XIII.] NITRATE OF SODA 253 



nitrate of soda gets called a stimulant or a scourge, and 

 is considered to rob the land. This, however, is no 

 more the case with nitrate of soda than with any other 

 single manure. Whenever crops are grown with nitrate 

 of soda alone, we are removing in the crop nitrogen, 

 phosphoric acid, and potash, only one of which is being 

 replaced, so that the land must inevitably become 

 poorer in the other two constituents. But when nitrate 

 of soda is employed with the potash and phosphoric 

 acid that are equally required by the plant, the fertility 

 of the land is maintained unimpaired, as may be seen 

 from the Rothamsted experiments, where crops have 

 been grown with such a mixture on the same land for 

 nearly seventy years without showing any decline in the 

 average yield. The other two fertilisers, nitrolim and 

 nitrate of lime, are not so widely known. Nitrolim 

 behaves in much the same way as sulphate of ammonia, 

 but is slower in its action, and ought to be put on the 

 land before a crop is sown. Nitrate of lime is very 

 similar to nitrate of soda, though it has not the same 

 injurious effect upon the texture of the soil. It should 

 be mentioned that nitrate of soda is poisonous to stock, 

 and deaths have been reported through animals licking 

 the bags, or drinking water in which nitrate of soda had 

 been dissolved. 



Soot, the other manure which has been men- 

 tioned as containing nitrogen and no other fer- 

 tilising ingredient, is chiefly used as a top-dressing 

 for wheat in the spring. For this purpose it is very 

 valuable, not only because of the fertilising effect 

 of the small amount of nitrogen it contains, but also 

 because it helps to protect the wheat from the attack 

 of slugs and snails, which are very active at that time of 

 the year. Moreover, the dark colour the soot imparts 

 to the soil is of value, because it causes an increased 



