306 ACTIONS OF ARTIFICIAL MANURES 





just as effective and active as the nitrate alone, and it sets 

 up no injurious action, either in the direction of acidity 

 or alkalinity in the soil, so that large amounts can be used 

 without detriment either to the tilth or the health of the soil. 

 There can be little doubt but that the discredit which the 

 practical farmer sometimes attaches to nitrate of soda as a 

 stimulant exhausting the soil, even as a " scourge " as it 

 has been called, is due to its effect upon the tilth. Although 

 nitrate of soda, when used alone, is a one-sided manure that 

 will greatly aid the plant . to remove the available phosphoric 

 acid and potash from the soil, it still supplies the most 

 important element of fertility, and cannot exhaust the soil in 

 any real sense. It gets described as an exhausting manure, 

 not because it robs the land in any special way, but simply 

 because it sets up the bad texture of the soil, which so easily 

 leads to an inferior yield in the following crop. 



The list, indeed, of these secondary interactions between 

 fertiliser and soil, which may have a potent influence on the 

 value of the fertiliser in practice, is not ended with the changes 

 set up by nitrate of soda and sulphate of ammonia ; there is 

 plenty of practical evidence that the effect of applying potash 

 salts such as kainit, muriate, or sulphate of potash, is not 

 wholly comprised in the provision of a certain amount of 

 potash for the nutriment of the crop. It has often been 

 remarked by those concerned with field experiments that 

 cases occur when the addition of potash salts to a mixture, 

 so far from increasing the return, actually reduces it. As a 

 rule, these results may be set down to the large experimental 

 error which is inevitable in all field trials ; but so convinced 

 have been some experimenters of the reality of the effect, that 

 they have begun to speak of the " depressing effect of potash " 

 upon the crop. Now from the point of view of nutrition 

 alone, such a depressing effect is impossible ; in some way 

 the effect must be special to the soil, and due to an 

 unsuspected interaction between soil and potash fertiliser. A 

 clue to the sort of action to be looked for may be found 



