Report of Experiments on the Growth of Wheat. 463 
tliom any mineral manure. During the first 2 years, the two 
plots, previously so differently manured, gave almost identical 
amounts of produce ; but from that time forward, 10Z>, which, in 
the earlier years, had the ammonia-salts omitted twice, and twice 
received the mixed mineral manure when 10a had none, gave 
every year several bushels of corn (with its proportion of straw) 
more than 10a. 
It is clear that 10a had become relatively very deficient in 
certain mineral constituents. Nor is this to be wondered at 
when the circumstances of the experiment are considered. To 
say nothing of silica and other constituents, the first 7 crops 
taken from 10a removed about l-? r time as much phosphoric acid, 
and more than twice as much potass, as were supplied in the 
first year (1843-4). On the other hand, 10b received in manure 
during the same 7 years, more than 1^ time as much phosphoric 
acid, and more than twice as much potass, as were removed in 
the crops. In other words, 10a was already much poorer, and 
10b much richer, in both phosphoric acid and potass, than at the 
commencement. 
If these circumstances are borne in mind the Summary 
Table XXIX., given overleaf, will have considerable interest. 
During the 6 years, 1845-1850, plot 10a received 424 lbs. 
more sulphate and 200 lbs. more muriate of ammonia than plot 
106 ; but during the same period plot 10b received 600 lbs. pearl- 
ash, 400 lbs. soda-ash, 200 lbs. sulphate of magnesia, 400 lbs. 
bone-ash, and 300 lbs. sulphuric acid (sp. gr. 1*7), whilst plot 
10a received no mineral manure. The result was, that whilst 
both plots gave a considerable increase, 10a gave a total of 13{: 
bushels of dressed corn, and 1278 lbs., or about 11 \ cwts., of 
straw, more than 10b — equal to an average annual increase of 2-^- 
bushels of dressed corn and nearly 2 cwts. of straw, due to the 
larger amount of ammonia-salts, notwithstanding the much more 
favourable condition of 106 as to mineral constituents. 
Over the next 13 years, 1851-1863, during which neither plot 
received mineral manure, and both the same amount of ammonia- 
salts annually, 10a, previously so much more exhausted of 
mineral constituents, gave 51J bushels of dressed corn, and 5483 
lbs., or about 49 cwts., of straw less than 105 — equal to an average 
annual deficiency of nearly 4 bushels of dressed corn, and of 3f 
cwts. of straw. It is worthy of remark, however, that although 
10b continues to give notably more produce than 10a, due to the 
supply, and to the less exhaustion, of mineral constituents during 
the earlier years, it appears to be of late progressively declining 
in annual yield, and even somewhat more rapidly than 10a ; for, 
if the average annual produce of the last 6 years be compared 
2 K 2 with 
