EXPERIMENTS ON THE MIXED HERBAGE OF PERMANENT MEADOW. 303 
10 years. The falling off of effect is, therefore, very great; and the proportional 
reduction of produce is more than twice as great as without manure. There is also 
a considerable reduction in the yield of nitrogen per acre ; but as the amount annually 
supplied in the manure was several times greater than the increase of nitrogen in the 
crop by its use, and the percentage of nitrogen in the produce was abnormally high, 
the deficiency of growth was obviously not dependent on a want of nitrogen. The 
reduction in the yield of mineral matter, on the other hand, is seen to be nearly 
40 per cent, over the second compared with the first 10 years. 
Leaving out of consideration the amounts of sulphuric acid and chlorine taken up, 
these being largely supplied in the ammonia-salts, there was, of all the mineral 
constituents derived from the soil itself, more taken up during the first 10 years 
under the influence of the ammonia-salts than without manure. Of lime, of potass, 
and of silica there was, however, considerably less taken up over the second 10 years 
than without manure ; of lime and of potass so much less' that of these there was 
actually less yielded up by the soil in the 20 years with the ammonia-salts than 
without manure. Of magnesia, and of phosphoric acid, there was, on the other hand, 
rather more yielded up over both periods with the ammonia-salts than without it. 
Of lime, of potass, and of silica, indeed, the percentage in the dry substance of the 
produce of the ammonia plot was abnormally low. 
That there should be actually less lime and potass taken up with the ammonia 
than without manure is probably to be explained by the fact that, under the influence 
of the purely nitrogenous manure, various species which commanded a more extended 
range of soil than those which remained, had been displaced. Under the influence of 
the ammonia-salts the total number of species found was greatly reduced ; the herbage 
became more and more gramineous ; Festuca ovinci sometimes yielded more than half, 
and Agrostis vulgaris more than a quarter of the total produce ; there was scarcely 
any leguminous herbage ; and of miscellaneous species there were but few in number, 
which contributed but a small proportion of the weight, excepting Rumex acetosa, 
which was objectionably flourishing. Thus, the produce consisted chiefly of the poorer 
grasses, which, moreover, showed very little tendency to form stem and seed, whilst 
the stunted foliage w T as of a very dark green colour, indicating a very high percentage 
of nitrogen in its dry substance, or rather a deficient assimilation of carbon in proportion 
to the nitrogen taken up. 
The next illustrations also show the effects of a continuous supply of nitrogenous 
without mineral manures. 
3. Nitrate of Soda alone ; Plots 15 and 17. 
Plot 15 received, for 18 years in succession, approximately the same amount of 
nitrogen per acre per annum as plot 5, but as nitrate of soda instead of as ammonia- 
salts ; and plot 17 has received annually half the cpiantity of nitrate. The experiments 
