WATER-HOLDING CAPACITY OF THE SOIL 65 



texture soils, as the clays, an increase in the air spaces 

 results in an increase of the capillary spaces, and conse- 

 quently an increase in the water-holding capacity. In 

 the coarse sandy soils an increase in the size of the air 

 spaces decreases the capillary spaces and consequently 

 decreases the water-holding capacity. (3) Hydroscopic 

 water is that water which is held mechanically in the soil 

 and which is not removed by air drying. This form of 

 water cannot be used by the plant. 



All plants are dependent upon the capillary water for 

 their growth. The amount of capillary water which a 

 soil can hold depends upon the total surface area repre- 

 sented by the soil particles. It is therefore apparent that 

 the loosening of the ground and the breaking up of the 

 soil particles during cultivation makes it easier for the 

 rain to enter the soil. Likewise the larger surface presented 

 by the greater munber of soil particles, increases the amount 

 of water that the soil will hold. The loose soil also tends 

 to prevent loss of the water by surface drainage. 



The capillarity and consequently the moisture content of 

 the soil is materially influenced by the different methods 

 of cultivation, such as deep or shallow plowing, subsoiling, 

 rolling or disking. The treatment adapted to insure the 

 best water supply, must vary with the rainfall, the nature 

 of the soil, and the crop in question. In many sections 

 the rainfall is ample to produce a good crop, but it is dis- 

 tributed so unevenly that all of the water cannot be utilized 

 by the crop at the time it falls. A great amount of this 

 water is lost if it is not properly handled and stored in the 

 subsoil for the future use of the plants. By judicious and 

 systematic cultivation the greater percentage of this mois- 

 ture can be conserved and used for the growing of the 

 plants. Cultivating after a rain is most essential for the 

 proper conservation of the soil moisture. This cultivation 

 should be given as soon after the rain as the soil can be 

 worked. When evaporation is allowed to take place after 

 a rain, there is not only a loss of water which has just fallen, 

 but there is a loss in the upper layer of soil as well. In 

 addition to these losses there may also be a loss of the water 

 5 



