Field Irrigation by Furrows 357 



steadily growing. If the ground is allowed to become 

 dry enough to check their growth and another irri- 

 gation follows, the tubers will then throw out new 

 growths and become irregular in form and unsalable. 



In Colorado the potatoes are usually planted in 

 rows 4 feet apart. This distance is much greater 

 than is required in humid climates, and it would seem 

 that were the same amount of seed planted upon 

 three -fourths of the ground, or even five -eighths, 

 making the rows 36 inches or 30 inches apart instead 

 of 48 inches, the ground could be more thoroughly 

 watered and larger yields per acre secured. 



It is certain that the practice of only watering 

 alternate rows, which is common where water is scarce, 

 does not permit the largest yields to be secured. It 

 has been shown by studies in the humid climate of 

 Wisconsin, and with only 30 inches between the rows, 

 as a mean of two years' trials, that watering between 

 all rows gave a yield of 317.3 bushels per acre ; 

 watering between alternate rows gave 277.1 bushels 

 per acre, when the natural rainfall alone gave 211.6 

 bushels per acre. That is to say, the irrigation 

 between all rows increased the yield over the natural 

 rainfall 105.7 bushels per acre, while irrigating between 

 alternate rows only increased the yield 65.5 bushels 

 per acre, making a difference between the two methods 

 of irrigation of 40.2 bushels of merchantable tubers 

 per acre. 



In these experiments the field was divided into alter- 

 nating groups, which were watered and not watered, 

 so that there were two rows in each irrigated plot 



