216 



Irrigation and Drainage 



In constructing this table, the season of growth 

 has been taken at 100 days for wheat and oats, 80 

 days for barley, 110 days for maize, 130 days for pota- 

 toes, and 60 days for one crop of clover hay. It has 

 further been assumed that the ground at seeding, time 

 is well supplied with moisture, while at harvest it is 

 only so much dried out as to have just become ready 

 for another watering. 



As in the experiments which gave the fundamental 

 data for the table above, the soil was more closely 

 planted than is practicable under field conditions, the 

 loss of water by evaporation from the soil of the field 

 is likely to be greater, relatively, than was the case in 

 the experiments ; hence, the observed duty of water is 

 likely to be lower than the table indicates. Again, 

 in the case of the smaller yields per acre, the evapo- 

 ration from the soil will necessarily be relatively larger 

 than where the heavier crops are produced ; hence, the 

 duty expressed for water when the yields are small is 

 likely to be farther from the possibilities than in the 

 cases where the yields per acre are larger. 



If the amount of water which the last table indi- 

 cates is required to produce a crop of the various 

 kinds is expressed in cubic feet, the figures will 

 stand : 



8,640,000 cu. ft. of water may produce 7,056 bushels of wheat 



8,640,000 " 



6,912,000 " ' 



9,5040,000 " ' 



11,232,0000 " ' 



1 5,184,000 " ' 



15,030 



7,906 



15,580 



149,620 



" oats 

 " barley 

 11 maize 

 " potatoes 



322.7 tons of hay, 



