Denitrification-induced nitrogen (N) losses from croplands may be greatly increased by intensive fertilization. However, the accurate quantification of these losses is still challenging due to insufficient available in situ measurements of soil dinitrogen (N2) emissions. We carried out two one-week experiments in a maize–wheat cropping system with calcareous soil using the 15N gas-flux (15NGF) method to measure in situ N2 fluxes following urea application. Applications of 15N-labeled urea (99 atom％, 130–150 kg N ha?1) were followed by irrigation on the 1st, 3rd, and 5th days after fertilization (DAF 1, 3, and 5, respectively). The detection limits of the soil N2 fluxes were 163–1565, 81–485, and 54–281 μg N m?2 h?1 for the two-, four-, and six-hour static chamber enclosures, respectively. The N2 fluxes measured in 120 cases varied between 159 and 2943 (811 on average) μg N m?2 h?1, which were higher than the detection limits, with the exception of only two cases. The N2 fluxes at DAF 3 were significantly higher (by nearly 80％ (P<0.01)) than those at DAF 1 and 5 in the maize experiment, while there were no significant differences among the irrigation times in the wheat experiment. The N2 fluxes and the ratios of nitrous oxide (N2O) to the N2O plus N2 fluxes following urea application to maize were approximately 65％ and 11 times larger, respectively (P<0.01), than those following urea application to wheat. Such differences could be mainly attributed to the higher soil water contents, temperatures, and availability of soil N substrates in the maize experiment than in the wheat experiment. This study suggests that the 15NGF method is sensitive enough to measure in situ N2 fluxes from intensively fertilized croplands with calcareous soils.

LIU Yan;WANG Rui;PAN Zhan-lei;ZHENG Xun-hua;WEI Huan-huan;ZHANG Hong-rui;MEI Bao-ling;QUAN Zhi;FANG Yun-ting;JU Xiao-tang

State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry,Institute of Atmospheric Physics,Chinese Academy of Sciences(CAS),Beijing 100029,P.R.China;College of Earth and Planet Science,University of Chinese Academy of Sciences,Beijing 100049,P.R.China;College of Resources and Environmental Sciences,China Agricultural University,Beijing 100193,P.R.China;School of Ecology and Environment,Inner Mongolia University,Hohhot 010021,P.R.China;CAS Key Laboratory of Forest Ecology and Management,Institute of Applied Ecology,Chinese Academy of Sciences,Shenyang 110164,P.R.China;College of Tropical Crops,Hainan University,Haikou 570228,P.R.China

农业科学学报（英文）

[1]LIU Yan;WANG Rui;PAN Zhan-lei;ZHENG Xun-hua;WEI Huan-huan;ZHANG Hong-rui;MEI Bao-ling;QUAN Zhi;FANG Yun-ting;JU Xiao-tang-.Quantifying in situ N2 fluxes from an intensively managed calcareous soil using the 15N gas-flux method)[J].农业科学学报（英文）,2022(09):2750-2766

15NGF

Quantifying,situ,fluxes,from,intensively,managed,calcareous,using,gas,method,Denitrification,induced,losses,croplands,may,greatly,increased,by,fertilization,However,accurate,quantification,these,still,challenging,due,insufficient,available,measurements,dinitrogen,emissions,We,carried,out,two,one,week,experiments,maize,wheat,cropping,system,following,urea,application,Applications,labeled,atom,were,followed,irrigation,1st,3rd,5th,days,after,DAF,respectively,detection,limits,four,six,hour,static,chamber,enclosures,measured,cases,varied,between,average,which,higher,than,exception,only,significantly,nearly,those,while,there,differences,among,times,ratios,nitrous,oxide,N2O,plus,approximately,larger,Such,could,mainly,attributed,water,contents,temperatures,availability,substrates,This,study,suggests,that,sensitive,enough,fertilized,soils

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