188 
Peruvian Guano. 
jurious effect. There are clay soils in Gloucestershire, Hereford- 
shire, and other counties, on which the application of ammoniacal 
salts to root-crops often diminishes the crop, and, at the best, is 
of no benefit whatever to the swedes or turnips. Again, on light 
sandy soils, although for a time highly nitrogenous manures may 
largely increase the yield of corn, yet their exclusive and long 
continued use leads to a rapid exhaustion of the soil in those 
mineral constituents of which an abundant supply is required 
by all cultivated plants. On the other hand, there are certain 
loamy soils on which Peruvian guano is used with great advan- 
tage for grass and corn crops, especially as a top-dressing for 
wheat and barley ; and the only question which arises is, whether 
the required nitrogen is more economically applied to the land 
in that shape, than as nitrate of soda, sulphate of ammonia, 
soot, &c. •» 
Preparation of Guano. 
When guano is used as a top-dressing, or is drilled in, more 
care should be taken than is frequently bestowed to apply it in a 
good mechanical condition. It should never be sown without 
having been submitted to the rather tedious and unpleasant 
process of sifting and grinding into a fine powder. The hard 
lumps, varying from the size of a pea to that of an egg, which 
always occur in good Peruvian guano, do not materially differ 
in composition from the finer particles, and should be reduced 
to as fine a powder as the rest. 
If guano is sown without such preparation, the fine dust will be 
carried away too readily by the wind, and the coarser portions 
will fall too much together in one place. In consequence of 
this unequal distribution, the young plants will be burned up 
where the lumps drop, near-by there will be a rank growth, and 
the crop will ripen unequally. The danger arising from unequal 
distribution is less when the manure is applied to the land in 
autumn before sowing the seed-corn. This practice should be 
adopted in all cases in which the soil contains a fair amount of 
clay, which, in virtue of its well-known absorbing properties, 
retains the fertilizing constituents of guano, so that the rain 
falling upon the land during the winter months, instead of re- 
moving the most valuable manuring substances, as in the case 
of light sandy soils, has the advantage of disseminating them 
uniformly through the soil. 
Mechanical Preparation of Guano. 
It has been recommended to sift the guano, to spread the lumps 
retained by the sieve on a clean stone-floor, and to pass a garden- 
roller over them, or to beat them down with the back of a shovel 
