Horticulture Principles and Practices

form of a can placed on the lawn within the area of coverage of the sprinkler may be used.
When the water in the can rises to the level of 1 inch (2.5 centimeters), it is time to move
the sprinkler to another location or shut it off. The amount and rate of application are
affected by soil characteristics. Sandy soils drain fast and clays drain slowly. The infiltration
rate in sandy soils is faster than in clay soils.
The best periods to apply water are early in the morning and late in the afternoon.
Evaporation of water, which is a major source of water waste in irrigation, is minimal during
these times. Overwatering a lawn is wasteful, but inadequate moisture may encourage
the growth of aggressive and hardy weeds. Healthy grass growth shades out weeds
in the lawn and impedes their growth. A combination of the alertness of the homeowner
and the nature (genetics and botany) of the species, as well as familiarity with the regional
climate and weather patterns, is helpful in the judicious application of water. Information
on turf culture is available from local extension agents and horticulturalists. The homeowner
should know the characteristics of the turf cultivar in the lawn. Some cultivars are
shallow rooted and benefit from shallow soaking, while others are deep rooted and benefit
from deep soaking. By listening to weather forecasts, one can take advantage of the
rain or know when to increase or decrease the frequency of watering.
Turfgrasses differ in their response to and recovery from adverse weather. Extreme
conditions of temperature or drought cause browning or yellowing of the grass. Lawns
under stress become dormant but recover with varying degrees of success when the stressor
is removed. A soaking rain after a drought rejuvenates lawns quite successfully, provided
the proper species is used.
18.5.3 FERTILIZING
A good green color is often associated with a healthy lawn. In trying to maintain this
color, some homeowners may go overboard and be in danger of overfertilizing their
lawns. Fertilization should be preceded by a soil test for best results. Fertilizers should
be applied when the lawn is actively growing. Since the main purpose of fertilizing is to
promote vegetative growth, the principal component of a fertilizer analysis is nitrogen;
however, excessive nitrogen may predispose plants to diseases. Fertilizers specially formulated
for lawns may be purchased from nursery shops. Some of these preparations
contain pesticides (e.g., herbicides, fungicides, and insecticides) and must be used
cautiously.
18.5.4 WEED CONTROL
The secret to a weed-free lawn is keeping the turfgrass healthy so that it develops into a
thick carpet. If the sod is not laid properly, the gaps between strips provide room for
weeds to grow. If the lawn is not mowed at the appropriate frequency and to the appropriate
height, weed growth is encouraged. Poor nutrition predisposes grasses to disease
and weakens them, making them less competitive against weeds.
When weeds appear, they should be removed before they set seed. Weed species
such as crabgrass are seasonal in occurrence, and thus when they infest a lawn they die
after the season is over, leaving bare spots in the lawn. Preemergence or postemergence
chemicals may be used. A popular chemical, 2,4-D, is used to selectively control
broadleaf weeds in lawns. Common lawn weeds include dandelion, plantain, burclover,
and puncture vine. Table 18–2 presents a sample of effective lawn herbicides against
common weeds. The final choice of a herbicide and for that matter any pesticide is
according to regional or state recommendations.
A few days before spraying a herbicide, the lawn should be mowed and watered
well. Lawns should not be watered after application of a herbicide, since the chemical
will be washed away. For a small lawn, a backpack tank sprayer or compression
tank sprayer may be used. This type of sprayer may hold up to 5 gallons (19 liters) of
fluid.
18.5 Turf Management 559