44 



PHILIPPINE AGRICULTURE 



FlG. 33. The same land shown in Figure 32 after irrigation 



Philippines they are used only near cities, and are not 

 likely to come into general use. 



Gravity. By far the cheapest irrigation is usually by 

 gravity alone. The water is taken from a creek or river 

 at some point high enough so that it will run through a 

 ditch or canal to the land to be irrigated. The canal 

 should be kept on the highest ground possible, so as to 

 have as much land as possible below it. If much land is 

 irrigated, branch ditches run from the main canal, and 

 are cut off by gates which can be opened and shut. In 

 this way the water is turned into different fields at differ- 

 ent times. It is better to irrigate fields thoroughly and 



