Date of Award:

5-1961

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Soil Science

Committee Chair(s)

R. L. Smith

Committee

R. L. Smith

Committee

Howard B. Peterson

Committee

DeVere R. McAllister

Committee

Lewis W. Jones

Abstract

Nitrogen has commonly been a deficient element in the cultivated soils of the world since the beginning of agriculture. The general acceptance of the practice of using manures as a means of increasing plant growth, as shown by the records of ancient civilizations, attest to this fact. Since the time of von Liebig there has been an increasing awareness of the importance of this deficiency in soils. As a result of a better understanding of the problem and the increasing availability of commercial forms of nitrogen, a rapid increase in the use of nitrogen fertilizers has taken place in the last few decades.

This increasing use of commercial forms of nitrogen is accompanied by the need for more information concerning the proper use of these materials in order to accomplish the greatest benefit. For example, with the advent of increasing use of ammonium fertilizer to improve soil productivity, there has arisen a possibility of lengthening the period from the date of the fertilizer application to the time of utilization by the crop. This advanced application, especially in the fall of the year, has many advantages and is widely advocated. The following questions need to be answered in connection with efficiency of such a practice: Will the ammonium form of nitrogen remain unoxidized in the soil over the winter months? Could it be only partially oxidized and result in an accumulation of nitrites that may cause toxicity or be lost from the soil in gaseous forms such as nitrous oxide? What are the chance for significant losses by volatilization before it is oxidized? How does the amount of moisture and the prevailing temperature affect these transformations?

The study reported here is an endeavor to contribute to more complete answers to some of these questions. Although much research has been conducted relating to the effects of moisture or temperature on nitrogen transformations in the soil, more information is needed covering greater variations in the moisture and temperature levels along with the interactions of these. Accordingly, experiments were conducted under carefully controlled conditions to measure the changes occurring in the inorganic soil nitrogen from an applied ammonium source, at various moisture and temperature levels.

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