and Common Salt on Manrjolds. 87 



times with apparently marked beneficial results, at others with- 

 out producing- any decidedly favourable effect. These contra- 

 dictor}' records of experience appeared to me to result probably 

 from the great variation in the proportions of available potash 

 Avhich we know to exist in soils of different characters. In 

 order to put this supposition to a practical test, and, as I thought, 

 to give the crude potash-salts the best chance of manifesting 

 their fertilising powers, I induced my friend and former pupil, 

 Mr. Kimber, of Tubney Warren, to undertake for me some experi- 

 ments on a very light newly-reclaimed sandy soil. The crop 

 experimented upon was long red mangolds. 



A sample of the crude potash-salts employed in the subjoined 

 experiments analysed by me was found to have the following 

 composition : — 



Composition of Crude Salts of Potash from Germany. 



Moisture 11-63 



Orjianic matter -73 



Oxide of irou "34: 



Sulphate of potash 24-03 



Sulphate of magnesia 1-14 



Chloride of magnesium 12-01 



Chloride of sodium (common salt) 47-85 



Sulphate of hme '78 



Magnesia -52 



Sand -97 



100-00 



It will be seen that beside chloride of magnesium these salts 

 contain 24 per cent, of sulphate of potash, and nearly twice as 

 much common salt. 



Having ascertained in the preceding year that common salt 

 alone produced a very considerable increase in the mangold 

 crop, grown on a light sandy soil very similar to that on which 

 I intended to try potash-salts, I considered it very desirable to 

 eliminate, if possible, the effects likely to be produced by the 

 common salt in the crude German salts, of which it forms so 

 large a proportion. Several experimental plots, therefore, were 

 top-dressed with common salt, varying in quantity from 2 to 

 8 cwts. per acre ; and in order to get some insight into the 

 natural variation in the agricultural capabilities of the experi- 

 mental field, two plots, one at either end, and a third in the 

 middle of the field, were left without any top-dressing. As 

 very few fields have a properly uniform composition, or are in 

 every part in precisely the same agricultural condition, the 

 reservation of two, or rather three, such plots is essential for 

 determining the limits of the variation in the natural productive 



