NITROGEN GROUP OF FERTILIZERS 19 



extreme solubility in water, it must be kept dry, and owing 

 to its deliquescent properties it must be kept away even from 

 moist air. If it becomes very damp it is likely to cake 

 together and to need breaking up again before application. 

 When applied to the soil a slight chemical change takes 

 place. To a limited extent the soda in nitrate of soda and 

 the lime in the soil change places with one another. 

 Continuous application of nitrate of soda will therefore 

 remove lime from the soil by drainage. Nitrate of soda 

 does not, however, remove quite so much lime as sulphate 

 of ammonia. Whilst sulphate of ammonia contains the 

 relatively unimportant ingredient sulphuric acid, nitrate 

 of soda contains the equally unimportant ingredient soda. 

 The former, of course, produces an acid reaction, and the 

 latter produces an alkaline reaction. Whilst the sulphate 

 of lime produced from sulphate of ammonia readily drains 

 away from the soil, in the case of the soda the loss by drainage 

 is less rapid. The soda acts chiefly upon the clay and humus 

 of the soil, and forms a colloidal solution, which results in 

 the transfer of the fine clay particles from the surface to 

 the sub-soil, reducing the fertility of the surface soil, whilst 

 the sub-soil becomes choked with material more or less 

 impervious to water. From the above causes both sulphate 

 of ammonia and nitrate of soda, when used in large excess, 

 as in the Woburn experiments, produce almost equally 

 bad results. The cure for these objectionable effects from 

 nitrate of soda lies in the use of lime or sulphate of lime. 

 The former can be supplied in basic slag, and the latter in 

 super-phosphates. The chief effect of the use of nitrate 

 of soda upon the crop grown is to stimulate the production 

 of green stuff. Hence it is of particular value for such 

 crops as gooseberries, cabbages, and turnips. L,ike sulphate 

 of ammonia, it may also be used as a top dressing for 

 application either to wheat or to hay. Both of these manures, 

 sulphate of ammonia and nitrate of soda, are much used in 

 intensive forms of tropical agriculture, on such crops as 

 tobacco and coffee. The impurities in nitrate of soda 

 include potassium iodide, potassium iodate, and potassium 



