Abstract
Crop management practices in intensive vegetable production can influence nitrous oxide (N2O) emissions from soils. This study quantified seasonal N2O emissions and N2O emission intensities, and investigated the factors driving emissions in different vegetable management practices. Emissions from four typical vegetable crops (two choy sums, a mustard, and a cabbage) were intensively measured over the 2016 autumn season on farms in Van Noi and Dang Xa communes in the Hanoi peri-urban area. Different N2O emissions were observed in the four leafy vegetable crops. The average daily emissions varied from 12.15 g to 40.08 g N2O-N ha-1 and the autumn season N2O emissions varied from 1.13 kg to 8.45 kg N2O-N ha-1 across the four crops. The greatest daily and season emissions were from cabbage, and the lowest were from mustard. Emission intensities varied among the types of vegetables and was the lowest at the mustard farm (37 kg CO2-e t-1), indicating that the crop management practices increased the mustard yield but retained a low N2O emission rate. Practices responsible for high N2O emissions were overuse of nitrogen fertilisers and furrow irrigation. An improvement in the farmers’ adoption of best practices in fertiliser application and irrigation could reduce N2O emissions without affecting crop productivity.
Highlights
Methane and nitrous oxide have global warming potential indexes relative to carbon dioxide of 25 and 298, respectivelyPreliminary N2O emissions of major vegetable cropping systems in peri-urban Hanoi, Vietnam (IPCC, 2014)
Water filled soil porosity was quite high as there were sufficient water supplies over the season. This facilitated N2O fluxes as these conditions were favourable for active organisms in producing N2O emissions
The seasonal N2O emissions were only 0.65 kg ha-1 with a nitrogen fertiliser rate of 225 kg ha-1 in Japan (Cheng et al, 2002) and 6.30 kg ha-1 with a nitrogen fertiliser rate of 450 kg ha-1 in China (Cao et al, 2006). These results indicated that high N2O emissions are strongly associated with nitrogen application rates in intensive vegetable production
Summary
Preliminary N2O emissions of major vegetable cropping systems in peri-urban Hanoi, Vietnam (IPCC, 2014). Agricultural activities are responsible for 84% of global N2O emissions (Smith, 2008). Vegetable production is estimated to contribute 9.5 107 kg N2O-N yr-1 (Rashti et al, 2015a). Average N2O emissions in subtropical climates have been measured at 1.61.9 kg N ha-1 yr-1, and 0.8-0.9 kg N ha-1 yr-1 in temperate climates (Bouwman et al, 2002; Stehfest & Bouwman, 2006). Vegetable production in the United States has been shown to contribute the highest N2O emissions at the rates of 6.5-8.5 kg N2O-N yr-1 (Mummey et al, 1998). Dryland crops including vegetables account for 30% of total greenhouse gas emissions (mostly N2O) from the agricultural sector in Vietnam (Ministry of Natural Resources and Environment, 2014)
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