134 ACTION OF SOIL ON FOOD OF PLANTS IN MANTJRE. 



particles for these nutritive substances, the more speedily 

 will the productive power of the soil be restored. 



Every arable soil possesses, for potash and the other 

 substances mentioned, a determinate power of absorption, 

 which may be expressed by the number of milhgrammes 

 absorbed by 1 cubic decimetre (^1000 cubic centi- 

 metres) of earth. Thus, for instance : — 



Cubic Cubic 

 decimetre inches Milligrammes Grains 



1 = 61 of lime soil from Cuba, absorbed 1360 = 21 potash 



1 „ loam „ Bogenhausen „ 2260 = 35 „ 



1 „ soU „ Weihenstephan 2601 = 40 „ 



1 „ soil „ Himgary „ 3377 = 52 „ 



1 „ garden mould Munich „ 2344 = 36 „ 



It will be seen at once that these differences in absorp- 

 tive power are very considerable. One volume of earth 

 from Weihenstephan absorbs nearly twice as much potash 

 as an equal bulk of soil from Cuba ; the Hungarian earth, 

 here examined, absorbs 2^ times as much. 



These figures show that a certain quantity of potash, 

 say 2600 milligrammes, if supplied to the Weihenstephan 

 soil, will spread in a space of 1 cubic decimetre of earth. 

 If we were to pour the potash, in solution, on a small 

 plot of ground, 1 square decimetre in area, the potash 

 would penetrate to a depth of 1 decimetre (=3-94 mches), 

 and no deeper; every cubic centimetre (=-061 cubic 

 inch) would receive 2*6 milhgrammes ( = -04 grain) of 

 potash, but the layers beneath would receive none, or at 

 least no appreciable quantity of it. 



If the same solution were poured on an equal area of 

 Hungarian or Cuban soil, the potash filtering through 

 would penetrate, in the former, to a depth of somewhat 

 above 7 centimetres (=2-7 inches); in the latter, to a 

 depth of 19 centimetres ( = 7-5 inches). 



The diffusibihty of potash in a soil is in an inverse 



