Gardening Without Irrigation: or without much, anyway

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in water. When insoluble starches and oils are required for plant energy, enzymes change them back into water-soluble sugars for movement to other locations. Eve

ate) less moisture because the sun glances off them. Some weeds can wilt temporarily and resume vigorous growth as soon as their water balance is restored.

e successfully with very little or no supplementary irrigation and without mulching,

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gs to its surface. This is adhesion. The more surface area there is, the greater the amount of moisture that can be held by adhesion. If we crushed that stone into dust, we would greatly increase the amount of

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d by various sizes of soil particles have been calculated. Soils are not composed of a single size of particle. If the mix is primarily sand, we call it a sandy soil.

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mes too weak to resist the force of gravity, and some water flows deeper into the soil. When water films are relatively thick the soil feels wet and pl

ion, roots are no longer forceful enough to draw on soil moisture as fast as the plants are transpiring. This condition is called the "wilting p

But there's more to it. For some crops, deep sandy loams can provide just about as much usable moisture as clays. Sandy soils usually allow more extensive root development, so a plant with a naturally aggressive and de

unique garden soil is actually capable of providing and how much you wil

il Los

plot and extract moisture, we'll make our tilled area 50 feet by 50 feet and make all our measurements in the center. And let's locate this imaginary plot in ful

nerally come in insignificant installments and do not penetrate deeply; all of the rain quickly evaporates from the surface few inches without recharging deeper layers. Most readers would reason that a soil moisture measurement taken 6 inches down on Septemb

be almost as much water present in September as there was in April. Bare earth does not lose much water at all. Once a

cracks. These ever-deepening openings allow atmospheric air to freely evaporate additional moisture.

ly on soil don't remove much water; that is caused by hot sun and wind working on plant leaves, making them transpire moisture drawn from the earth through their root systems. Plants desiccate soil to the ultimate depth and lateral exten

e. A column of water in a vertical tube (like a thin straw) adheres to the tube's inner surfaces. This adhesion tends to lift the edges of the column of water. As the tube's diameter becomes smaller the amount of lift becomes greater. Soil particles form inter

moisture needs of crops. But conventional agriculture focuses on maximized yields through high plant densities. Capillarity is too slow to support dense crop stands where nu

nts Obt

ntinues to extend, parts behind the tip cease to be effective because, as soil particles in direct contact with these tips and hairs dry out, the older roots thicken and develop a bark, while most of the absorbent hairs slough off. This rotation from being actively foraging tissue to becoming more passive conductive and

nown to make more roots than most plants.) I calculate that a cubic foot of silty soil offers about 30,000 square feet of surface area to plant roots. If 3 miles of microscopic root tips and hairs (roughly 16,000 lineal feet) draws water only from a few millimeters of surrounding s

ity: The Key to Wa

e more fertilizer helps after plants "bump," but still the rate of growth never equals that of younger plants. For years I assumed crowded plants stopped producing as much because competition developed for light. But now I see that unseen competition for root room also slows them down. Even if moisture is regularly rec

spire is determined first by the nature of the species itself, then by the amount of leaf exposed to sun, air temperature, humidity, and wind. In these respects, the crop is like an automobile radiator. With cars, the more metal surfaces, the

a Surprise

pts your ability to water. Perhaps you are homesteading and your well begins to dry up. Perh

is maximum subsoil moisture. Then eliminate all newly started interplantings and ruthlessly hoe out at le

centers, or about 21 plants. Remove at least every other row and every other plant in the three or fou

surface inches to dry out and form a dust mulch. You water-w

ater will stay unused in the barren soil through the entire growing season. If a crop canopy is established midway through the growing season, the rate of water loss will approximate that listed in the table in Chapter 1 "Estimated Irrigation

of days. But if that same crop were planted less densely, it might grow a few weeks without irrigation. And if that crop were planted even farther apart so that no crop canopy ever developed and a considerable amount of bare

enjoy deep, open, moisture-retentive soils, all except those with the shallowest soil can increase their use of the free moisture nature provides and lengthen the time between irrigations. The next chapter discusses making the most of whatever

amount harvested does not drop proportionately. In most cases having a plant density one-eighth of that recommen

pictures of my own "irrigationless" garden. Looking at th