Nitrate of Soda versus Ammonia-salts. 101 



wheat. When the same mineral manure was used with a 

 larger quantity of ammonia- salts, the result was still in 

 favour of the barley, but in a less degree than with the 

 smaller amount. 



After applying 4001 b. of ammonia- salts per acre per 

 annum to barley for six years, and then reducing the 

 amount to 2001b., the plots so treated gave for ten years 

 in succession more produce than those which had only 

 received 2001b. annually from the commencement. From 

 this it is inferred that the excessive supply of 4001b. had left 

 a residue of nitrogen within the soil which was available for 

 succeeding crops. 



The experiments on barley with nitrate of soda and 

 ammonia- salts respectively, do not happen to be exactly 

 comparable with one another ; but, so far as can be judged, 

 a given amount of nitrogen as nitrate of soda yielded more 

 produce than the same amount as ammonia-salts, and 

 especially so in dry seasons. This is probably due to the 

 greater solubility of the nitrate, or its products of decompo- 

 sition, and to their action on the subsoil, disintegrating it and 

 rendering it more porous ; thus affording more surface for 

 the absorption and retention of moisture and manure, and 

 greater permeability to the roots, rendering the plants less 

 dependent on the fall of rain during growth. 



A table presenting the average annual produce by 275lb. 

 nitrate of soda (containing the same quantity of nitrogen as 

 2001b. of ammonia-salts) per acre per annum, both alone and 

 with mineral manure, during the four years 1868-71, brings 

 out the remarkable fact that the average produce is almost 

 identical by the nitrate alone and by the nitrate and mixed 

 alkali-salts together. Though much higher, it is again 

 almost identical by the nitrate and the superphosphate, and 

 by the nitrate, superphosphate, and mixed alkali-salts. The 

 little effect hitherto of the potash, soda, and magnesia-salts 

 is here again illustrated. 



Eape-cake is estimated to contain, on the average, about 



