482 Report of Experiments on the Growth of Wlieat. 
straw less than plots 7. There is no evidence, therefore, of any 
marked effect from the carbonaceous organic matter of the rape- 
cake. 
Plot 10 was manured during the 12 years in the same way 
as 15i, with the exception that the sulphates of potass, soda, and 
magnesia, were omitted. It should be further observed, that 
whilst during the first 8 years of the 20, plot 15a received of potass 
in manure, nearly, and 156 over, 400 lbs. more, plot 19 received 
nearly 200 lbs. less, than was removed in the crops. There was, 
therefore, a considerable relative deficiency of potass in the soil 
of plot 19, and it gave an annual average produce of nearly 
3J; bushels of dressed corn, and about 4i cwts. of straw, less than 
plot 3 5b. 
It is worthy of remark that the produce of plot 19, like that of 
plots 11, where also the supply of phosphoric acid was relatively 
large, showed a comparatively high proportion of corn to straw, 
notwithstanding the deficient amount of total produce due to the 
relative exhaustion of potass in both cases. It may also be men- 
tioned, that the straw has frequently been observed to be finer, 
the grain more thin-skinned, and the crop more evenly ripened, 
where the bone-ash has been acted upon by hydrochloric instead 
of sulphuric acid. 
From the results of this series it may be concluded — that there 
is no practical or economical advantage in rendering bone-ash 
soluble by the expensive hydrochloric instead of the cheaper 
sulphuric acid ; that rape-cake benefits the wheat crop by its 
supply of nitrogen and of mineral constituents, but immaterially 
by the supply of available carbon within the soil from decom- 
posing organic matter ; and that where a liberal phosphatic and 
nitrogenous manure was used for many years, the available 
supply of potass to the growing crop became very injuriously 
diminished. 
Summary Statement of the Results of the last 12 Years. 
1. The average annual produce of wheat per acre, over the last 
12 of 20 years of the growth of the crop on the same land, and of 
more than 20 since the application of manure of any kind, was 
15^ bushels of dressed corn, and there was no material diminu- 
tion in the yield in the later years : the proportion of corn to 
straw was as high as in the produce by farmyard manure, and 
higher than in the majority of cases with the more productive 
artificial manures, but the weight per bushel of dressed corn was 
very low. 
2. Farmyard manure, applied every year in amount containing 
considerably more of every constituent than was removed in the 
crop, increased the average annual produce to nearly 35^ bushels 
