CANE SUGAR. 



The third method is the most rational method, and the one which is most 

 largely applied. The system advocated by Maxwell 1 is shown in Fig. 22. 

 Water from the main water ditch A A is diverted into the laterals bb, andfrom 

 these laterals allowed to flow in two directions along the furrow in which the 

 cane has been planted ; this twin flow of water may be compared with the 

 diagram in Fig. 21, illustrative of the practice in Mauritius. In Fig. 22 the 

 laterals are only thirty feet apart, so that the water only flows fifteen feet ; a 

 longer flow results in those portions of the cane row near the lateral receiving 

 an excess of water, and those more remote not receiving enough. In case the 

 flow of water is scanty or the soil is very porous, such a system is necessary 

 so as to allow water to reach all parts of the field ; but it would often be 



FIG. 22. 



hard to lay out. As illustrative of a wasteful and harmful method of irrigation, 

 Maxwell gives the following diagram (Fig. 23\ where the water from the main 

 ditch A A flows along the cane rows for the whole length of the field 

 exaggerating the waste and damage due to long furrows. 



The length of the furrow is very largely controlled by the porosity of the 

 soil ; with light, sandy, porous soils, a short furrow is necessary to prevent 

 undue waste of water; and where the soil is clayey, so that the water 

 penetrates more slowly, a longer furrow is allowable. 



Quality of Irrigation Water. Maxwell 1 arbitrarily fixed the 

 * danger point ' of irrigation water at 100 grains of salt per imperial gallon; 

 Hilgard 10 states that 40 grains is the usual limit. Eckart 11 found cane in 

 lysimeters grew unchecked when the soil water contained 195 grains chlorine, 

 as sodium chloride, per U.S. gallon and obtained in lysimeters a normal growth 



98 



