146 
THR FLORIST AND TOMOLOGIST. 
well aware of its importance, and it is to such that my remarks may be said to 
be more particularly directed. 
The operation of trenching may be said to act beneficially in a variety of 
ways. It renovates the soil by bringing up to the surface that which has become 
exhausted by the roots; and by turning down the top soil which has been 
exposed, it supplies a congenial medium for future crops to feed upon; and the 
exhausted soil being in its turn exposed to atmospherical action and influences, 
becomes again charged with fertilising matter, and in a fit state to be turned 
down again at a subsequent trenching. It equalises the action of drainage, 
thereby giving greater facility for the roots to penetrate through the soil, and 
it serves a most important purpose in opening up the earth to a great increase in 
the circulation of air and moisture through the soil, which, acting chemically 
upon the mineral and gaseous constituents thereof, prepare these for absorption 
by the roots. 
Trenching must not be performed in an indiscriminate manner on all soils 
and subsoils alike, but must be varied in the manner of operation according to 
the character of each. In old garden soils, which are generally deep and 
homogeneous, a simple interchange of the top and bottom spits is usually 
considered sufficient for most practical purposes ; but in commencing to break up 
new ground, it is very possible to make a great mistake in the first instance by 
trenching too deep, and bringing up too much of the subsoil to the surface. 
This requires caution, because there should not be a greater quantity brought 
up than will be well exposed to the influence of the atmosphere during the sub¬ 
sequent processes of surface-cultivation and tillage; but at the same time it is 
advisable to increase the depth of the soil which is moved, by turning over 
the subsoil at the bottom of each trench to the depth of a spit, and breaking 
it up, so that the roots and moisture may penetrate it. In performing the 
operation care should be taken to have the trenches sufficiently wide to enable 
the operator to be quite certain that the bottom is equally moved all over, 
because, if there is a ridge of hard unmoved earth left at the junction of 
the trenches, the bottom will form a series of ditches, which in any but porous 
subsoils will only serve for the retention of water. By successive trenchings at 
regular intervals, and bringing up a little more of the subsoil each time, the 
depth of what may be called the staple soil will soon be sufficiently increased. 
There are no subsoils so bad as to be incapable of improvement by a 
judicious performance of this operation, whether clay, chalk, or gravel. The great 
object is to move the soil deep enough, and only to bring a couple of inches or 
so of the bad subsoil to the top at each trenching, which by exposure and 
admixture with dung soon becomes equal to the best surface soil. Even gravelly 
subsoils may be brought to the top gradually; and although the surface will 
becpme stony it will not interfere with productiveness, but it may be as well to 
pick off some of the largest stones from time to time. 
The importance of moving the soil to a good depth in old garden soil can 
hardly be overrated, not only because air, moisture, and consequently the roots 
are thereby enabled to permeate the mass freely, but also because the residuum 
of former crops together with the manurial matters washed down from the 
frequent surface-applications of rich substances necessary to bring most kitchen- 
garden crops to perfection, require to be from time to time brought up to the 
surface, and purified, by exposure to the air, from many deleterious qualities 
which thev contract under such circumstances. In such soils as these the 
operation is equivalent, and sometimes superior to, a good dressing of manure. 
There is another great advantage attending the operation which should not 
be lost sight of in gardens where labour and water are scarce, which is, that 
plants in soils so thoroughly moved seldom suffer from drought when once they 
