488 Report of Experiments oti tlcc Growth of Wlueat. 
is as much, if not more, than would be generally employed ; and 
it is seen that, with it, the quantity expended for each bushel of 
increase was very nearly the previously assumed amount of 5 lbs. 
When double the quantity per acre was used, which would be 
much more than appropriate for most soils and seasons, rather 
more than 5 lbs. (5'37), when 3 times the amount 7"35 lbs., and 
when 4 times y'47 lbs., were required. Thus, when excessive 
amounts of ammonia are employed, much more is expended for 
the production of a given amount of immediate increase of crop, 
than when only moderate quantities are used ; and it has been seen 
how very slowly the excess may become available in after years. 
Still more unfavourable was the result when 400 lbs. of 
ammonia-salts (equal 100 lbs. ammonia) were employed under 
defective conditions as to the supply of mineral constituents. 
On plots 17 and 18, on one or the other of which that amount 
was each year employed succeeding the application of the mixed 
mineral manure in the preceding year, it required 6*69 lbs. of 
ammonia to produce 60 lbs. of increase of corn with its propor- 
tion of straw. On plots 12, which might be deficient in avail- 
able supply of magnesia and possibly of potass, on plots 13 
which were probably relatively deficient in magnesia, and on 
plots 14 probably in the later years in potass, the amount of 
ammonia required was from 5'76 to 5'85 lbs. instead of only 
5 - 37 lbs. on plots 7, where, with the same amount of ammonia- 
salts, the mineral manure each year supplied all three bases — 
potass, soda, and magnesia. Then again, on plots 11, to which 
no direct supply of either potass, soda, or magnesia, had been 
made throughout the 20 years (only small quantities in rape- 
cake) 8"57 lbs., on plot lOi, with a deficiency almost certainly 
of potass and phosphoric acid, and probably of magnesia also, 
1T2 lbs., and on plot 10a, with a still greater deficiency of 
mineral constituents, 21 "57 lbs., or more than 4 times the normal 
amount of ammonia, were required to be provided for the pro- 
duction of 60 lbs. increase of corn, and its proportion of straw. 
Very similar results were obtained when nitrogen, about equal 
in amount to that in 100 lbs. of ammonia, was supplied in the 
form of nitrate of soda, instead of ammonia-salts. When the 
nitrate was used year alter year with the mixed mineral manure 
(plot 9a), it required nitrogen about equal to that in 5'41 lbs. of 
ammonia to produce 60 lbs. increase of corn and its proportion 
of straw, against 5 '37 lbs. when ammonia-salts were used 
(plot 7). But when the same amount of nitrate was used without 
the mineral manure, an amount of nitrogen averaging about 
12 '8 lbs. of ammonia was annually expended to produce the 
same result. 
It may be observed, too, that assuming the farmyard manure 
