THE SOIL AND ITS IMPROVEMENT. 103 



Barn -yard Manure. This varies greatly in value accord- 

 ing to the animals it is obtained from, the food on which they 

 are fed, and the care with which it is treated. The actual 

 value of the manure comes in all cases from the food, and not 

 from the animal. No animal can put into the manure heap 

 any substance that was not contained in the food, and the 

 manure produced from any animal can never contain any 

 more plant food than was contained in the food the animal 

 consumed. 



There has been much misconception on this subject, and 

 many persons have imagined that a field could be enriched by 

 simply pasturing sheep on it. The manure produced by the 

 sheep will be valuable, but it can not by any possibility be of 

 more value than the crop they ate off would have been if turned 

 under, except in the fact that it might decompose in the soil 

 more rapidly. Poultry are often spoken of as being of great 

 value because they produce such rich manure, and some enthu- 

 siastic individuals have claimed that poultry would pay for 

 their feed in their manure. But the manure produced by a 

 flock of poultry while eating a bushel of corn could not contain 

 any more plant food than was contained in the corn, and in fact 

 would contain somewhat less. Nevertheless, there is a difference 

 in the value of the manure according to the animal producing it, 

 which arises from two causes. 



First. Some animals take more plant food out of the food 

 given them than others, and so leave less of it in the manure. 

 The manure produced from a ton of corn fed to animals which 

 are neither giving milk nor gaining in weight, will contain 

 almost precisely the same amount of nitrogen, phosphoric acid, 

 and potash that was contained in the corn. But if the ton 

 of corn is fed to cows giving milk or to young animals that are 

 growing rapidly, the manure produced will not contain more 

 than from fifty to seventy-five per cent of the nitrogen, phos- 

 phoric acid, and potash that was contained in the food. Hence 

 the value of manure produced from a given amount of food 

 will vary much, according to the animal to which the food is 

 given, not because any animal can add to the amount of plant 



