EXACT CONSTITUTION OF SOME FERTILE SOILS. 283 



§3. Of the exact chemical constitution of certain soils, and of the results 

 to be deduced from them. 



But the importance of this attention to rigorous analysis will more 

 clearly appear, if I exhibit to you the constitution of a few of the nume- 

 rous soils analyzed by Sprengel, in connection with the agricultural quali- 

 ties and capabilities by which they are severally distinguished. 



The following analyses are selected from a much greater number made 

 by Sprengel, and embodied in his work on soils, " Die Bodenkunde." 



I. — FERTILE SOILS. 



Soils are fertile which contain a sutficient supply of all the mineral 

 constituents which the plants to be grown upon them are likely to re- 

 quire. 



1°. Pasture. — The following numbers exhibit the constitution of the 

 surface soil in three fertile alluvial districts of Hanover, where the land 

 has been long in pasture. 



Soil near From the banks of the Weser 

 Osterbruch. near Hoya. near Weserbe 



Silica, Quartz, Sand, and Silicates. 84-510 71-849 83-318 



Alumina 6-435 9-350 3-085 



Oxides of Iron 2-395 5-410 5-840 



Oxide of Manganese .... 0-450 0-925 0-620 



Lime 0-740 0-987 0-720 



Magnesia 0-525 0-245 0-120 



Potash and Soda extracted by water T)-009 0-007 0-005 



. Phosphoric Acid 0-120 0-131 0-065 



Sulphuric Acid 0-046 0-174 0-025 



Chlorine in common Salt . . 0-006 0-002 * 0-006 



Humic Acid 0-780 1-270 0-800 



Insoluble Humus .... 2-995 7-550 4-126 



Organic matters containing Nitrogen 0-960 2*000 1-2-20 



Water. 0-029 0-100 0-050 



100 100 100 



These soils had all been long in pasture, the second is especially cele- 

 brated for fattening cattle -when under grass. It will be observed that in 

 none of them is any of the mineral ingredients wholly wanting, though 

 in all the quantity of potash and soda capable of being extracted by 

 water is very small. This is ascribed to the fact of their having been 

 long in pasture, during which the supply of these substances is gradually 

 withdrawn by the roots of the grasses. It is well known how, in our or- 

 dinary soils, grass is often renovated — how the mosses, especially, are de- 

 stroyed — by a dressing of wood ashes, which owe their effect to the alkali 

 they contain. In the above soils the gradual decomposition* of the sili- 

 cates would continue to supply a certain portion of alkaline matter for an 

 indefinite period of time. 



You will perceive that the soil which is the most celebrated for its fat- 

 tening power, is also the richest in alumina, lime, phosphoric acid, sul- 

 -phuric acid, and vegetable matter. 



