412 Report of Experiments with different Manures 
larger crops were grown ; though it was so not at all com- 
mensurately with either the potash or the phosphoric acid. How 
far the increased amount of Silica, such as it was, was due to its 
being liberated in available form by the chemical action of the 
constituents of the manures employed, or how far only to the 
increased distribution and range of collection of the roots of the 
more actively growing crop, we are not able to decide. 
To call to mind even more clearly than by the above state- 
ments how great is the drain upon the soil, more particularly of 
potash, phosphoric acid, and of silica, by a heavy hay-crop, it 
will be useful to quote here a few figures from the Table. 
Whilst the unmanured produce contained only 32^ lbs., and 
that by ammoniacal salts alone only 38^ lbs. oi potash, that grown 
by the mineral manure alone (supplying potash) contained 
72J lbs., that by the mineral manure and smaller amount of 
ammoniacal salts nearly 122 lbs., and that by the mineral manure 
and the larger amount of ammoniacal salts nearly 133 lbs. of 
potash, per acre annually. 
The phosphoric acid was increased from about 7f lbs. per acre 
per annum without manure, to scarcely 10^ lbs. with ammoniacal 
salts alone, to 16;|^ lbs. with mineral manure alone, and to about 
lbs. by the mineral manure and ammoniacal salts together. 
The silica amounted to 41 lbs. per acre per annum in the pro- 
duce without manure, to 47^ lbs. in that by ammoniacal salts 
alone, to nearly 45| lbs. in that by mineral manure alone, to 
80| lbs. in that by the mineral manure and the smaller amount of 
ammoniacal salts, and to a little more than 73 lbs. in that by 
the mineral manure and the larger amount of ammoniacal salts. 
We have already prominently called attention to the fact that 
the hay-crop, both from the large amount of mineral constituents 
it generally carries from the land, and from the generally more 
inadequate return of them by the home or other manures, is 
liable to be much more exhausting to the soil than the rotation 
crops of a farm. It has been stated, too, that potash was perhaps 
the constituent most likely first to show a deficiency. These ash- 
analyses, and the discussion to which they have led, cannot fail 
to impress upon the mind of the farmer still more forcibly the 
necessity of a due return to the land, at least oi potash and jo/ios- 
phoric acid, if not even of available silica (wiiich would be 
accomplished by farmyard-manure), if he would hope to obtain 
anything like maximum crops of hay, year by year, by the aid of 
artificial nitrogenous manures. 
It has just been seen how very variable is the composition of 
the ash of the mixed herbage of meadow-land according to the 
manure employed. It has before been shown that the composi- 
