SOILS 



merits of plant-food contained in soils, especially 

 if those elements are in an organic form, is pre- 

 sent in such a condition that plants are unable 

 to make use of it. 



The following table shows the chemical com- 

 position of soils recommended as suitable for 

 the cultivation of Vines, Ferns, and Palms, ordi- 

 nary garden flowers, and stove plants respec- 

 tively : — 



Percentage Composition of various Loams. 



Constituents. 



For 

 Vines. 



For 

 Ferns 



and 

 Palms. 



For 

 Garden 

 Flowers. 



For 



Stove 

 Plants. 



* Organic matter (fi- ) 

 brous mould), j 



Sand, ... 



Iron oxide, 



Alumina (clay), 



Lime, ... 



Potash, 



Phosphoric acid, 



10-39 



78-44 

 0-20 

 9-98 

 0-66 

 0-20 

 0-13 



11-09 



80-28 

 0-50 

 7-50 

 29 

 0-20 

 0-14 



13-70 



74-20 

 0-62 



10 00 

 0-67 

 0-33 

 0-48 



19 38 



66-80 

 0-26 



1300 

 0-19 

 0-31 

 0-06 



Total, 



* Containing nitrogen, 



100-00 



0-468 



100-00 

 0-367 



100-00 

 0-229 



100-00 

 0-238 



Doubtless the best soil for ordinary horticul- 

 tural purposes, and especially for vine-growing, 

 is a good yellow turfy loam, which has been 

 piled up until well seasoned, with the organic 

 matter partially decomposed. 



Sands. — Sufficient attention is not always paid 

 to the selection of the sand used for horticul- 

 tural purposes. Truffaut says: "We should 

 take care that the sands we use are not contami- 

 nated with soil, or even by the least trace of 

 clay; for without that precaution sands lose all 

 their main properties". 



In England the fine quartz sand and the 

 marine alluvial sand from the district of Bead- 

 ing (Surrey) are frequently used. In France 

 the alluvial sands of the Loire and the Allier 

 are held in high esteem on account of their 

 multiplicity of ligneous plants. In Bedfordshire 

 is found a quartz-like sand of large grains and 

 transparent, which imparts to the compost into 

 which it enters some very remarkable physical 

 properties. The same description of sand is 

 found on the coast of St. Martin a Etamps, and 

 in the neighbourhood of Dormans, France. 



Both in England and on the Continent road- 

 scrapings are frequently employed as a com- 

 ponent part of horticultural composts. Such 

 material is useful as giving a mixture of sand, 

 a certain quantity of fine mould, with chemical 

 ingredients of both a mineral and nitrogenous 

 character. 



The following table shows the percentage 



chemical composition of road -scraping 

 Trappes (Seine-et-Oise), France: — 



141 



from 



Composition of Road-scrapings in parts per 100. 



Sand, 93-87 



Organic matter,... ... ... ... ... 3 -65 



Mould, 0-90 



Nitrogen, ... . . 0-15 



Phosphoric acid, 0*06 



Lime, 0-14 



Iron oxide, 0"3 



Potash, 0-48 



The data thus given shows that road-scrapings 

 must act beneficially rather by their mechanical 

 influence on the compost with which they may 

 be mixed than by any manurial ingredient they 

 contain. 



Nitrogen in Soils. — It is just about a century 

 since the question of the sources of the nitrogen 

 of vegetation became a subject of experimental 

 inquiry, and also of conflicting opinion. It is 

 about half a century since Boussingault was led 

 by a study of the chemistry of agricultural pro- 

 duction to see the importance of determining 

 the sources of the nitrogen periodically avail- 

 able to vegetation over a given area of land. 

 Somewhat later the Eothamsted experiments, 

 now in their fifty-second year, were commenced 

 by Sir John Lawes and Sir Henry Gilbert, and 

 in the progress of these investigations many 

 facts have been elicited bearing upon this im- 

 portant subject. Still, almost from the date of 

 Boussingault's first researches the question has 

 been one of controversy, and even at the present 

 time very conflicting views are entertained re- 

 specting it. 



Messrs. Lawes and Gilbert have frequently 

 pointed out how entirely inadequate is the 

 amount of combined nitrogen coming down in 

 the measurable aqueous deposits from the atmo- 

 sphere to supply the nitrogen of the vegetation 

 of a given area. Other possible supplies of 

 combined nitrogen from the atmosphere have 

 also been considered, and pronounced inade- 

 quate. Again, the question whether or not plants 

 assimilate the free or uncombined nitrogen of 

 the atmosphere has been the subject of laborious 

 experimental inquiry, and also of critical dis- 

 cussion, at Eothamsted. Finally, the question 

 whether the stores of the soil itself are an 

 important source of the nitrogen of our crops, 

 both of the farm and of the garden, has also 

 been considered. 



It may at the outset be frankly admitted that 

 so long as the facts of production alone are 

 studied, without knowledge of, or reference to, 

 the changes in the stock of the nitrogen in the 



