3IO Journal of Agricultural Research voi xix, No. 7 



Both constants are large. They show that the field is not merely hetero- 

 geneous but that portions which are high in nitrogen are high also in 

 carbon and vice versa. 



Waynick {21) has given a series of 81 determinations of nitrification 

 in samples of soil drawn from a field on the University of California 

 farm at Davis. 



The field had been planted to corn in 1914, to Sudan grass in 191 5, 

 and to grain sorghum in 191 6. In 1917 it had lain fallow and was 

 without vegetation when the samples were taken October 20. 



The particular area chosen was apparently as uniform as one could well find , being 

 level, of uniform texture and color, and free from small local depression of any kind. 



These samples were taken on eight radii of a circle 100 feet in diameter. 

 The samples were separated by a radial distance of 5 feet. Disregarding 

 the one central sample, we may group the remainder by twos in order to 

 determine whether there is a correlation between adjacent samples. The 

 coefficients thus obtained will, of course, not be comparable with those 

 deduced for cases in which the yields or soil samples were uniformly dis- 

 tributed over the field. They will, however, serve to indicate whether 

 or not this field is heterogeneous in the sense that differences prevailed 

 sufficiently large to influence the properties of adjacent samples in a 

 manner to make them more similar than pairs of samples taken at 

 random over the field. His samples were drawn in two series — the first 

 from the superficial 6 inches, the second from the deeper-lying level, 6 

 to 24 inches. 



Waynick's Table i gives the residual nitrate in soil as sampled. From 

 it we deduce 



For the upper 6 inches, r = o.404±o.o63, r/E;.= 6.4. 

 For the subsoil, r= •596± .049,^/^^=12.2. 



Table 2 gives the nitrate produced from the soil's own nitrogen after 

 28 days' incubation. We deduce 



For the upper 6 inches, r = 0.065 ±0.075, r/E^^ 0.86. 

 For the subsoil, r= .o59± .o75,r/£r= .79. 



Table 3 shows the nitrate produced from 0.2 gm. of ammonium sul- 

 phate in 100 gm. of soil. The correlation coefficients are 



For the upper 6 inches, r = 0.298 ±0.069, ^/^r = 4-34- 

 For the subsoil, r= .351 ± .066, r/Er= 5.31. 



Finally, Table 4 shows the nitrate produced from 0.2 gm. of blood in 

 100 gm. of soil. The results in this case are 



For the upper 6 inches, r = o.i20±o.o74, r/Ef= 1.62. 

 For the subsoil, r= .297± .069, r/Er = 4-32. 



