AGRONOMY 43 



understanding and applying the following laws of 

 husbandry : ^ 



(1) " A soU can be termed fertile only when it 

 contains all the materials requisite for the nutri- 

 tion of plants in the required quantity, and in 

 the proper form." 



(2) " With every crop a portion of these in- 

 gredients is removed. A part of this again added 

 from the inexhaustible store of the atmosphere ; 

 another part, however, is lost for ever if not 

 replaced by man." 



(3) " The fertility of the soil remains unchanged 

 if all the ingredients of a crop are given back to 

 the land. Such a restitution is effected by manure 

 and by the atmosphere." 



(4) A soil may contain an abundance of potash, 

 lime, phosphoric acid, iron, etc., and yet be almost 

 barren, if these substances exist as insoluble 

 compounds. 



(5) A fertUe soil must be of such a texture as to 

 admit free access of air (for chemical and bacterial 

 changes to occur), although at the same time it 

 must not be too porous, but firm enough to afford 

 proper support to growing trees, shrubs or plants. 



(6) The soil must be capable of retaining a cer- 



' A. B. Griffiths, Mamwres cmd their Uses, p. 20 ; A Treatise on 

 Manures, p. 7. 



