Date of Award:

5-1959

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Soil Science

Committee Chair(s)

H. B. Peterson

Committee

H. B. Peterson

Committee

James P. Thorne

Abstract

Nitrogen is the most widely needed and the most widely used of the fertilizer elements. Yet, in spite of the voluminous research work of evaluating the nitrogen status of soils, laboratory tests for the purpose of predicting need of nitrogen fertilizer are not very widely used. In general, laboratory tests for nitrogen supplying power have not given satisfactory results. Methods currently employed by a few laboratories can be classified either as biological or chemical. In the former method, the soil is incubated under optimum conditions and the amount of nitrate released over a given period of time is measured and used as an index to the nitrogen supplying power of the soil. In the latter method a portion of the total nitrogen is released by chemical means and measured. An attempt is made using chemical methods to release the same amount or a constant portion of the amount of nitrogen that normally would be furnished to a growing plant by the soil during one season.

An obvious disadvantage of the biological or nitrification method as a basis for predicting fertilizer needs is the relatively long time required to complete a test. On the other hand, some investigators (5) have found that nitrification test values have correlated better with nitrogen supplying power of soils as measured by growing plants in the greenhouse than have chemical test values.

The need for a laboratory method of evaluating the nitrogen status of the irrigated soils of Utah has been recognized for a number of years. This need becomes more keenly felt as the use of the soil test for available phosphorus increases. Until now, past cropping and past fertilizer history and future crop needs have been the main criteria on which to base nitrogen fertilizer recommendations. While these criteria are certainly of value, they are, nevertheless, incomplete; some indication of the present status of the soil nitrogen is needed.

This study was undertaken to develop a new method and to better evaluate present methods of measuring the nitrogen supplying power of the irrigated soils of northern Utah. The alkaline permanganate hydrolyzation as developed by Kresge and Merkle (12), a modification of the alkaline permanganate hydrolyzation, and the incubation method as developed in Iowa (14) along with the total nitrogen and organic carbon were studied in relation to greenhouse results with 111 soil samples collected from the irrigated farm areas of northern Utah. The effects of texture and past crop on the status of the soil nitrogen were also studied.

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