CANE SUGAR. 



water is applied to make up the losses from evaporation. This loss is, from 

 experiments upon the transpiration of the sugar cane, about '006 to '009 cusecs 

 per acre. Generally a flow of '0176 cusecs per acre is sufficient for the cane, 

 but the majority of irrigation works do not afford more than half this quantity. 



" The nature of the soils determines the necessity for irrigations after the 

 rainy season has stopped : some soils contain so much water that irrigation is 

 quite unnecessary, the roots of cane aged 10 to 12 months being quite satisfied 

 with the natural humidity of the soil. In the case of sandy soils where 

 drainage is easy, or in very stiff clays where the deep growth of the roots is 

 prevented, so that the root system is contained in the upper layers, it is some- 

 times necessary to introduce a little water into the ditches to prevent the 

 drying up of the roots." 



A point of great interest in regard to irrigation water in Java is the great 

 mammal value of the silt carried in the water. According to de Meijier 7 the 

 Solo river carries on an average 1 kilo of silt per cubic foot ; the silt of the 

 Brantas canal water contains from -43 to -60 per cent, potash, from '35 to -65 per 

 cent, phosphoric acid and -25 to '27 per cent, nitrogen. It is this large quantity 

 of mineral matter in a finely divided state that saves sugar cane planters in 

 Java from the purchase of mineral manures. 



Formosa. At the time of writing, very extensive irrigation schemes, 

 under the control of the Japanese Government, are being pushed forward. 



Economic Distribution of Water. ^So far as the somewhat 

 scanty information available on cane irrigation in Java allows an opinion to 

 be formed, it seems that the irrigation serves as a means of saving the cane 

 during the dry season and not, as is often the case in Hawaii, of obtaining the 

 maximum possible crop. It has been established that cane 15 months or so 

 old consumes and requires for its maximum growth the largest amount of 

 water, and in Hawaii such cane often receives as much water as it can utilize. 

 In Java, however, there does not seem to be a sufficiency for both young and old 

 cane ; in this case it is the former that receives the water as the older cane can 

 still remain in fair vegetative vigour on the supplies of soil water, where the 

 younger cane would fail to become established. 



In Hawaii it not infrequently occurs that the supply of water is insufficient 

 to afford the optimum quantity to all the cultivation ; here there is a balance of 

 opinion in favour of stinting the young cane and giving the full amount to the 

 old cane. Mauritius experience favours the irrigation of young cane to the 

 detriment of the older. 



Hence we have here a question of very great importance concerning which 

 no experiments seem to be on record, and which would be very hard to plan 

 satisfactorily. 



Water transpired by Cane. Maxwell 1 found as the result of 

 experiment that when cane was grown in tubs, in seven months 79,310 grms., 

 or 174-5 Ibs. of water were transpired by the plant, there being formed 568'9 



96 



