Influence of Growth oj Cowpeas on Soil Properties 443 



vidual cores also substantiates the conclusion derived from preliminary 

 tests, that a thoroughly mixed composite is an authentic measure of the 

 actual nitric nitrogen in the soil. 



T.A.BLK I. — Relative compacUiess {number of drops of ram) of soil on the various plots at the 

 beginning of the experiment {June IQ, 1912) 



Table II. — Quantity of nitrate as NO^ in the soil of all plots {June 24, 1912)^ 



Quantity of nitrate (p. p. m.)- 



13 c 



14 c..., 



15 c 



16 c 



17 c 



18 c 



19 c 



20 c 



21 C 



22 C 



Average. .. 

 Composite 

 Final 



6.14 

 6-93 

 6.46 

 7. 26 

 12. 25 

 3-93 

 9- IS 

 5.86 



7-43 

 9-30 



3.21 

 6. 13 



3-51 

 3.20 

 3-76 

 3-25 

 4- 05 

 3-69 

 3-37 

 3-76 



5- II 

 2-37 

 3-27 

 3.66 



3-05 

 4.78 

 2. 09 



4-35 

 2. 26 

 2.58 



7.46 

 8.06 

 7.76 



3-79 

 3.81 

 3.80 



3-35 

 3-56 

 3-45 



Plate XLII shows the general plan of the experiment and the thrifti- 

 ness of the cowpeas at the early date of July 17 — about a month after 

 planting the cowpeas. 



a The nitrate determinations were made by using the phcnoldisulphonic-acid method, as suggested by 

 Schreiner, Oswald, and Failyer, George H., in Colorimetrie, trubidity, and titration methods used in soil 

 investigations. U. S. Dept. Agr. Bur. Soils Bui. 31, p. 39-41, 1906. 



