IRRIGATION AND ROTATION OF CROPS. 9 



of water may be controlled by lifting" it less than thirty feet. 

 In such places windmills may be successfully used for pump- 

 ing the water, providing reservoirs of large capacity can be 

 cheaply made into which water may be pumped the year 

 around, to be used as needed. Thresher engines, which are 

 seldom used except in the late summer and fall, may some- 

 times be used to advantage for pumping- water for crops and 

 often at very low cost. Gasoline engines are occasionally 

 used in some irrigation works. They are very desirable, 

 but at present the price is too high to warrant their general 

 use. In putting in a pumping plant, the pump should be put 

 as near the water supply as possible. 



Reservoirs should be on some elevated point. They are 

 easily made by digging out the earth and puddling the 

 bottom and sides with thick clay, which should be at least 

 one foot in thickness and well packed when wet. A good 

 way to pack it is to drive horses over it. When clay cannot 

 be obtained the bottom may be made tight with a thin coat- 

 ing of coal tar and sand, but clay is preferable, and what is 

 known as blue clay is generally best. Cement is liable to 

 crack badly from frost and is not adapted to this purpose. 

 Made in this way, reservoirs are very cheap and easily re- 

 paired. It is important to have them very large where the 

 supply of water is limited: where the supply is large, the 

 reservior may be much smaller. 



Application of Water. — Sloping land is necessary for most 

 successful irrigation, as it is very difficult to apply water to 

 the surface of level land. The slope should be sufficient to 

 permit the water to flow quickly along its surface and yet not 

 enough to cause it to wash. For irrigation purposes the rows 

 should not be over 300 feet long. The best results are gener- 

 ally obtained from irrigating soils having considerable 

 sand in their composition. Drifting sands may often be 

 made to produce good crops by irrigation and manuring, and 

 lands having some sand in their composition are much better 

 adapted to irrigation than clay soils, since the latter often 

 bake badly or become sticky so that they cannot be cultivated 

 immediately after applying water to them. 



Rules for Applying Water to Land. — Water should not be ap- 

 plied unless the crop is suffering for it, but cultivate the soil 



