A Laboratory Study of Effect of Agricultural Land Packers on Soil

by Lal, Radhey

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.