A laboratory study of effect of agricultural land packers on soil
Date
1967
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Degree Level
Doctoral
Abstract
Agricultural land packers are generally used following the seeding
operation. It has been found that fields which have been packed usually
give higher yields than those which have not been packed, although the
reasons for this result are not understood. A laboratory study was undertaken
to determine the effect of packing and the effect to determine the
effect of packing and the effect of packer weight on soil density and
moisture loss. A soil bin system was designed and constructed for the
proposed study. The bulk density of the soil in the box was measured with
a gamma ray density system. A 12-inch cultivator shovel was used to till
the soil before packing. Two agricultural land packers, a crowfoot and a
coil type were used to pack the soil. Four different weights of packers
ranging from 60 pounds to 160 pounds per foot of width were used for both
packers at three depths of cultivation and at two moisture levels. Based
upon the theoretical analysis of gamma transmission, a linear relationship
was found between the count rate and the moisture content, and between the
count rate and the dry bulk density. These relationships were used in
determining the undisturbed bulk density of soil.
It was found that the packed density of the soil was essentially
the same for all packer weights used. No differences in packed density were
detected with changes in depth of cultivation, moisture level, or the type
of packer. The packed density increased with depth. Based upon these
results an equation of packing was developed which related packed density to
Depth.Experimental results were then checked against the theoretical
calculations based upon a pressure-sinkage equation. Laboratory compaction
tests and consolidation tests were carried out with a Proctor density apparatus
and a consolidation apparatus respectively. The results from the compaction
tests were compared with the experimental values. The Bossinesq equation
was used to draw iso-pressure curves. Densities were calculated by graphical
integration of iso-pressure curves using the density-pressure relationship
obtained from the consolidation tests. A comparison was made between the
densities obtained graphically and experimentally. The trend of calculated
values was similar to that of the experimental values to a depth of four
inches.
A comparison of the moisture loss from a sample of soil which was
cultivated only to that from a sample which was cultivated and packed showed
no difference during a period of seven days.
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Degree
Doctor of Philosophy (Ph.D.)
Department
Agricultural Engineering
Program
Agricultural Engineering