32 



T. Lyttleton Lyon and James A. Bizzell 



parts; turnips, 473 parts; grass, 379 parts. All these figures are some- 

 what lower than those of the present writers. 



In the weighable tanks at Cjrottingen, rye, barley, wheat, and potatoes 

 were raised, and the water utilization was computed by Von Seelhorst 

 (1906 b) from the rainfall after deductions had been made for evaporation 

 and drainage. The evaporation from the soil was estimated, since it 

 was evident that the evaporation from a bare soil surface would not 

 be the same as from a soil surface shaded by plants. Calculated in this 

 way, wheat on loam soil required 333 parts of water, and rye 375 parts, 

 for one part of dry matter in the grain, and potatoes required 278 grams 

 of water for one part of dry matter in the tubers; on sandy soil, rye required 

 482 parts of water for one part of dry matter in the grain. These results 

 are not comparable with any of the others cited, because of the method of 

 calculation, and data for the other method of calculation are not available. 



A summary of these results and of the results from the present experi- 

 ments is given in table 14: 



TABLE 14. Water Utilization by Plants in Lysimeters 



As in the case of transpiration, there is a tendency for water utilization 

 also to run higher in America than in Europe. This seems inconsistent 

 with the fact that the percentage percolation thru a bare soil was greater 

 in the writers' experiments than in most of the European ones. The 

 rotations in Europe did not vitilize a materially larger quantit}^ of water 

 than did the rotation in these experiments, but the European rotations 

 included potatoes and root crops, both of which require much water, 

 and the writers' rotation included maize, which is economical of moisture. 



32 



