Field Experiments on Clover- Seeds. 475 



potash is applied, unquestionably must affect tlie result, and Ave 

 therefore require experience of the use of such compounds, espe- 

 cially those which, either on account of their excessive or defi- 

 cient solubility, inay prove to be inefficacious or hurtful to vegeta- 

 tion. Again, it appeared to me probable that although the 

 exclusive use of potash might not be marked by any very striking 

 results, in conjunction with soluble phosphate of lime it might 

 produce a more beneficial effect and enhance the utility of the 

 latter. We know from experience that the exclusive application 

 of ammoniacal salts to the land does not produce nearly so 

 good an effect on many crops as their combination with super- 

 phosphate, and the supposition that a mixture of phosphatic and 

 potash manures would have a similarly beneficial effect, therefore 

 appears not unreasonable. 



Considerations of that kind determined me to suggest the 

 application of potash in the form of two salts, widely differing 

 from each other as regards their solubility in water. The first, 

 chloride of potassium, or muriate of potassium, as it is com- 

 monly called, is a highly soluble and deliquescent salt ; which, 

 moreover, is the cheapest form in which potash can be 

 purchased. The second, sulphate of potash, is a salt cha- 

 racterised by its slow solubility in cold water. Bearing in 

 mind that simultaneously with potash we present to the growing 

 plant chlorine in one of these salts and sulphuric acid in the 

 other, and that chlorine, as well as sulphuric acid, are normal and 

 essential ash-constituents of plants, 1 desired, if possible, to 

 eliminate in separate trials the share in the manuring effects 

 which the acid constituents of the two potash salts used in the 

 experiments might have. To this end I recommended separate 

 trials with chloride of sodium, and with sulphate of lime. In 

 cliloride of sodium we possess a readily soluble salt, which 

 compares well in this respect with chloride of potassium, whilst 

 the chlorine is united with soda, of which we know that it does 

 not produce any distinct fertilizing effect upon vegetation. In 

 order to eliminate the share of sulphuric acid in the total 

 manuring effect of sulphate of potash, I might have suggested 

 sulphate of soda for trial, but my choice fell upon sulphate of 

 lime, because in one of the experiments soluble phosphate 

 of lime was to be used, which compound can only be practically 

 used in conjunction with sulphate of lime, inasmuch as the 

 preparation of soluble phosphate of lime is necessarily accom- 

 panied by the production of much sulphate of lime. The 

 experiment with sulphate of lime thus answers the twofold 

 purpose of eliminating the share of sulphuric acid in the total 

 effect of sulphate of potash, and that of sulphuric acid (used in 



