300 Report of Experiments on the Growth of Barley, 
years' trial, the extra application was discontinued. Under these 
circumstances any great increase of produce by 400 lbs. compared 
with 200 lbs. of ammonia-salts could not be expected. Still, as 
the last column of the Table shows, the second increment of 
200 lbs. did, under favourable conditions of mineral manuring, 
raise the produce by more than 4 bushels of grain, and by from 
5^ to 7|- cwts. of straw ; bringing it up, with superphosphate 
of lime, to 49| bushels of corn, and 34 cwts. of straw ; and 
with superphosphate and the "mixed alkali-salts" together, to 
50i bushels of corn, and 36| cwts. of straw. 
There is proportionally much more increase of straw than of 
corn, especially when both the superphosphate and mixed alkali- 
salts were used. There is also a lower weight per bushel of 
dressed corn, and a much lower proportion of corn to straw, than 
with the corresponding mineral manures, either alone, or with 
the smaller quantity of ammonia-salts. It is clear, therefore, 
that the extra quantity of ammonia-salts considerably increased 
the luxuriance; but that the amount of plant produced was more 
than could, under the conditions of the seasons, form a fair pro- 
portion of corn, and ripen well. 
Although the second increment of 200 lbs. of ammonia-salts, 
has thus not yielded anything like the same amount of increase 
as the first, in the seasons of the application, it will afterwards be 
seen (Section IV.) that there was a considerable residue of nitrogen 
left within the soil, which remained available for future crops 
through many succeeding seasons. 
After the six years of the double application, the amount of 
ammonia-salts was reduced to 200 lbs. per acre per annum, and 
the experiment continued for ten consecutive seasons. From that 
time, however, an amount of nitrate of soda (275 lbs.) containing 
the same amount of nitrogen as 200 lbs. of ammonia-salts, was 
substituted for the latter ; and the results obtained during the four 
years of the experiment which have so far elapsed, are given in 
Table XXXV. 
It is remarkable 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 superphosphate, and by the nitrate, superphos- 
phate, and " mixed alkali-salts." The little effect, hitherto, of the 
potass, soda, and magnesia-salts is here again illustrated. The last 
column shows that, over the four seasons in question, the nitrate 
gave, under each of the conditions of mineral manuring, both more 
corn and more straw than the corresponding amount of ammonia- 
salts. In what degree, however, this difference should be attri- 
buted to a greater effect of the nitrate, and in what to a still 
effective residue from the excessive supply of ammonia-salts 
