124 Irrigation and Drainage 



the growing season of the specific crop in question, in order to 

 know whether tillage alone will answer for that crop, unaided by 

 irrigation. The first crop of clover, for example, must be largely 

 made by the rains of May and June in the states which have been 

 named, while the crop of potatoes will be determined more largely 

 by that which falls between June and October. The period of 

 barley would extend from May 1 nearly through July ; oats, from 

 May to the middle of August ; and maize, from the middle of May 

 to the middle of September. 



In the table which follows, the amount of rain which falls 

 during the growing season of barley, oats and maize has been 

 given, and from the averages have been deducted the amounts 

 which it is quite certain do not become available for crop produc- 

 tion, on account of loss by drainage and by the light rains not 

 penetrating deeply enough to be of service agriculturally: 



Table shoivino the mean rainfall for the growing season for barley, oats 



and maize Rainfall in inches for 



In estimating the loss from percolation and small showers, 2 

 inches has been assumed as the amount of percolation in the case 

 of barley and oats, and 1.5 inches for maize. The amount deducted 

 for small, ineffective showers has been gotten by taking the total 



