298 
Report of Experiments on the Growth of Barlei/, 
phate and the mixed alkali-salts 18| bushels of corn, and 14|^ 
cv/ts. of straw ; when with the superphosphate and sulphate of 
potass 21^ bushels of corn, and 15|^ cwts. of straw; but when 
with the mixed alkali-salts without superphosphate, only 12| 
bushels of corn and 8^- cwts. of straw. 
Thus, the effect of a given amount of ammonia is seen to differ 
very greatly according to the character of the mineral constituents 
supplied with it. The results clearly show, what common expe- 
rience also teaches, how effective a manure for barley is super- 
phosphate of lime, provided only there be also a sufficient 
available supply of nitrogen within the soil. It is, however, as 
a rule, much less effective with winter-sown than with spring- 
sown corn-crops ; the latter, with their short period of growth, and 
relatively greater dependence on root-development near the sur- 
face, requiring more liberal supplies within a limited range of 
soil. 
Considering the characters of the soil, and the results obtained 
with other crops, to say nothing of general practical experience, 
it is only what would be anticipated, that the addition to the 
ammonia-salts of superphosphate of lime would be much more 
effective than that of salts of potass, soda, and magnesia ; but it 
is hardly what would be expected that, over twenty years in. 
succession, the soil would yield an average of even rather more 
corn, only ^ cwt. less straw, and only 57 lbs. less total produce, 
with ammonia-salts and superphosphate, than with the ammonia- 
salts, superphosphate, and the mixed alkali-salts together. The 
illustration is a striking one of the potass-yielding capabilities of 
such a soil. As already intimated, there are symptoms of a 
slight change during the last few years ; but the fact is of great 
practical and scientific interest, that by ammonia-salts and super- 
phosphate of lime, without potass or other bases, considerably 
more than the average barley crop of the country has beeii 
obtained for twenty years in succession. 
Table XXXIV. shows the produce and increase obtained by 
the same mineral manures as those employed in three of the four 
experiments last considered, but, in each case, with double the 
amount of ammonia-salts ; namely, 400 lbs. per acre per annum, 
used, however, for only the first six years of the twenty. The 
increase is given over the produce without manure, over that by 
the corresponding mineral manures without ammonia, and over 
that by the corresponding mineral manure with only 200 lbs. of 
ammonia-salts. (Table XXXIV. next page.) 
It is obvious that, with an average annual produce of 46 or 47 
bushels of barley, over twenty years, by the mineral manures and 
200 lbs. of ammonia-salts per acre, the limit of the ripening 
capabilities of the seasons must have been nearly reached. 
