110 



CHAPTER VII 



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J 



Fig. 21 



and in perspective on Plate XI. The supply ditch is indicated at the 

 left, and from this water is fed to the level ditches, laid out at intervals 

 of 150 to 200 feet, and with a fall of from | to | per cent, grade. From the 

 level ditches lead the water-courses, laid out at distances varying from 

 30 to 75 feet, the distance depending on the nature of the soil and on the grade. 

 Paralleling the level ditches and at right angles to the water-courses are 

 the cane rows, from 5 to 6 feet apart, down which the water flows. The 

 furrows in which the cane is planted are laid out with the level, and on 

 their accuracy depends much of the efficiency obtained in the application 



of the water. On very level land it is pos- 

 5 sible, and on porous soils advisable, to allow 

 the water delivered from the water-courses 

 to flow both ways in the furrow, thus halving 

 the length of travel. From the time of 

 planting up to about three months before 

 harvest it is the object of the plantations 

 to irrigate the whole area once every week, 

 though frequently the available supply of water is insufficient. During 

 the three months preceding harvest only enough water is supplied to main- 

 tain the vitality of the cane, and during this time it actually evaporates its 

 own water. 



Perit.^ — In Peru the cane is entirely dependent on irrigation, the melted 

 snow from the Andes being the source of water. The arrangement of the 

 ditches generally followed is shown in Fig. 21. The regadora, or main canal, 

 leads across the higher part of the field ; from this, by means of a temporary 

 opening, water is brought to the cavesera, and is allowed to flow out and run 

 over the cintas or beds of five rows. The fields are all on the slope, and the 

 water is seldom pumped back, but is allowed to flow to the fields at a lower 

 level. This method of using the water may be compared with the system 

 of water-courses and furrows at right angles to each other used in Hawaii, 

 whereby a long travel for the water is avoided. 

 Where water is scarce, the system shown in Fig. 22 

 is used, a a being dividing ridges made with the hoe, 

 and which cause the water to run in a zigzag fashion 

 over the field. At the time of planting the fields are 

 irrigated every five to eight days, water being cut off 

 three months before the harvest. 



~^ 



e 



-$ 



Fig. 22 



Mauritius. — On the few plantations where irriga- 

 tion is practised a system essentially similar to that 

 described as in use in Hawaii is followed. The water 

 is obtained entirely from streams and reservoirs, no 



pumping plants being yet installed. The potentiality of irrigation here is 

 equal to that already obtained in the Hawaiian Islands. 



Egvpt.^ — The source of water is the Nile, and cane is watered as soon as 

 it is planted in February ; thence irrigations follow every ten days till 

 the end of August, after which the cane is watered every fifteen or twenty 

 days till the end of October, at which time irrigation is stopped. 



Demerara. — The method by means of which fields may be irrigated will 

 be readily understood on referring to Figs. 40 and 41 ; a drain, indicated 

 by the line g, is dug parallel to the cross canal c and connected to it. Down 

 the centres of the beds irrigation drains 15 inches wide and 9 inches deep 



