Agricultural Greenhouse Gas Inventory Research Platform - InveN2Ory. Fertiliser experimental site in Bedfordshire, 2011

N - Datasets

Cardenas, L. M., Webster, C. P. and Donovan, N. 2017. Agricultural Greenhouse Gas Inventory Research Platform - InveN2Ory. Fertiliser experimental site in Bedfordshire, 2011. Freshwater Biological Assoc. https://doi.org/10.17865/ghgno613

AuthorsCardenas, L. M., Webster, C. P. and Donovan, N.
Abstract

At the Rothamsted Research Woburn farm near Woburn, east of England (loamy sand topsoil texture), direct nitrous oxide emissions were measured from replicated (x3) plots (10 x 6 m) following spring applications of manufactured nitrogen (N) fertilisers to winter wheat. A control treatment was included where no N fertiliser was applied. Ammonium nitrate (AN) fertiliser (34.5% N) was applied at 5 different rates; 60, 120, 180, 240 and 300 kg N/ha, and urea fertiliser (46% N) at a rate of 180 kg N/ha, in three split applications (mid-March, early-April and early-May). In separate AN and urea treatments, a commercially available nitrification inhibitor was tested; dicyandiamide (DCD) was sprayed at a rate equivalent to 10 kg DCD/ha onto the plots immediately after each N fertiliser application. The N supplied by the DCD was accounted for in the total N application of 180 kg N/ha, which was applied in three splits. A DCD only treatment was also included, where DCD was sprayed onto the soil surface in three split applications giving a total N application of 20 kg/ha. Additionally, AN fertiliser was also applied in five equal splits in mid-March, early-April, late-April, early-May and late-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. Grain yields and total N offtakes were measured following harvest in September 2011. The Bedfordshire, 2011 experiment contains data sets of; annual nitrous oxide emissions, annual nitrous oxide emission factors, soil moisture, top soil mineral nitrogen (selected dates), temperature, rainfall and associated crop (yield, total and grain nitrogen offtakes) and soil measurements.

Year of Publication2017
PublisherFreshwater Biological Assoc
Digital Object Identifier (DOI)https://doi.org/10.17865/ghgno613
Keywordsnitrous oxide
ammonium nitrate
urea
arable land
Winter wheat
sandy soils
Publication dates
Online05 Apr 2017
FunderDepartment of Environment, Food and Rural Affairs
Scottish Government
Welsh Government
Department of Agriculture, Environment and Rural Affairs (DAERA), Northern Ireland
Data files
File Access Level
Open
Data collection period15 Mar 2011 to end of 08 Mar 2012
Geographic location
Bedfordshire, East of England, UK
Geographic region bounding box
(51.92, -.74) to (52.09, -.47)
Geographic coverageBedfordshire, East of England, UK
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 an expanded neoprene rubber strip (Portmere rubber, SO14 5QZ) to form an air-tight seal following chamber enclosure with a lid (Cardenas et al., 2010). 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) a headspace sample was taken using a 50-ml syringe. Using a double needle system the sample was flushed through 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 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, when required and at the time of sampling, an additional chamber was stacked (using the neoprene runner strip as a seal) 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 and not stored for more than 2 days (to minimise potential leakage) using gas chromatographs fitted with an electron-capture detector and an automated sample injection system. The gas chromatographs were calibrated on a daily basis using certified N2O standard gas mixtures. An exchange of samples of chamber air and standard gas mixtures between labs from the different research organisations involved in the InveN2Ory programme of experiments who operated the GCs were carried out, to avoid the possibility of any bias in the results towards high or low values. 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; 2/3 measurements per week immediately following fertiliser application, 2 per week for the next 2 weeks then weekly. Then 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.50 sampling days starting from the day before 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.

Data preparation and processing activities

Nitrous oxide fluxes from the five replicate chambers per plot were averaged. Cumulative fluxes were calculated using the trapezoidal rule to interpolate fluxes between sampling points.

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