Ammonia-salts versus Nitrate of Soda. 147 



without mineral manures, the nitrogen being, however, pre- 

 sented as nitrate instead of in the form of ammonia. Plot 15 

 received, for eighteen years, approximately the same amount 

 of nitrogen per acre per annum as plot 5, but as nitrate of 

 soda instead of as ammonia-salts ; plot 17 has received 

 annually half the quantity of nitrate. A slight difference in 

 the periods will be noticed in the Table XXXII., page 148, in 

 which the results are recorded. 



Although plot 15 and plot 5 received the same amount of 

 nitrogen per annum, namely, 821b., yet, in the case in which 

 this nitrogen was applied in the form of ammonia- salts 

 (plot 5) there was an average annual increase of produce 

 over the eighteen years of only 4891b., whilst with the same 

 amount of nitrogen applied as nitrate of soda (plot 15) the 

 corresponding increase was 16181b., or 11291b. more. In 

 other words, whilst the ammonia-salts gave an average 

 annual increase of little more than one-fifth over the 

 unmanured produce, the nitrate gave more than one and two- 

 thirds as much. The decline of produce in the second, as 

 compared with the first period, was 10*3 per cent, without 

 manure, 25*1 per cent, with ammonia- salts, and only 3'1 per 

 cent, with the nitrate. The nitrate yielded one -fifth more 

 nitrogen than the ammonia salts ; whilst the decline of 

 nitrogen in the second period was nearly 9 per cent, without 

 manure, more than 17 per cent, with ammonia salts, and only 

 2J per cent, with the nitrate, 



Striking as are these different effects of ammonia-salts and 

 nitrate, they are even inore marked in the amounts of 

 mineral matter taken up. The quantities of mineral matter 

 removed without manure and with ammonia-salts are almost 

 identical, whereas the nitrate of soda crops took up half as 

 much again. More lime, more magnesia, and considerably 

 more potash, phosphoric acid, and silica were removed by the 

 nitrate produce than by that of the ammonia-salts. 



The explanation of these results must be sought in the 

 herbage. Under the nitrate a greater total number of species 



L 2 



