300 



IRRIGATION PRACTICE 



frequently, growth is seriously retarded. It is well to 

 secure a good growth early, and to develop early a deep 

 root-system that may endure the heat of midsummer. It 

 is seldom advisable to irrigate oftener than every two 

 weeks, and every three or four weeks frequently gives 

 satisfactory results. Irrigation should cease about the 

 middle of August, leaving about sixty days for the ripen- 

 ing of the potatoes. Potatoes are seriously injured by 

 over-irrigation. The first visible effect of too much water 

 is a light green color acquired by the leaves. The Utah 

 Station conducted experiments on the effect of varying 

 quantities of water on the yield of potatoes. Some of the 

 results obtained are found in the following table: 



The total quantity of water used varied from 5 to 60 

 inches, or twelvefold. The yield of potatoes increased 

 meanwhile from 154 bushels to 304 bushels, or not quite 

 double. The yield to the inch of irrigation water fell, as the 

 water was increased, from 30.8 bushels to 5.1 bushels or 

 about one-sixth. As shown in the last column of the above 

 table, the percentage of marketable potatoes in the total 

 crop increased, with the increase in water, up to medium 

 quantities, after which it fell definitely. Clearly, the laW 



