THE HORTICULTURIST. 



CHAPTER I. 

 SOILS CONSIDERED WITH REFERENCE TO HORTICULTURE. 



THE term soil is applied to that thin stratum on the surface of the 

 ground which is occupied by the roots of the smaller herbaceous vege- 

 tables ; on uncultivated surfaces it varies in depth with its nature and 

 the character of the plants growing on it ; but on lands in cultivation, 

 the soil extends to the depth usually penetrated by the implements of 

 culture. The principal materials of which soils are composed are 

 earths formed of the debris of different kinds of rocks, combined with 

 organic matter derived from decomposed vegetables or animals. Earths 

 without organic matter will only support plants of the lowest grade, 

 such as Lichens and Mosses ; and where soils are found supporting the 

 higher classes of plants, endogens and exogens, the vigour of these will 

 generally be found to be greater or less according to the proportion of 

 organic matter which the soil contains. This organic matter, when 

 supplied by art, is called manure. The subject of manures will be 

 most conveniently treated in our next chapter. Here we shall confine 

 ourselves to the consideration of soils, and treat, first, of their origin 

 and kinds, and secondly, of their improvement. 



Origin and Kinds of Soils. 



The earthy part of all soils must necessarily have been derived from 

 the debris of rocks, and the organic part from the intermixture of 

 decayed vegetable or animal matter. The earthy mass so produced 

 varies in colour, but, from containing humus and mould, it is always 

 darker in a greater or less degree than subsoils, which in general are 

 without organic matter. Soils also contain mineral salts and metallic 

 oxides, some of which are beneficial, others harmless, and some few 

 injurious, to plants. The chemical constitution of a soil can only 

 be known by analysis, which cannot, in general, be depended on, 

 unless performed by professional or experienced chemists.* The me- 



* It is now becoming a general custom for landed proprietors to send a pound or 

 more of soil to an experienced chemist, to obtain an analysis of it, so as to know 

 what mineral manures it may be best to use, in order to supply the constituents 

 the laud may stand in need of. 



B 



