308 ACTIONS OF ARTIFICIAL MANURES 



contact with carbonate of lime a small quantity of free carbonate 

 of potash is produced. As the extent of the change that is set 

 up depends upon the relative quantities of the reacting bodies 

 in the soil, where the carbonate of lime would generally be in 

 great excess, the proportion of the potash salts converted into 

 carbonate would be comparatively large. 



Moreover, common salt has exactly a similar action, and 

 this at once provides us with an explanation of the many 

 unintelligible and often contradictory reports of the action of 

 salt as a fertiliser. It has variously been reported as enabling 

 the soil to retain more moisture, as injuring the soil, especially 

 when the land has been flooded with sea water, as sometimes 

 increasing but occasionally as diminishing the crop. These 

 reports coincide with those concerning the action of potash, 

 and the effect in both cases may be set down to the defloc- 

 culation brought about by the small trace of carbonate of soda 

 or potash that is formed by the action of the carbonate of lime 

 in the soil upon the soluble potash or soda salt. 



Deflocculation brought about by potash salts or by common 

 salt is rarely a matter of much practical importance, but it may 

 be obviated by using superphosphate as the phosphatic manure 

 going with the potash salts, and again by applying the latter 

 fertiliser in the winter. This will give time for the reactions 

 between fertiliser and soil to be completed, and for some of the 

 useless by-products like the carbonate of soda to be washed out. 

 If on arable land, there will also be time for the spring frosts 

 to restore the texture of the land before the preparation of the 

 seed bed is taken in hand. No fear need be entertained that 

 the valuable potash salts will be washed out of the soil. Way's 

 and Voelcker's papers show that they are retained, and Dr B. 

 Dyer, in his examination of the Rothamsted soils, found that 

 of the potash annually applied and not utilised by the crop, 

 very little had been washed away, even after fifty years of the 

 treatment. 



It will be noticed that all the effects of fertilisers upon soil 

 which have been discussed are due to chemical changes of a 



