50 SOILS AND MOISTURE 



adequate drainage to render them sufficiently porous for a proper 

 circulation of air. Sandy soils are made of coarser particles and 

 therefore looser. For this reason the capillary water is not re- 

 tained for any considerable time and the soil is properly aerated. 

 Injudicious sprinkling of lawns, gardens, or potted plants will re- 

 sult in the formation of a compact surface crust. This acts ex- 

 actly like a clay soil and draws the water away from the region of 

 the roots to the surface of the soil where it is lost by evaporation. 

 Potted plants are best watered by standing the jar in the water 

 until the soil is wet. Further watering is not required until the 

 jar sounds hollow when tapped — a matter of several days. So 

 gardens and lawns sjiould be thoroughly soaked during the night. 

 The ordinary sprinkling only moistens the surface and leaves the 

 soil in a worse condition for holding the moisture than before, be- 

 cause on drying it bakes and the hard crust draws up the water to 

 the surface where the dry air readily evaporates it. The top soil 

 of the garden should be kept loose by raking or hoeing, since the 

 loose soil can not withdraw water from the root and thus acts 

 just as a mulch of straw or leaves or as the grass of the fields in 

 retaining the water in the soil. Sometimes it is desirable to have a 

 compact surface layer of soil, as for example in sowing a field to 

 grain or grass. This is accomplished by rolling the field, which 

 not only gives a smooth surface to facilitate the cutting of 

 the crop but also makes a compact stratum at the surface 

 which draws the moisture up to the grains causing them to 

 grow. Otherwise in such field the surface of the soil containing 

 the grains would be so dried out by the winds often in a single 

 day, as to prevent their sprouting. In this connection the fact 

 must not be lost sight of that a very considerable portion of 

 water in the soil cannot be withdrawn by evaporation. It is often 

 surprising to note how plants continue to flourish during a drought 

 when the earth is sun baked. This is because the films of water 

 about the soil particles cannot be withdrawn by the dryest and 

 hottest air. The bulk of this water, however, is available to the 

 roots, which, branching through the soil, send out root hairs in 

 all directions and so absorb practically not only all the water in 

 their neighborhood, but owing to the capillary action of the soil, 



