48 BULLETIN 140, U. S. DEPARTMENT OF AGRICULTURE. 
ward capillary movement of moisture. When soils have been chosen 
to advantage with a view to their adaptation to any given crop there 
is no virtue, it may be repeated, in the presence therein of stones, 
popular opinion as often expressed with regard to tree fruits notwith- 
standing. This fact may be no better demonstrated possibly than 
by some subsoils which are so clayey and stiff that they would have 
little value for tree fruits were it not for the presence of stones which 
in part offset their excessive compactness. Such a subsoil condition 
may make it feasible to plant an area that otherwise would be im- 
practicable. But it is a difficult condition to determine; in most 
cases it is an unwise risk to run ; and, furthermore, the soil and sub- 
soil section should be of such character with regard to both texture 
and structure that no stones are needed to render them sufficiently 
pervious for the satisfactory movement of capillary moisture. 
The common statement that stones conserve moisture in the soil, 
as is "proved" by its condensation on the underside of stones in 
its upward movement from the subsoil toward the surface, is very 
misleading. Granting that moisture is conserved to the extent of 
the area of the dimensions of the stones, the amount so controlled 
is not sufficient to render cultivation unnecessary for the conserva- 
tion of more moisture, hence the dust mulch is still necessary to 
accomplish this end in cultivated orchards. In uncultivated or- 
chards, where mulching is effectively practiced by hauling in rela- 
tively large quantities of material from outside the orchard, the 
presence of stones on or near the surface is usually of some assist- 
ance in conserving moisture, and this advantage is increased as the 
effectiveness of the artificial mulch (because too little in quantity) 
decreases. Stones are of most assistance in conserving moisture in 
neglected orchards where neither cultivation nor mulching is prac- 
ticed, but even in this case the benefit is negligible. 
The term hardpan is in common use to designate a subsoil con- 
dition which delays the ready percolation of moisture. Its common 
use, however, has led to marked misunderstanding at least in the 
eastern States, as it unfortunately includes everything ranging from 
true hardpan to a clay loam which may constitute a desirable sub- 
soil for orchard purposes. A true hardpan consists not of a sub- 
soil containing sufficient clay to make it retentive of moisture, but 
of a mixture of sand, gravel, silt, and clay with more or less cement-_ 
ing material which so binds these ingredients together that the move- 
ment of soil moisture either downward or upward is seriously t im- 
peded; or a hardpan may consist of a thin layer of mineral matter, 
formed by deposition of salts of iron, lime, or other minerals in 
solution after the formation of the soil or during the process. i Such 
conditions within several feet of the surface are very undesirable.^ 
They sometimes occur in both Massachusetts and Connecticut, 
