[Illustration:  FIG. 23.  To show how bottles may be used in place of lamp chimneys shown in Figs 22 and 24.]

[Illustration:  FIG. 24.—­CAPILLARITY OF SOILS To show the relative powers of soils to take water from below.]

[Illustration:  FIG. 25.—­WATER-ABSORBING AND WATER-HOLDING POWERS OF SOILS.]

=Experiment.=—­Fill a pan or bucket with moist sand, another with moist clay, and a third with moist organic matter; set them in the sun to dry and notice which dries last.  The organic matter will be found to hold moisture much longer than the other soils.  The power of the other soils to hold moisture through dry weather can be improved by mixing organic matter with them.

We find then that the power of soils to absorb and hold moisture depends on the amount of sand, clay, or humus which they contain, and the compactness of the particles.  We see also how useful organic matter is in improving sandy and clayey soils.

THE EFFECT OF WORKING SOILS WHEN WET

By this time the soils we left in the pans (see page 26), sand, clay, humus and garden soil, must be dry.  If so, examine them.  We find that the clay which was stirred when wet has dried into an almost bricklike mass, while that which was not stirred is not so hard, though it has a thick, hard crust.  The sand is not much affected by stirring when wet.  The organic matter which was stirred when wet has perhaps stiffened a little, but very easily crumbles; the unstirred part was not much affected by the wetting and drying.

The garden soil after drying is not as stiff as the clay nor as loose as the sand and humus.  This is because it is very likely a mixture of all three, the sand and the humus checking the baking.  This teaches us that it is not a good plan to work soils when they are wet if they are stiff and sticky; and that our stiff clay soils can be kept from drying hard or baking by the use of organic matter.  “And that’s a witness” for organic matter.

The relation of the soil to moisture is very important, for moisture is one of the greatest factors if not the greatest in the growth of the crop.

The power to absorb or soak up moisture from any source is greatest in those soils whose particles are smaller and fit closer together.

It is for this reason that strong loams and clay soils absorb and hold three times as much water as sandy soils do, while peaty or humus soils absorb a still larger proportion.

The reason why crops burn up so quickly on sandy soils during dry seasons is because of their weak power to hold water.

The clay and humus soils carry crops through dry weather better because of their power to hold moisture and to absorb or soak up moisture from below.  It is for this reason also that clay and peaty soils more often need draining than sandy soils.

When rain falls on a sandy soil it enters readily, but it is apt to pass rapidly down and be, to a great extent, lost in the subsoil, for the sand has not sufficient power to hold much of it.