94 THE PRINCIPLES OF AGRICULTUKE. 



pigs, or other animals, to run upon the manure heap, 

 so as to keep it in a compact condition. 



2. The Escape of Liquids. The liquid parts of manure 

 contain more than one half their value. It is important 

 that some dry, spongy substance, as straw, leaves, dried 

 muck, or dry soil, be used to absorb and retain them. 

 The nitrogen which serves to form ammonia by fermen- 

 tation, is largely contained in the liquids, and the pres- 

 ence of these substances in some measure prevents the 

 escape of ammonia, by combining with it or absorbing it. 



The same purpose may be more fully accomplished by 

 applying to the liquids sulphuric acid, or gypsum, which 

 is partly composed of that acid. 



3. Exposure to Rain. The liquid parts contained in 

 manure, and held by absorbents, are readily washed out 

 by heavy rains. Both ammonia and nitric acid, the two 

 available forms of nitrogen, are largely lost in this way, 

 as well as some other elements. 



When manure is piled in heaps upon land which is to 

 be cultivated, it is true that these elements are washed 

 into the soil. This, however, involves waste, as the 

 small plots beneath the heaps are too much overstocked 

 with these valuable substances to be able to render any 

 adequate returns in the crops. 



To prevent waste by washing, manure should be kept 

 under cover ; or, if exposed, should be so protected as 

 to receive only a small amount of rain, which would do 

 no harm. 



Methods of Applying Manure. Whatever particular 

 methods are employed in applying manure to the soil, 

 there are two general principles that should always be 

 borne in mind : 



1. It should be applied as soon as possible. All 



