124: 



THE SOIL. 



decomposing by fusion the silicates, and then treating 

 with hot muriatic acid, we can obtain all the potash 

 and silicic acid contained in the soil. Without risk of 

 error we may assume that those nutritive substances 

 which can be extracted by cold muriatic acid are most 

 feebly retained by the soil, and approach nearest the 

 elements in physical combination ; or, at all events, so 

 near, that by the common disintegrating agencies they 

 very easily pass into this form of combination. 



In this way Dr. Zoeller subjected to analysis two 

 kinds of wheat soil the loam of Bogenhausen and of 

 "Weihenstephan, the latter of which in particular repre- 

 sents an excellent wheat soil. One hundred parts of 

 these two soils yielded to cold muriatic acid 



If these quantities of nutritive elements are present 

 in an available condition in these soils, that of "Weihen- 

 stephan would contain of phosphoric acid almost 400 

 times, of potash TOO times, and of silicic acid rather 

 more than 190 times, as much as a wheat crop re- 

 quires : in the soil of Bogenhausen the amount of phos- 

 phoric acid, potash, and silicic acid would be twice as 

 large as the hypothesis presupposed. 



The w r ell-known analyses of similar soils by other 

 chemists show that the assumed estimate of the nutri- 

 tive substances required in a good wheat or rye soil is 

 rather below than above the actual amount ; and, in 

 fact, the future prospects of agriculture would be very 

 gloomy, if the ground was not far richer in nutritive 

 substances than has here been hypothetically assumed. 



This is, perhaps, the place to state the distinction 

 between the fertility of a field and its productive pow- 

 ers. According to the experiments of Nageli and Zoel- 

 ler, mentioned above, the turf maybe so saturated with 

 the necessary nutritive substances as to become an ex- 



