COMPOSITION OF SOILS. 



73 



ihe quantity of potash contained in the 

 ashes. By this means a mode was furnished 

 of distinguishing the different soils upon 

 which the tobacco under examination had 

 been cultivated, as well as the peculiar class 

 to which it belonged. Another striking fact 

 WAS also disclosed through these analyses. 

 Certain celebrated kinds of American tobacco 

 were found gradually to yield a smaller 

 quantity of ashes, and their value dimi- 

 nished in the same proportion. For this in- 

 formation I am indebted to M. Pelouze, pro- 

 fessor of the Polytechnic School in Paris. 



There are certain plants which contain 

 either no potash, or mere traces of it. Such 

 are the poppy, (papaver somniferwn,} which 

 generates in its organism a vegetable alka- 

 loid, Indian corn, (zea wui?/s,)and helianthus 

 tuberosu-s. For plants such as these the pot- 

 ash in the soil is of no use, and farmers are 

 well aware that they can be cultivated with- 

 out rotation on the same soil, particularly 

 when the herbs and straw, or their ashes, 

 are returned to the soil after the reaping of 

 the crop. 



One cause of the favourable action of the 

 nitrates of soda and potash must doubtless 

 be, that through their agency the alkalies 

 which are deficient in a soil are furnished to 

 it. Thus it has been found that in soils de- 

 ficient in potash, the nitrates of soda or pot- 

 ash have been very advantageous; whilst 

 those, on the other hand, which contain a 

 sufficiency of alkalies, have experienced no 

 beneficial effects through their means. In 

 the application of manures to soils we should 

 be guided by the general composition of the 

 ashes of plants, whilst the manure applied 

 to a particular plant ought to be selected 

 with reference to the substances which it 

 demands for its nourishment. In general, a 

 manure should contain a large quantity of 

 alkaline salts, a considerable proportion of 

 phosphate of magnesia, and a smaller pro- 

 portion of phosphate of lime ; azotised ma- 

 nure and ammoniacal salts cannot be too 

 frequently employed. 



In the following part of this chapter I 

 shall describe a number of analyses of soils 

 executed by Sprengel, together with obser- 

 vations on their sterility and fertility, as 

 stated by that distinguished agriculturist. 

 It is unnecessary to describe the modus ope- 

 randi used in the analyses of these soils, for 

 this kind of research will never be made by 

 farmers, who must apply to the professional 

 chemist, if they wish for information regard- 

 ing the composition of their soils. 



Under the term surface-soil, we mean that 

 portion of soil which is on the surface ; 

 whilst by subsoil we mean that which is be- 

 low the former, and out of the reach of the 

 ordinary plough. 



CHEMICAL COMPOSITION OF CERTAIN SOILS, 

 ACCORDING TO ANALYSIS. 



1. Surface-soil (A) a good loamy soil, 



*rom the vicinity of Gandersheim. It is re- 



10 



markable for producing uncommonly fine 



red clover when manured with gypsum. 



(B) is an analysis of the subsoil. 100 parts 



contain : 



(A) (B) 



Silica, with fine siliceous sand -91*331 93883 



Alumina 1*344 1*944 



Peroxide of iron, with a little pro- 

 toxide 1-562 2-226 



Peroxide of manganese - - 0'082 0.320 



Magnesia and silica, in combina- 

 tion with sulphuric acid and 

 humus - - - - 0-800 0'720 



Magnesia, with silica and humic 

 acid combined - - 0'440 0'340 



Potash, in combination with silica 0*156 0'105 



Soda, principally in combination 

 with silica, and a little as com- 

 mon salt - - - - 0'066 0'060 



Phosphoric acid - - - 0'098 0190 



Sulphuric acid in combination 

 with lime .... 0-111 0'012 



Chlorine (in common salt) - 012 0*012 



Humus, with traces of azotised 

 matter 4'100 0*184 



100-000 100000 



An inspection of the above analyses will 

 show that the soil contains a very small pro- 

 portion of salts of sulphuric acid a circum- 

 stance which accounts for the favourable 

 action of gypsum upon it. 



2. The surface-soil (A) is a fine-grained 

 loamy soil from Gandersheim, distinguished 

 for the remarkably large crops of beans, 

 peas, tares, &c., which it produces when 

 manured with gypsum. (B) is the analysis 

 of the subsoil. 100 parts contain : 



(A) (B) 



Silica, with fine siliceous sand - 90*221 92*324 



Alumina - - - 2*106 2'262 



Peroxide and protoxide of iron - 3*951 2*914 



Peroxide of manganese - - 0*960 2*960 



Lime, principally combined with 



phosphoric acid and humus - 0*539 0*532 



Magnesia, with silicate of pot- 

 ash. &c. 

 Potash 



Soda - 



Phosphoric acid - 



Sulphuric acid (in gypsum) 

 Chlorine (in common salt) 

 Humus and azotised matter 

 Loss - 



0*730 0-340 



0-067 0-304 

 O'OIO a trace 



0-367 0-122 



a trace 0*010 



0*100 0*004 



0.900 



0-140 0-228 



100*000 100-000 



The analysis of this soil shows, that, with 

 the exception of gypsum, every ingredient 

 is present which is requisite for the nourish- 

 ment of leguminous plants. Hence it is 

 that gypsum exerts such a favourable influ- 

 ence upon it. 



3. Surface-soil (A) a strong loamy sand, 

 from Brunswick. (B) the analysis of the 

 subsoil. 100 parts contain : 



CA) (B) 



Silica, with coarse siliceous sand 95'698 96*880 

 Alumina - - - 0'504 0*890 



Peroxide and protoxide of iron - 2*496 1*496 

 Peroxide of manganese - a trace a trace 



Lime - - - - 0*038 0.019 



Magnesia - - - 0*147 0*260 



Potash and soda, the greatest 



part in combination with silica 0*090 0*079 

 Phosphate of iron - 0*164 0*110 



