Ammonia-salts, with and without Superphosphate. 173 



when the superphosphate as well as the ammonia- salts was 

 used ; but in both cases there was nearly the same percentage 

 reduction in yield of hay, of nitrogen, and of mineral matter 

 over the last ten compared with the first seven years (Table 

 XXXI.) More lime, magnesia, phosphoric acid, and sulphuric 



TABLE XLII. AVERAGE PER ACRE PER ANNUM, BY 400LB. AMMONIA- 

 SALTS, AND SUPERPHOSPHATE OF LIME ; PLOT 46. 



Average per Acre per Annum. 



acid were taken up than could be accounted for in the super- 

 phosphate supplied. There was also more potash, more soda, 

 and more silica. The excess of all these mineral ingredients 

 must have been supplied by the soil itself. In the second 

 period, as compared with the first, there was a very great 

 decline in the average annual amount taken up of almost every 

 mineral constituent, except phosphoric acid and magnesia, in 

 which the reduction was much less. Further, whilst in the 



