EXPERIMENTS OX THE MIXED HERBAGE OF PERMANENT MEADOW. 339 
has received only 275 lbs. per acre per annum. Yet, with one exception, in each of 
the 21 succeeding years, the plot to which the double amount of nitrate had pre¬ 
viously been applied has yielded more produce; and in the twentieth year since 
the double application (1877), it yielded 3f bushels more corn, and 3^ cwts. more straw, 
per acre. The excess of yield has also been more marked in the drier seasons. The 
soils and subsoils of these two plots have not been examined. But, judging from the 
results which have been described, the question suggests itself—whether the explana¬ 
tion be not that where the excessive amount of nitrate was applied in the earlier 
years, the subsoil was so acted upon, disintegrated, and rendered more porous, that it 
offered a greater surface for the retention of the otherwise easily washed-out nitrate, 
a greater surface for the retention of moisture, and greater permeability to the roots ; 
thus increasing the store, both of available food and available moisture, at command 
of the plant, and facilitating the penetration of the roots in search of them ? 
To conclude, in regard to the greater effects of a given amount of nitrogen as 
nitrate of soda than as ammonia-salts when applied to the mixed herbage of grass 
land: it is obvious that the result is dependent on a great variety of circumstances. 
The nitrogen of the nitrate distributes much more rapidly through the soil and subsoil. 
The flora becomes greatly modified. Plants of different habits, both of aboveground 
and underground growth, are developed. Accordingly, the roots obtain possession of 
different ranges of soil and subsoil ; and according to their range, and to their func¬ 
tional capability of food-collection, they gather up the more. With these favourable 
soil-conditions, the plant takes up more from the atmosphere within a given time. 
But, how far it does so simply as a result of a more favourable condition of the cell and 
sap, due to a more favourably balanced supply of nitrogenous and mineral food, in¬ 
ducing greater activity of a given leaf-surface, or how far it is that, conjointly with 
greater vegetative activity, there is, as there necessarily must be, also a constantly 
increasing above-ground surface, and hence a complex and cumulative action, is a 
question beyond the scope of our observed facts to determine. That the increased 
assimilation of carbon over a given area cannot be entirely accounted for by the suppo¬ 
sition that the particular species of plants developed have a greater assimilative power 
for a given leaf-surface than those they have replaced, would appear from the fact that, 
when a given amount of nitrogen, as nitrate of soda and ammonia-salts respectively, is 
applied for one and the same description of crop—barley, for example—there is also 
found a greater fixation of carbon—that is more growth over a given area—under the 
influence of the nitrate. 
11. 275 lbs. Nitrate of Soda, with Mixed Mineral Manure, containing Potass; Plot 1G. 
The next selection of results shows the effects of the mixed mineral manure with 
only 275 lbs. of nitrate of soda per acre per annum ; that is, only half as much as was 
applied on plot 14, and containing, of course, only half as much nitrogen as the 
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