Abstract
Abstract. A field experiment was designed to study the effects of nitrogen (N) source and urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) or nitrification inhibitor dicyandiamide (DCD) on nitrous oxide (N2O) emission and N use efficiency (NUE) in a sandy loam soil. Six treatments including no N fertilizer (control), N fertilizer urea alone (U), urea plus NBPT (NBPT), urea plus DCD (DCD), urea plus NBPT and DCD (NBPT plus DCD) and nitrate-based fertilizer nitrophosphate (NP) were designed and implemented separately during the wheat growth period. Seasonal cumulative N2O emissions with urea alone amounted to 0.49 ± 0.12 kg N2O-N ha−1 and were significantly (P < 0.05) reduced to 0.28 ± 0.03, 0.31 ± 0.01 and 0.26 ± 0.01 kg N2O-N ha−1 by application of DCD, NBPT and NBPT plus DCD, respectively. Cumulative N2O emissions from NP were 0.28 ± 0.01 kg N2O-N ha−1. A single N2O flux peak was identified following basal fertilization, and DCD and/or NBPT inhibition effects mainly occurred during the peak emission period. The NP application significantly (P < 0.05) increased wheat yield by 12.3% and NUE from 28.8% (urea alone) to 35.9%, while urease and/or nitrification inhibitors showed a slight increase effect. Our results clearly indicated that the application of urea as basal fertilizer, but not as supplemental fertilizer, together with DCD and NBPT is an effective practice to reduce N2O emissions. The application of NP instead of urea would be an optimum agricultural strategy for reducing N2O emissions and increasing crop yield and NUE for wheat cultivation in soils of the North China Plain.
Highlights
Nitrous oxide (N2O) is a potent and long-lived atmospheric greenhouse gas, with an annual increasing rate of 0.26 % over the past few decades and a contribution of 7 % to the annual increase in radiative forcing (IPCC, 2007)
The N use efficiency (NUE) was calculated at 28.8 % for the urea alone treatment and this was slightly increased to 29.2–31.2 % when urea was applied with NBPT, DCD or the combination of NBPT and DCD
Ju et al (2011) obtained a similar result in the North China Plain, finding that emissions of N2O derived from Ca(NO3)2 were lower than those from NH4(SO4)2 during the maize growth season (0.38–0.81 vs. 1.31–3.52 kg N2O-N ha−1)
Summary
Nitrous oxide (N2O) is a potent and long-lived atmospheric greenhouse gas, with an annual increasing rate of 0.26 % over the past few decades and a contribution of 7 % to the annual increase in radiative forcing (IPCC, 2007). Agricultural soils are identified as the major source of atmospheric N2O, contributing 4.1 Tg N yr−1 (IPCC, 2013) to the global atmospheric N2O budget of ∼ 14 Tg N yr−1 (Fowler et al, 2009). Field management practices along with soil and climatic factors are recognized as being determinants of N2O emissions from agricultural soils (Stehfest and Bouwman, 2006; Gagnon et al, 2011). The large inputs of industrially fixed N in agriculture are a major perturbation to terrestrial N cycling and a major contribution to accelerating N2O emissions (Galloway et al, 2008). China is a major agricultural producer (West et al, 2014), and the amount of applied N fertilizer has increased from During the period 1990–2005, agricultural N2O emissions were globally estimated to have increased by 17 % (US EPA, 2006), and are projected to increase by 35–60 % by 2030 due to the continuous increase of global N fertilizer consumption and animal manure production (FAO, 2003).
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