1908.] PUBLIC DOCUMENT — No. 33. 35 



Combining the results of this year with those for previous 

 years, on the basis of total yield per plot, the relative stand- 

 ing is : — 



Per Cent. 



Nitrate of soda, 100.00 



Barnyard manure, . . . . . . .95.91 



Dried blood, 91.35 



Sulfate of ammonia, . . . . . . .84.13 



No nitrogen, 70.96 



Averaging our results on the basis of increase in crop as 

 compared with the no-nitrogen plots, the relative standing for 

 the entire period of the experiment, 1890-1907, inclusive, is 

 as follows : — 



Relative Increases in Yields {Averages for the Eighteen Years'). 



Per Cent. 



Nitrate of soda 100.00 



Barnyard manure, . . . . . . .85.92 



Dried blood, 70.21 



Sulfate of ammonia, ....... 45.36 



It will be noticed that, in spite of the fact that the mixture 

 of grass with the clover, as has been pointed out, tends to 

 obscure the effects of the fertilizer treatment on the latter, the 

 combined yield of hay and rowen on the no-nitrogen plots this 

 year is much greater than on the sulfate of ammonia, and prac- 

 tically the same as on barnyard manure. The yield of clover 

 without doubt was actually greater on the no-nitrogen plots 

 than it was on either the dried blood or the nitrate of soda. 

 The fact has been for some time known that clovers, on account 

 of their ability to draw nitrogen from the air under suitable 

 conditions, are able to make relatively vigorous growth on 

 soils to which no nitrogen is applied, provided these receive 

 generous applications of such elements of plant food as lime, 

 phosphoric acid and potash. Just why, however, the clover 

 should do so much better, as was the case, on the no-nitrogen 

 plots than on the other plots in this field is not at present ap- 

 parent. It must be remembered that these other plots have 

 received equal applications of lime, phosphoric acid and potash. 

 It has been suggested that the failure of the clover to do well 



