SAVING WATER BY CULTIVATION 41 



accomplishing this is to plow the land in the fall and, 

 unless fall crops are planted, to allow it to lie in a rough 

 state throughout the winter. Where the precipitation 

 comes largely during the summer and spring, it is much 

 more difficult, because of the growing crops, to keep the 

 top soil in a condition to absorb water readily. 



Much water is nearly always lost at the time of thaw- 

 ing and melting snow. In such districts all furrows and 

 rows of plants should be made to conform with the slope 

 of the land. A furrow plowed up and down a gentle slope 

 forms an admirable channel for the escape of water, while 

 a furrow plowed at right angles to the slope tends to catch 

 and to hold back the water which flows downward. 

 This is also true with regard to planting. Drill culture 

 is now the only acceptable method of planting; and it is 

 always desirable, from the point of view of preventing the 

 run-off, to plant the rows of crops at right angles to the 

 general slope of the land. Each row then tends to pre- 

 vent excessive run-off. 



In irrigation, the loss due to run-off is frequently a 

 very serious matter. When water is applied by the 

 flooding method, it is relatively easy to control the run- 

 off by building dikes around the field. In fact, some kind 

 of diking is usually thrown up around large fields, when- 

 ever water is applied by the flooding method. The vari- 

 ous systems of irrigation by flooding differ chiefly in the 

 means devised for preventing the surface loss of water. 

 If no diking is used, the lower end of the field is usually 

 crossed by a ditch, which receives the waste water and 

 carries it to some other field. 



In the furrow method of irrigation it is very difficult, 

 if not impossible, to prevent wholly the run-off. By the 

 furrow method, water is usually applied at one end of the 



