46 Irrigation and Drainage 



Table showing the mean amount of water used by various plants in Wisconsin 



in producing % a ton of dry matter 



Water required to Dry matter A.M-P inr-hps of 



*o.of pr C Y t b er f Water used produced ^r p^onlf 



trials ^S?s INCHES TONS dry matter 



Barley 5 464.1 20.69 5.05 4.096 



Oats 20 503.9 39.53 8.89 4.447 



Maize 52 270.9 15.76 6.59 2.391 



Clover.... 46 576.6 22.34 4.39 5.089 



Peas 1 477.2 16.89 4.009 4.212 



Potatoes.. 14 385.1 23.78 6.995 3.399 



Total 138 Average 446.3 23.165 5.987 3.939 



In computing the results in this table, the combined area of 

 all cylinders, the combined weights of dry matter produced, and 

 the combined amounts of water used, have been divided by the 

 number of trials with each kind of crop and the average results 

 used in making the calculations. 



In considering these results, it should be kept in mind that 

 the water used by the several crops is made to include that which 

 was lost through the soil by surface evaporation, because it was 

 not easy to measure this separately or to prevent it without intro- 

 ducing abnormal conditions. It is quite certain, however, that 

 during all of these trials the rate of loss from the soil has been 

 somewhat less than would have occurred under the best possible 

 management with field conditions. 



Attention should be called to the fact, also, that the large 

 amount of water used, averaging for the 138 trials 23.165 inches, 

 is greater than field conditions would demand, if nothing were 

 lost by percolation, for the reason that we have planted so as to 

 utilize less surface area than is the practice in the field ; and it is 

 to this fact, also, that the very large average yields, when com- 

 puted per acre, are due, rather than to the growth of plants of 

 abnormal size. 



THE MECHANISM AND METHOD OF TRANSPIRATION 

 IN PLANTS 



Since water plays so large a part in the life and develop- 

 ment of land plants, and since such large quantities of it are 



