NATURAL MANURES. 53 



Indirect manures are valuable in proportion to the 

 effect which they have upon the soil constituents, and 

 this effect may be due to both physical and chemical 

 causes. Through this distinction, in reference to the 

 action of manures, we are ready to classify them into 

 natural manures and artificial manures. 



Natural Manures. A natural manure is one which 

 may be either direct or indirect, but which has been 

 derived from natural sources, or, in other words, which 

 has not undergone any specific treatment or manufac- 

 ture. These include all vegetable and animal refuse of 

 the farm and yard, also factory wastes, which contain 

 one or more of the essential constituents. Natural ma- 

 nures are as a rule bulky, and are low grade in the sense 

 that they contain small amounts of the direct plant-food 

 constituents. 



Farmyard manure is one of the most important and 

 useful of the natural manures ; it is both a direct and 

 an indirect manure : direct, in containing nitrogen, phos- 

 phoric acid, potash, and lime, which are actual fertiliz- 

 ing constituents; and indirect, in containing organic or 

 vegetable matter, which aids in the improvement of the 

 physical character of the soil. 



It is sometimes called a "general manure," because, 

 as it contains all of the constituents of plant growth, it 

 is liable to be generally useful on all soils. 



Farmyard Manure. Yard manure varies in its 

 composition according to the character of the animals 

 producing it, and the quality of the food, and the object 

 of feeding. Its composition is also influenced by the 

 amount and kind of litter used, and its management after 



