Agronomy and Horticulture Department
Date of this Version
As used in this paper, humus refers to that portion of the soil organic matter peptized by four per cent ammonium hydroxide. That fraction peptized by four per cent ammonium hydroxide, precipitated by acids, and insoluble in alcohol, is designated as black pigment. It is called humic soil by many writers.
A THESIS Presented to the faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Department of Agronomy. Lincoln, Nebraska: 1938