How to Water the Garden

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The most water-efficient, automated system around is drip irrigation.
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Water provides more than just liquid to a plant; it's also the medium that enables nutrients and minerals to enter the roots.

Reprinted from MOTHER EARTH NEWS NO. 94. 
 

Here’s how to water the garden, a sometimes confusing job done as
efficiently (and effectively) as possible.
 

How to Water The Garden

At this very moment, somewhere on our vast planet, it’s
raining. But at the MOTHER EARTH NEWS EcoVillage garden, we’re in the
middle of a typical summer dry spell . . . so I’ve been
busy soaking the bases of our tomato plants with a watering
wand.

Most of us — with the twist of a spigot — can turn
a garden hose into an umbilical cord linking us to vast
(yet not inexhaustible) underground rivers. And
since many of us don’t need to worry about the availability
of water, being blessed with adequate supplies, we can
often afford, instead, to fret about when to water
. . . how much moisture to put down . . . what
implements and techniques are most
appropriate to use . . . and how to conserve as
much water as possible while still nurturing the crops.

These are the concerns we’ll address in this article. But
first, let’s review some fundamentals about . . .

Soil and Water

Water provides more than just liquid to a plant;
it’s also the medium that enables nutrients and minerals to
enter the roots. (Roots don’t digest dirt — they’re not
“woody earthworms” — but instead obtain their nutrients
only in solution.) What’s more, through the process of
photosynthesis, some of water’s hydrogen is split off to
become a constituent of the carbohydrate compounds that
make up most of the body tissue of growing plants.

Interestingly, water also enables plant roots to obtain
nutrients that are beyond their physical reach. At varying
depths below our feet lies the water table. Above that is
soil containing minute, air-filled vestibules. When enough
moisture surrounds each soil particle to create a
continuous film from roots to water table, plants can, by
capillary action, draw water and thus food from places far
beneath their roots. (When this happens, the soil is said
to have reached field capacity.)

If, on hot summer days, the crops use more water than is
replaced, dry air spaces are created within the soil, and
the bridge to the water table is broken. Conversely, if a
real downpour hits and the air spaces become flooded to the
point of excluding oxygen altogether, plants can
literally drown — because roots must have air
available, as well as water.

Whether or not your garden soil will retain water
well without becoming over-saturated is determined, for the
most part, by its structure. But don’t feel that you must
live with the type of soil that’s currently in your plot.
The great equalizer, compost, can help improve any ground
that has trouble properly absorbing or retaining
water.

Take sandy soils, for instance. They often have large
spaces between their particles that allow for excellent
drainage — if there is existing moisture in the soil.
If, however, as might be the case in an extremely sandy
soil, those spaces are completely filled with air, they can
actually become a barrier to water penetration.
Rain will be able to penetrate no deeper than the first few
inches, so even though the garden has gotten a good
soaking, deeper levels will remain bone-dry. When that
happens, plant roots tend to seek out only the upper few
inches of soil and will thus be quite susceptible to heat
and moisture loss.

Compost added to such a sandy soil will act as a
moisture-retaining wick. It should be incorporated
deeply — say, six to eight inches — so it will also
help attract roots downward.

Silty soil acts in much the same way. Its powdery,
flour-like texture can let water slip right through . . .
just as the soil itself would sift through your open
fingers. In the process, that water will quickly leach
nutrients from your plants. Here again, compost will give
your plot a better water retaining capacity.

Clay soils have another problem: They have so few air
spaces that they’re too easily flooded by water. A
sticky, slimy, wet clay soil can easily drown roots. The
addition of as much organic matter as possible is a definite must in order to lighten the soil to allow plant
roots more room to breathe. At the Eco-Village, we turn in
at least an inch of compost (and preferably more) before
planting any crop in our clay-heavy beds.

Turning under green manure (or cover) crops is often
another good way to add more humus to the soil. Our own
clay plot, however, doesn’t have sufficient below ground air
to stimulate the needed decomposition of turned-under
crops, so we actually cut down most of the green matter and
compost it before working it in.

On the other hand, adding sand to clayey soil
is not
supposed to help its texture — the clay
allegedly “swallows” it up! As an old gardening maxim puts
it: Put clay in sand, money in the hand; put sand in clay,
throw money away. But when we finally tested this adage
last summer by working about an inch of sharp creek sand
into a few beds along with their compost allotment, the
sand did make a noticeable improvement in both texture and
drainage.

When to Water the Garden

Early mornings and evenings are almost magical times in
every garden. The low rays of the sun impart a certain aura
to leaves and fruit that’s lacking in the harsh light and
heat of midday. And, as chance would have it, those are
also the best times of day to water.

Here at the Eco-Village, we water our established beds a
few hours before dusk, when the day’s work is behind us and
the tranquility of early evening is descending. The soil,
heated throughout the day, will warm the water as it
percolates downward, making the liquid less chilling (and
stressful) to the plants. Furthermore, watering in the
early evening allows time for the foliage to dry before
nightfall — preventing the sustained dampness that
favors the spread of fungi and mildews. In addition, plants
do much of their actual growing at night (employing the
stored products of photosynthesis), so they can well use a
late-day boost to their aqueous reserves. And evening is
generally a time of reduced wind and cooler
temperatures — so water added then will be less likely
to evaporate (an important conservation consideration).

Of course, if you find that you spend most of your time in
the garden during morning hours, you can water then
instead. While doing so may not provide quite as many
advantages as does early-evening watering, at least it
avoids the hazards of adding water in the heat of the day
(which can seriously stress plants) or at nightfall (which
encourages disease). It also provides the earth with a
deep, long drink early on that can help bring your plants
through the coming hot afternoon.

Do remember one thing, though: It’s never a good idea to
work in your garden when the plants are wet (whether from
rainfall or overhead watering). You can easily damage crops
at such a time or — worse — spread disease.
(Carrots, tomatoes, beans, and squash are especially
vulnerable to handspread disease.)

How Often and How Much

Just as you may choose between two generally preferred
times to water, there are also two schools of thought on
how often to water. Daily light watering
regularly replenishes the water that growth and evaporation
use up. This way, the soil’s water “arteries” remain intact
and reach deep into the ground. And occasional
deep
watering accomplishes the same goal by
periodically drenching the soil thoroughly.

Choose whichever technique you prefer — just DON’T go
with occasional light watering. Such half-hearted
efforts will keep only the top inch or two of soil moist .
. . coaxing roots to grow only near the surface where they
can readily dry out.

To make sure you’re watering enough — whether you go
for the daily-light or the occasional-deep method — get
a trowel, a soil tube, or an auger, and after you’ve
watered, dig down about a foot to see just how deep your
added moisture is penetrating. This is a very important
learning step. With time, you’ll develop a feel for how to
keep the soil at its optimum saturation level. But until
you gain such expertise, digging to see what’s really
happening underground is the way to go (and learn).

The first time or two you check, you may well discover that
you’ve been watering too shallowly. Many people make that
mistake, failing to realize that it can take three-quarters
of an hour to fully water one 10 foot by 10 foot plot!
Indeed, the average garden needs about one inch of rain or
irrigation per week . . . which figures out to about 62
gallons per 100 square feet. If you provide that much in
one weekly watering, it should soak the ground to a depth
of about one foot. (Dig and see!)

Of course, most times, natural rainfall will provide some
of that moisture, and you’ll only have to make up the
difference. You can estimate the amount of natural
precipitation you’ve received by following your local
weather reports, by putting a large can in the garden and
measuring how deep the water in it is after each rain,
or — if you like precision — by making your own
rain gauge from a funnel and cylindrical tube. For the last
method, use a funnel with steep sides, and set it where
it’s not exposed to ground splashings or heavy winds (about
a foot off the ground is good). You can also add a thin
film of oil to the cylinder to reduce evaporation losses.
To determine the number of inches of rainwater in the
cylinder that will equal one inch of rainfall, divide the
squared radius of the funnel by the squared radius of the
cylinder. Thus, if your funnel has a three-inch radius and
your collecting tube a one-inch radius, every nine (3 2 + 1 2) inches of water collected in the cylinder will equal
one inch of rainfall.

What about droopy leaves? Won’t they tell you that you need
to water? Well, not necessarily. Plants often wilt
some on a hot summer day as a way of shutting down their
systems to conserve moisture. If you water at that
time, you can shock the flowers and vegetables and cause
more harm than good. (In fact, if you overhead-water on
such occasions, the plants may actually lose
moisture; the leaves will give up internal liquid to try to
balance the perceived atmospheric humidity and end up worse
off.)

Instead, look for signs of wilting during morning and
evening hours. If the leaves are drooping then, it’s almost
a sure sign that your plants need water — and fast!
(One exception: Plants can also wilt if their roots are so
wet that they’re flooded. A quick trowel-in-the-dirt will
determine the true cause if you have any doubts.) Remember,
though, that some waxy-leaved plants, such as cabbage,
onions, and garlic, don’t show water stress as clearly as
others. On the other hand, peas, celery, spinach, and
lettuce are very susceptible to drought conditions and will
let you know in no uncertain terms!

Garden Watering Tools

A quality garden hose is the heart of any watering system.
A hose that will resist its inborn urge to kink and cut off
flow is all but priceless. So don’t skimp on this
purchase — you’ll never regret it. Standard diameters
are 1/2 inches, 5/8 inches, and 3/4 inches. The larger the diameter, of
course, the greater the flow. (By the way, if you garden
with raised beds, you can set rebar posts — with bamboo
or PVC collars — at the corners of your growing areas .
. . and the posts will conveniently steer your hose
around the beds!)

A watering wand is a hose attachment that consists of along
tube with a rose nozzle at the end. It’s kind to your back,
allowing you to stand upright while gently but thoroughly
soaking the soil at ground level. The wand is just the
thing for ground-watering melons, squashes, tomatoes, and
other plants susceptible to leaf molds and fungi. It’s also
an efficient water user, since it places the liquid right
where you want it, rather than spraying it all through the
air and garden. We use ours frequently.

There are other common hose attachments for hand-held
watering, including the fireman-type nozzle, the spray gun,
and fan sprayers. All of these can be useful, but you do
have to stand there and hold them . . . which takes time
and increases the likelihood that you may skimp on
watering. To make your operation a bit more automated, use
a rotary or oscillating sprinkler. (The latter is generally
easier to use, since most of us lay out our gardens in
rectangular — not circular — patterns.) Sprinklers won’t apply
water entirely evenly, however, and they need to be moved
periodically to prevent spot-flooding and runoff problems.
(You can buy automatic timers to shut them off after
specified periods.) A good source for sprinklers and other
hose attachments is Smith & Hawken, Mill Valley, CA.

Sprinklers have other drawbacks. They waste a lot of water,
both by evaporative loss and by wetting pathways — and
weeds — as much as crops. They can increase salt
buildup in your soil or on your plants (do your crops’
leaves have a powdery residue on them or a burned-edge
look?). And they wet the leaves of your disease-susceptible
crops.

The most water-efficient, automated system around is drip
irrigation — invented when an Israeli engineer by the
name of Symcha Blass spotted the beneficial effects of a
leaky spigot on the growth of a nearby tree. Drip
irrigation systems today come in two types: plastic hoses
with small valves — called emitters — spaced every
couple of feet, and microporous plastic pipes that weep
liquid along their entire length. Both systems use from
one-third to one-half less water than do overhead watering
methods . . . put the liquid right at your crops’ roots . .
. and help increase yields by reducing the stress of
extreme fluctuations in moisture levels. Indeed, tests at
Ohio State University have shown that peppers and
cantaloupes grown with drip irrigation and black plastic
mulch produced more than twice the yield of those grown
without those two aids.

Drip systems do have some possible drawbacks. Their
openings can clog (to avoid that, put an appropriate filter
in your waterline). They can start to break down after
prolonged exposure to sunlight (that won’t happen if you
keep the line just underground). And they must be moved
whenever you’re going to do any serious cultivation.

Their biggest disadvantage, at least for people with larger
gardens, is cost . . . around $15 to $30 per hundred feet
of tubing. Perhaps the best way to deal with that
consideration is to buy a small “starter” drip system and
try it out for a season so you can evaluate its
effectiveness. Indeed, we intend to assess the merits of a
number of such systems this summer at the Eco-Village.
We’ll tell you what we find out! [EDITOR’S NOTE: And we
did! Our article “Ooze Who
in Drip
Irrigation” — just last issue — compared
six beginning drip kits.]
 

Water Conservation

Many times, conserving water will be as important
as getting some to your crops. Particularly during July or
August dry spells, you’ll want to make sure your garden
uses and loses as little water as
possible.

In a row garden, one of the easiest ways to cut water
demand is to plant three to five rows close together and
thereby reduce wasted (and watered) pathway space. Of
course, gardening in raised beds will save even more space.
Since such beds incorporate a greater depth of loosened
soil, they also absorb water better than row plantings do.
In addition, raised-bed gardening frequently incorporates
the art of spacing plants so that their mature leaves just
touch — thus creating a “living mulch” that further
blocks evaporation and conserves moisture.

Combine raised beds, living mulch, and
double-digging (to loosen the soil as deep as possible),
and you’ll have a highly efficient water-conserving garden:
John Jeavons’ Ecology Action group in Willitts, California,
has obtained excellent yields of vegetables using these
biodynamic/French intensive techniques and
one-eighth the water of conventional gardening!

While you obviously want to establish your garden away from
the drip line of trees (their roots practically
inhale water), those large plants do have their
place as windbreaks. Much more water is lost to evaporation
from wind than most of us realize. So you’d do well to
utilize any available trees, houses, hedges, or fences to
slow down the drying effects of hot summer breezes.

Mulching with dry materials such as hay, straw, wood chips,
or even black-and-white newspaper pages most definitely
helps protect bare soil from evaporative water loss. Keep
in mind, though, that you shouldn’t mulch too early in the
growing year, or the covering will retard the warming of
your soil. Also, carbon-laden mulches do tie up nitrogen
while they’re decomposing, so you should be sure that
heavily mulched soil has ample nitrogen. (Fish emulsion,
blood meal, cottonseed meal, and well-aged manure are some
good nitrogen supplements.)

The Fundamental Point

Finally, always remember that while expensive irrigation
systems or conservation strategies will help you
save water, the most significant way to conserve moisture
is to make soil improvement your top priority. A humus-rich
soil — created by using lots of compost and cover
crops — will hold the water it gets while still
allowing for aeration. Indeed, the soil should be our first
concern in all aspects of farming and gardening, because
nurturing the diverse life it sustains is the strongest
step we can take toward growing healthy plants.

A Few Water-Saving Tricks

There are plenty of small-scale steps you can take to make
efficient use of garden water. Here are four no-cost tricks
you might try:

  1. Don’t stake plants. Let your tomatoes, beans, and other
    climbers sprawl (on clean, dry mulch), or else grow bush
    varieties. By doing so, you’ll expose less leaf area to the
    drying effects of sun and wind.
  2. Grow some vegetables in partly shaded areas. Lettuce,
    parsley, peas, cabbages, and broccoli — among
    others — can do quite well on just five hours of direct
    summer sunlight a day. Fine netting shades crops well.
  3. Punch small holes in the bottoms of large cans or
    plastic milk jugs, set the containers next to thirsty
    plants, and then fill them with water.
  4. Hill up the sides of raised beds to create basins that
    will trap and hold as much rainwater as possible.