MANUAL FOR SUGAR GROWERS. 35 



practice has made any substantial advance, some form 

 of subsoil draining is resorted to. If we dig down 

 a sufficient depth into the soil we shall reach a level 

 where the soil is always moist, except in periods of 

 prolonged drought, a level at which the amount of 

 moisture is but slightly affected by the changes from 

 wetness to dryness, etc., experienced by the soil 

 nearer the surface ; the pores of the soil at this level 

 are practically permanently filled with water, and 

 we may designate this the permanent water-level. 

 The depth at which the permanent water-level will 

 be met with entirely depends on the character and 

 position of the soil ; should it be at such a depth 

 that there is ample room above it for the de- 

 velopment in the overlying soil of the full root- 

 system of the crop, then, such a soil will not be bene- 

 fited by subsoil drainage ; it is drained naturally. 

 But such soils are rarely met with, the permanent 

 water-level is usually at no great distance from the 

 surface, and it has been repeatedly explained that 

 roots will only grow in soil whose pores are filled 

 with air. The roots never grow down below the per- 

 manent water-level ; if this is near the surface, it fre- 

 quently happens that the depth of soil available for 

 healthy root-development is far too limited to allow 

 the growth of a full and luxuriant crop ; consequently, 

 if the season be a favorable one, the root-develop- 

 ment being limited, the crop can only be moderately 

 large ; while, if the season be wet, the small depth of 

 soil becomes waterlogged, and active root-growth is 

 impeded ; on the other hand, if the season be dry, the 

 roots, having only a shallow range, soon lack mois- 



