Ammonia-salts and Minerals in Alternation. 43 



phosphoric acid, there is no difficulty in tracing the increased 

 produce obtained on 106 over 10a to the minerals applied to 

 the former in 1848 and 1850. These large applications of 

 potash and phosphoric acid, although in the form of soluble 

 compounds, appear to enter into very fixed combinations, 

 somewhat similar to those already existing in the soil, and in 

 this respect they differ altogether from compounds of nitric 

 acid and ammonia, as the latter appear to be either washed 

 away or destroyed, unless they are fixed by vegetation, whilst 

 the former are fixed by the soil itself, and are only taken out 

 of it by means of vegetation. 



CONTINUOUS GEOWTH OF WHEAT UPON THE 

 SAME LAND WITH AMMONIA-SALTS AND 

 MINERAL MANUEES IN ALTERNATING YEAES. 



The ' experiments on plots lOo- and 106 show that potash 

 and phosphoric acid were still producing an influence upon 

 the wheat crop thirty-three years after their application. 

 Turning now to plots 17 and 18, it will be possible to trace 

 the unexhausted residue of another substance perfectly 

 soluble in water namely, salts of ammonia. On these plots 

 the mineral manures and the ammonia-salts are never used 

 together. When plot 17 receives minerals, plot 18 receives 

 ammonia- salts, and when plot 18 receives minerals, plot 17 

 receives ammonia-salts. Therefore, during the thirty-two 

 years, each plot received sixteen applications of mineral 

 manures and sixteen applications of ammonia- salts. For the 

 crops of the first eight years (1844-1851) the two plots received 

 different artificial manures, yielding a very similar produce. 

 Table VII. records the average produce of the mineral 

 manures, and also of the ammonia- salts over four periods of 

 eight years each, and, for comparison, the average produce 

 on plot 5, receiving minerals alone, is given. 



The bottom line, giving the average of the entire thirty- 



