GENERAL MANURES. 125 



Such substances as pen manure, an<l guano, 

 which add nil the requisite substances for an 

 ordinary crop, are known as general manures. 

 Pen manure, guano, etc., are also 'organic' 

 manures, being the direct, product of living 

 beings, as opposed to such substances as nitrate 

 of soda, basic slag, etc., which are spoken of as 

 artificial or chemical manures. 



GENERAL MANURES. 



1. Farm-yard manure, stable manure, and 

 pen manure contain all the constituents of 

 plant food in well adjusted proportions. The 

 actual amount of plant food contained in these 

 manures is often comparatively small. Their 

 great value is due to the fact that they add a 

 large amount of organic matter to the soil. 

 Light soils are thus enabled to retain more 

 water and the crops on them to withstand 

 droughts better. Heavy soils are rendered 

 more porous and easier to work. Such 

 manures, therefore, are of great value to the 

 cultivator and are useful for almost all soils 

 and crops. When manuring has to be done 

 on a large scale it is not always easy to pro- 

 cure sufficient quantities of these substances 

 and recourse must then be had to the substances 

 generally known as artificial manures. 



