12 Morris J. Blish 



Table II shows the results of humus-nitrogen determination by 

 the Hilgard and the Alway-Bishop methods, using Lincoln sur- 

 face soil in all instances. 



Table II. Humus Nitrogen in Lincoln Surface Soil 



Determination Number 



Average 137 .160 



Total nitrogen in L. S. soil averaged .244 per cent. Per cent, of nitro- 

 gen in humus = 7.3 per cent. 



Humus 



, . = 0.0. 



total nitrogen 



The following set of tables shows the humus content of the 

 soils from each of the five fields of each area of the Transition 

 series. Also, the humus-nitrogen ratios are given for the first 

 two feet of each field ; lower than this the ratio has but little 

 significance, since a slight error, or variation in a humus de- 

 termination, causes an exceedingly large variation in the ratio, 

 and the per cent of error in the humus determination of a svib- 

 soil is necessarily large, so that below the first two feet the ratios 

 are not very constant. The per cent of nitrogen in humus is 

 given for the first foot of all soils. This is the only depth in the 

 case of samples from the individual fields on which humus nitro- 

 gen determinations were made. They were run on the composites 

 from all depths, however, but owing to the unreliability of a 

 humus determination below the first two feet, they are of little 

 significance. 



In the following set of tables, the humus content was de- 

 termined gravimetrically for all samples from the first and second 



122 



