CANE SUGAR. 



rise in humidity of 12-5 per cent, decreased the evaporation 50 per cent., 

 although the temperature rose 1'5 Fahrenheit. 



Cessation Of Irrigation. In Hawaii it is customary to stop the 

 supply of water when the cane has flowered. Such cane is usually harvested 

 from three to six months after flowering, and during this time little or 

 no growth takes place, the cane actually evaporating its own water ; and at 

 the same time it probably elaborates reducing sugars into cane sugar. Such 

 cane may receive during the time of ripening a small amount of water to 

 maintain its vitality. 



Optimum Quantity of "Water. Experiments by Eekart 13 

 showed that under the conditions prevailing at the Experiment Station of the 

 Hawaiian Sugar Planters' Association, the maximum return of cane was 

 obtained with a three-inch weekly irrigation. Commenting on these results, 

 he writes: " These experiments have a practical bearing on irrigation on 

 plantations, as they show that while the larger volumes of water gave an 

 increased production of sugar, such increase of sugar would, under some 

 conditions be obtained at a loss. For instance, if we were to take the average 

 cost of lifting 1,000,000 gallons of water one foot to be $0*09, where three 

 inches per week irrigation were applied it would cost $42-77 per acre at the 

 100 feet level. One inch of water at the same elevation would cost $14-90. 

 The additional cost of irrigation in increasing the yield of sugar 2081 Ibs. 

 would be 2-6 cents or 1*3 cents per pound. At 200 feet elevation, the cost per 

 pound of sugar gained by increased irrigation would be 2-6 cents, and at 300 

 feet elevation, 3-9 cents. Naturally, these calculations are for a soil similar to 

 that at the Experiment Station and receiving about the same rainfall." 



Optimum Percentage of Water in Soil. Eckart 13 found that 

 when three inches of water was applied per week, the soil at the Experiment 

 Station in Honolulu contained on an average 31-38 per cent, of water; this 

 soil can according to him absorb 40'74 per cent, of water in situ; hence he 

 finds that the best results are obtained when the soil is saturated to 77 per 

 cent, of the maximum. This is a larger figure than is found with most other 

 crops. 



Cost Of Irrigation. The total capital expended in the Hawaiian 

 Islands on sugar cane irrigation is probably not less than 3,000,000 ; but 

 statistics are incomplete and this is certainly a very conservative estimate. 

 Amongst figures that have been published, may be quoted those referring to 

 Ewa, where the total cost of erection of pumps delivering 22,000,000 gallons 

 daily was 370,000' ($1,775,000). The Olokele ditch 13 miles long, through 

 a mountainous country and delivering 60,000,000 gallons daily, cost 75,000; 

 the cost of the Kekaha canal on Kauai, of the same length and capacity, was a 

 similar figure. The Koolau ditch built through very difficult country and ten 

 miles long cost 91,000; it delivers 80,000,000 gallons daily. The Kohala 

 ditch on Hawaii which is 14 miles long, 12 feet wide at top, 7 feet wide at 



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