354 Irrigation and Drainage 



cultivation should be with a double -wing cultivator, 

 which will form a furrow midway between the rows 

 and at the same time throw the soil up under the 

 vines, forming a high, broad ridge of mellow soil 

 above the roots in which the tubers may set and over 

 which the water should never rise. The furrows thus 

 formed fit the field for irrigation. 



When the time for irrigation has arrived, which 

 should be deferred as long as the vines continue to 

 grow vigorously, water will be taken from the head 

 ditch and subdivided between as many rows as it will 

 supply, as represented in Figs. 92, 93 and 94, where 

 the first one shows the canvas dam just put in place 

 in a head ditch in a field near Greeley, Colorado. 

 Fig. 93 shows the irrigator, with rubber boots and 

 spade, opening the head ditch to let the water into 

 the furrows ; while Fig. 94 shows the water 30 minutes 

 later, as it is flowing between rows 40 rods long. 



It will be noted that the water has been let into 

 only alternate rows, and this is a common practice 

 where water is scarce. It is also a frequent practice 

 where water must be taken in rotation and the time 

 is too short to go over the whole field. In such 

 cases, when the next turn comes the water would be 

 sent down the remaining rows. 



Very great care is taken not to let in so much 

 water as to fill the furrows and flood the hills, for 

 it is far better to let the water rise under the hills 

 by capillarity. 



In another field near the same city, two men were 

 irrigating 47 acres of potatoes planted in rows 120 



