THE POTATO 107 



the crop and the most economical in the use of 

 water is to irrigate only alternate furrows at each 

 irrigation. Water should be on the ground until 

 it is sufficiently wet, sometimes from twelve to 

 twenty-four hours. If the soil is very mellow and 

 readily permeable, then four to eight hours is 

 generally sufficient. The irrigation should con- 

 tinue until the moisture 'subs' between the fur- 

 rows until it meets. Orchards are commonly 

 irrigated by the furrow method. Care should be 

 taken to keep the water away from the trees, as it 

 is found that they thrive better when the water 

 does not touch them but percolates into the soil 

 and reaches the roots. When all the ground be- 

 tween the trees is moistened the roots spread uni- 

 formly. Grain and alfalfa may be irrigated with 

 corrugations and in this section it is the most com- 

 mon method. By its use water is evenly distrib- 

 uted over the fields, is absolutely under control 

 all the time, and where the land is in proper shape 

 the work is quite rapid and probably less expen- 

 sive than any other method except by the border 

 system. 



"The flooding system of irrigation can be used 

 for watering grain and alfalfa. The laterals are 

 most commonly run parallel to the slope, water 

 being taken out from only one side of the lateral 

 and extending to the next one. Sometimes on 

 nearly level land they are run down the steepest 

 slope, the irrigation water being taken out from 

 each side and extending midway to the next lat- 

 eral. Under this method the distance between 

 laterals should not be over 200 feet and it is better 

 to have them closer together, not over 100 feet. 

 These laterals may be either permanent or made 

 over each year, as in the case of grain crops. 



