Nitrogen use efficiency and N<sub>2</sub>O and NH<sub>3</sub> losses attributed to three fertiliser types applied to an intensively managed silage crop

Abstract

Abstract. Three different nitrogen (N) fertiliser types, ammonium nitrate, urea and urea coated with a urease inhibitor (Agrotain®), were applied at standard rates (70 kg N ha−1) to experimental plots in a typical and intensively managed grassland area at the Easter Bush Farm Estate (Scotland). The nitrogen use efficiency of the fertilisers was investigated as well as nitrogen losses in the form of nitrous oxide fluxes (N2O) and ammonia (NH3) during fertilisation events in the 2016 and 2017 growing seasons. Nitrous oxide was measured by the standard static chamber technique and analysed using Bayesian statistics. Ammonia was measured using passive samplers combined with the Flux Interpretation by Dispersion and Exchange over Short Range (FIDES) inverse dispersion model. On average, fertilisation with ammonium nitrate supported the largest yields and had the highest nitrogen use efficiency, but as large spatial and seasonal variation persisted across the plots, yield differences between the three fertiliser types and zero N control were not consistent. Overall, ammonium nitrate treatment was found to increase yields significantly (p value < 0.05) when compared to the urea fertilisers used in this study. Ammonium nitrate was the largest emitter of N2O (0.76 % of applied N), and the urea was the largest emitter of NH3 (16.5 % of applied N). Urea coated with a urease inhibitor did not significantly increase yields when compared to uncoated urea; however, ammonia emissions were only 10 % of the magnitude measured for the uncoated urea, and N2O emissions were only 47 % of the magnitude of those measured for ammonium nitrate fertiliser. This study suggests that urea coated with a urease inhibitor is environmentally the best choice in regards to nitrogen pollution, but because of its larger cost and lack of agronomic benefits, it is not economically attractive when compared to ammonium nitrate.

The impact of atmospheric N deposition and N fertilizer type on soil nitric oxide and nitrous oxide fluxes from agricultural and forest Eutric Regosols

“…This suggests that adding Agrotain® to urea may have some beneficial effect reducing emissions of N 2 O and NO. Similarly, Cowan et al (2019) and Smith et al (2012) found that the use of a urease inhibitor in the field can provide some mitigation of N 2 O emission both in UK crop and grasslands, and Kuang et al (2019) reported reduced N 2 O emissions from a laboratory study using a sandy loam from North West China. This was also concluded in a global meta-analysis evaluating a range of enhanced-efficiency fertilizers, including fertilizers with urease inhibitors (Akiyama et al 2010).…”

“…It is a dry N stabilizer developed by Koch Agronomic Services (2020). A previous study found that the influence of Agrotain® on soil N concentration and N gas emission occurred within approximately two weeks after fertilizer application (Cowan et al 2019).…”

Nitrous oxide emission factors of mineral fertilisers in the UK and Ireland: A Bayesian analysis of 20 years of experimental data

“…farm machinery or by hand). The studies report data collected using the flux chamber approach with the exception of a single study which reports data collected using the eddy covariance method (see Cowan et al, 2019b ). The flux chamber method uses an airtight enclosure placed over the soil which allows for gas emissions from the surface to accumulate (typically 30 to 60 min).…”

“…Some of the EFs in the published studies are calculated by taking a yearly average after several fertiliser applications, while others report emissions for a shorter period after the event (e.g. Skiba et al, 2013 , Cowan et al, 2019a , Cowan et al, 2019b ). The fluxes derived from the data taken from the AEDA archives report EFs for emissions up to 25 days after fertilisation.…”

Ammonium-Based Compound Fertilisers Mitigate Nitrous Oxide Emissions in Temperate Grassland

“…Increasing NUE in fertilisers are associated with a slower release of nutrients by reducing N losses, which is considered to improve yields and mitigate N 2 O emissions [16,17]. Although stabilized fertilisers have been formulated to accomplish high yield and NUE by reducing N losses, many findings showed that the effectiveness of these fertilisers are often influenced by environmental conditions, soil characteristics, and management practices [18][19][20][21][22]. Soil moisture is an important factor affecting the magnitude of N 2 O emissions from fertilised soil by limiting oxygen concentrations in soil [23] and determining the extent of mineral N accumulations [24].…”