2 Morris J. Blish 



Page 



Table ii. Humus Nitrogen in Composites and Per Cent, of Nitro- 

 gen in Humus 127 



Table 12. Humus Nitrogen Ratio for Composite Samples from Dif- 

 ferent Areas 128 



Table 13. Arrangement of Soils of Each Area, Individually, with 



Regard to Depth of Color 129 



Table 14. Arrangement of Soils of all Six Areas in Order of Color 



of Moist Soils 135 



Table 15. Arrangement of Humus Extracts of the Transition Soils 



According to Color of Solution in Flasks 139 



Table 16. Comparison of Gravimetric and Colorimetric Determina- 

 tions of Humus in the Composites 140 



Table 17. Comparison of Gravimetric and Colorimetric Humus De- 

 terminations on Individual Fields 141 



Table 18. Comparison of Photometric and Gravimetric Humus De- 

 terminations 142 



Table 19. Comparison of the Results of Different Methods of Ex- 

 tracting Humus 143 



INTRODUCTION 



The main object of this investigation has been to determine the 

 distribution of the humus, to a depth of six feet, throughout the 

 soils in representative virgin prairies of the so-called " transition 

 region " of Nebraska. This region is the large area which ex- 

 tends westward from the Missouri River for a distance of over 

 three hundred miles and which is covered, for the most part, with 

 loess soil. This is, agriculturally, the most important soil in the 

 state of Nebraska, and covers more than half the area of the 

 state. The term " transition region " is employed to convey the 

 idea of a gradual transition from a semi-arid condition, in the 

 western part of the loess area, to a humid condition in the eastern 

 part. 



The term " humus " in this thesis is used to represent the humi- 

 fied organic matter in the soil, which is soluble in dilute alkalies. 

 By the term " soil " is meant all soil through a depth of six feet, 

 no line being drawn between surface-soil and subsoil. 



The ratio of humus to total nitrogen was determined in the case 

 of all soils of the first and second feet, while in all first-foot 

 soils the nitrogen content of the humus was determined. 



1 12 



