moisture by healthyasianfood

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									THE MOISTURE OF THE SOIL
Did any one ever explain to you how important water is to the soil, or
tell you why it is so important? Often, as you know, crops entirely fail
because there is not enough water in the soil for the plants to drink.
How necessary is it, then, that the soil be kept in the best possible
condition to catch and hold enough water to carry the plant through dry,
hot spells! Perhaps you are ready to ask, "How does the mouthless plant
drink its stored-up water?"

The plant gets all its water through its roots. You have seen the tiny
threadlike roots of a plant spreading all about in fine soil; they are
down in the ground taking up plant food and water for the stalk and
leaves above. The water, carrying plant food with it, rises in a simple
but peculiar way through the roots and stems.

The plants use the food for building new tissue, that is, for growth. The
water passes out through the leaves into the air. When the summers are
dry and hot and there is[Pg 10] but little water in the soil, the leaves
shrink up. This is simply a method they have of keeping the water from
passing too rapidly off into the air. I am sure you have seen the corn
blades all shriveled on very hot days. This shrinkage is nature's way of
diminishing the current of water that is steadily passing through the
plant.

A thrifty farmer will try to keep his   soil in such good condition that it
will have a supply of water in it for   growing crops when dry and hot
weather comes. He can do this by deep   plowing, by subsoiling, by adding
any kind of decaying vegetable matter   to the soil, and by growing crops
that can be tilled frequently.

The soil is a great storehouse for moisture. After the clouds have
emptied their waters into this storehouse, the water of the soil comes to
the surface, where it is evaporated into the air. The water comes to the
surface in just the same way that oil rises in a lamp-wick. This rising
of the water is called capillarity.

Fig. 5.
Fig. 5. An Enlarged View of a Section of Moist Soil, showing Air Spaces
and Soil Particles

It is necessary to understand what is meant by this big word. If into a
pan of water you dip a glass tube, the water inside the tube rises above
the level of the water in the pan. The smaller the tube the higher will
the water rise. The greater rise inside is perhaps due to the fact that
the glass attracts the particles of water more than the particles of
water attract one another. Now apply this principle to the soil.
Fig. 6.
Fig. 6. The Right Way To Plow

The soil particles have small spaces between them, and the spaces act
just as the tube does. When the water at the surface is carried away by
drying winds and warmth, the water[Pg 12][Pg 11] deeper in the soil rises
through the soil spaces. In this way water is brought from its soil
storehouse as plants need it.
Fig. 7.
Fig. 7. Apparatus for testing the Holding of Water By Different Soils

Of course when the underground water reaches the surface it evaporates.
If we want to keep it for our crops, we must prepare a trap to hold it.
Nature has shown us how this can be done. Pick up a plank as it lies on
the ground. Under the plank the soil is wet, while the soil not covered
by the plank is dry. Why? Capillarity brought the water to the surface,
and the plank, by keeping away wind and warmth, acted as a trap to hold
the moisture. Now of course a farmer cannot set a trap of planks over his
fields, but he can make a trap of dry earth, and that will do just as
well.

When a crop like corn or cotton or potatoes is cultivated, the fine,
loose dirt stirred by the cultivating-plow will make a mulch that serves
to keep water in the soil in the same way[Pg 13] that the plank kept
moisture under it. The mulch also helps to absorb the rains and prevents
the water from running off the surface. Frequent cultivation, then, is
one of the best possible ways of saving moisture. Hence the farmer who
most frequently stirs his soil in the growing season, and especially in
seasons of drought, reaps, other things being equal, a more abundant
harvest than if tillage were neglected.

								
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