Studies on the nitrification inhibitor, \nitrapyrin\" [2-chloro-6(trichloromethyl) pyridine] in relation to availability and transformation of nitrogen in soil"
Creators: name: Jayatilake, K A K
Publisher: name: University Of Tasmania
Year: 2023

description: 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."