Importance of Nitrogen to Growth of Plants. 



241 



that the timothy should grow better on the Hmed portion if it also grew 

 better where nitrate of soda was added. If increase in water-soluble 

 i;itrogen was the result of the increased growth of alfalfa and not the 

 cause of it, then the water-soluble nitrogen should be greater upon the 

 limed alfalfa plat than upon the limed timothy plat. 



The following table gives the average results of samples taken at 

 seven dates, May 22 to September 5 by Clark and determined by Bizzell : 



Table XI Shows Parts of NO3 per Million of Dry Soil as Affected by 

 Liming, Alfalfa and Nitrate of Soda. 



It should be stated that the effect of lime on the growth of alfalfa 

 lias thus far in this experiment been very much less marked than in any 

 previous experimei^ts which we have conducted. Since there was very 

 little apparent effect of lime on growth it could not be expected con- 

 sistently that much difference in water-soluble nitrogen would be found 

 if the water-soluble nitrogen is related to the growth of alfalfa. 



It will be seen by examining the above table that only small differ- 

 ences were found. Such differences as exist, however, tend to indicate a 

 greater amount of water-soluble nitrogen on the limed alfalfa than upon 

 the limed timothy and less upon the limed timothy than the unlimed 

 timothy. It is also interesting to note that the amount of water-soluble 

 nitrogen averages less on all timothy plats than on the alfalfa plats, 

 which suggests that the alfalfa may have secured parts at least of its 

 nitrogen from the air and thus made less demands upon the soil for 

 nitrogen than did the timothy. 



Another factor enters into this experiment. The series of untreated 

 plats were in a depression while the limed and nitrate of soda were on the 

 sides of this depression. The influence of this is shown in the following 

 table, the results being an average of seven determinations as stated 

 above : 



16 



