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Data Collection
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Cardenas, Laura, Donovan, Neil
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nitrous oxide; ammonium nitrate; application rates; arable land; Winter wheat; sandy soils
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2 November 2016
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4 March 2008 10 March 2009 |
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Devon, South West England, UK
Devon, South West England, UK
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Direct N2O emissions were measured with three static flux chambers (40 cm wide x 40 cm long x 25 cm high) per plot, covering a total surface area of 0.48 m2. The chambers were of white (i.e. reflective) PVC and un-vented with a water-filled channel running around the upper rim of the chamber allowing an air-tight seal to form following chamber enclosure with a lid (Smith et al., 2012). Chambers were pushed into the soil up to a depth of 5 cm and remained in place throughout the experiment, except during fertiliser application, drilling and harvesting when chambers were removed, locations were marked, and chambers were re-instated to the same position as prior to removal. Chambers remained open except for a short time on each sampling day. On that day, ten samples of ambient air were taken to represent time zero (T0) N2O samples. From each chamber, after a 40-minute enclosure period (T40) one headspace sample was taken using a 50-ml syringe and flushed though a pre-evacuated 20-22 ml glass vial fitted with a chloro-butyl rubber septum and held at atmospheric pressure. The N2O flux was calculated using an assumed linear increase in N2O concentration from the ambient N2O concentration (T0) to the N2O concentration inside the chamber after 40-minutes enclosure (T40) (Chadwick et al., 2014). Throughout each experiment, the linearity of emissions through time was checked routinely from two chambers located on the highest N rate plots. A minimum of five samples were taken from each chamber at 15 min intervals commencing at closure i.e. T0 and spanning the T40 sampling time. In order to permit sampling from a growing crop, at the time of sampling an additional chamber was stacked (using the water-filled channel) onto each permanent chamber and the chamber enclosure period extended. In order to minimise the effect of diurnal variation, gas sampling was carried out between 10:00 am and 14:00 pm and where possible between 10:00 am and 12:00 pm as suggested by IAEA (1992) and referred to in the IPCC good practice guidance (IPCC, 2000). Gas samples were analysed as soon as possible after collection (to minimise potential leakage) using gas chromatographs fitted with an electron-capture detector and an automated sample injection system. Following receipt in the laboratory, two replicates of one standard N2O gas were kept with the samples and were used to verify sample integrity during storage. The gas chromatographs were calibrated on a daily basis using certified N2O standard gas mixtures. Following fertiliser application, N2O flux measurements were carried out on the three consecutive days after the onset of fertiliser prill degradation and thereafter following a daily rainfall exceeding 10 mm or every 10-14 days (14-21 days November to March) giving a total of c.50 sampling days over the 12-month sampling period. Prior to the first fertiliser application N2O measurements were taken to provide baseline information. Measurements were taken over 12 months to follow IPCC good practice guidance and so that the results were directly comparable to the IPCC 2006 methodology default emission factor.
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References: Chadwick, D.R., Cardenas, L., Misselbrook, T.H., Smith, K.A., Rees, R.M., Watson, C.J., Mcgeough, K.L., Williams, J.R., Cloy, J.M., Thorman, R.E. and Dhanoa, M.S. (2014). Optimizing chamber methods for measuring nitrous oxide emissions from plot-based agricultural experiments. European Journal of Soil Science 65, 295-307. IAEA (1992). Manual on Measurement of Methane And Nitrous Oxide Emissions from Agriculture. International Atomic Energy Agency (IAEA), Vienna, IAEA-TECDOC-674, ISSN 10111-4289. (IPCC, 2000). Good Practice Guidance And Uncertainty Management in National Greenhouse Gas Inventories. Penman, J., Kruger, D., Galbally, I., Hiraishi, T., Nyenzi, B., Emmanul, S., Buendia, L., Hoppaus, R., Martinsen, T., Meijer, J., Miwa, K. znd Tanabe, K. (Eds). IGES, Japan. Smith, K.A., Dobbie, K.E., 2001. The impact of sampling frequency and sampling times on chamber-based measurements of N2O emissions from fertilized soils. Global Change Biol. 7, 933–945 Smith K.A., Dobbie K.E., Thorman R., Watson C.J., Chadwick D.R., Yamulki S. and Ball B.C. (2012). The effect of N fertilizer forms on nitrous oxide emissions from UK arable land and grassland. Nutrient Cycling in Agroecosystems 93, 127-149.
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Freshwater Biological Assoc
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10.17865/ghgno111
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and Donovan, Neil
(2016)
Experimental determination of nitrous oxide emission factors for arable land. Experimental site in Devon, 2008.
[Data Collection]