Degree Type
Dissertation
Date of Award
1985
Degree Name
Doctor of Philosophy
Department
Agronomy
Abstract
The need for laboratory methods of obtaining an estimate of the amount of nitrogen (N) likely to be made available for crop growth by mineralization of soil organic matter during the growing season has long been evident, and numerous biological and chemical methods have been proposed. However, the methods showing the most promise are too complicated and time-consuming for use in soil testing laboratories, and there is an urgent need for a simple and rapid chemical method of assessing potentially available organic N in soil;Studies reported led to development of two rapid chemical methods of assessing potentially available organic soil N. One involves determination of the NH(,3)-N produced by steam-distilling the soil sample with pH 11.2 phosphate-borate buffer for 8 min. The other involves determination of the NH(,4)('+)-N produced by heating the soil sample with 2 M KCl at 100(DEGREES)C for 4 hours. Both methods are simple and precise, and their results are not significantly affected by air-drying or air-dry storage of the soil sample before analysis. They are well suited for use in soil testing laboratories because they do not require filtration or transfer steps. Studies using 33 Brazilian soils showed that the results obtained by these methods were highly correlated with those obtained by anaerobic and aerobic incubation methods of assessing potentially available organic N in soil;The two chemical methods developed were further evaluated by applying them to 30 Iowa soils and by comparing their results and those obtained by other chemical methods with the results of the aerobic and anaerobic incubation methods considered to be the best laboratory methods thus far proposed for assessment of potentially available organic N in soil. The chemical methods used included the acid KMnO(,4) method, the alkaline KMnO(,4) method, the CaCl(,2)-autoclave method, and the NaHCO(,3) UV method. The data obtained showed that the results of the two chemical methods developed were highly correlated with the results of the incubation techniques used for comparison and that the correlations observed with these two methods were higher than those observed with the previously proposed chemical methods. It is concluded that these two rapid and simple chemical methods are the best chemical methods thus far developed for assessment of potentially available organic N in soil and that they deserve consideration for use in soil testing laboratories.
DOI
https://doi.org/10.31274/rtd-180813-8686
Publisher
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Copyright Owner
Clesio Gianello
Copyright Date
1985
Language
en
Proquest ID
AAI8604465
File Format
application/pdf
File Size
96 pages
Recommended Citation
Gianello, Clesio, "Chemical methods of assessing potentially available organic nitrogen in soil " (1985). Retrospective Theses and Dissertations. 8695.
https://lib.dr.iastate.edu/rtd/8695
Included in
Agricultural Science Commons, Agriculture Commons, Agronomy and Crop Sciences Commons, Chemistry Commons