204 SOILS AND MANURES 



they contain appreciable quantities of all three fertilising 

 ingredients nitrogen, phosphoric acid and potash. They 

 may be used as additive substances, but their more im- 

 portant function is restitution. The so-called natural 

 manures are, for the most part, general manures. They 

 may be of organic origin, i.e., consist of animal or vege- 

 table matter or a mixture of the two, or they may be 

 wholly or partly mineral and may even be artificially 

 prepared or manufactured. 



Special manures are not complete and only a few of 

 them contain appreciable quantities of more than one 

 fertilising ingredient. They are classified as nitrogenous, 

 phosphatic or potash manures, according to the nature 

 of the fertilising ingredient they contain. By combining 

 two or more special manures, general manures can be 

 produced and may be used for purposes of restitution. 

 They are used, however, principally as additive sub- 

 stances to satisfy the special requirements of the soils 

 or crops to which they are applied. The so-called artificial 

 manures are for the most part special manures. They 

 may be of organic or of mineral origin, and may be 

 subdivided accordingly. They are generally prepared or 

 manufactured substances and are usually purchased, not 

 produced on the farm. 



This classification of manures may be stated in tabular 

 form thus: 



I. GENERAL MANURES. 



1. Of animal origin -- nitrogenous guanos, liquid 

 manure, sewage manures, etc. 



2. Of vegetable origin green plants and plant refuse, 

 seaweed, damaged feeding cakes, etc. 



3. Of mixed (animal and vegetable) origin farmyard 

 manure, composts, night soils, etc. 



4. Of mineral origin mixed special manures, etc. 



