l68 SOILS AND FERTILIZERS 



products as linseed meal and cottonseed meal for feed- 

 ing stock, and take good care of the manure, than to 

 use the materials directly. 



205. Lasting Effects of Manure. — No other ma- 

 nures make themselves felt for so long a time as farm 

 manures. In ordinary farm practice an application of 

 stable manure will visibly affect the crops for a num- 

 ber of years. At the Rothamsted Experiment Station, 

 records have been kept for over fifty years as to the 

 effects of manures upon soils. In one experiment 

 manure was used for twenty years and then discon- 

 tinued for the same period. It was observed that 

 when its use was discontinued there was a gradual de- 

 cline in crop-producing power, but not so rapid as on 

 plots where no manure had been used. The manure 

 which had been applied for the twenty-year period 

 prior to its disuse made itself felt for an ensuing 

 period of twenty years. 



206. Comparative Value of Manure Produced on 

 Two Farms. — The fact that there is a great differ- 

 ence in the composition and value of manures pro- 

 duced on different farms may be observed from the 

 following examples : 



On one farm 10 tons of timothy are fed. The 

 liquid manure is not preserved and 25 per cent, of the 

 remaining fertility is leached out of the solids, while 

 5 per cent, of the nitrogen is lost by volatilization. 

 It is estimated that half of the nitrogen and potash of 



