318 



THE IRRIGATION AGE. 



From the data in the rainfall columns it is seen that the most of 

 the rain falls during the cooler months of the year, which are the 

 months of minimum plant growth.. This is a special climatic draw- 

 back. The most advantageous combination of climatic conditions 

 is the concurrence of high temperature and maximum rainfall, or a 

 moist, hot season, and a dry, cool season, which combination occurs 

 in the sugar zone of Queensland. It is very apparent that water does 

 not possess a maximum value if it falls during the cool season and 

 when the crop is not in ful] growth and able to make use of it. For 

 this reason a less value and importance have to be ascribed to the 

 rainfall of these islands than might otherwise be. 



The table shows that, during the years 1898 and 1899, the rainfall 

 covering the period of seventeen months was only 26,01 inches, or 18.3 

 inches per annum. It should also be understood that the extra defi- 

 ciency in the rainfall can not be measured by the simple amount of 

 that deficiency, for the reason that, instead of the cloudy, wet days 

 when the rain should have fallen, dry days of high evaporation 

 occurred, thus aggravating the natural situation and causing a greater 

 need for the water supplied by artificial means. When the totals x>f 

 the data contained in the table are brought together, it is seen, how- 

 ever, that the difference in the total amounts of water consumed by 

 the respective crops are not material and no greater than has been 

 reasonably accounted for. 



Before proceeding to furnish the full results of the two crops 

 attention may be called to the comparative value of the water which 

 fell as rainfall and that of the water applied in irrigation, taking the 

 sugar equivalent as the expression of value. It is possible to do this 

 by the use of data obtained during the season of 1897-98, when tests 

 were carried out in the experiment field under identical conditions of 

 soil, cultivation, and fertilization. In these tests twenty plats of cane 

 were grown by the aid of irrigation in addition to the rainfall, and 

 eight tests were made without any irrigation (PI. IV,) the results 

 being as follows: 



YIELD OF IRRIGATED AND UNIRRIGATKD CANE. 



