31:2 CHEMICAL MANURES. 



the same result than with muriate of potash. But the high percentage 

 of chlorine in crude potash salts has other drawbacks, so much the 

 greater because it has been forgotten to point them out. Chlorine 

 exerts a disastrous influence on the physical constitution of the 

 soil and on vegetation. Moreover, it cannot be denied that the 

 secondary salts which accompany the potash strongly attack the 

 reserves of fertilizing ingredients in the soil. The potash is 

 evidently absorbed by the soil, if it be supplied to it as chloride or 

 as sulphate of potassium ; the latter combines with the silica of the 

 silicates of lime, soda, and magnesia, whilst the secondary ele- 

 ments such as the chlorine in muriate of potash, sulphuric acid in 

 sulphate of potash, combine with lime, soda, and magnesia. In the 

 first place calcium chloride is formed, in the second calcium sulphate. 

 But as calcium chloride is very soluble in water, it is carried by it 

 down into the depths of the soil, and thus lost to the crop. This 

 fact agrees perfectly with that other fact w^hich has been established, 

 viz. that potassic manures, especially the chlorinated manures, rob 

 the soil of its lime ; thus 100 kg. (220 lb.) of kainit, containing 31 

 kg. (78-2 lb.) of chlorine, cause the soil to lose 100 kg. (220 lb.) 

 of lime. It follows, therefore, that the use of potassic manures entails 

 the use of calcareous manures. Mercker advises to apply to the 

 soil as much quick-lime as potash salts. It thus follows that the 

 comparative cheapness of crude potash salts, such as kainit and 

 sylvinite, is nothing but a snare, because to take everything into 

 account, the price of these salts ought to be increased by the price 

 of the lime, the loss of which they entail. In marshy land the 

 simultaneous application of lime is particularly necessary. In 

 such soils in fact the potash salts are rapidly robbed of their acid 

 in such a way that in the absence of lime the chlorine forms free 

 hydrochloric acid which poisons the plant. Lime, moreover, is an 

 indispensable corrective to the secondary effects which crude 

 potash salts never fail to produce, the most important of which is 

 the prevention of nitrification in the soil. Holdefleiss, in experi- 

 ments with farmyard dung, completely suppressed it by means of 

 potash salts. The solvent action exerted by the secondary salts 

 of potassic manures is very well brought out in Lawes and 

 Gilbert's experiments. They obtained an increased yield with 

 salts free from potash. The plots experimented on received every 

 year from 1854, 4 kg. of sulphate of ammonia and 350 kg. of 

 superphosphate. The following amount of salts were added per 

 hectare : — 



