VEGETABLE GARDEN:
IRRIGATING THE GARDEN |
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MG
Manual Reference
Ch.10, pp. 17 - 20 |
[Irrigating the Garden:
irrigating | rooting depths ]
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Adequate soil moisture is essential for good crop
growth. A healthy plant is composed of 75% to 90% water, which is
used for the plant's vital functions, including photosynthesis,
support (rigidity), and transportation of nutrients and sugars to
various parts of the plant. During the first 2 weeks of growth,
plants are becoming established and must have water to build their
root systems. |
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While growing, vegetable crops need about an inch of
water per week in the form of rainwater, irrigation water, or
both, from April to September. Keep a rain gauge near the garden
or check with the local weather bureau for rainfall amounts, then
supplement rainfall with irrigation water if needed. There are
ways, however, to reduce the amount of water you have to add. |
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During dry periods, one thorough watering each week of
1 to 2 inches of moisture (65 to 130 gallons per 100 square feet)
is usually enough for most soils. Soil should be wetted to a depth
of 12 inches each time you water and not watered again until the
top few inches begin to dry out. Average garden soil will store
about 2 to 4 inches of water per foot of depth. |
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Reducing water demands
All of this water, however, may not be available to plants,
particularly if the soil is a heavy clay. Clay particles hold soil
moisture tightly. If, for example, there are 4 inches of water per
foot of this type of soil, there may be as little as 2 inches
available for plants. A relatively high level of humus in the
soil, brought about by the addition and breakdown of organic
matter, can improve this proportion to some extent. By causing
clay particles to form aggregates or large clumps of groups of
particles, humus also adds air spaces to tight clays, allowing
moisture to drain to lower levels as a reserve, instead of
puddling and running off the top of the soil. |
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The moisture-holding capacity of sandy soils is also
improved by addition of organic matter. Though most soil water in
sandy soil is available, it drains so quickly that plants are
unable to reach water after even a few days following a rain.
Humus in sandy soil gives the water something to cling to until it
is needed by plants. Addition of organic matter is the first step
in improving moisture conditions in the garden. |
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Mulching is a cultural practice which can significantly
decrease the amount of water that must be added to the soil. A 4
to 6 inch organic mulch can reduce water needs by as much as 1/2
by smothering weeds (which take up and transpire moisture) and by
reducing evaporation of moisture directly from the soil. Organic
mulches themselves hold some water and increase the humidity level
around the plant. Black or clear plastic mulch also conserves
moisture but increases soil temperatures dramatically during the
summer (to the detriment of some plants and the benefit of others)
if not covered by other mulch materials or foliage. |
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Shading and the use of windbreaks are other
moisture-conserving techniques. Plants that wilt in very sunny
areas can benefit from partial shade during the afternoon in
summer. Small plants, in particular, should be protected. Air
moving across a plant carries away the moisture on the leaf
surfaces, causing the plant to need more water. In very windy
areas, the roots often cannot keep up with leaf demands, and
plants wilt. Temporary or permanent windbreaks can help
tremendously. |
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During those times when cultural practices simply
aren't enough, when rainfall is sparse and the sun is hot,
watering can benefit the garden with higher yields, or may save
the garden altogether in severe drought years. |
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Irrigation, when properly used, can benefit the garden
in many ways: |
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- Aids in seed emergence.
- Reduces soil crusting.
- Improves germination and plant stand
- Reduces wilting and checking of growth in transplants.
- Increases fruit size of tomato, cucumber, and melon.
- Prevents premature ripening of peas, beans, and sweet corn.
- Maintains uniform growth.
- Improves the quality and yields of most crops.
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Table 10.6
TOTAL CONSUMPTIVE USE AND DAILY PEAK USE OF WATER
Intermountain Desert and Western High Plains
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250-300
Days |
210-250
Days |
180-210
Days |
150-180
Days |
120-150
Days |
90-120
Days |
|
Season |
Daily |
Season |
Daily |
Season |
Daily |
Season |
Daily |
Season |
Daily |
Season |
Daily |
Crops |
Use
(in.) |
Use
(in.) |
Use
(in.) |
Use
(in.) |
Use
(in.) |
Use
(in.) |
Use
(in.) |
Use
(in.) |
Use
(in.) |
Use
(in.) |
Use
(in.) |
Use
(in.) |
Beans |
22.0 |
0.25 |
17.0 |
0.20 |
14.0 |
0.20 |
14.0 |
0.18 |
14.0 |
0.17 |
12.0 |
0.15 |
Corn |
---- |
---- |
30.0 |
0.35 |
26.0 |
0.30 |
24.0 |
0.28 |
22.0 |
0.24 |
---- |
---- |
Potatoes |
---- |
---- |
23.0 |
0.30 |
21.0 |
0.28 |
20.0 |
0.25 |
19.0 |
0.22 |
17.0 |
0.20 |
Peas |
---- |
---- |
---- |
---- |
10.0 |
0.19 |
10.0 |
0.18 |
10.0 |
0.17 |
9.0 |
0.15 |
Tomato |
---- |
---- |
20.0 |
0.22 |
18.0 |
0.20 |
17.0 |
0.18 |
16.0 |
0.17 |
---- |
---- |
Melons |
22.0 |
0.25 |
20.0 |
0.22 |
18.0 |
0.20 |
16.0 |
0.18 |
---- |
---- |
---- |
---- |
Truck Crops |
20.0 |
0.25 |
18.0 |
0.22 |
14.0 |
0.20 |
12.0 |
0.18 |
12.0 |
0.16 |
10.0 |
0.15 |
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From: Irrigation Principles and
Practices. 4th Ed. Vaughn Hansen |
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Irrigation methods
The home gardener has several options for applying water to
plants - a watering sprinkler can, a garden hose with a fan nozzle
or spray attachment, portable lawn sprinklers, a perforated
plastic soaker hose, drip or trickle irrigation, or a
semi-automatic drip system. Quality equipment will last for a
number of years when properly cared for. When deciding on which
type of watering equipment to use there are a number of things to
consider. |
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Several types of drip or trickle equipment are
available. The soaker hose is probably the least expensive and
easiest to use. It is a fibrous hose that allows water to seep out
all along its length at a slow rate. There are also hoses with
holes in them that do basically the same thing; water drips out
the holes. With the latter type, a flow regulator usually has to
be included with the system so that water can reach the end of the
hose, yet not be sprayed out at full force. A special double-wall
type of irrigation hose has also been developed which helps to
maintain an even flow. Finally, there is the emitter type system,
best used for small raised-bed or container gardens, in which
short tubes, or emitters, come off a main water supply hose;
emitters put water right at the roots of the desired plants. This
is generally the most expensive form of irrigation and the most
complex to set up, but it has the advantage that the weeds in the
area are not watered, and evaporation from the soil is minimized.
This type of system is best used in combination with a coarse
mulch or black plastic. Drip systems generally have some problems
with clogging from soil particles and/or mineral salts from water
taken from springs or wells. New designs take into consideration
the clogging problem; some include filters and self-flushing
emitters. It is wise to make a complete investigation and
comparison before purchasing a drip irrigation system. |
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