27 



extremes that is, the great majority may be dressed with 

 sulphate with good results. The above remarks, however, 

 indicate the general principles which must govern the mode 

 of application, according as the character of the soil ap- 

 proaches most nearly to one or other of the extremes 

 mentioned. 



RESIDUE FROM SULPHATE OF AMMONIA. 



On the question whether any valuable residue is left 

 after the first crop has been removed, some difference is 

 found in the evidence afforded by different experiments. 

 In both the Rothamsted and the Woburn wheat experi- 

 ments, special attention has been paid to the point. At the 

 former experimental station, plots have been manured with 

 mineral manures alone and with ammonia salts alone in 

 alternate years. Thus, when the mineral manures are 

 applied, there is abundance of mineral matter, and any 

 residue that may be left from the previous year's dressing 

 of ammonia salts ; while when ammonia salts are used, there 

 is a full supply of nitrogen and the residues left from the 

 last mineral manuring. On theheavy land at Rothamsted, 

 the mineral manures with residues of ammonia salts gave, 

 on the average of forty years, 15^ bushels of wheat per 

 acre, against 15 bushels on land which had received mineral 

 manures only each year of the same period. This seems 

 to show that, on the soil experimented with, there is practi- 

 cally no valuable residue. 



It should be noticed, however, that for the first twenty- 

 four years of the experiment, the crop grown with minerals 

 and residues of ammonia was rather better in proportion 

 to that obtained by the use of minerals alone, though, it 

 will be remembered, the ammonia salts were at the time 

 applied in the autumn, and therefore were not giving their 

 full effect. 



At Woburn, on comparatively light land, an experiment 

 carried out on similar lines, except that mineral manures 

 were applied every year, gave rather different results. On 

 the average of fifteen years, the following results were 

 obtained with sulphate of ammonia and nitrate of soda 

 respectively : 



TABLE XII. 



Manures. Ammonia Salts. , Nitrate of Soda. 



The average produce of the land continuously manured 

 with minerals only was 14-4 bushels for the same period. 



