Dec. 6, 191S 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. i). 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. i). 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 ]\Iay 31, 191 2. Plots F, G, and H -vere 

 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 v^rere drilled to Black cowpeas 

 with an ordinary wheat drill, dropping the cowpeas in rows 8 inches 

 apart at the rate of 1% 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. — Soil-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 dexdce was a frame made of 2- by 4-inch lumber supported on 

 legs made of the same material (fig. i). Over this some galvanized 

 screen was tightly stretched to serve as a support for a thin piece of 

 black cheesecloth, w^hich 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. 



