ANIMAL MANURES 205 



Fermentation produces ammonia and other gases which 

 escape into the air and so are wasted. The chief mineral 

 constituents are nitrogen, potash, phosphorus, and lime. 

 Now these four elements are essential to plant life, and as 

 they are all contained in animal manures they are known 

 as " complete " fertilisers, to distinguish them from 

 simple chemical fertilisers like nitrate of soda. 



But animal manures contain a still more important 

 ingredient, " Humus." Chemists have mixed what are 

 called " complete " fertilisers from chemicals, and I give 

 some recipes in the next chapter ; but however complete 

 and carefully compounded they may be, they lack one 

 ingredient of the utmost importance, namely, " Humus." 



Humus and the Soil : Humus may be denned as the 

 product of complete putrefaction of animal or vegetable 

 refuse. So far as I am aware no chemist has ever been able 

 to make it, hence the failure of artificial fertilisers as 

 complete substitutes for organic manures. 



I do not think plants absorb humus directly into their 

 systems through their roots. My own theory is that the 

 humus must be decomposed first by soil bacteria, and so 

 changed into soluble compounds. 



Humus is essential to plants for at least two reasons, 

 namely, to hold moisture, and to keep the soil warm. It 

 is a blackish-brown material, soft to the touch, and very 

 readily dirties the hands or clothes. It is what gives the 

 soil its black colour, and this black colour is most important. 

 It absorbs the sunshine while the sun is out, and radiates 

 it after the sun has gone in. Soils which do not contain 

 humus are subject to sudden changes of temperature, 

 those which do contain it are more equable and warm. 



Some Useful Manures : I place farmyard manure first. 

 It is the best for general purposes in the garden, and any 

 soil, whether sandy, clayey, gravelly, chalky, or good loam, 

 will benefit greatly by having a dressing of it in winter. 

 Usually it consists of a mixture of manures, and if well 

 turned over during its process of decomposition its richness 

 is conserved. Analysis shows that it contains considerable 



