EXPERIMENTS ON THE MIXED HERBAGE OF PERMANENT MEADOW. 329 
degree the assimilation of nitrogen, over a given area; and it has increased, in about 
the same proportion as the increase of hay, the amount of total mineral matter taken 
up over that on plot 9, where the same amount was applied by manure. The addition 
of silicates during the last 14 years of the 20 has further increased the amounts of 
hay yielded, and of nitrogen and mineral matter taken up. 
Bearing in mind that in the fourth, fifth, and sixth, of the first 10 years, only the 
same amount of ammonia-salts was applied on the plots 11 as on plot 9, and that the 
double amount was applied in each of the last 10 years, it will be observed that there 
was nevertheless a considerable falling off in the produce of hay, and in the quantity 
of mineral matter taken up, during the second 10 years, where the silicates were not 
also applied. Where the silicates were applied, however, the falling off in the produce 
was very trifling, and that of the mineral matter taken up much less than where they 
were not applied ; whilst, under their influence, there was also a considerably greater 
increase in the amount of nitrogen taken up over the second 10 years. 
With regard to the nitrogen, it is remarkable that, with the enormous amount of 
about 200 lbs. of ammonia, corresponding to about 164 lbs. of nitrogen, applied per 
acre per annum, for so many years, there was, so far as can be judged, as large if not 
a larger proportion of that supplied taken up by the growing herbage as where only 
half the quantity was employed. There was, in fact, a proportionally much greater 
increase in the assimilation of nitrogen than in the amount of total growth—that is, 
produce of hay—by doubling the application. In other words, the percentage of 
nitrogen in the produce was very much increased. It was, indeed, very abnormally 
high ; and, as already pointed out, such a condition indicates a deficient assimilation of 
other constituents in proportion to the nitrogen taken up. This result may be due to 
a deficiency of available mineral constituents, or to the limitation of the climatic 
characters of the seasons for the assimilation of a larger amount of carbon by the 
quantity and quality of the leaf-surface presented over a given area; or the effect may 
be due to a combination of these causes. 
The further increased total yield of hay, of nitrogen, and of mineral matter, where 
the silicates of soda and lime were used, and at the same time a decrease over the 
second period compared with the first in the amount of mineral matter, but an increase 
in that of the nitrogen, taken up, would seem to indicate a relative deficiency of avail¬ 
able supply within the soil of mineral constituents compared with that of nitrogen. 
Still, a limitation of the climatic characters of the seasons may have had some share 
in the limitation of the amount of cai'bon assimilated, or, in other words, of the amount 
of produce grown. 
With a view, if possible, of further elucidating the conditions and the results of the 
growth induced, let us briefly consider—what was the difference in the botanical 
character of the herbage developed by the single and by the double application of 
ammonia-salts, and without and with silicates, respectively ? and what were the chief 
differences in the chemical composition of the hay ? 
MDCCCLXXX. 2 U 
