70 CULTIVATION AND TILLAGE 



surface of the soil are broken and the direct connection 

 of the water in the subsoil with that of the upper layer 

 is interrupted. Cultivating prevents the close contact of 

 the surface soil with that of the lower layers and destroys 

 the passageways for the water to escape into the air and 

 be lost. Whenever evaporation from a surface takes place, 

 there is a constant movement of the water upward from 

 the lower depths, and in order to conserve the supply of 

 water this capillary escape of moisture must be prevented. 

 This is easily accomplished by maintaining a layer of fine 

 earth on the soil. This means that shallow cultivation is 

 important in conserving and in holding the soil moisture. 

 The depth of the soil mulch must of necessity vary with 

 the nature of the soil. On a small scale, a garden rake 

 can be used and the pulverization is usually complete, but 

 on a large scale a disk or a harrow is commonly employed. 

 If a disk harrow is used the disks should be set at an angle. 

 The surface cultivation should be 2 or 3 inches in depth. 

 The finer the soil is on the surface, the better the moisture 

 is held. Shallow surface cultivation should be practised 

 in connection with any method of treating the land, whether 

 deep plowing, subsoiling or spading. 



Water-holding Capacity of the Soil Influenced by Cultivation. 

 — Cultivation not only increases the amount of surface on 

 which the plant can feed, but it also enlarges the water 

 supply by giving the soil a greater capacity for holding it. 



There are three forms of water found in a soil: (1) Bot- 

 tom water is that water which stands in the soil at a general 

 level and completely fills all of the spaces between the soil 

 particles. Bottom water is only available for the plants, 

 when it can be brought up to the higher levels by capil- 

 larity. If the general level of the water table is too high 

 plants cannot grow, and drainage must be provided. (2) 

 Capillary water, which is that water held in a thin film 

 around the particles of soil above the bottom water. The 

 height to which this water can be raised by capillary action 

 depends upon the size and the arrangement of the soil 

 particles as well as the type of soil. Ordinarily the capillary 

 action of the water is confined to a few feet. In close 



