t 556 ] 



character of clay which is difficult to drain. Hilgard says 

 " soils impregnated with alkaline carbonates may generally 

 be recognised by their extreme compactness and refractoriness 

 under tillage, and by the fact that they are apt to form ( low 

 spots' in the general surface of non-alkaline land, i. e. 

 places where turbid clay water, dark with dissolved humus 

 will lie for weeks after the higher land appears dry." 



910. The pt>tash in the soil occurs chiefly in the form 

 of hydrated double silicates or hydrated double humates of 

 potash and alumina. Had it not been for the double silicates, 

 the potash in the soil would have been washed out and carried 

 into the sea, Because soda is less readily retained than 

 potash by these double silicates, that the sea water is charged 

 chiefly with NaCl washed out from soils instead of KC1. NaCl 

 is dissolved out from the soil and carried away to the sea by 

 the water of percolation more freely .than any other salt, 

 This fact makes it so easy to reclaim saline soils like those of 

 the Sunderban. Iji the decomposition and disintegration of 

 rocks, soda salts are most readily parted with and washed 

 away into the sea, potash being more or less retained by the 

 soil by absorptive action at the expense of soda salts which 

 are the first to be washed away. In -the natural condition, for 

 instance, a piece of basalt may contain i\ per cent, of potash 

 and y| of soda r but the same basalt after decomposition as 

 soil may show equal proportions (about 2\ per cent.) of potash 

 and soda. 



911. Potash does not accumulate so much in fruits and 

 seeds as in straw and leaves which are returned to the soil in 

 one form or another. In the building up of animal tissues 

 also potash does not form an important ingredient. In a 

 Mrell managed farm therefore whence grain and animals only 

 a^re sold, potassic manures will not be found of much use. But 

 that certain crops, such as root-crops, especially beet; 

 potatoes and tbbacco are benefited by potassic manure, is a 

 matter of universal experience. It is only where the crops 



