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Studies on the nitrification inhibitor, "nitrapyrin" [2-chloro-6(trichloromethyl) pyridine] in relation to availability and transformation of nitrogen in soil

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Jayatilake, K A K (1988) Studies on the nitrification inhibitor, "nitrapyrin" [2-chloro-6(trichloromethyl) pyridine] in relation to availability and transformation of nitrogen in soil. Research Master thesis, University of Tasmania.

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Abstract

Nitrification inhibitors have been claimed to offer a means of achieving better control
of the delivery of applied fertilizer nitrogen to crops. However, considerable
variability in reported usefulness of nitrification inhibitors indicates a need for further
research on their effectiveness under different agricultural conditions.
A series of experiments was conducted to examine effects of the nitrification
inhibitor nitrapyrin [2-chloro 6-(trichloromethyl) pyridine] on soil N availability and
transformation and the influence of certain factors (soil pH, relative mobility,
temperature etc.,) on its effectiveness.
Because urea is rapidly becoming most favoured on a world scale attention
was focussed on this as a form of fertilizer N. After selecting a suitable soil type a
field experiment was set-up to compare the N supplying capacity of urea to that of
other common commercial N fertilizers and to evaluate N utilization efficiency of a test
crop (barley cv. Triumph). Urea compared unfavourably with ammonium nitrate and
calcium nitrate but was better than ammonium sulphate in terms of plant growth and
yield on the acid soil used thus warranting improvement practices viz. the use of lime
as a soil amendment and/or nitrification inhibitor as a fertilizer amendment.
The effect of liming on certain N transformation processes and on the
effectiveness of "nitrapyrin" was studied in the glasshouse and the _laboratory.
Liming promoted urease activity, nitrification and potential denitrification of soil
whereas nitrapyrin significantly reduced nitrification. Liming reduced the
effectiveness of nitrification inhibition probably because of faster recovery of nitrifiers
in limed soil. The importance of considering the total duration of inhibition in
establishing inhibitor effectiveness was underlined. Nitrapyrin also had a marked
effect on production of nitrous oxide by denitrification.
There was no visible phytotoxic effects of nitrapyrin nor was there any
measurable effect on plant height or top dry matter production of barley during 45
days of growth in the glasshouse. However, liming resulted in better plant growth.
The relative mobility of nitrapyrin compared to urea and ammonium-N may be
a critical factor in determining its effectiveness as an inhibitor. In leaching column
experiments, it was found that most of the added urea moved with the wetting front
while the rest was hydrolysed. Added ammonium-N moved more slowly but at a
sufficent speed to effect separation from nitrapyrin. Nitrapyrin scarcely moved at all.
Measured effects of temperature, soil moisture and air flow on persistence of
nitrapyrin indicated that it is likely to persist longer in cool, moist soils exposed to
minimal air flows.
Nitrapyrin application had little or no effect on the growth of barley (cv.
Triumph) in a field experiment in which, amongst other treatments, a single
application of urea plus nitrapyrin was compared with a split application of the same amount of urea without nitrapyrin. Higher yields were obtained with split application
of urea. Liming enhanced vegetative growth but this was not reflected uniformly in
final yield of dry matter or grain.
In conclusion, although control over nitrification was obtained by use of
nitrapyrin under glasshouse/laboratory conditions its use could not be justified under
field conditions experienced during this study. Field management practices such as
liming and the method of nitrapyrin application may affect the performance of the
inhibitor.

Item Type: Thesis (Research Master)
Keywords: Soils, Nitrification inhibitors, Urea as fertilizer
Copyright Holders: The Author
Copyright Information:

Copyright 1988 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Includes bibliographical references. Thesis (M.Agr.Sc.)--University of Tasmania, 1990

Date Deposited: 19 Dec 2014 02:28
Last Modified: 11 Mar 2016 05:55
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