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T. Lyttleton Lyon and James A. Bizzell 



a larger flow of drainage, one of them gave less than the corresponding 

 hmed tank. Failure of the limed soil to give a larger percolation cannot 

 be due to larger crops, as the yields of dry matter were somewhat larger 

 on the unlimcd tanks, besides which tanks 4 and 8 were continually bare 

 of vegetation. 



WATER UTILIZATION BY CROPS 



The effect of the growth of plants was to reduce considerably the 

 percolation from the soil on which they grew, as was to be expected. 

 The difference in percolation between the planted and the unplanted 

 tanks in these experiments, which as shown in table 6 (page 16) was 

 nearly 7| inches, probably does not represent the entire transpiration of 

 the plants that grew on the soil, because without doubt there was more 

 evaporation from the bare soil than from the soil on which plants grew, 

 owing to the protection from sun and wind afforded to the soil by the 

 vegetation itself. On the other hand, the transpiration was not less than 

 7| inches as an annual average for the production of these crops, all of 

 which, with the possible exception of that raised in 1912, were large, as 

 may be seen in table 1 of the appendix (page 92). 



While the data at hand do not admit of the calculation of the actual 

 transpiration ratio for the crops and the period concerned, they permit 

 of an estimation of the minimum quantity of water transpired per pound 

 of plant dry matter produced. This is obtained by sul^tracting the 

 drainage of the planted tanks from the drainage of the unplanted tanks, 

 and amounts to 290 pounds of water to every pound of dry matter in 

 the crop produced, or a ratio of 1 : 290. This appears in tabular form 

 in table 10: 



TABLE 10. Minimum Transpiration for All Crops Raised durjng Five-Years Period 



Minimum transpiration ratio 1 : 290 



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