Full Product Manual

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Determine Plant Water Requirements Page 23
Microclimate Factor
A microclimate is a sub-climate. Even small residential sites will have areas with
entirely different climatic conditions. For example, areas in direct sunlight versus
areas in the shade. The two areas may have identical plantings but the water
requirements of the plants will be very different. Ideally, each microclimate
would be zoned separately. However, when this is not practical, drip irrigation is
flexible enough to meet the needs of these special conditions.
EXAMPLE
Assume that you have a hydrozone that contains only sparsely planted shrubs.
Locate the row labeled “Shrubs,” and read across to the “Low” column. You’ll
find that the density factor for this plant is 0.5. “Low” would be entered in the
top half of the “density factor” box on your worksheet and “0.5” would be
entered in the bottom half of the box.
A less obvious example of different microclimates might be areas close to a house
or a driveway, where reflective heat will change the water requirements com-
pared to an area surrounded by turf. In fact, experiments have shown that
plantings surrounded by pavement may have a PET as much as fifty percent
higher than the same types of plants in a park setting.
For each plant in the hydrozone, record on your worksheet an estimate of the
microclimate: low, average, or high, based on the water adjustment the area will
require. A “low” microclimate will require less water, and a “high” microclimate
will require more water. Record your estimate in the top portion of the “microcli-
mate factor” box. Later, you can assign a value to the microclimate factor, using
Table 4-4 as a guideline.
EXAMPLE
Assume that you have a hydrozone planted with shrubs only. This hydrozone
is adjacent to the street, and it is surrounded by cement walkways. Therefore,
you estimate the microclimate factor as high. If you locate the “Shrubs” row in
Table 4-4 and read across to the “High” column, you’ll find that the microcli-
mate factor for this plant is 1.3. “High” would be entered in the top half of the
“microclimate factor” box and “1.3” would be entered in the bottom half of the
box on your worksheet.
TABLE 4-4: ESTIMATED MICROCLIMATE FACTORS
Plant Type Low Average High
Trees 0.5 1.0 1.4
Shrubs 0.5 1.0 1.3
Ground covers 0.5 1.0 1.2
Mixed trees, shrubs, ground cover 0.5 1.0 1.4
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