[ 87 ] 



So while by subsoil drainage our soils will lose* no 

 appreciable percentage of plant food not already stored 

 therein up to their maximum retention capacity, all 

 the excess salts now lying thick on the surface will 

 be redissolved, carried down through the soil, so far as 

 needed, decomposed therein, all useful portions re- 

 tained which are necessary to make up the full capital 

 stock that the particular soil can hold, and the excess 

 together with useless or injurious matter passed away 

 with the drainage water. 



Varying as does the composition of this always com- 

 plex saline efflorescence, in different localitiest very 

 different additions to the soil, organic or mineral, may 

 be necessary to enable it to seize the maximum share 

 of the utilisable portions of the " reh " when by sub- 

 soil drainage it is filtered downwards. 



All these are details which must be worked out by 

 experiment on scientific principles ; the broad truth 

 remains that save under, for India, exceptional circum- 

 stances, the only practicable mode of purifying land 

 now sterilised by this '' reh,'^^ or protecting land in 

 course of being so sterilised, is by passing the excess 

 of saline matters away by subsoil drainage. 



It is needless to add that, independent of this spe- 

 cial evil, subsoil drainage, and the deep working and 

 oxidization of the soil that it involves, by multiplying 



* In solution, of course, is meant ; mechanically, anything may, 

 by bad arrangements, be swe2>t away. 



t Lime, soda, potassium, magnesia, as carbonates, chloride, 

 sulphates, nitrites, and nitrates, all occur, but the soda salts are 

 usually the chief constituents, and the nitrites and nitrates are 

 scarce. 



