84 AGRICULTURE 



or drains. Speaking generally, a sandy or 

 gravelly soil is most suitable for the purpose 

 of irrigation. If the land is too strong it is 

 apt to become sour and, in the process of a 

 short time, infertile. 



In this country the chief benefit from 

 irrigation is derived from the suspended and 

 dissolved substances that are carried to the 

 soil and to the plants through the agency of 

 the water. The substances in suspension 

 are to a large extent deposited in the soil and 

 tend to change its physical condition. Those 

 substances which are in solution are partly 

 laid hold of by the roots of plants to serve as 

 food. That it is the substances present in the 

 water, rather than the water itself, which 

 confer the benefit, is evident from the fact 

 that if one examines a meadow, especially 

 in the earlier part of the growing season, one 

 can see that the herbage is much more 

 vigorous close to the water channels, than 

 at parts of the field farther removed from the 

 source of supply. The water, more or less 

 charged with plant food, is distributed over 

 the area by means of suitable channels, and 

 those plants growing nearest to the water- 

 courses have necessarily the best opportunity 

 of securing nourishment. The water, more or 

 less deprived of its plant food, then flows to 



