]. The wheels of this machine eighteen inches in
diameter, with rims one inch thick at the inner part, beveled two
and a half inches to a sharp outer edge, are placed on a shaft, five
inches apart. In practice about five hundred pounds of weight are
added.
This machine, according to Campbell, crowds a one-inch wedge into
every five inches of soil with a lateral and a downward pressure and
thus packs firmly the soil near the bottom of the plow-furrow.
Subsurface packing aims to establish full capillary connection
between the plowed upper soil and the undisturbed lower soil-layer;
to bring the moist soil in close contact with the straw or organic
litter plowed under and thus to hasten decomposition, and to provide
a firm seed bed.
The subsurface packer probably has some value where the plowed soil
containing the stubble is somewhat loose; or on soils which do not
permit of a rapid decay of stubble and other organic matter that may
be plowed under from season to season. On such soils the packing
tendency of the subsurface packer may help prevent loss of soil
water, and may also assist in furnishing a more uniform medium
through which plant roots may force their way.
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