The use of this plow will renovate old bottom-lands, the surface of which has been exhausted by shallow plowing and continual cropping. It brings up from below fresh material, which the atmosphere speedily prepares for crops.
Old fields, a long time in grass, are very much benefited.
Constant plowing at about the same depth will often form a hard under-floor by the action of the plow, through which neither roots nor rain can well penetrate; subsoiling will relieve a field thus conditioned.
Soils lying upon clay or hard compact gravel are opened and remarkably improved by the process. The wet, level, beech-lands would be greatly benefited by deep plowing in the _fall of the year_, subjecting the earth, to a considerable depth, to the action of the frosts, rains, etc., and giving a downward drain for superfluous moisture.
Although we have incidentally alluded to the benefits of subsoiling, they deserve a separate and individual enumeration.
1. In very deep molds or loams it brings up a supply of soil which has not been exhausted by the roots.
2. In soils whose fertility is dependent upon the constant decomposition of mineral substances, subsoil plowing is advantageous by bringing up the disintegrated particles of rock, and exposing them to a more rapid change by contact with atmospheric agents.
3. Subsoiling guards both against too much and too little moisture in the soil. If there is more water than the soil can absorb, it sinks through the pulverized under-soil. If summer droughts exhaust the moisture of the surface they cannot reach the subsoil, which affords abundant pasture to the roots.
These are two entirely different processes. The _Fire Blight_ (of the middle and western States), is a disease of the circulatory system, induced by a freezing of the sap while _the tree is in a growing and excitable state_. It always _must_ occur before the leaves are shed in the autumn. Winter-killing is of two kinds—resulting from severe cold, and from untimely heat. The loss of tender shrubs, roses, etc., at least, before they are fully established, and of half-hardy fruit-trees, is occasioned by the winter sun shining warmly upon them while frozen, and suddenly thawing them. The point of death is usually near the surface of the ground, where the under-ground bark and upper bark come together. Whole orchards are destroyed in this way; and, if examined, the bark may be found _sprung off_ from the wood. This may occur at any time during the winter.