Does sub-soiling overcome drought?
How does it deepen the surface soil?
Notwithstanding its great benefits on land, which is sufficiently dry, sub-soiling cannot be recommended for wet lands; for, in such case, the rains of a single season would often be sufficient to entirely overcome its effects by packing the subsoil down to its former hardness.
On lands not overcharged with water, it is productive of the best results, it being often sufficient to turn the balance between a gaining and a losing business in farming.
It increases nearly every effect of under-draining; especially does it overcome drought, by loosening the soil, and admitting air to circulate among the particles of the subsoil and deposit its moisture on the principle described in the chapter on under-draining.
It deepens the surface-soil, because it admits roots into the subsoil where they decay and leave carbon, while the circulation of air so affects the mineral parts, that they become of a fertilizing character. The deposit of carbon gives to the subsoil the power of absorbing, and retaining the atmospheric fertilizers, which are more freely presented, owing to the fact that the air is allowed to circulate with greater freedom. As a majority of roots decay in the surface-soil, they there deposit much mineral matter obtained from the subsoil.
Why is the retention of atmospheric manures ensured by sub-soiling?
Why are organic manures plowed deeply under the soil, less liable to evaporation than when deposited near the surface?
How does sub-soiling resemble under-draining in relation to the tillering of grasses?
When the subsoil consists of a thin layer of clay on a sandy bed, what use may be made of the sub-soil plow?