476 Report of Experiments on the Growth of W/ieat. 
On plots 7, the amount of ammonia-salts was again doubled, 
400 lbs. being 1 now used. The average annual produce amounted 
to 36f bushels of dressed corn, and to 4212 lbs. = about 37^ cwts. 
of straw ; and the increase over the produce with the mixed 
mineral manure alone was very nearly 18 bushels of dressed corn, 
and 2315 lbs. = about 20h cwts. of straw. 
The proportion of increase for a given amount of ammonia- 
salts was in corn not quite so great, but in straw rather more, 
when 400 than when only 200 lbs. of ammonia-salts were used. 
But 400 lbs. is a very heavy dressing ; and although it may, 
under favourable circumstances, give proportionally as much 
increase as a smaller amount, it is doubtless more than in the 
case of the soil in question, or indeed of most soils, is calculated 
to give on the average of seasons, a maximum result for a given 
amount of ammonia employed. 
Still, even with GOO lbs. of ammonia-salts (plots 8) there was 
a further increment, and with 800 lbs. '(plots 16) still a further 
increment of increase ; though at a much diminishing rate for a 
given amount of ammonia the greater the quantity employed, 
and the diminution was the greater in the corn than in the straw. 
Thus, by the addition to the mixed mineral manure of 200 lbs. 
of ammonia-salts there were obtained 9f, by 400 lbs. nearly I 8, 
by 600 lbs. little more than 19 h, and by SOO.lbs. little more than 
20 bushels increase of corn ; and of increase of straw there was 
obtained by 200 lbs. of ammonia-salts 1115 lbs., by 400 lbs. 
2315 lbs., by 600 lbs. 2818 lbs., and by 800 lbs. 3255 lbs. Ex- 
hibited from a more striking point of view, the result is, that 
each successive increment of 200 lbs. of ammonia-salts gave 
increased produce as under : — 
Corn. Straw. 
1 Z Bush. pks. " lbs. 
1st increment (200 lbs. applied) gave 9 3 i and 1115 
2nd increment (400 lbs. applied) „ 8 0i „ 1200 more than 200 lbs. 
3rd increment (GOO lbs. applied) „ 1 2k „ 503 „ 400 lbs. 
4th increment (800 lbs. applied) „ 0 2 „ 437 „ GOO lbs. 
It is seen that any additional produce yielded by the use of 
more than 400 lbs. of ammonia-salts per acre, was obtained at 
the cost of very much more ammonia for a given amount of 
increase. Moreover, as an inspection of Table XXX. will show, 
the weight per bushel of dressed corn was less, and the proportion 
of corn to 100 of straw very much less, under the influence of 
the excessive amounts of ammonia-salts. 
Before leaving this series of experiments, attention should be 
called to the fact, that where 400 lbs., and upwards, of ammonia- 
salts were used in conjunction with the mixe'd mineral manure, 
the produce, both corn and straw, exceeded that by farmyard 
