Nitrification inhibitors and fertiliser nitrogen application timing strategies to reduce N2O. Site in Devon, 2010

Misselbrook, TomORCID logo, Cardenas, LauraORCID logo, Camp, V. and Donovan, Neil (2017) Nitrification inhibitors and fertiliser nitrogen application timing strategies to reduce N2O. Site in Devon, 2010. [Data Collection]
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At Rothamsted Research, North Wyke, near Okehampton, south-west England (clay loam topsoil texture), direct nitrous oxide (N2O) and ammonia (NH3) emissions were measured from replicated (x3) plots (12 x 13 m) following spring applications of manufactured nitrogen (N) fertilisers to grassland. A control treatment was included where no N fertiliser was applied. Ammonium nitrate (AN) fertiliser (34.5% N) or urea fertiliser (46% N) was applied at a rate of 120 kg N ha-1 in two equal split applications (mid- and late April), with or without the commercially available nitrification inhibitor - dicyandiamide (DCD). The DCD was applied in a solution (15 kg DCD ha-1) and sprayed onto the plots immediately after N fertiliser application. The N supplied by the DCD was accounted for in the 120 kg N ha-1. As separate treatments, AN and urea fertiliser were also applied in four equal splits, 1 week apart from mid-April to early May i.e. 'little and often'. Following N fertiliser application, measurements of direct N2O-N were made over c.12 months, using 5 static chambers (0.8 m2 total surface area) per plot and analysed by gas chromatography. Ammonia-N emissions were measured for 3 weeks after each split N fertiliser application, using a wind tunnel technique (one per plot). Indirect N2O-N emissions were estimated from the measured NH3 losses and using the Intergovernmental Panel on Climate Change (IPCC) default emission factor; namely 1% of volatilised N is lost as N2O-N. Soil moisture (0-10 cm) content and soil mineral nitrogen content (0-10 cm from 2-split AN and control treatments only) were measured at every N2O sampling event, along with continuous measurements of rainfall, air and soil temperatures (5 cm). Grass yields and N offtakes were also measured following the first and second grass cuts in late May and early August 2010. The Devon, 2010 experiment contains data sets of; annual nitrous oxide emission, annual nitrous oxide emission factor, total ammonia loss, soil moisture, top soil mineral nitrogen (selected treatments), temperature, rainfall and associated crop (grass yield and nitrogen offtakes) and soil measurements.
Item Type Data Collection
Creators Misselbrook, Tom, Cardenas, Laura, Camp, V., Donovan, Neil
Keywords nitrous oxide; ammonium nitrate; ammonia; urea; nitrification inhibitors; grassland soils; clay soils
Date 3 February 2017
Temporal coverage
From
To
13 April 2010
15 March 2011
Geographic coverage Devon, South West England, United Kingdom Devon, South West England, United Kingdom
Bounding Area
North Latitude
East Longitude
South Latitude
West Longitude
50.85
-3.75
50.68
-4.04
Data collection method Direct N2O emissions were measured with five static flux chambers (40 cm wide x 40 cm long x 25 cm high) per plot, covering a total surface area of 0.8 m2. The chambers were of white (i.e. reflective) PVC and un-vented with a weighted lid and neoprene seal allowing an air-tight seal to form following chamber enclosure. Chambers were pushed into the soil up to a depth of 5 cm and remained in place throughout the experiment, except during fertiliser application and grass cutting 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) a headspace sample was taken using a 50-ml syringe. Using a double needle system the sample was 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 three chambers located on the highest N rate plots. A minimum of four samples were taken from each chamber at 20 min intervals commencing at closure i.e. T0 and spanning the T40 sampling time. 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, three 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 each fertiliser application, N2O flux measurements were carried out in line with the following sampling schedule until the next fertiliser application or for the final application until the end of the monitoring period; measurements were taken for 5 days immediately following fertiliser application, daily for a further 5 days during the next week, twice weekly for the next two weeks, every other week over the next c. four months, decreasing in frequency to monthly until the end of the 12 month sampling period. Prior to the first fertiliser application N2O measurements were taken to provide baseline information. This sampling schedule resulted in an annual total of c.40 sampling days starting from the day of the first fertiliser application. 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.
Additional information 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.
Publisher Freshwater Biological Assoc
Digital Object Identifier (DOI) 10.17865/ghgno357

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