Dec. 6, 1915 
Influence of Growth of Cowpeas on Soil Properties 
441 
No crop was planted on plot D, which was unplowed and kept clean 
(PI. XLII, fig. 1). Plot E was also unplowed, but was planted to cow- 
peas (PI. XLII, fig. 2). Plot F was plowed and planted to cowpeas 
(PI. XLII, fig. 1). No crop was planted on plot G, which was plowed, 
artificially shaded, and kept clean (PI. XLII, fig. 2). Plot H was also 
plowed and kept clean, but was without shade or cowpeas (PI. XLII, 
fig. 2). 
The plots were laid out on May 31, 1912. Plots F, G, and H were 
carefully spaded at this time. Plots D and E were scraped with a hoe 
to remove trash and weeds, but no further treatment was given, A 
week later, on June 11, plots E and F were drilled to Black cowpeas 
with an ordinary wheat drill, dropping the cowpeas in rows 8 inches 
apart at the rate of bushels per acre. The drill was operated by 
pulling it at the end of a long rope so that the horses were not permitted 
Fig. i.—S oil-shading device, showing construction. 
to walk over the plots. On June 9, after planting, all plots were gently 
scraped with a hoe to give them an equal start. 
The main point at issue was a study of the soil compactness and nitrate 
content of plots in relation to the various treatments at the beginning and 
end of the growing season. An artificial shade was erected on plot G at 
a time when the cowpeas on plots E and F were matting over the soil. 
The shade device was a frame made of 2- by 4-inch lumber supported on 
legs made of the same material (fig. 1). Over this some galvanized 
screen was tightly stretched to serve as a support for a thin piece of 
black cheesecloth, which was found to be efficient in shading the soil from 
the direct rays of the sun and still only slightly impeding the rain. 
Tests for compactness of the soil were made by counting the number 
of times a weighted ram had to be dropped from a specified height in 
order that a conical pin be driven a given distance in the soil (fig. 2). 
Fifteen determinations of this character were made in each plot and the 
average of these taken as representative. 
