SOILS. 



151 



forced to buy extensive quantities every year 

 from the Belgians, who appear to have at their 

 disposal a leaf -mould, improperly called " Ghent 

 heath-mould", which is the ideal soil for the 

 culture of Azaleas. The French, like the Eng- 

 lish horticulturists, have to obtain, with great 

 trouble and considerable expense, leaf-moulds 

 of inferior quality. The author has, therefore, 

 devoted much attention, and has made valuable 

 scientific researches, in order to overcome the 

 difficulties of the situation. 



His method was first to find out what chemical 

 plant-food the Azalea abstracts from the soil 

 during growth. Then, by submitting to analyses 

 various leaf -moulds in which cultivation has 

 shown the best results, to ascertain what are 

 those elements which, by their abundance, pro- 

 duce the greatest fertility ; and, as a consequence, 

 what are the constituents lacking in an inferior 



leaf-mould that must be added in the form of 

 manure to ensure success. 



At Versailles, during the first and second 

 periods of growth of the Azalea, the horti- 

 culturists employ peat-moulds obtained from 

 the neighbourhood of Maurepas (Seine-et-Oise), 

 which are similar to those coming from the 

 district of Rambouillet. 



The Ghent mould in its density and compact- 

 ness is very nearly identical with that found in 

 the vicinity of Maurepas, although there is in 

 its composition a greater quantity of vegetable 

 matter, in a not very advanced stage of decom- 

 position. Therefore the quantity of fine mould, 

 after passing through a sieve, is less than in the 

 case of the other moulds. 



The following table shows the comparative 

 value, according to the chemical composition, of 

 four descriptions of leaf -mould : — 



Composition of Leaf-moulds : Constituents given in parts per 1000. 





Leaf-mould 



from 

 Rambouillet. 



Leaf-mould 



from 

 Maurepas. 



Peat-mould 



from 

 Maurepas. 



Leaf-mould 

 from 

 Ghent. 



Quantity of Fine Mould in 1000 lbs. bulk, 



800 



615 



730 



590 



Nitrogen, 

 Phosphoric acid, 



Lime, 



Potash, 



Silica, 



Iron oxide, ... 

 Organic matter, 





5-9 

 1-2 

 2-6 

 3 5 

 836-0 



95-3 



47 

 1-3 



1-8 

 5-0 



805-5 



17 



170-0 



5-0 

 0-6 

 1-9 



31 



790-5 

 2-6 



188-0 



11-7 

 1-6 

 3-5 



1-4 

 341-0 



640-0 



The data thus given shows that the Ghent 

 mould is exceedingly rich in nitrogen, which is 

 to be accounted for by the greater abundance 

 of organic matter, and its large proportion of 

 lime, which favours nitrification. The three 

 other moulds contain only about one -half as 

 much nitrogen as the Ghent mould, and they 

 do not vary very greatly among themselves in 

 this constituent. 



It is known that the production of nitrates 

 in a soil is of the greatest importance to vege- 

 tation, nitrates being the form in which nitro- 

 genous food is chiefly assimilated by plants; 

 the abundance or poverty of nitrates in a mould 

 thus determines to a large extent the luxuriance 

 of plant -growth which the soil is capable of 

 producing. Hence can be easily understood the 

 cause of the exceeding richness of the Ghent 

 mould, each one thousand pounds containing 

 640 pounds of organic matter, 3J pounds of 

 lime, and 341 pounds of silica (sand), to assist in 

 aeration and drainage. Phosphoric acid is also 

 very abundant in Ghent mould, the quantity of 



this constituent in the Maurepas peat, on the 

 contrary, being extremely small. 



On the other hand, while the leaf -moulds 

 from Versailles are slightly weaker in phosphoric 

 acid than the Ghent mould, they are considerably 

 ahead in potash, containing on the average just 

 about three times as much. 



It seems fairly evident, therefore, that the 

 superiority of Ghent mould for the culture of 

 the Azalea consists in its richness in organic nitro- 

 gen. It is probable also that, independently of its 

 liberal supply of organic matter, of lime, potash, 

 and phosphoric acid, the beneficial effects of the 

 mould are in a considerable degree due to its 

 influence on the mechanical condition of the soil 

 with which it may be incorporated, rendering this 

 more porous and easily permeable to the surface 

 roots, upon the proper development of which 

 the success of Azalea culture so much depends. 



Culture of Azalea indica at Versailles. — The 

 variety selected for experiment was that known 

 as Madame Van der Cruyssen, and the investi- 

 gations extended over three years. 



