DEFLOCCULATION BY POTASH SALTS 307 



in the observations which have been recorded in some of 

 the cases where the use of potash had resulted in a lowered 

 yield, that the ground remains a little wetter after the applica- 

 tion of kainit or other potash salts. This apparent wetness 

 has been set down to the water-absorbing properties of potash 

 salts, which are chiefly due to the magnesium chloride always 

 present in them; but as already indicated with regard to 

 nitrate of soda, the small amount of water which is absorbable 

 by any ordinary manurial dressing would be inappreciable 

 when diffused through the soil. The wetness suggests 

 deflocculation, and the appearance of many of the plots 

 receiving potash at Kothamsted would bear out this view. 

 On the mangold field in particular the characteristic defloccu- 

 lation features shown by the plots receiving nitrate of soda, 

 especially their way of drying with a tough glazed crust on 

 top, are reproduced on the plots receiving sulphate of potash, 

 and the worst plot of all is that which receives both of these 

 fertilisers. Tested by the suspension of a small quantity of 

 soil in a large bulk of pure water, the opinion is confirmed 

 that the soil of these potash plots is completely deflocculated. 

 Another practical case has fallen under the observation of 

 the writer where the application of 8 cwt. per acre of kainit 

 to a piece of heavy land, which had not long before been limed, 

 so destroyed the texture of the soil that the ploughman knew 

 at once when he entered upon the plot in question because 

 of the heavier draught of the plough. Accepting, then, 

 deflocculation as an explanation of the injurious effects of 

 potash salts upon clay soils, the question that remains is 

 the origin of the alkali, for alkali it must be that has brought 

 about the deflocculation. The interaction with the zeolites 

 of the soil, by which means potash is normally retained by 

 the soil, wbuld not give rise to any substance of an alkaline 

 nature. 



The carbonate of lime in the soil next suggested itself as a 

 possible reacting substance,' and a series of experiments have 

 showed that when weak solutions of potash salts remain in 



