58 GENERAL CONSIDERATIONS 



are taken at the same time for increasing the food 

 supply its use will tend to give temporarily increased 

 crops at the expense of permanent fertility. In other 

 words, as has been so forcibly said, if used alone, it 

 tends to enrich the fathers, but to impoverish the sons. 



Manuring. — This general term is applied to all 

 those processes by which plant food is added to the 

 soil for the purpose of maintaining or increasing its 

 fertility. Some soils are naturally so deep and fer- 

 tile that they may be cultivated continuously for 

 many years without diminished productiveness, but 

 even the richest will in time show signs of exhaustion 

 if no plant food is returned to them. The problem 

 of manuring is, therefore, one of the most important 

 that can engage the attention of the farmer. The 

 only exception to this statement is to be found in 

 those few favored localities, like the Nile Valley, 

 where the overflow from some great river brings 

 down annually rich deposits from the washings of the 

 lands near its source. 



Stable Manure. — This is one of the most widely 

 used and important substances for enriching the soil. 

 It consists of the solid and liquid excrement of 

 domestic animals mixed with more or less straw or 

 other litter that has been used as bedding in the 

 stables. It is more widely useful than any other 

 fertilizing material and can be used to advantage on 

 nearly all crops. It not only supplies all three of the 

 useful chemical elements, — nitrogen, phosphorus, 

 and potash in some quantity, — but it adds a large 

 amount of easily fermentable organic matter to the 

 soil and thus improves its mechanical condition. If 



