POTASSIC MANURES. 



313 



TABLE CVIII.— EFFECT OF SOLUBLE MINERAL SALTS ON GRAIN 



CROPS. 



It will be seen from these figures that salts free from potash 

 have furnished yields almost more heavy than the pure potash salt. 

 These salts, therefore, have mobilized the reserves of fertilizing in- 

 gredients in the soil, so as to bring them to the support of the 

 plant. The soil has thus been, in a way, robbed of its normal 

 reserve in favour of a few^ crops. This robbing of the soil would 

 have been brought out in a more serious manner if the experi- 

 menters, instead of using sulphates, had used chlorides, because then 

 it would be complicated by loss of lime. In fact, it is not stated 

 that here again the nutritive substances of plants including phos- 

 phoric acid may not be rendered soluble and consequently carried 

 down into the depths of the soil. The same phenomena must 

 perforce occur with kainit, sylvinite and carnallite ; the comparative 

 low proportion of pure potash salts makes their action almost nil com- 

 pared with that of the secondary salts which accompany it in these 

 products. There is here a very interesting subject for study by 

 agronomists. It would be specially useful to find if drainage water 

 contains fertilizing substances in those cases where crude potash 

 salts are used. Amongst these fertilizing substances, phosphoric 

 acid may be found, for we must not forget that phosphate of lime 

 is soluble in a great number of saline solutions. There might also 

 be found in the drainage water as much potash as was spread on 

 the soil, which would prove that the use of crude potash salts as 

 manure would be absolutely illusory. It is probable that there will 

 be no delay in giving up the use of crude potash salts, so as to keep 

 solely to the pure potash salts, in spite of their higher price, when 

 the devastating action of the secondary elements which accompany 

 the potash in the crude salts is realized.^ 



1 Whilst muriate of potash should be used sparingly and with the greatest 

 discrimination, kainit when fairly free from chlorine is a safe and most valuable 

 manure, especially for potatoes. The translator considers it sound practice to 



