

THE PRINCIPLES OF IRRIGATION 

 PRACTICE 



CHAPTER I 

 THE MEANING OF IRRIGATION 



WATER, soil, air and sunshine are the four great groups 

 of physical forces that determine the growth of plants. For 

 the production of plant crops, all of these must be present 

 and active. Water, therefore, is essential to plant-growth 

 and crop-production. 



The water that falls upon the earth in the form of rain 

 and snow is the source of all the water used in agriculture. 

 To be of value in plant-growth, this water must be stored, 

 for longer or shorter periods, in the soil in which plants 

 are growing. Whenever the soil becomes too dry or too 

 wet, or if the total quantity is insufficient or too large, 

 plant-growth is hindered. It is the concern of agriculture 

 to maintain in the soil the proper quantity of water during 

 the growth of crops. 



1. Annual rainfall. Water, in the form of rain or 

 snow, falls over the whole earth. No place is known where 

 some rain does not fall at some time during the year. 

 However, the quantity that falls varies greatly in different 

 regions. Over the so-called deserts the annual rainfall is 

 often less than 5 inches, while in various places near the 

 seashore or among the mountains, the annual rainfall 

 A (1) 



