on Permanent Meadow Land. 
411 
ripe as were those of the smaller Graminaceous crops : and it is 
as the Graminaceous plants progress to ripeness, that their ashes 
increase so much in percentage of silica. It would appear from 
these considerations, that there was a deficient supply of available 
silica for the o:reatlv-increased o;rowth. But a better view of the 
probable mineral requirements, or deficiencies, of the crop, will 
be gained by attention to the actual or increased amounts of the 
several constituents in the acrea//e produce under the different 
manuring conditions, as shown in the second and third Divisions 
of the Table (XIII.). 
By the use of ammoniacal salts alone, the amount of total 
mineral constituents taken off in the crop is about 1^ time 
as much as without anv manure at all. From the obvious 
limit that there was to the Graminaceous increase bv ammoniacal 
salts alone, it is assumed that, in the case of some of the mineral 
constituents of the soil, its supplies were drained to the utmost 
that the range of distribution of the underground feeders of the 
plant would permit. Supposing this to be the case, it is seen 
that the gain in both potash and silica was proportionally less 
than that of any other important constituent. But, as soon as 
potash is added in manure, even though without ammoniacal 
salts, the acreage amount of it in the crop is increased in larger 
proportion than that of any other important mineral constituent, 
except phosphoric acid. Tlie silica, which was not supplied in 
the manure, was comparatively but little increased in the pro- 
duce. When the ammoniacal salts as well as mineral manure 
were employed, the amount of jiotash in the acreage produce 
was nearly twice as much as when the mineral manures were 
used alone : and it was from 3 to 4 times as much as when no 
manure at all. or ammoniacal salts alone, were employed. Under 
the same circumstances, the acreage amount of phosphoric acid 
increased in almost an equal degree. So also did that of the sul- 
phuric acid. The silica even, was about doubled ; though there 
was no supply of it in manure. And, lastly, the magnesia, but 
especially the lime (though both were supplied in the manure) 
increased in verv much less acreage amount than the potash. 
From the whole it appears, that the much less acreage produce 
of hay, when the ammoniacal salts were used alone, than when they 
were used in conjunction with the mixed mineral manure, was due 
to a deficiency of available potash and p/iosj)horic acid within the 
range of the roots of the crop. It also appears probable, that 
there was a relative deficiency of available silica, notwithstand- 
ing that the range of collection of the roots of the crop would be 
considerably increased where the ammoniacal salts and the non- 
siliceous mineral constituents were employed. It is true tliat 
the ao'eafje yield of Silica was considerably increased where the 
