Comparison of grain yields and N2O emissions on Oxisol and Vertisol soils in response to fertiliser N applied as urea or urea coated with the nitrification inhibitor 3,4-dimethylpyrazole phosphate

Abstract

Abstract. The potential for elevated nitrous oxide (N 2 O) losses is high in subtropical cereal cropping systems in northeast Australia, where the fertiliser nitrogen (N) input is one single application at or before planting. The use of urea coated with the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) has been reported to substantially decrease N 2 O emissions and increase crop yields in humid, high-intensity rainfall environments. However, it is still uncertain whether this product is similarly effective in contrasting soil types in the cropping region of north-east Australia. In this study the grain yield response of sorghum (Sorghum bicolor L. Moench) to rates of fertiliser N applied as urea or urea coated with DMPP were compared in crops grown on a Vertisol and an Oxisol in southern Queensland. Seasonal N 2 O emissions were monitored on selected treatments for the duration of the cropping season and the early stages of a subsequent fallow period using a fully automated high-frequency greenhouse gas measuring system. On each soil the tested treatments included an unfertilised control (0 kg N ha -1 ) and two fertilised treatments chosen on the basis of delivering at least 90% of seasonal potential grain yield (160 and 120 kg N ha -1 on the Vertisol and Oxisol respectively) or at a common (suboptimal) rate at each site (80 kg N ha -1 ). During this study DMPP had a similar impact at both sites, clearly inhibiting nitrification for up to 8 weeks after fertiliser application. Despite the relatively dry seasonal conditions during most of the monitoring period, DMPP was effective in abating N 2 O emissions on both soils and on average reduced seasonal N 2 O emissions by 60% compared with conventional urea at fertiliser N rates equivalent to those producing 90% of site maximum grain yield. The significant abatement of N 2 O emissions observed with DMPP, however, did not translate into significant yield gains or improvements in agronomic efficiencies of fertiliser N use. These results may be due to the relatively dry growing season conditions before the bulk of crop N acquisition, which limited the exposure of fertiliser N to large losses due to leaching and denitrification.

Nitrification inhibitors can increase post-harvest nitrous oxide emissions in an intensive vegetable production system

“…3 ). This is in agreement with the reductive effect of NI reported from cereal cropping systems under similar soil and climatic conditions, where a N 2 O emission reduction ranging from 30–80% has been reported 24 25 26 . It is also within the range of reduction reported for intensively managed vegetable systems 5 15 16 23 27 28 .…”

Effect of enhanced efficiency fertilisers on nitrous oxide emissions in a sub-tropical cereal cropping system

“…3). This is in good agreement with results from studies in other sub-tropical cereal systems in Australia (De Antoni Migliorati et al 2014;Jamali et al 2015;Schwenke et al 2015;De Antoni Migliorati et al 2016) where emission pulses were generally observed after heavy rainfall or irrigation. These emission pulses are typically triggered by the combination of high soil moisture, high availability of NO 3 --N following fertilisation and high soil temperatures.…”

Global Research Alliance N2O chamber methodology guidelines: Considerations for automated flux measurement

“…This unit is based on the original system as described in Breuer et al. (2000) and has been used extensively in Australia (Barton et al., 2008; Barton, Butterbach‐Bahl, Kiese, & Murphy, 2010; De Antoni Migliorati et al., 2015, 2016; De Rosa et al., 2016, 2018; Kiese & Butterbach‐Bahl, 2002; Mumford, Rowlings, Scheer, De Rosa, & Grace, 2019; Rowlings et al., 2012, 2013; 2015; Scheer et al., 2011, 2012, 2014, 2016; Schwenke et al., 2015, 2016; Schwenke & Haigh, 2016; van Delden, Rowlings, Scheer, & Grace, 2016; van Delden, Rowlings, Scheer, De Rosa, & Grace, 2018; Wang, Dalal, Reeves, Butterbach‐Bahl, & Kiese, 2011; Wang et al., 2016) as a key component of the Australian National Agricultural Nitrous Oxide Research Program (NANORP) (Grace, 2016; Grace et al., 2010). The modified system, which we call the “Queensland” system, is now produced by Queensland University of Technology (Brisbane, Australia) in collaboration with Karlsruhe Institute of Technology (Garmisch, Germany) (Figure 2).…”