Digging
For pulverisation and mixing-in of manures, Digging is best performed (says Loudon) in dry weather; but, for the purpose of aeration, a degree of moisture and tenacity in the soil is more favourable. In Digging, a uniform depth should be preserved throughout, the full length of the spade being inserted nearly vertically, and the spit turned over, so that what was before underneath may now be exposed to the air. An open trench, the length of the ground to be dug, should first be made, and the soil thus removed transferred to the place where it is intended to finish. In order to leave the surface, when completed, evenly disposed, the trench must be kept tolerably straight, and of about an even width. Ground that has been occupied by garden crops in summer, is best thoroughly dug in the autumn, and manure added. It should not be broken by the spade, but left rough for full exposure to the frost, and for the consequent aeration in winter. The following spring, such soil will be found to work well, and may be prepared, by levelling down, for any desired crop. The strength of the manure will also have become incorporated with the soil underneath-a condition that cannot be obtained by adding it at planting time. The width of ground taken as a spit must not exceed about 9in. in heavy soils, or the bottom will be left undisturbed. Digging is best performed when the soil is somewhat dry, and should never be practised when it is frozen or covered with snow. Light soils, or those resting on a gravelly bottom, may be worked at many times when it would be very unwise to tread on those of a clayey nature. The workman, when Digging, should stand nearly erect, insert the spade vertically, to secure the removal of soil to the full depth, and turn the spit from the direction in which he is standing. If a competent man, he will be able to reverse the position of his hands on the spade, and proceed either way with equal facility.
Double-digging is performed by having a trench of double width, removing a spit of the earth on the top, then Digging underneath, and allowing that portion to remain. Another width is then marked out, the top soil from this placed on the other, and each portion treated successively in a similar manner. This method is often adopted where sub-soils are poor, so that the depth of two spits may be reached, without introducing the inferior soil to the surface.