Degree Type

Dissertation

Date of Award

1989

Degree Name

Doctor of Philosophy

Department

Agronomy

First Advisor

M. A. Tabatabai

Abstract

The effect of pH (4, 6, and 8) on nitrogen mineralization was evaluated in three Iowa surface soils treated with crop residues (corn (Zea mays L.), soybean (Glycine max (L.) Merr.), and sorghum (Sorghum vulgare Pers.), or alfalfa (Medicago sativa L.)) and incubated in leaching columns under aerobic conditions at 30°C for 20 weeks. In general, N mineralization was significantly depressed at soil pH 4, compared with pH 6 or 8. The types of crop residues added influenced the pattern and amount of N mineralization.;A study on the effect of 19 trace elements on the nitrate reductase activity of four Iowa surface soils showed that most trace elements inhibited this enzyme in acid and neutral soils. The trace elements Ag(I), Cd(II), Se(IV), As(V), and W(VI) were the most effective inhibitors, with >75% inhibition. Mn(II) was the least effective inhibitor, with aliphatic acids > mineral acids. The results on the effect of these acids on metal release in soils under these conditions, or by sequential extractions, showed that increasing the acid strength from 1 mM to 10 mM resulted in significantly greater amounts of metal release. The amounts of metals released followed the order: Mn > Fe > Al > Zn, with aliphatic acids > aromatic acids > mineral acids.

DOI

https://doi.org/10.31274/rtd-180813-12194

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Minhong Fu

Language

en

Proquest ID

AAI9014898

File Format

application/pdf

File Size

249 pages

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