FARM MANURES 353 



dry it. After a heavy rain the puddles in the yard 

 are black with richness that has leached from these 

 piles of manure. This is the fertility of the farm, 

 running to waste. Manure handled in this way may 

 lose over half of its plant food. Roberts found 

 that a ton of manure exposed in this way for six 

 months lost 42 per cent, of its plant food. Another 

 ton exposed from April 25 to Sept. 22 lost 60 per 

 cent, of its nitrogen, 47 per cent, of its phosphoric 

 acid and 76 per cent, of its potash, a loss in value 

 from $2.80 per ton to $1.06. When the pile of 

 exposed manure is finally hauled away it has lost 

 a large part of its soil-improving value. A dark- 

 coloured stain on the side of the barn is pretty 

 good evidence of shiftless farming in this respect. 



The loss of plant food from manure by leaching 

 depends largely upon the climate; the wetter it 

 is the greater the loss. In the arid and semi-arid 

 regions it is not large; but in every case it is large 

 enough to set every farmer to thinking how he may 

 best prevent it. 



Loss from Fermentation. Another way in which 

 manure often loses value is by heating, or fermenta- 

 tion. When manure is piled up, especially horse 

 manure, it begins to heat and decay. This fer- 

 mentation is caused by the growth of bacteria. 

 These need heat and air; the warmer the manure 

 is, and the more loosely it is piled, so that it is full 

 of air, the more quickly it heats. The nitrogen in 

 fermenting manure is rapidly changed into am- 

 monia, which escapes into the air. Every one has 

 noticed the pronounced "smell" of manure piled 

 up loosely and heating. It is plant food escaping. 



The heating of manure also injures it in another 

 way. Part of the vegetable matter in it, which 

 becomes humus when applied to the soil, is burned. 



