10 



Farmyard Manure. 



[APRIL, 



o-2 per cent, of phosphoric acid and i -o per cent, of potash, the 

 variations in composition between individual samples of any 

 one kind of straw being as great as the variation between 

 average samples of wheat, oat and barley straw. Speaking 

 generally, straw grown in the north of England and Scotland 

 is richer than straw grown in the south and east of England, 

 because the vegetative growth has been more prolonged and 

 the migration of food materials from the straw into the corn 

 has not been quite so thorough. Straw will absorb from two 

 to three times its weight of water, but again the variation in 

 absorbing power between different samples of the same kind 

 of straw is greater than that between different kinds of straw. 

 In practice, wheat straw is the most highly esteemed, as cleaner 

 and wearing better under the feet of the animals than any other 

 kind of straw ; oat straw comes next and is often almost as 

 good as wheat straw ; barley straw is least liked, as it is often 

 brittle and dusty. 



However the farmyard manure has been made, it thus starts 

 with a mixture of excrement, urine, and litter, which become 

 more or less consolidated and mixed together by the trampling 

 of the animals. Other changes, however, intervene very rapidly, 

 and these, in the main, are brought about by bacteria, which for 

 convenience, may be divided into two groups, one acting on the 

 cellulose and other carbon compounds of the straw that 

 make up the bulk of the manure, and the other acting on 

 the nitrogenous compounds that do not weigh so much but 

 supply the main fertilising properties of the dung. 



Among the more important of the organisms dealing with 

 nitrogenous material are those which attack the urea in the 

 urine, and by adding to it the elements of water, give rise to a 

 carbonate of ammonia which very readily dissociates into 

 free ammonia and carbonic acid, both gases, and therefore 

 capable of escape into the atmosphere. This change into 

 ammonium carbonate is an extremely rapid one ; in the 

 liquid draining from a yard or a manure heap, or even 

 in the liquid manure tank, little or no urea can be de- 

 tected, so complete has been the change to ammonia. As 

 long as the liquid containing the ammonium carbonate is 

 protected from evaporation no loss of nitrogen will result, but 

 the more surface it exposes to the air and the higher the tern- 



