Factors affecting nitric oxide and nitrous oxide emissions from ...

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List of Plates Plate 3.1 Schematic of the reaction vessel inside LMA-3D and picture of LMA-3D (Images from: http://www.unisearch-associates.com/luminox.htm)...............................................16 Plate 3.2 Closed gas circuit used for NO flux measurement, showing soil core inside gas sampling Mason jar. ..........................................................................................................20 Plate 7.1 Experimental site used for both summer and winter experiments...................................171 xx
Chapter 1 Introduction Managed pastures occupy 20% of the Earth’s surface (Snaydon, 1981). In New Zealand the managed pasture system is the dominant livestock production system. Nitrogen (N) inputs into grazed pasture systems include biological N fixation, fertiliser and ruminant excreta. When grazing pasture, ruminants partition excreta-N between the faecal and urine pools with approximately 70% of the ingested N being returned to the pasture in the excreted urine. The concentration of ruminant urine ranges widely from approximately 8 to 15 g N L -1 (Whitehead., 1970). The actual N loading in bovine urine patches may range up to 1000 kg N ha -1 (Haynes & Williams, 1993). This is a rate of N that exceeds the immediate requirements of the pasture and subsequently N is lost from the pasture system via several pathways including ammonia volatilization, nitrate leaching and gaseous oxides of N, in the form of nitrous oxide (N2O), nitric oxide (NO) and nitrogen dioxide (NO2), with NOx defined as (NO + NO2). Some of the NO and NO2 in the atmosphere may be converted to nitric acid (HNO3). This ultimately leads to the deposition of nitrate and acidity via acid rain such as soil acidity and eutrophication. Nitrous oxide is a recognized greenhouse gas and, as noted below, it is intricately connected to the mechanisms that produce or consume NO. Thus its measurement is included in this work. The N2O molecule is recognized as a greenhouse gas; its photochemical reactions in the stratosphere have been reported and discussed by Nicolet & Peetermans (1972) and Warneck (1988). The concentration of N2O decreases with altitude in the stratosphere due to the chemical reaction: ( ) 1 N O hv N O D (for wavelengths
Page 1 and 2: Factors affecting nitric oxide and
Page 3 and 4: In experiment two (chapter 5) the o
Page 5 and 6: Acknowledgements I am deeply thankf
Page 7 and 8: Table of Contents Abstract.........
Page 9 and 10: 6.3.7 NOx fluxes...................
Page 11 and 12: List of Tables Table 2-1 Global Inv
Page 13 and 14: Table 7-1 Mean and S.E.M of soil pH
Page 15 and 16: Figure 4.16 Initial soil pH and NH4
Page 17 and 18: Figure 5.29 Q10(5-15 o C) values fo
Page 19: Figure 7.13 Soil N2O-N fluxes over
Page 23 and 24: 2.1 Introduction Chapter 2 Review o
Page 25 and 26: As noted in the introduction N2O is
Page 27 and 28: Figure 2.3 Transformation of minera
Page 29 and 30: 2.5 NOx emissions from urine patche
Page 31 and 32: emissions but not NO. This at odds
Page 33 and 34: 2.6.4 Temperature Soil temperature
Page 35 and 36: 3.1 Introduction Chapter 3 Material
Page 37 and 38: difference. The LMA-3D was also abl
Page 39 and 40: NO 2 reading on LMA-3D (ppbV) 60 50
Page 41 and 42: Concentration (NO-N g m -3 ) 20 18
Page 43 and 44: depth of 7 cm and drying them in th
Page 45: 3.9 Laboratory experiments A Paparu
Page 48 and 49: 4.2 Materials and Methods 4.2.1 Soi
Page 50 and 51: 4.3 Results 4.3.1 Soil NH4 + -N con
Page 52 and 53: NO 2 - -N (g g -1 dry soil) 5 4 3 2
Page 54 and 55: NO x-N Soil pH N 2O-N NH 4 + -N NO
Page 56 and 57: 4.3.3 Soil NO3 - -N concentrations
Page 58 and 59: Table 4-7 Net NH4 + -N depletion an
Page 60 and 61: 4.3.6 Soil surface pH After urine a
Page 62 and 63: When data were pooled over all samp
Page 64 and 65: The NO-N flux was influenced by a s
Page 66 and 67: 4.3.8.1 Net NH4 + -N depletion and
Page 68 and 69: When the mean NO-N flux rate betwee
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4.3.9 N2O fluxes In the absence of
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The cumulative N2O emissions as a p
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µg N 2O-N g -1 soil h -1 0.025 0.0
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concentrations (Tables, 4-2 - 4-5),
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4.4 Regression analysis 4.4.1 Predi
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4.4.2 Prediction of N2O-N When log1
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Soil surface pH increases occurred
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Unlike the NO-N fluxes, which were
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optimum pH was observed for net NO-
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Future work could further examine t
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5.2 Materials and Methods 5.2.1 Tre
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NH 4 + -N (g g -1 dry soil) 1000 80
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NH 4 + -N (g g -1 dry soil) NH 4 +
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NO 2 - -N (g g -1 dry soil) 14 12 1
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NO 2 - -N (g g-1 dry soil) NO 2 - -
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Table 5-3 Pearson correlation betwe
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5.3.3 Soil NO3 - -N concentrations
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NO 3 - -N (g g -1 dry soil) NO 3 -
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Rate of depletion/accumulation (ng
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NH4 + -N:NO 3 - -N ratio 180 160 14
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Surface soil pH 8.0 7.5 7.0 6.5 6.0
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HNO 2 (ng g -1 dry soil) 60 50 40 3
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g NO-N m -2 h -1 140 120 100 80 60
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g NO-N m -2 h -1 50 40 30 20 10 0 2
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Q 10 (15-22 o C) 80 60 40 20 0 11%
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Table 5-9 Mean NO-N flux as a perce
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These treatment effects led to a si
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g N 2O-N m -2 h -1 g N 2 O-N m -2 h
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Temperature Moisture NO-N NH 4 + -N
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Temperature Moisture NO-N NH 4 + -N
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Q 10 (15-22 o C) 100 80 60 40 20 0
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N 2O-N: NO-N 500 400 300 200 100 0
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WFPS (%) 100 80 60 40 20 0 5 10 15
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Table 5-18 The results of multiple
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Table 5-19 The significance of vari
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Table 5-22 The results of multiple
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pool. For example, when averaged ov
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depletion rate, was the soil pH. It
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0.20 g H2O g -1 soil, and temperatu
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the current experimental results. U
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134
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collected from cows at the Lincoln
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NH 4 + -N (g g -1 dry soil) 1200 10
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concentrations increasing at differ
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6.3.4 Net NH4 + -N depletion and NO
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Soil pH 8.0 7.5 7.0 6.5 6.0 5.5 5.0
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6.3.7 NOx fluxes Urine-N applicatio
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Cumulative NO-N (% of urine-N appli
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6.3.7.1 NO-N flux rate as a percent
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6.3.8 N2O fluxes The mean N2O-N flu
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Cumulative N 2 O-N ( % of uine-N ap
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6.3.10 Soil WFPS Soil moisture cont
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Table 6-6 Correlation of log10NO-N
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log 10 NO-N predicted log 10 NO-N p
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6.5 Discussion 6.5.1 Soil inorganic
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The concentrations of HNO2 were thu
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% of NO 2 - -N pool beings turnedov
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6.6 Conclusions Urine-N application
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7.2 Materials and Methods 7.2.1 Fie
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7.2.4 Meteorological data and soil
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7.3.5 Soil ammonium: nitrate ratio
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treatments showed a significant eff
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7.3.7 Theoretical HNO2 concentratio
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7.3.8 Rainfall and Water Filled Por
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7.3.10 NOx fluxes The only gas dete
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7.3.12 N2O-N: NO-N ratio There were
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Table 7-3 Results of multiple regre
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Measured/Predicted NO-N flux 400 30
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The predicted NO-N fluxes were inte
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Table 7-7 Regression coefficients d
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logN 2 O-N 4 3 2 1 0 logN 2 O-N vs
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lowering of the net NH4 + -N deplet
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approximately 6 degrees , NO3 - -N
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204
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8.2 Materials and Method Materials
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8.3.4 Net NH4 + -N depletion rates
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8.3.6 Theoretical HNO2 concentratio
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8.3.8 Soil temperature Mean soil te
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8.3.10 N2O fluxes The N2O-N fluxes
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8.4 Regression analysis 8.4.1 Predi
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The rainfall was regular (after day
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days. This was considerably higher
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to be proportional to the rate of N
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9.7 Future studies The relationshi
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Bronson, K. F., Sparling, G. P., &
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Galbally, I. E. (1989). Factor cont
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Maljanen, M., Martikkala, M., Kopon
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Scholes, M. C., Martin, R., Scholes
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Van Slyke, D. D. (1911). A method f
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