magnesium (Mg)

sulfur (S)‡

Nutrients needed in comparatively small amounts

Source

Nutrients

soil

iron (Fe)‡

copper (Cu)

zinc (Zn)

manganese (Mn)

molybdenum (Mo)

boron (B)

nickel (Ni)

chlorine (Cl)

NOTES:

* Fertilization always needed.

† Fertilization probably needed at planting; less likely to be needed on established turf.

‡ Fertilization possibly needed.

Nitrogen

(N)

Phosphate

(P 2 O 5 )

Potassium

(K 2 O)

NITROGEN

16-6-6

Figure 1. A sample label from a “complete”

lawn fertilizer bag.

ANR Publication 8065

Practical Lawn Fertilization

Table 2. Information on selected commercial fertilizers used on lawns

Fast Release

Analysis

Amount needed

Relative

Remarks

soluble nitrogen

(% N-P-K)

to apply 1 lb

to apply 0.5 kg

cost/lb

(N) fertilizers

actual N/1,000 sq ft

actual N/100 sq m

of actual N

(lb, approx.)

(kg, approx.)

ammonium nitrate

33-0-0

3.0

1.5

low

Can burn. Contains immediately available

nitrate. Used for winter nitrogen fertilization.

ammonium

16-20-0

6.0

3.0

low

Used mainly as a preplant fertilizer for

phosphate sulfate

soil incorporation.

ammonium sulfate

21-0-0

5.0

2.5

low

Acidic soil reaction. Can burn turf if over

overapplied.

calcium nitrate

15.5-0-0

6.5

3.3

low

Quickly available. Can burn turf. Used for

winter fertilizer.

urea

45-0-0

2.0

1.0

low

Converts quickly in soil to available

ammonium nitrogen. Very high burn

potential.

Natural organic

% N

materials and

fertilizers

activated biosolids

4–7

high

Significant phosphorus and moderate

(sewage sludge)

nitrogen; some potassium present.

digested biosolids

1.5–3

high

Low nitrogen availability; some (sewage

sludge)

phosphorus present.

poultry manure

3–4

high

Good source of nitrogen, phosphorus.

Odor may be rather strong.

steer manure

high

Low nitrogen, good source of phosphorus

and potassium, but not a favored turf weed

fertilizer. May introduce weed seeds and/or

increase salinity.

Slow-release

% N

fertilizers

coated/soluble fertilizer

varies

varies*

high

Foot traffic and mowing equipment may

crush coated fertilizer and destroy slow-

release properties, especially on putting

greens.

ESN (neutralized

varies

varies*

high

Coating is semipermeable, allowing

ionic elastomers)

release of dissolved ureas through

membrane for up to 6 months.

IBDU (isobutyl-

varies

varies*

high

Nitrogen released by slowly dissolving

enediurea)

in soil water. Long-lasting response.

methylene-urea

varies

varies*

high

Similar to UF but quicker nitrogen release.

polymer-coated ureas

varies

varies*

high

More controlled release than SCU with

addition of plastic to sulfur coat.

sulfur-coated urea

32–41

2.5–3.0

1.3–1.5

moderate

Release can be up to 16 weeks for some

formulations.

UF (ureaform)

3.0

1.5

high

Nitrogen released by soil microorganisms.

Poor winter release; faster summer release.

NOTE: * Follow manufacturer’s recommendations for application rates.

ANR Publication 8065

Practical Lawn Fertilization

Figure 2. Grass “burned”

by spill of lawn fertilizer.

expensive than soluble fertilizers per

pound of actual nitrogen content. Some of

these natural materials may contain weed

seeds or salts, and some may have unpleas-

ant odors. Their advantage is that they

release nutrients over an extended period

of time.

Slow-release chemical fertilizers allow

nitrogen to become available over longer

periods of time than do soluble fertilizers,

and they won’t burn turf even when applied

at comparatively high rates, such as 2

pounds of actual nitrogen per 1,000 square

feet (1 kg per 100 sq m) and higher. Such

products contain much higher concentra-

tions of required plant nutrients than do

the natural organics, eliminating the bulki-

ness associated with natural organic fertil-

izers. Slow-release chemical products can

be applied less frequently than soluble fer-

tilizers, but their release rate can vary

depending on the product type, amount of water applied, temperature, and activity

of soil microorganisms. They are often recommended for sandy soils and other situ-

ations where fertilizers are easily leached out of the turf root zone or into under-

ground water supplies, reducing water quality for drinking and other beneficial uses.

HOW OFTEN AND WHEN SHOULD YOU FERTILIZE?

Creating a fertilizer program that is right for your lawn involves many factors.

Turfgrass species, type of fertilizer, climate, soil, desired quality level, and bud-

getary considerations all play a role. The guidelines presented in table 3 give a basic

fertilization schedule that should produce acceptable turf. More frequent fertiliza-

tion would be required for specialty turfs such as playing fields and golf course

putting greens; more would

also be required in autumn

to maintain the green color

of warm-season grasses in

mild-winter regions or any-

time a greener, more lush

lawn is desired.

Generally, you should

fertilize at the beginning of

the optimal growing sea-

son(s) when the grass starts

to grow vigorously and is

free from heat or cold stress.

To create a good turf fertiliz-

er program, it is important

to know the type of turf-

grass being grown. The two

main groups of turfgrasses,

warm-season and cool-sea-

Table 3. Turfgrass fertilization program showing when to apply equivalent of 1 lb actual N/1,000 sq ft

(0.5 kg actual N/100 sq m)*

Months to apply fertilizer

Turfgrass

type

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Southern California

X †

warm-season

X †

cool-season

Central Valley, North and Central Coast

X †

warm-season

X †

cool-season

Mountain Regions

X ‡

X †

cool-season

NOTES:

* With slow-release products, follow the manufacturer’s suggested rates of application.

† This is the best time to apply a complete fertilizer (containing N, P, and K), if necessary.

‡ After snow melts.

ANR Publication 8065

Practical Lawn Fertilization

son grasses, have different growing periods in California; the proper times to fertil-

ize each group are not the same.

Warm-season grasses make most of their growth in the warmest months and are

often dormant (brown) in winter. Warm-season species include hybrid and common

bermudagrass, zoysiagrass, St. Augustinegrass, buffalograss, seashore paspalum, and

kikuyugrass. Warm-season grasses are best adapted to the Central Valley and

Southern California, including the inland deserts. Fertilize when grass is green, but

avoid excessive nitrogen in the summer when the grass is already growing fast.

Many warm-season grasses developed for Southern California can be coaxed to stay

green in the winter by regular nitrogen fertilizer applications into the late fall and

winter, except where frosts and colder temperatures are common.

Cool-season grasses grow well in spring, fall, and in winter where the climate is

moderate to mild. In areas having summer temperatures of 80ºF (26ºC) and higher,

these grasses often come under heat stress, which results in reduced growth,

increased disease potential, and poor appearance. Avoid nitrogen fertilizer applica-

tions in hot times of the year on cool-season grasses. Commonly used cool-season

species include tall fescue, Kentucky bluegrass, perennial ryegrass, and red fescue.

They are best adapted to coastal areas, Northern California (except the Central

Valley), and mountainous regions of the state.

HOW MUCH FERTILIZER SHOULD YOU APPLY?

The amount of fertilizer to apply depends on the fertilizer product (% nitrogen and

release rate), the square footage (area) of lawn, and the purpose the lawn serves

(athletic field or low-traffic lawn).

At planting . Fertilize soil before planting seed, sod, plugs, or stolons. A general

recommendation for a preplant fertilizer for most California soils is to apply 12

pounds of ammonium phosphate-sulfate (16-20-0) per 1,000 square feet (6 kg per

100 sq m), rototilled into the top 4 to 6 inches (10 to 15 cm) of soil.

Existing lawns. Most mature lawns benefit from about 4 pounds of actual nitro-

gen per 1,000 square feet (2 kg per 100 sq m) per year (see table 3 ) . Recent

University of California research on grasses suited to low nitrogen and water appli-

cations (e.g., zoysiagrass and buffalograss) found that they could perform ade-

quately with only 2 pounds per 1,000 square feet (1 kg per 100 sq m) of actual nitro-

gen per year. Grass growing in light shade requires less fertilizer than grass growing

in full sun. Turfgrasses under a grasscycling program need slightly less nitrogen; tur-

fgrasses under heavy wear from foot traffic or sports require more nitrogen to

encourage faster growth to repair damage.

Generally, a maximum of 1 pound of actual nitrogen per 1,000 square feet (0.5

kg per 100 sq m) should be applied at one time when using a soluble chemical fer-

tilizer. Nitrogen is the major element, so it is the element that the application rate

is based on. Also, nitrogen is the most soluble element and has the most potential

for burning the grass if applied too heavily. Often, less than 1 pound of actual nitro-

gen can be applied, but 1 ⁄ 2 to 1 pound of actual nitrogen per 1,000 square feet (0.25

to 0.5 kg per 100 sq m) at a time is the usual recommendation. Slow-release fertil-

izers can be safely applied at higher rates. See the product label for specific recom-

mendations on rates and frequency of application; the frequency can range from

every 6 to 8 weeks to as long as every 6 months.

Calculating application rates. To find out how much of a particular fertilizer is

needed to supply 1 pound of actual nitrogen, simply divide 100 by the first number

of the analysis shown on the bag. This will give you the number of pounds of the

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