5io INVESTIGATION BY CULTURE EXPERIMENTS 



effect, but this cannot be known, because there is no comparison 

 plot on which the same amount of untreated manure was used. 

 If we average plots i and 2, we find that 6 tons of phosphated 

 manure on plot 6 produced more than 70 per cent as much in- 

 crease as 15 tons on plots i and 2. Comparison with the Penn- 

 sylvania and Ohio experiments does not help much in trying to 

 decide if the raw phosphate was effective when mixed with the 

 manure at Ottawa, in part because the applications are propor- 

 tionately different, and in part because the manure itself produces 

 different effects on different soils. With the data presented, any 

 possible comparisons can be made by the student. 



Except for the oat crops which, as stated, usually respond readily 

 to nitrogen, ammonium sulfate with the 60 pounds of nitrogen 

 produced a smaller average effect than the sodium nitrate with 

 30 pounds of nitrogen, thus indicating that the sodium in the 

 nitrate exerted appreciable influence. 



Apparently, iron sulfate produced some small effect, but it is 

 doubtful if it is greater than would have been produced by 60 

 pounds of sodium chlorid. For this and other comparisons in- 

 volving few plots, the author calls attention to the fact that there 

 are some marked natural variations among the individual plots in 

 these series; and in such cases no final conclusions can be drawn. 

 In the oat series, plot 3 produced 9 bushels more oats per acre than 

 plot 12 as an average for the first nine years, and 14 bushels more 

 for the next ten years. Plot n in the oat series is evidently a 

 plot which yields below normal. 



The quotations from Doctor Saunders show that some 

 parts of the field were naturally wetter than others, and on 

 page 51 of the Annual Report for 1897 the statement is made 

 that " plots 12, 13, and 14 were on a piece of rising ground on 

 light soil." 



The records for 1903 and 1904 give the yields for the last two 

 years of green manuring with catch crops of clover, while 1906 

 and 1907 furnish later records after the fertilizer applications 

 were renewed, beginning with 1905. 



In Table 107 are given probably the most significant data from 

 the root crops (and potatoes) that were grown on alternating 

 half plots in these series during the seven years, 1891 to 1897. 



