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How to water wisely and well.

How to water wisely and well When it's time to water, it's important to get it directly down to plant roots where they can use it, while at the same time preventing wasteful runoff. The simplest and least expensive ways are with a basin, a soaker hose, or a deep-root irrigator.

It's difficult to tell how much water you're applying when using these methods; you need to check moisture penetration during application so that water doesn't go beyond the root system.

Also, when you use a slow-dripping hose or soaker hose, it's easy to forget that the water is running, which can waste a lot of water.

To avoid this problem, you can install a hand-operated dial-type timer between the hose bibb and hose, or use a kitchen timer to remind you to turn off the water.

Soil basins

Basins are circular ridges of soil (shown at left) that concentrate water at the roots of trees and shrubs. They are most useful for plants growing in open soil when there is no lawn or ground cover planted around them. Basins can also be used for vegetables that need wide spacing, such as squash and tomatoes.

Build the main berm just outside the plant's drip line. Make a second ring 4 to 6 inches from the trunk to keep water off it. As the plant grows, continue extending the basin to just outside the plant's drip line (if practical)--this way, you water the entire root zone.

(For newly planted trees and shrubs, direct water to roots by building the outside berm on the outer edge of the rootball. Move it out as the plant grows.)

You can construct your basin so it's easy to measure how much water you've applied. For instance, when filled twice, a basin with a 4-inch-high rim should wet clay soil to a depth of about 36 inches. For more information on how many times you need to fill a basin to wet tree roots 6 feet deep, see following article.

Another way to deep-water inside a basin is with a slow-dripping hose. Turn on the faucet and let the hose dribble for several hours.

Soaker hoses

Soaker hoses supply water at a slow enough rate (output depends on water pressure) for the soil to absorb it.

Wrapped in multiple circles around a tree (at right) or stretched out along a hedge, they make it easy to get water right to the roots. They're best for temporary situations or for plants that need irrigating only a few times a year during the warm season.

Perforated types emit water from holes uniformly drilled along a hose. They can be used face down so water goes directly into the soil or turned up for broader coverage.

Ooze tubing can also be used as a soaker hose. For temporary situations, it can be hooked up directly to a hose bibb, but it's susceptible to clogging this way and can ooze too fast if water pressure is high. For longer life, install it with a filter and pressure regulator like the kinds used for a drip system (for more information about drip irrigation, see part 3 of this special section).

Deep-root irrigators

When attached to a regular garden hose, root irrigators inject water into the soil through a hollow probe. This gets water right down into a tree's or shrub's root zone without wasteful runoff.

Irrigators are particularly useful for trees growing in sidewalks, patios, or other areas with a minimum of open soil. They take more effort than soaker hoses or drip irrigation, but they're inexpensive and help aerate heavy or compacted soil. Some types also can supply fertilizer.

To use one turn on the faucet, keeping the shutoff valve on the irrigator turned off, if it has one. Then turn on the valve while slowly inserting the probe into the root zone (if you insert the probe while the water is off, the opening may clog with soil).

Since most homes have fairly high water pressure (45 psi or more), you may only need to turn the faucet 1/4 turn (to avoid a stream too powerful).

For established shrubs, insert the probe 6 to 12 inches into the soil. For trees, go no deeper than 18 inches; even large trees have most of their moisture-absorbing feeder roots in the top 2 feet of soil.

Start about 2 feet out from the trunk. Space applications 3 feet apart under the plant's drip line. Pay close attention to how much water you're using (check soil moisture by using a trowel or soil sampling tube).

Where to get root irrigators. Most nurseries and home centers sell root irrigators. Prices range from $10 to $32.

To help prevent water waste, look for types that have an on-off valve. Shaft length is also important. All brands are long enough to water any kind of tree or shrub, but tall gardeners may prefer one with a longer shaft (about 3 1/2 feet), which requires less bending over than a short one (about 2 feet).

How much water do your plants need, and how often do they need it? Much depends on climate, exposure, and the plant you're watering. But more important than any of these variables is soil type.

If you know whether your soil is mostly sand, clay, or loam, you can better determine how much and how often you need to water. And if you check its moisture content periodically with a soil sampling device such as the ones pictured at left, you can determine just when to water.

First, know your soil

Your soil may not be all sand, clay, or loam, but it will be more like one than another.

Sandy soils, composed of the largest particles, are generally well aerated. Water moves through them fast, they hold little water, and they dry out quickly. When you irrigate, the water seems to be absorbed in a moment. If you pick up a handful of moist sandy soil, it forms a cast but barely holds together.

Clay soils, made up of fine particles, are usually poorly aerated and absorb water slowly. When you irrigate, the water puddles up fast. Once wet, such soils hold a lot of water. A handful of wet soil makes a slippery ball that oozes through your fingers in ribbons; when you let it go, it doesn't crumble. Clay soils give up moisture slowly, turning crusty, and cracking when dry.

Loam soils, with an idea balance between large and small particles, are well aerated, easy to wet, and dry out at a moderate rate. A handful of loam forms a pliable ball that breaks apart with a gentle touch.

Some soils change textures at different depths. A layer of clay or compacted soil under sandy soil or loam can restrict drainage and keep the upper level unusually wet. To check drainage, dig a 2-foot-deep hole and fill it with water.

After it drains, fill again. If it hasn't drained again in 48 hours, your soil probably has a drainage problem. The solution is to install drainage tiles, drill through the obstruction with a soil auger, or plant in raised beds.

The photograph at right, done in cooperation with soil scientists from the University of California at Davis, shows how soil textures influence water penetration. Tests have shown it takes about 3/4 inch of water to wet sand to a depth of 12 inches, and 2 1/2 inches of water to wet clay to the same depth.

How to "read" your soil

To find out how deeply you're wetting the soil, or whether or not it's time to water, use a soil sampling tube like the one pictured at left. Push it into the ground, twist it back out, and you'll have a 10-inch or longer core that lets you see how wet the soil really is. (Models with extensions can go up to 3 feet deep.)

If the soil core is moist only 2 inches deep, and roots could easily go down 6 to 12 inches, you need to water three to six times as long. Water again and take another core until you get moisture to the depth roots should grow.

Some gardeners just push a metal rod (about 1/4 inch in diameter) into the ground; it should move easily through moist soil and be harder to push when it hits dry soil.

Very few plants grow well in soil that is constantly saturated; it should be allowed to dry partially between waterings. This replenishes oxygen in the soil, which is necessary for healthy growth.

Plants give visible signs when the soil is too dry: leaves lose their luster and may pick up a blue or gray cast; growth slows, and eventually, they wilt. By checking the soil, you can water before the onset of such stress--which can make plants lose leaves, vegetables turn bitter, tomatoes develop blossom-end rot, fruit trees drop fruit.

Note: Soil sampling tubes are difficult to find. Likely sources are companies that sell irrigation equipment. Or try well-stocked nurseries and hardware stores.

Or order by mail. Unique Landscape Necessities, 5733 Ocean View Blvd., La Canada Flintridge, Calif. 91011 (818/957-0188), sells 21-inch stainless-steel models for $26.95 plus $5 for shipping. A.M Leonard, Inc., 6665 Spiker Rd., Box 816, Piqua, Ohio 45356 (800/543-8955), sells 21-inch plated steel models for $24.95 and 36-inch models for $36.75; add 15 percent for shipping. Necessary Trading Co., Box 305, New Castle, Va. 24127 (800/447-5354), sells 18-inch chrome-plated steel ones for $27.95 plus $4.50 shipping.

Deep-watering for

deep roots

Each plant has a maximum depth to which its roots will grow. But they reach that depth only if soil is moist and contains enough air and nutrients. Deep watering encourages deep rooting, giving the plant a greater soil reservoir from which to draw water. The advantage? Deep-rooted plants can go longer between waterings and withstand drought better.

To water effectively, you have to know how much water it takes to wet your soil to the depth you expect roots to grow. The table below shows maximum rooting depths, under ideal conditions, of some popular plant groups. (Also take into account how your soil type affects root growth.)

Guidelines for

effective watering

To wet tree roots to a depth of 6 feet, fill the watering basin as follows. (To build a basin, see preceding article.)

Clay. Fill basin, let drain, repeat three more times.

Loam. Fill basin once, let drain completely, repeat.

Sand. Fill basin once. (If water soaks in so fast the basin won't fill, leave the hose on full--at 5 to 10 gpm--for 10 to 15 minutes for a 25-square-foot basin.)

To wet a 4- by 5-foot flower bed to a depth of 2 feet, sprinkle as follows, with hose delivering 2 to 3 gpm (check your hose delivery with a watch and a bucket of known volume).

Clay. Sprinkle for a total of 30 minutes. (If there is run-off, pause occasionally to let water soak in.)

Loam. Sprinkle bed evenly for 20 minutes.

Sand. Sprinkle for 10 minutes. Water the bed evenly from one side to the other.

Spreading mulch over soil that plants grow in is, in most situations, simply good gardening. But today, as much of the West faces enforced water conservation, mulching is a flat-out necessity.

Mulches have three primary benefits:

* They reduce evaporation of water from the soil. Potential savings are greatest in hot, dry climates.

* They reduce weeds. Weeds compete with your desirable plants for water. Mulches cover weed seeds and shade any seedlings, inhibiting growth.

* They insulate soil from extreme temperature changes. Mulches keep the upper inches of the soil cooler during the day, warmer at night.

A good mulch can even encourage worms, which aerate and enrich soil. To thrive, earthworms require an abundant supply of organic matter and moisture. They seem to disappear in soil that is dry, cold, or wet. The typical generously mulched garden is also generously populated with earthworms.

To conserve water, the most important time to mulch is late spring, once soil is warm. The most important place to put mulch is over the plants' drip zone.

Organic mulches

Three categories of organic mulches are available to home gardeners. To be sure which kind you're getting, check the label or ask when you buy.

Composed mulches are any of the many commonly available materials derived from decaying plant or animal material. All the mulches pictured above except the bark and peat moss are composted. Eventually, when they decompose, they benefit soil by improving its structure and preventing crusting. Some composted mulches have nutrient value.

Partially composted materials include manure and mushroom compost. We don't recommend these two for use as summer mulches, because they usually have a high level of salts, which can damage plants. Apply them in fall so that winter rains can wash out the salts before spring.

Noncomposted mulches--fresh sawdust or shavings--offer the same benefits as other organic ones. But as these products decompose in or adjacent to soil, they will outcompete plant roots for their most important nutrient--nitrogen. For this reason, these materials also don't make good summer mulches without additional nitrogen fertilizer.

To safely use noncomposted or fresh sawdust or shavings as mulch and prevent nitrogen deficiency, apply 3 pounds of actual nitrogen per cubic yard of material. Use controlled-release nitrogen fertilizers, such as ureaform (38-0-0).

Commonly available kinds

Pictured above are the six natural-material mulches most often available in nurseries and garden centers. In fall, any of them can be rotary-tilled into the soil to decompose over the winter and improve soil.

The worst that can be said of some organic mulches is that they encourage such nuisances as sowbugs and snails by creating a dark, moist, cool environment. Coarse-textured organic materials, such as decorative bark, provide these pests with the most hiding places.

Commercial compost typically consists of sludge mixed with wood by-products. With about 2 percent nitrogen, it has more nutrient value than the other commonly available mulches and can hold 100 percent of its own weight in water. Expect to pay $4 to $5 per 2-cubic-foot bag, $30 per cubic yard, or 18 cents per square foot, 2 inches deep.

Apply a 1-inch-deep layer around vegetables or ornamentals. Roses and similar heavy-feeding plants benefit from deeper layers. For more information, see the section "A word about sludge compost" at right.

Aged sawdust is an excellent material to add to your own compost. It costs $3 per 3-cubic-foot bag, around $20 per cubic yard, or approximately 12 cents per square foot, 2 inches deep.

In late spring and in midsummer, apply 1- to 2-inch layers around ornamentals. Use with caution near vegetables and fast-growing plants: the mulch might steal nitrogen.

Shredded bark--sometimes called walk-on bark--is available throughout the West. It looks natural and is slow to decompose; the irregular pieces hold well on slopes and in windy areas. It costs $7 for a 3-cubic-foot bag; in bulk, it costs about $40 a cubic yard, or 24 cents per square foot, 2 inches deep. Use it in 2-inch layers.

Aged redwood sawdust costs $6 per 3-cubic-foot bag; in bulk it runs about $24 a cubic yard or 15 cents per square foot, 2 inches deep. In late spring, apply a 1- to 2-inch layer around vegetables and ornamentals.

It is not composted, and is slow to decompose. When you apply it, add half the amount of nitrogen fertilizer recommended for fresh sawdust.

Decorative bark is mostly white fir or pine, chiefly from Arizona and South Carolina. Sizes are graded: 1/4- to 3/4-inch bark is usually called pea, 3/4- to 1 1/2-inch is acorn, 1 1/2- to 2 1/2-inch is jumbo. Bark chips range widely in price: $1.50 to $4 per cubic foot in bags, $20 to $40 per cubic yard in bulk. A 2-inch layer, delivered in bulk, would cost--roughly--20 to 25 cents per square foot.

For an effective water-saving mulch, you need to spread coarse bark chips in a thicker layer than you would other materials--3 to 6 inches deep. Small chips tend to scatter; large ones are more wind resistant but can float away. All turn gray with age.

Peat moss seems more expensive than it is because it's compressed. When you open a bale, its contents expand about 1 1/2 times.

Spread peat moss 2 to 4 inches deep. Use the coarse grade if possible; it's more wind resistant. Peat moss is acidic and holds moisture very well, but when thoroughly dry it repels water and can blow away; use a wetting agent to rewet it.

You'll pay about $15 for a 5.6-cubic-foot compressed bale, or about 30 cents per square foot when spread 2 inches deep. It's not sold in loose bulk.

How much do you need?

One cubic yard (27 cubic feet) of mulch covers 108 square feet with a layer about 3 inches deep. Three cubic yards covers 1,000 square feet 1 inch deep. A 2-cubic-foot bag covers 8 square feet 3 inches deep. A 5.6-cubic-foot bale of compressed peat moss will expand to cover about 40 square feet with a layer 2 to 3 inches deep.

A word about

sludge compost

Recycling municipal sewage sludge in home gardens is an ingenious use of a nutrient-rich but otherwise useless material. As cities grow and places of disposal diminish, recycling sludge becomes increasingly important.

A deserved criticism of sludge is that it may contain contaminants, especially cadmium. Sunset hired an independent laboratory to test sludge composts from the Bay Area and Los Angeles for cadmium. The highest level, 8.2 parts per million, was in Los Angeles. The Bay Area's showed 4.9 ppm. According to a manual published by the California Department of Health Services in 1983, sludge compost with cadmium levels up to 50 ppm is safe for use in home gardens.

What does it take to save large trees like 30-year-old redwoods, 5-foot-diameter Monterey pines, or 35-foot birches, which suffer severely during prolonged periods of drought? Time, work, and, most important, water.

What justifies using large quantities of water this way? Though water is a precious resource, so are big landscape trees. It's worth going to great lengths to save them. You should examine them closely and, if necessary, do everything you can to find enough water to irrigate them properly.

Recognizing drought stress

Drought stress reveals itself in many ways. The drawing at right shows some common symptoms.

Several tree species suffer more than others during long droughts. These include alders, giant sequoias (Sequoiadendron giganteum), birches, coast redwoods, some cypresses, deciduous magnolias, flowering cherries, Monterey pines, and trees growing in lawns that have had water cut back.

Coast redwoods, usually densely foliaged, get scraggly, and tops die; they also produce an unusually heavy crop of cones. Monterey pines can turn a scorched reddish bronze, and once-proud birch trees can end up leafless.

Even native oaks suffer during long droughts. One deep watering in late spring or early summer could help; remember to keep the water at least 6 feet away from the trunk. If your oaks are dropping a lot of leaves and if their foliage is much thinner than usual, or if there is a lot of short, new growth originating along large main branches, consult an arborist.

In many cases, diseases, or insects such as borers, compound problems by preying on trees weakened by drought stress.

Whatever pest infestation may be in evidence, the first thing to do for your tree is to relieve the drought stress with efficient irrigation.

If you suspect your tree is suffering from lack of water, or even if you just want to prevent future problems, examine the soil at several locations beneath the tree.

Use a shovel or a soil probe to check down to a depth of 8 to 12 inches. If the soil is crumbly or rock-hard and dry, it's time to irrigate.

Watering: How long? How

much? How deep?

The drawings below show ways to water big trees.

Space soaker hoses 2 to 3 feet apart; operate them at a pressure that results in a spray about 18 inches high (make sure spray doesn't hit the tree trunk) for 10 to 11 hours or overnight. Move the hoses as needed to wet the entire root area to a depth of 18 to 24 inches.

With the soakers running so long, it's impossible to keep a constant vigil over them. But check moisture penetration often so that water doesn't go beyond the root zone.

Other techniques can be used to water large trees, but few apply water as slowly and evenly as soaker hoses.

What if your water is

being rationed? Do you

save water or save trees?

Big trees are valuable. If they should die, it would cost hundreds of dollars to have them removed, and they couldn't be replaced.

But before you use any large quantity of water, check with your water department to find out exactly what restrictions apply (some areas allow watering only at night, others only with drip or ooze-type irrigation) and what penalties exist. Learn how to read your water meter, so you can be aware of just how much water you're using. Also consider stretching waterings over longer periods of time; and use any drop of water that can be conserved elsewhere, even if you have to deliver it by bucket.

In some areas, severe penalties apply if you go over your allotment. You may have to truck water to your trees. Figure about 400 gallons for each 400 to 500 square feet of root area.

Monitor soil moisture throughout the summer. Trees most stressed will need at least one more irrigation before fall. If a tree has a lot of dead branches or fails to respond to watering, consult a certified arborist about possible complications.
COPYRIGHT 1991 Sunset Publishing Corp.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Sunset Drought Survival Guide for Home and Garden; includes related articles
Date:May 1, 1991
Previous Article:How to save water in the house.
Next Article:Bring your irrigation system up-to-date.

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