154 



THE GAEDENEE'S ASSISTANT. 



1. The leaf -moulds, both of Maurepas and 

 of Ghent, are sufficiently rich in mineral con- 

 stituents, and the nitrification of the organic 

 nitrogen is active enough to supply all that 

 is wanted by the Azaleas. 



2. Ghent leaf -mould always furnishes the 

 plants with a greater quantity of assimilable 

 nitrogen, of phosphoric acid, and of lime. 



3. It is during the second year of culture 

 that Azaleas derive from the soil the maximum 

 of plant-food. 



4. Azaleas abstract from the soil the follow- 

 ing elements, arranged in order of prominence 

 — silica, nitrogen, lime, potash, phosphoric acid, 

 and iron oxide. 



5. In order to imitate as nearly as possible the 

 Belgian horticulturists, who obtain such excel- 

 lent results with Azaleas, it is necessary to add to 

 the leaf-moulds obtained from the environs of 

 Paris a certain quantity of phosphatic manure. 



After the experiments made at Versailles in 

 1892, a manurial application was given to a 

 two -years -old Azalea plant, planted in Mau- 

 repas leaf -mould, at the rate of 155 grains of 

 phosphate of lime and 300 grains of nitrate of 

 soda on each square yard of soil, which produced 

 a very sensible effect, causing the plant to grow 

 with exceptional vigour. The leaves became 

 larger, and of a deeper -green colour. Two 

 primings of the plant were able to be performed 

 instead of one. 



For several years it has been observed that 

 a mixture of mould and of dried-blood manure, 

 applied as a top-dressing, produced an analogous 

 effect upon Azalea plants, the colour being more 

 pronounced and the vigour greater. 



Finally, it may be asked, What is the sig- 

 nificance of these facts'? In the first place, it 

 is that the character of development of the 

 Azalea depends very much upon the proportion 

 of nitrogen available within the soil, because, 

 where there is restricted growth of plant, there 

 will not be vegetative activity, or, in other 

 words, a great accumulation of texture-forming 

 substances, upon which the plant must eventu- 

 ally rely for flower formation and maturation. 

 But in order that the nitrogen may work suc- 

 cessfully it becomes absolutely necessary that 

 there shall also be plenty of available minerals 

 in the soil to combine with the nitrogen, nitro- 

 gen being the element which is mostly con- 

 ducive to vegetable growth, and therefore if 

 present in excess likely to interfere with, if 

 not altogether prevent, maturity of growth. 

 For there can be no doubt that strength of 

 plant depends on favourable development of 



the woody substance, and the more this pre- 

 vails, the more will the accumulated nitrogen 

 be diluted — in other words, show a lower 

 proportion to the other constituents, [j. j. w.] 



CHAPTEE XV. 



MANURES. 



Organic Manures — Inorganic Manures — The 

 Effect of Manures. 



Though the general term manures is well 

 understood by almost every gardener, recent 

 progress in horticultural science has had a 

 tendency to give a distinctness and definiteness 

 to the term which was previously impossible on 

 account of the lack of accurate knowledge, but 

 which, while yearly becoming better understood, 

 is not yet so clear in the minds of all gardeners 

 as to make a further study of the subject of no 

 value. 



All substances which, when added to the soil, 



increase its fertility may be considered as man- 



| ures. These may act either directly, by supply- 



j ing food to plants, or indirectly, by rendering 



I the substances already contained in the soil 



I available for the nourishment of plants. The 



necessity of the application of manures is self- 



j evident ; for, as plants withdraw certain elements 



from the soil, the latter would in course of 



■ time become exhausted if no restoration of 



them were made. 



Manures may be divided into two classes: — 



1. Organic manures, or those of vegetable 

 ; and animal origin. 



2. Inorganic manures, or those of mineral 

 origin. 



The immediate effect of a manure depends 

 (1) on its solubility, and (2) on the suitability 

 of the plant-food which it contains for the use 

 of the plant it is applied to. 



Manures may be further classified into " gen- 

 eral " and " special ". General manures are 

 those which contain all the essential constituents 

 of plant-food, while special manures are those 

 which are valuable chiefly for one such con- 

 stituent, though sometimes more are present. 



Though the general manures contain all the 

 necessary constituents of plant-growth, yet they 

 do not necessarily contain them either in the 

 amount or the proportions required by a par- 

 ticular plant, so that their use may not be 

 economical. For example, if the soil contains 

 an ample supply of nitrogen and potash, but is 



