Chapter 12. Water and Air A Vital Pair

Plant life is intimately bound to water. Air is equally vital in the soil as well as, of course, above ground. In fact, these two are part­ners; they operate harmoniously in the soil to the advantage of plants growing therein. But water—or rather, the lack of it—is gen­erally more troublesome.

No part of the United States, whether fog-shrouded islands off the coast of Maine, a Midwestern prairie or a seashore spot in Cali­fornia, has escaped periods of drought during which not enough rain fell to maintain plant life. Most sections of the country can expect droughts like this about one year in four.

More often than not, water needs of plants are not considered until cultivation, fertilization and other contributions to growth have been provided. Watering is frequently given no thought until heavy rains of spring and early summer have evaporated and growth begins to show signs of suffering for water. However, if full advantage is to be taken of time, effort and money expended to build up Gardener's Loam, provision for a reliable water supply should receive attention in the initial garden planning.

A Basic Food

Above all, water is a food. Less than 2 per cent of plant tissues are composed of minerals absorbed from soil elements; roughly 98 per cent of the tissues come from air and water. Even the 2 per cent from soil can enter and move through plants only in soluble form. It has been estimated that to produce a single pound of dry matter requires absorption, use and evaporation of at least 700 pounds of water. Of this, less than 1 per cent is retained in plant tissues, either as moisture or as elaborated food. During a single day, a mature tomato plant gives off as much as a gallon of water, while an acre of hay during a single growing season may transpire as much as 700 tons of water.

All this water is derived from soil except for the little absorbed through foliage from dew and rains. Consider where this soil water must come from. In humid parts of the country, it accumulates from snows in winter and heavy rains in spring, with a somewhat smaller accumulation from summer and fall rains. During dry periods, some gardeners may have to add as much as 10 per cent of a season's water supply from city mains or wells. Many gardeners never water at all. In dry districts as much as 100 per cent of the total water needs of plants must be supplied by irrigation. This does not mean that in humid climates artificial watering should be neglected. Often the application of a little extra moisture avoids stunting or slowing of plant growth by preventing plant tissues from hardening. The added moisture may be small in volume but, because it comes at a critical time during the growing season, often makes the difference between a good garden and one that is at best mediocre.

A private well is a fortunate solution to watering problems. The well need not be elaborate. A driven pipe with a pitcher pump can supply all water needed for emergency irrigation in most areas. Elec­trical or gasoline-driven pumps are not expensive and will ease the pumping chore.

Domestic Water Supplies

Sometimes untreated ground water is too loaded with undesirable salts to be usable. Here the gardener must depend upon local munic­ipal sources for water other than that supplied by rain. The first thing I did when I bought my present home was to order 200 feet of %-inch copper pipe, which is cheap, durable, easy to lay and will withstand some freezing even if not properly drained. Placement of water taps at convenient intervals allows me to quickly sprinkle the entire back yard if necessary. I am fortunate in having a 1 ^4-inch copper pipe to the street, which gives me plenty of pressure. If you are building or repairing your house, I recommend that you have that size of pipe installed.

An Early Start

Except for my Merion Kentucky bluegrass lawn, which does better if it is run slightly dry, I don't wait until soil dries out before I start irrigating. Rather than allow the accumulated moisture of spring to pass off, I start applying water as soon as we go for a week without rain. I then turn on the sprinklers and keep them running until the soil is moist six inches down. Of course, that does not mean I have put on an over-all six inches of water: in a true Gardener's Loam the organic matter provides many pore spaces throughout the soil mass that trap air in little bubbles. Many of these pores are so small that water bridges over them by surface tension and does not enter.

I find that when I apply 2% inches of water, as measured in coffee cans set at intervals, moisture will have penetrated approximately six inches. Every gardener should check the water intake capacity of his soil by actually measuring how much water penetrates to what depth. With experience you can learn to judge moisture by feel. Once you have felt your soil when it is in good tilth and adequately supplied with moisture, you will be able to judge the condition of the soil by merely picking up a handful and giving it a squeeze or two.

Organic Soil Sponge

Soils high in humus and other organic matter always dry out more slowly than do sandy types that allow water to run through with little or no absorption. An interesting fact is that when soil does a good job of blotting up moisture, this also takes care of the problem of air supply. As already pointed out, true Gardener's Loam can carry large amounts of moisture without losing its capacity for hold­ing air. Soils in gardens vary between 35 and 65 per cent pore space. Water is held in these spaces in three forms—as free water (usually in vapor form except when soil is "drowned" out with excess water), as a film on the surface of soil particles, and as absorbed water inside porous minerals and organic particles. Air and water, while partners, are antagonists too. They move together into pore spaces when con­ditions are favorable for growth, but at times excess water can drive out air.

We should not think of the air in pore spaces as identical to the air of the atmosphere. For one thing, soil air contains about six or seven times as much carbon dioxide (in soils containing any amount of organic matter) and is slightly poorer in oxygen. This is due to constant absorption of oxygen by roots, leaving carbon dioxide be­hind. Leaves, as we know, absorb carbon dioxide from the atmos­phere and use it to manufacture carbohydrates. If pore spaces are so small that soil "ventilation" is poor, the result is a build-up of carbon dioxide because more oxygen cannot move in to replace that removed by roots.

Small pore passages are the mark of clay soils and other fine-textured types. This makes clay soils difficult to aerate and drain. Large pore spaces are non-capillary; that is, they are normally filled with air because they are so large in cross section that gravity can pull excess water out of them. This is what happens in soils high in sands. The ideal soil condition is one where sand, clay, silt and or­ganic matter provide a soil with large crumb particles. These allow moisture to drain off readily, but inside the crumbs are small air-holding pore spaces which cannot be drowned out. The organic mat­ter serves as a soil sponge to absorb reserve water.

Plants Can Drown

Some plants, notably cattails, sedges and others that live in bogs, can survive with their roots in water. Others can tolerate a soil where pore spaces are close to saturation but contain some air. Most gar­den plants, however, do best when practically all the water in pore spaces is in vapor form, when film water is close to capacity, and when absorbed water is high. This is the invaluable "moist, well-drained soil" about which many garden experts write so much and so vaguely.

If our ideal Gardener's Loam has been built up, the only barrier to correct control of air and water is drainage. This is a basic re­quirement, but it is often left to chance. I have seen carefully-worked gardens where a loose, friable soil had been created, but no provision made to lead away water which found this loose soil easy to penetrate. As a result, the area (surrounded by an underlayer of hard clay) became a "bathtub" into which moisture drained, form­ing a swamp during wet weather.

To check drainage, try to obtain a water-tight barrel or a steel drum that holds about 50 gallons of water. Fill this and then upset it over your garden plot or lawn. If the water soaks in within a few minutes without forming puddles, consider yourself lucky. If it runs off quickly and little of it is absorbed by the soil, grading to reduce the slope may be necessary.

Grading sounds like a real engineering job, which it often is if done on a large area. However, the slope of a small garden, perhaps 30 feet across, should be easy to change so that runoff is slowed up and water penetrates readily.

The trick is to use "cut-equals-fill" techniques. If you want to change the grade ten inches, don't take all ten inches off the top side. Instead, remove five inches from the upper end of your garden and add it on the lower end. This sounds complicated, yet can be carried out over a weekend or two without too much work.

CORRECTING POOR DRAINAGE

If water from the upset barrel remains on the surface for several hours without soaking in, or if water stands there for several days after a spring rain, drainage is poor and must be improved. A basic principle is that water must have some place to go. No matter how well prepared soil may be, it can become waterlogged if no outlet is provided for excess moisture during spring or other periods when rainfall is heavy.

Check both absorption (by the upset barrel test just mentioned) and accumulation. The latter can be tested by digging a hole about 18 inches deep in spring and watching to see if water accumulates and stands in it following heavy rains. If so, then a drainage line of tile should be run to a lower point to take off excess moisture. If the garden soil is loose and friable, this line need not cross the garden at all, but can run from the lowest corner of the plot to some lower area of the property. On small city lots a drain into a storm sewer may be necessary, since few such lots are large enough to allow digging a line to a lower spot.

If no outlet can be provided, a dry well can be used as a partial answer to the drainage problem. A dry well must be big enough to take the surrounding soil's excess water until it can be lost by leach­ing, by evaporation or by transpiration. With a dry well there is no chance for run-off—the fourth way soils lose water—into a low area. One solution I have found for blotting up the water that gathers in a dry well is to plant a willow tree over the well. A willow will tolerate wet feet, and will transpire a barrel or more of water a day when in growth.

Erosion

Although erosion is a serious problem in farm soils, few gardens are large enough to consider this factor. When gardens must be made on slopes, common sense will dictate that the rows run along the slope rather than up and down, and that soil be made as absorp­tive as possible. Too, whenever a crop is harvested, some sort of a cover crop or mulch should go on as soon as possible to prevent wash-outs. Many kinds of effective soil-binding ground covers are available to gardeners whose landscapes contain slopes too steep (or otherwise unsuited) for grass.

Tillage as a Moisture Saver

The old reason given for cultivation was to maintain a dust mulch to "save moisture." We now know that tillage wastes about as much moisture as it saves. As crumbs of soil are kicked up by tillage equip­ment, all sides are exposed to air, allowing far more moisture to escape than if nothing were done. The only saving by tillage comes from weed destruction.

High Water Table

To overcome the problem of high water table, you can resort to an old Dutch trick—raised beds. Ever since tulips were first introduced into Holland in 1560, the Dutch have had to fight this problem and thus can teach us a trick or two.

First step is to wait until the water level is at its lowest point, usually late July or early August. Then scrape off the topsoil (which is usually quite rich in such spots) and pile it at one end of the property. Next, use any available non-rotting fill to build up the level about 12 inches. Do not use stiff clay or similar non-porous material, however. One of the best materials to use is ordinary steam cinders, available cheaply from power generating plants or from industrial plants with high pressure boilers. Sometimes the cinders can be had for the hauling. In this use, the cinders need not be weathered or washed: they will be under so much soil that sulfur compounds they contain will be well neutralized.

Then replace the topsoil, correcting pH if necessary and adding organic matter. The area should then be a foot higher than it was before, with an aeration layer under the surface to take care of ex­cess moisture. If funds are limited, don't hurry the job. Do a little at a time but do it right. Piled black dirt won't be hurt if left for a year or more. You'll be surprised how many weeds will grow out of that pile: keep killing these as they appear and don't let them set seed.

Don't try to make a permanent lawn on such filled ground for a year at least: let it assume its final level first. It needs time to settle.

Overcoming Sandy Soil Problems

The opposite condition to the one just mentioned is the sandy soil so well drained that even particles of organic matter are not held, but disappear along with the water. If the gardener tries to build up humus in such a soil, he is likely to be disappointed.

The remedy is costly in time and labor. It consists of removing the soil to a depth of 12 inches (for flower and vegetable gardens) and laying down a "floor" of tarpaper. Then a layer of organic matter is applied over the tarpaper, and the sand replaced.

After this treatment, organic matter and fertilizer will still be washed down by rain, but their descent will be halted by the tar­paper. Plant roots find stored food at this level and grow well. In a matter of five to six years, the paper rots out but by this time the mass of roots and accumulated organic matter are enough to act as a blotter for moisture and plant nutrients.

This system has worked for me, even in Florida, where every known plant food deficiency can be seen on sandy soils because nutrients disappear almost as soon as applied.

Chapter Digest

Water and air comprise one of the leading partnerships in nature. The total success of Gardener's Loam depends largely on the harmonious relationship of these partners. Plants wilt if either one takes over the soil for a prolonged period—which explains the recommendation of a "moist, well-drained soil." Plants are made up almost entirely of materials obtained from water and air. And, since pla'nts can use only water-soluble nutrients, an artificial water supply should be assured as a supplement to rainfall.