138 ACTION OF SOIL ON FOOD OF PLANTS IN MANURE. 



acid in these soils, we have the following propor- 

 tion : 



Hungarian. Garden mould I. Bogenhausen. Garden mould II. Forest soil. 

 1-0 1'09 1-31 2-43 17-6 



The same quantity of silicic acid which would satu- 

 rate 1000 cubic centimetres of Hungarian earth, would 

 furnish a maximum supply for 1311 cubic centimetres 

 of Bogenhausen loam, 2430 cubic centimetres of gar- 

 den mould II., and 17,600 cubic centimetres of forest 

 soil. 



Ammonia, in the pure state, or in the form of salts 

 of ammonia, is absorbed by arable soil just in the same 

 way as potash : one kilogramme (= 2'2 Ibs.) of the fol- 

 lowing earths will absorb respectively these quantities 

 of ammonia : 



Cuban. Schleissheim. Garden mould. Bogenhausen. 



Milligr. Grains. Milligr. Grains. Milligr. Grains. Milligr. Grains. 



6520=85 3900=60 3240=49*9 2600=40 



which gives the following numbers for the relative 

 diffusibility of ammonia : 



Cuban. Schleissheim. Garden mould. Bogenhausen. 



1-0 1-24 1-50 2.12 



The absorptive power of arable soils for phosphate 

 of lime, phosphate of magnesia, and phosphate of mag- 

 nesia and ammonia, may be determined in the same 

 way, and the relative diffusibility of these several con- 

 stituents in different soils may be expressed numerically. 



By the term ' absorption number,' we designate, in 

 the following pages, the quantity reckoned in milli- 

 grammes ( 0-0154: grain) of the several mineral con- 

 stituents, which one cubic decimetre (=61 cubic in- 

 ches) of earth extracts from their solutions. 



To determine the condition of a field, the action of 

 the manures applied to it, and the depth to which the 

 several nutritive substances will penetrate, it is import- 

 ant to establish proportionately the absorptive power 

 of the soil for each of them ; thus, for example, 1 cubic 

 decimetre of Bogenhausen loam absorbs : 



