132 



THE planter's GUIDE. 



and deep as possible, in order in some sort to counter- 

 balance those disadvantages. 



There are few persons so happily situated as to be 

 able to command much animal or vegetable manure for 

 the use of trees. Such artificial modes of enrichment or 

 improvement must therefore be resorted to as science or 

 experience has pointed out. By following such guides 

 we may often learn so to alter the constituent parts of 

 soils as to increase their fertility, by the addition of 

 ingredients in which they are deficient, and in some 

 cases by the subtraction of such as too copiously abound 

 in them ; or else by effecting chemical changes of some 

 constituent part by incineration, or by the application 

 of mineral manures. Soils, considered as agents of 

 vegetable culture, are subjected to operations which effbct 

 changes on them either mechanically or chemically. Of 

 the former description there are none so important for 

 the use of trees as deepening and pulverising. Deepening 

 can be executed with effect only by trenching or double- 

 digging, (for the plough can do little in such a business,) 

 and pulverising is naturally combined with that process. 

 The depth of pulverisation, as Sir H. Davy well observes, 

 must depend on the nature of the soil and subsoil. In 

 rich clayey soils it can scarcely be too deep ; and even in 

 sands, unless the subsoil contain some principle noxious 

 to vegetables, deep comminution should be practised. 

 When the roots are deep, they are less liable to be 

 injured by excessive rain or excessive drought, and the 

 radicles are shot forth into every part of the soil.''^- In 

 a word, nothing but water stagnating under the trench in 

 consequence of a clayey bottom, and the risk of the roots 



* Elements of Agricultural Chemistry. 



