FARM MANURES 



615 



from Rothamsted. The crop was mangolds, and the re- 

 covery of the constituents carried by the manure was 

 very low : 



RECOVERY OF NITROGEN IN A CROP OF MANGOLDS 



The length of time through which the effects of an 

 application of farm manure may be detected in crop 

 growth is very great. Hall l cites data from the Roth- 

 amsted experiments in which the effects of eight yearly 

 applications of 14 tons each were apparent forty years 

 after the last treatment. This is an extreme case; ordi- 

 narily, profitable increases may be obtained from manure 

 only from two to five years after the treatment. The fact 

 remains, nevertheless, that of all fertilizers farm manure 

 is the most lasting, lends the most stability to the soil, 

 and is really a soil builder par excellence. 



520. Place of manure in the rotation. With a num- 

 ber of trucking crops, the application of manure directly 

 to the crop year after year has proved to be advisable. 

 In an ordinary rotation, however, where less intensive 

 methods are employed, it is evident that manure may 

 vary in its effect according to the place in the rotation at 



1 Hall, A. D. 

 1910. 



Fertilizers and Manure, p. 213. New York. 



