THE ROTHAMSTED EXPERIMENTS 371 



thirds as much as the total phosphorus now contained in the plowed 

 soil of the adjoining plot. Furthermore, the surface soil of the farm 

 manure plot to the same depth now contains 1 700 pounds of total 

 phosphorus. Plots 5, 7, n, 12, 13, and 14 now contain as much 

 phosphorus as plot 2, while plots 4, 10 a, and 10 b, none of which has 

 received any phosphorus fertilizer during the 55 years, now contain 

 about the same amount as plot 3. 



Because of the extreme difficulty with some very persistent 

 weeds on the unfertilized land, one half of plot 3 was fallowed in 

 1904 and the other half in 1905, but this weed trouble is now being 

 controlled by drilling the wheat in somewhat wider rows and hand 

 hoeing when necessary. Manifestly, the actual yields from one 

 half of plot 3 for 1905 and from the other half for 1906 ought not 

 to be used in making averages for wheat after wheat every year; 

 but it will be seen from Table 63 that the average yield of continu- 

 ous wheat is about three fourths of the yield of wheat alternating 

 with fallow, and consequently this factor has been employed as 

 stated. 



In Table 62 are given the actual annual yields of wheat harvested 

 from certain Rothamsted plots since 1844. 



Space is taken for these complete records because the author 

 feels that they will be of genuine interest to the more careful 

 readers, and also because every reader is entitled to such records 

 of these oldest and most valuable soil investigations, in order that 

 he may make any comparisons that may be desired. Questions 

 may occur to the reader that neither the author nor any other 

 writer has even thought of; and, since these are the longest con- 

 tinuous records the world affords, they are likely to furnish the 

 best data for helping to solve some very practical questions. For 

 example, is it a true saying that, as a rule, poor crops are followed 

 by good crops the next year? If so, then what kind of a crop should 

 follow an exception to this rule; that is, should two poor crops in 

 succession be followed by an .exceptionally good crop? It is also 

 said that an extra good crop is likely to be followed by another 

 good crop. 



One might eliminate the poorest yield or the best yield in every 

 eight-year period, for example, and then determine if the average 



