442 
Journal of Agricultural Research 
Vol. V, No. 10 
The first observations were made on June 19, 1912. The soil was very 
friable at this time. Several showers had fallen since planting time, and 
consequently the plots were in excellent tilth. 
A definite system was followed in locating places for compactness 
determinations, similar to the plan for taking samples for analysis. This 
eliminated any chance of duplicating a measurement of a given spot at 
later times. Tests were made at least 18 inches apart to avoid further 
any influence due to overlapping. In manip¬ 
ulating the mechanical device (fig. 2) auger 
plate E was placed squarely on the ground 
and pin D was set in the aperture. Sheath F 
was then slipped over pin D, and ram G was 
dropped on the pin until it was driven into the 
soil sufficiently deep for mark b on the ram to 
be even with the top of sheath F. The ram 
was raised each time to mark a and then 
dropped freely by its own weight (7,445 gm.). 
This operation was repeated, recording each 
drop, until mark c on the ram was even with 
the top of sheath F. Thus, the pin was driven 
a distance of 4^ inches in the ground each time 
a test was made. The number of drops neces¬ 
sary to produce this effect was the measure of 
the relative compactness of soil in the various 
plots. The results of these trials are given in 
Table I. 
The fluctuation between the readings as seen 
in Table I can not be accounted for other than 
that it represents the normal variation of soil 
friability over large areas. Increasing the 
number of readings did not materially alter 
the average secured. Therefore, the authentic 
Fig. 2 Devicefortestingthecom- average compactness of the plowed and that of 
pactness of the soil. the unplowed plots stand in the ratio of 1 to 4 
at this time. Moisture determinations were made on the following day, 
with no rain intervening, and were as follows: All plots—first foot, 26.2 
per cent; second foot, 26.5 per cent; third foot, 29.3 per cent. 
On June 24 all plots were lightly cultivated with a hoe, in order to 
remove the weeds which had begun to appear. At this time the cow- 
peas were doing very well and stood about 4 inches high. Samples for 
nitrate analysis showed the soil to contain at the beginning of the experi¬ 
ment the amounts given in Table II. 
As might naturally be expected, there is most nitric nitrogen in the 
surface foot, with a gradual decrease downward. The analysis of indi- 
