160 Irrigation and Drainage 



laterally to a distance of 3.5 to 4.5 feet ; hence, if 

 necessary, the rows of corn might be placed as far as 

 7 to 8 feet apart, and yet be able to take moisture 

 from the whole field. Taking the extreme case of 

 rows 8 feet apart and plants 2 feet apart in the row, 

 the number of plants per acre would be 2,725. Sup- 

 posing each plant to produce a large stalk and large 

 ear, the total weight of dry matter for the acre might 

 be 2,157.5 pounds, giving 18.32 bushels of shelled 

 corn. This yield of dry matter per acre would call 

 for only 2.577 acre -inches of water to produce it, at 

 the rate of the results which have been obtained from 

 52 trials in Wisconsin. 



Potato roots spread laterally to the distance of 2 

 to 2.5 feet ; hence these might be planted in rows 4 

 to 5 feet apart without ' having the roots overlap in 

 the feeding ground. The chief advantage of wider 

 rows for potatoes in the sub -humid climate comes in 

 its permitting intertillage after the vines have reached 

 full size, and thus better conserving the scanty mois- 

 ture, so important in the later development of the 

 tubers, and which would travel laterally by capillarity 

 toward the roots in case they did not reach the center. 

 The table which follows shows the actual distribution 

 .of soil moisture in the upper 18 inches of a potato 

 field in which the rows extended east and west, and 

 were planted 3 feet apart, under flat cultivation ; 



