The First Book of Farming

of Soi

orbed exists in the soil principally in

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nd during wet seasons and is often found standing on the surface of the soil after heavy or long continu

us that roots need air, we can readily see that free water would give the root hairs enough moisture, but it would at the same time drown them by cutting off the air. Therefore free water is

-CAPILLA

n small tubes or is drawn

-CAPILLA

t point where the glass plat

G.

about the base of this cone of soil has been dr

G.

s the amount of water required to cover the half pound of pebbles in the tumbler B with a film of moisture. The colo

LARY

ll notice that the water rises in the tubes (Fig. 26), and that it rises highest in the smallest tube. The force which causes the water to rise in these tubes is called the capillary force, from t

pposite two about one-eighth of an inch with a sliver of wood. Then set them in a plate of water or colored liquid and notice how the water rises between the pi

ine soil; then pour water around the base of the pile and note ho

moisture which is drawn by capillary force or soaks into the spaces betwee

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apillary water and is sometimes called film water or film moisture. Take a handful of soil that is moist but not wet, notice t

s plants are well supplied with film water and are not drowned by the presence of free water. Capillary water may sometimes completely fill the spaces between the soil particles; when this occurs the roots are drown

roots of most plants will not grow in it. It is, therefore, of interest to the farmer to see that free water does not come within at least three or four feet of the surface of the soil so that the roots of his crops may have plenty of well ventilated soil in which to develop. If there is a tendency for free water to fill the soil a large part of the time, the farmer can get rid of it by draining the land. We get he

he greatest capaci

e film water that the pebbles can carry. Repeat this with sand and compare the two amounts of water. A striking illustration can be made by taking two slender bottles and placing in them amounts of colored water equal to the amounts of film water held by the pebbles and sand respectively. In the accompanying illustration (Fig. 29), A represents the amount of wa