SOILS. 



137 



for market. To prepare the material for use, 

 it must be broken up and sifted, removing the 

 larger undecomposed roots which hold the mass 

 together. 



The second description of mould, le terreau 

 de feuilles (leaf -soil), is different from the former, 

 being obtained from the forests, and is the re- 

 sult of the decomposition of the fallen leaves 

 mixed with the earth upon which they rest; 

 that obtained from under the oak-trees is con- 

 sidered the best. These soils are light in char- 

 acter, and peculiarly suited for the growth of 

 most greenhouse plants. The peculiar property 

 of this leaf-mould is, that it facilitates drainage 

 and aeration, causing a quick and active plant- 

 growth, with a free development of root. The 

 partial decomposing leaves and roots forming 

 the mould require a free passage of air to allow 

 of the nitrification of the organic matter, and, 

 given this, the roots of the growing plants put 

 into it develop rapidly. But as both the drain- 

 age and evaporation from such mould are great, 

 frequent waterings become necessary in actual 

 work. The mould has also a large absorptive 

 power: one hundred parts by weight of the 

 mould will take up one hundred and ninety 

 parts by weight of water. 



As it is known that the fertility of all classes 

 of soil is closely connected with its powers of 

 retaining plant-food, several experiments have 

 been tried as to the retentive properties of leaf- 

 mould for different manurial substances, which 

 have shown that it has a great absorbent power 

 for potash and phosphoric acid, but that nitrate 

 of soda is retained in a much less degree. These 

 facts agree with what has been found in ordinary 

 agriculture. 



The following table shows the amount of 

 selected chemical constituents in 100 parts of 

 the finely sifted leaf-mould obtained from the 

 neighbourhood of Rambouillet (Seine-et-Oise): — 



Selected Constituents in, parts per hundred of Mould. 





Per cent 



Nitrogen, ... 



... 0-587 



Phosphoric acid, ... 



... 0-116 



Lime, 



... 0-260 



Silica (sand), 



... 83-600 



Humus (organic matter), 



... 9-530 



It is known that soils containing humus 

 will absorb ammonia from the atmosphere, 

 and thus increase their store of nitrogen. The 

 organic remains of former crops or plants- are 

 also oxidized, the nitrogen being converted 

 into nitric acid. The fragments of either silica 

 or limestone will at the same time be more or 

 less disintegrated by the combined action of 



water and air, assisted by the carbonic acid and 

 humic acid arising from the decomposition of 

 vegetable matter, and a portion of the insoluble 

 plant-food will thus gradually be brought into 

 a state suited for assimilation by the roots of 

 growing plants. 



From several carefully conducted experiments 

 by Georges Truffaut it was found that the leaf- 

 mould on being passed through a sieve yielded 

 80 parts per 100 of fine soil, and that the weight 

 of fine dry earth in one hectolitre, which is 

 equal to about 3J cubic feet or 2J bushels, ^vas 

 143 lbs. The sif ted-out portion was composed 

 mainly of leaves in an early stage of decompo- 

 sition, wliich would act on the soil to which it 

 was added by virtue of its physical properties. 



The following table shows the weight of each 

 fertilizing element in one hectolitre of leaf- 

 mould, and its degree of assimilability : — 



Assimilable Elements in one Hectolitre of Sifted Leaf-mould. 





Lbs. 



Total nitrogen, 



0-59 



Lime, 



0-34 



Phosphoric acid, ... 



0-15 



Potash, 



0-46 



Silica (sand), 



108-68 



Humus, 



12-39 



Assimilable Elements. 



Grammes 

 Nitric nitrogen provided in 6 months by 



nitrification, ... ... ... ... 34*45 



Phosphoric acid (soluble), 2 -60 



Potash (soluble), ... ... ... ... 47 '45 



Knowing, therefore, what are the substances 

 directly assimilable by plants in one hectolitre 

 of leaf-mould, it may be of importance at this 

 stage to inquire the best means of applying to 

 the soil the elements that are wanting, or are 

 not present in sufficient quantity. 



Nitrogen. — Although the nitrification in the 

 leaf-mould may be sufficiently active for the 

 gardener to dispense with artificial nitrogenous 

 manures in most cases, yet there are certain 

 species of plants which rapidly develop a large 

 mass of foliage, and these cause a rapid and 

 extensive demand on the nitrogen. For such 

 plants it will always be advisable to use nitrate 

 of soda, nitrate of potash, or guano in solution 

 when watering, and to supply these manures 

 frequently and in small quantities. The presence 

 of crystalline nitrate of soda in direct contact 

 with plant-roots is sometimes hurtful, and the 

 growing plants do not get the full benefit of the 

 supply. 



Phosphoric acid. — Assimilable phosphoric acid 

 occurs in very small quantity in leaf-mould; it 

 is therefore necessary to add it in the form of 



