CHEMISTRY IN RELATION TO HORTICULTURE. 



113 



considered, but to the gardener this does not present the importance it 

 does to the agriculturist, as he has the means of controlling it to 

 a great extent. The nature of the subsoil requires, however, to be 

 taken into account, and for fruit trees and hops a deep soil of some- 

 what heavy nature is an essential. Roses also require a heavy soil, 

 but potatoes and carrots do best on sandy loams, and peaty soils are 

 most suited for heaths, azaleas, and rhododendrons, as also for foliage 

 plants and ferns. So many, however, are the variations which the 

 gardener is able to effect in the texture of the soils he has to do with 

 that it is unnecessary to dwell longer on this point, especially as it is 

 one affecting the mechanical and physical conditions rather than the 

 chemical nature or constituents of the soil, or the supply of plant 

 food. In all these cases, however, it is essential to keep in mind the 

 securing of proper drainage, without which there will be want of aeration 

 and oxidation, and the cessation of those processes which go on in the 

 soil resulting in the setting free and taking up of nutrient matter. 



Manure. 



The next subject for consideration — in its chemical aspects — is the 

 supply to the soil, by means of manure of one kind or another, of those 

 constituents necessary or desirable for the plant, but lacking in the soil. 

 To this subject an entire lecture might quite well be devoted, and it is 

 not my present object to do more than touch on general points involved 

 in the use of manures. Manures may be considered as of two main 

 kinds — natural and artificial. Under the former head are included the 

 most general of all — farmyard or stable manure, decaying vegetable and 

 animal matters, such as leaves, garden refuse, and nightsoil, and waste 

 materials like soot, shoddy or wool, hoofs and horn dust, dried blood, 

 wood ashes, &c. Under the second head come the products of chemical 

 manure factories — superphosphate ; bones in their various forms, raw, 

 steamed, and dissolved ; mixed artificial manures ; basic slag, &c. — and 

 other substances, either imported or prepared, which may be termed 

 "chemical fertilisers." Among these are Peruvian and other guanos, 

 nitrate of soda, nitrate of potash, kainit and other potash salts, common 

 salt, &c. Other materials again there are which are used partly for 

 manurial benefit, but largely also for the mechanical and physical im- 

 provement that they effect on soils : of this class are lime, compost, 

 pond mud, sewage sludge, &c. The most general manure is, of course, 

 farmyard or stable manure, and this is of varying character and com- 

 position according as whether it be made from horse dung, cattle dung, 

 or pig droppings, and according to the kind of absorbing material, or 

 litter, used — be it straw, peat-moss, or earth. The essential feature 

 common to all is that the manure practically supplies all the ingredients 

 necessary for the growth of plants, though it may still be the case that 

 these may require supplementing, for special cases, by the use of artificial 

 manures which give a more abundant supply of a particular ingredient, 

 such as potash, phosphoric acid, or readily available nitrogen. Farmyard 

 manure may be used either fresh or in a thoroughly rotten state. In 

 the former condition it is most serviceable for the amelioration of heavy 



i 



