156 SOILS AND FERTILIZERS 



is lost during the process of digestion, and the 

 action of the digestive fluids upon the food makes the 

 manure more readily available as a fertilizer than the 

 food- which has not passed through any fermentation 

 stages. It is better ecomony to use products as lin- 

 seed meal and cottonseed meal for feeding stock, and 

 to take good care of the manure, than to use the mate- 

 rials directly as fertilizer. 



199. 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 visably 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 

 farm manure was used for twenty years and then dis- 

 continued 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 

 made itself felt for an ensuing period of twenty years. 



200. 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 fertility is leached out of the solid excre- 



