METHOD OF IRRIGATION 195 



the soil, before the lower end of the field is reached. Under 

 the flooding method, a high head of water may be used on 

 nearly all soils, but a low head is suitable only for heavier 

 soils. It follows that the furrowing method is best adapted 

 where the head of water is low; the flooding method where 

 the head is high. This deduction has found practical 

 expression over the whole irrigated area. 



If irrigation water is abundant, and a high head may 

 consequently be secured, the flooding method is usually 

 employed. If water is scarce, the main consideration is 

 to make the total supply cover the largest number of 

 acres, and the furrowing method is ordinarily employed, 

 since by this method a small quantity of water may be 

 made to cover much land. It has been shown that the 

 productive power of water decreases as the total quantity 

 applied to a given area is increased. That is, with each 

 additional inch of water, less dry matter is produced. 

 Consequently, where water is scarce, it is more profitable 

 to spread the small quantity of water over a large area of 

 land. To do this, the furrow method is indispensable. In 

 irrigation practice, therefore, although the reason is not 

 always understood, the furrowing method is invariably 

 used wherever the supply of water is low. 



The nature of the crop determines, also, the method of 

 irrigation. Some plants are more sensitive than others to 

 contact with water. It is believed by many that the 

 sugar beet is injured whenever irrigation water is allowed 

 to come into contact with it, especially if the day is hot. 

 This may be true at times, but this danger is much exag- 

 gerated. Only when water stands against a plant for 

 some time is injury really likely, and, then, injury comes 

 either when the water is so hot as to cause sun-scald 

 or so cold as to chill the plant. In either case, the process 



