王盈盈(1997—),女,安徽阜阳人,硕士研究生,主要从事水稻土氮去向和氮周转研究。E-mail:
我国农田化肥氮用量高,造成较多肥料氮土壤残留,残留肥料氮既可被后季作物吸收利用,也可迁移进入环境。稻麦轮作是我国长江中下游农业区代表性种植制度,然而稻麦轮作农田土壤残留化肥氮的作物后效及去向目前尚不清楚。利用15N示踪长期试验,连续追踪了2004年小麦季施用30%的15N标记尿素后其土壤残留15N在之后17个稻麦轮作年的变化动态及被后季作物吸收利用特征。试验起始小麦季设100 kg·hm–2(N100)和250 kg·hm–2(N250)两个施氮量处理,后续作物均不再施用氮肥。结果发现,34.5%~37.9%施入氮被当季小麦吸收,随后各轮作年稻麦作物吸收残留氮量随年限增加呈指数下降;17年中有12.2%~15.8%残留氮被后季作物吸收,其中,水稻对残留氮吸收能力较强,为9.2%~11.8%,小麦为3.3%~4.0%;观测期内化肥氮累积利用率为50.1%~50.3%。氮肥施入小麦当季,0~20 cm土层残留为22.9%~33.5%,之后逐年减少;17年后降至7.8%~9.8%,但仍占0~100 cm土层氮残留量(9.9%~13.4%)的73.5%~78.5%。同位素质量平衡估算的观测期内氮肥累积总损失率为36.3%~39.9%,与基于当季小麦氮肥利用率和0~20 cm土壤残留率计算得出的当季化肥氮总损失率32.0%~39.2%接近。作物籽粒、秸秆及土壤15N丰度在观测期内均随时间呈指数递减;根据预测结果,不施氮下其降至15N自然丰度背景值仍需28~37年。上述结果表明,稻麦农田化肥氮损失主要发生在当季,土壤残留后效持续时间长,但再迁移进入环境数量低。协同化肥氮当季损失的高效阻控和土壤残留的有效调控应是稻麦农田氮肥优化管理的关键环节。
The high chemical nitrogen (N) fertilizer input in cropland soils of China has caused a large accumulation of residual fertilizer N in the soil in the current-season. This soil-residual fertilizer N can either be absorbed by subsequent season crops or lost to the environment through gaseous and hydrological pathways. The rice-wheat rotation is a dominant vital cropping system in the middle and lower reaches of the Yangtze River agricultural region in China. However, the residual effects and fate of the soil-residual fertilizer N in this cropping system remain unclear.
In this study, a 15N tracer long-term in-situ experiment was used to continuously monitor the fate and the residual effect of soil-residual fertilizer N in the following 17 years under non-fertilizer N application in a rice-wheat cropping system. The experiment had two N fertilizer treatments, with 100 (N100) and 250 (N250) kg·hm–2 of labelled urea (30 atom%) applied in the first wheat season, and no N fertilizer was added in the subsequent 17 years of the rice-wheat rotation.
The results suggested that 34.5%-37.9% of the applied fertilizer N was taken up by the first wheat crop, and then the amount of residual N uptake by the rice and wheat decreased exponentially in the following rice-wheat rotation years. Over the following 17 years, 12.2%-15.8% of the applied fertilizer N was taken up by the subsequent crops (9.2%-11.8% for rice and 3.3%-4.0% for wheat), leading to the accumulative crop N recovery of 50.1%-50.3%, which was significantly higher than the in-season N use efficiency. We found that 22.9%-33.5% of the applied fertilizer N remained in the 0-20 cm soil after in-season wheat was harvested, which was then gradually decreased to 7.8%-9.8% after 17 years, but still accounted for 73.5%-78.5% of the total residual N in the 0-100 cm soil layer (9.9%-13.4%). The cumulative total loss of fertilizer N over the observation period estimated from the isotope mass balance was 36.3%-39.9%, which was close to the total loss of fertilizer N of 32.0%-39.2% calculated based on the N fertilizer use efficiency and the residual rate of 0-20 cm soil in the current season. The 15N abundance of crop grain, straw and soil all decayed exponentially with time during the observation period, which predicted that it would still take 28-37 years for the crop to decrease to the natural 15N abundance background value without N application.
Overall, fertilizer N losses in the rice-wheat cropping system mainly occurred in the current-season, and the residual effects of fertilizer N in soil lasted for a long time, but a negligible amount of this residual N can be lost to the environment. The keyways to optimal N fertilizer management in rice-wheat rotation are effectively reducing in-season fertilizer N losses and better utilizing soil-residual fertilizer N.
水稻-小麦轮作农田是全球重要的农业生产系统,主要分布在东亚和南亚的亚热带和暖温带地区,种植面积约2 400万hm2,对全球粮食安全至关重要[
利用同位素示踪技术,国内外对农田土壤残留化肥氮对作物的有效性研究已有一些报道,但主要集中在旱地作物系统,且大多研究观测时间均不长,主要以后续一季或若干季为主。例如,党廷辉等[
目前,世界范围内较长时间全面追踪残留化肥氮去向方面的研究报道尚不多见。文献仅见欧洲学者Sebilo等[
原状土柱长期定位试验位于江苏常熟农田生态系统国家野外科学观测研究站(31°32′45′′N,120°41′57′′E)。该站地处长江下游平原腹地,属于亚热带北部湿润季风气候区,年平均气温为17℃,年平均降水量为1 211 mm。稻麦轮作是该地区主要种植模式,水稻在6月初种植,10月底收获,小麦在11月初种植,次年5月底收获。
原状土柱长期试验土壤为壤质黄泥土,表层土(0~20 cm)的基本性质为:有机质27.8 g·kg–1,全氮1.31 g·kg–1,pH 6.05,阳离子交换量15.0 cmol·kg–1,为常熟市典型的水稻土类型,占全市水稻土面积约45%。原状土柱长1 m,直径为1.14 m,底部铺有石英沙层并安有封闭底座,共六根埋入稻田。试验始于2003年10月的小麦季,设两个水平施氮处理N100和N250,代表分别施入100 kg·hm–2和250 kg·hm–2的标记尿素(15N丰度为30%),其中30%作为小麦基肥施入,其余40%和30%分别作为小麦分蘖肥和穗肥施入。磷、钾肥用量分别为P2O5 60 kg·hm–2和K2O 120 kg·hm–2,作为基肥一次性与表层土(0~20 cm)混施。第一季小麦于2004年5月收获,之后所有土柱不再施用任何氮肥,后季磷、钾肥用量与第一季施用量一致,照常维持稻麦轮作。田间管理与当地一致。
每季作物成熟后收获地上部分,105℃下杀青30 min,75℃烘干至恒重,分为籽粒与秸秆两部分,称重后全部粉碎过60目筛以测定全氮含量与15N丰度。作物收获后在每个土柱分5点进行S型取样,使用2.3 cm直径土钻取表层0~20 cm的土壤,挑除根系风干后粉碎过100目筛以测定全氮含量及15N丰度。截止目前,共完成35季作物及土壤的观测与分析(2004年小麦至2021小麦)。为了解残留化肥氮在土壤中的分布情况,2021年小麦收获后,使用土钻取0~100 cm的土壤剖面样品,分为0~20 cm、20~40 cm、40~60 cm、60~80 cm和80~100 cm五个土壤深度,挑除根系风干后过100目筛测定全氮含量及15N丰度。样品全氮含量使用碳氮元素分析仪(PRIMACS SNC90-IC-E,Skalar,荷兰)测定;样品15N丰度使用同位素质谱分析联用仪(ZX_2009,Thermo Fisher,德国)测定。
15N原子百分超(APE)/%=样品或15N标记肥料的15N丰度- 15N自然丰度;
作物各器官氮素来自15N标记肥料的百分比(Nitrogen derived from fertilizer,NDFF)
作物各器官氮积累量/(kg·hm–2)=各器官全氮含量/%×各器官干物质量/(kg·hm–2);
作物地上部总氮量/(kg·hm–2)= Σ各器官氮积累量/(kg·hm–2);
作物吸收肥料氮量/(kg·hm–2)= Σ各器官氮积累量/(kg·hm–2)×各器官NDFF/%;
作物吸收土壤氮量/(kg·hm–2)=作物总氮量/(kg·hm–2)–作物吸收肥料氮量/(kg·hm–2);
不同土层土壤干物质量/(kg·hm–2)=取样深度/m×土柱面积/m2×土壤容重/(kg·m–3)×(1–土壤含水率)/10000;
土壤中肥料残留量/(kg·hm–2)=土壤干物质量/(kg·hm–2)×土壤全氮含量(%)×土壤15N APE/%× 100%;
作物回收率/% =作物地上部吸收肥料氮量/第一季施氮量×100;
作物累积回收率/% =作物地上部累积吸收肥料氮量/第一季施氮量×100;
土壤残留率/% =土壤中肥料残留量/第一季施氮量×100;
氮肥损失率/% = 100% – 15N累积回收率– 15N土壤残留率;
所有试验数据结果采用Excel 2019软件进行数据的处理和分析,用Origin 2021软件进行绘图和模型拟合。采用SPSS 26.0统计软件
化肥氮施入后,当季小麦籽粒产量N250处理显著高于N100处理(
稻麦籽粒产量变化
Changes in grain yield of rice and wheat
作物秸秆吸氮量远低于籽粒吸氮量(
稻麦籽粒和秸秆的吸氮量变化
Changes in nitrogen uptake by grains and straws of rice and wheat
作物及土壤中的15N丰度可反映后季作物利用土壤残留化肥氮及其土壤残留动态(
作物籽粒(a)、秸秆(c)和0~20 cm土壤(e)的15N丰度及其拟合模型(b,d,f)
The 15N abundance values(a, c, e)and the fitting model(b, d, f)of grain, straw and 0-20 cm soils in each crop seasons
15N丰度在作物以及土壤中的消减趋势符合指数衰减模型(
N100和N250处理当季小麦氮肥利用率分别为34.5%和37.9%(
每季15N回收率(a)、累积回收率和表层土壤残留率(b)变化
Changes in nitrogen recovery rate(a), cumulative recovery rate and 0-20 cm soil residual rate(b)in each crop seasons
当季小麦收获后,N100和N250处理表层土壤(0~20 cm)化肥残留氮分别为33.5%和22.9%(
2021年麦季结束后,分层采集0~100 cm剖面土壤,分析连续种植35季后化肥氮在土层中的分布特征。由
2021年麦季结束时0~100 cm各土层全氮(a)、土壤15N丰度(b)和残留率(c)比较
Distribution of soil total N content(a), 15N abundance(b)and residual 15N rate(c)in 0-100 cm soil profile in the last season
高低氮处理下,化肥氮施入当季小麦的氮肥回收率为34.5%~37.9%,0~20 cm表层土壤残留率为22.9%~33.5%(
试验期间化肥氮在稻麦轮作系统的总去向
Total fate of fertilizer N in rice-wheat cropping system during the experiment/(% of applied 15N)
处理 |
第1季化肥氮去向 |
后34季残留化肥氮总去向 |
35季化肥氮总去向 |
|||||||
回收率① | 土壤残留率(0~20 cm)② | 残留氮总回收率③ | 土壤残留率(0~20cm)② | 残留氮未知去向④ | 总回收率⑤ | 土壤残留率(0~100 cm)⑥ | 总损失率⑦ | |||
①N recovery rate;②Soil residual rate(0-20 cm);③Total recovery of residual N;④Unaccounted fate of residual N;⑤Total recovery rate;⑥Soil residual rate(0-100 cm);⑦Total loss. | ||||||||||
N100 | 34.5 | 33.5 | 15.8 | 9.8 | 7.9 | 50.3 | 13.4 | 36.3 | ||
N250 | 37.9 | 22.9 | 12.2 | 7.8 | 2.9 | 50.1 | 9.9 | 39.9 |
试验结束时,根据作物累积回收率和0~100 cm土层的残留率可准确计算出化肥氮的总损失。在化肥氮施入后的35个生长季内,氮肥总损失率为36.3%(N100)和39.9%(N250)。该比例与基于当季小麦氮肥回收率和0~20 cm土壤残留率计算得出的当季氮肥总损失率相似(32.0%~39.2%)。
研究结果表明,在试验初期施入的100~250 kg·hm–2 15N标记肥料中,有35%~38%被当季小麦回收利用,这与前人报道[
此外,同一种土壤上不同作物对残留化肥氮的回收率也会存在差异[
试验期间0~20 cm土壤氮素表观平衡估算
Estimation of apparent nitrogen balance in 0-20 cm soil during the experiment period
土壤残留化肥氮对补充和维持土壤有机氮库起着重要作用。结果(
大量研究表明,施入稻田的化肥氮在第一季收获后主要残留在0~20 cm的土壤中,残留量可占总残留量的60%~90%[
基于当季小麦氮肥利用率和0~20 cm土壤残留率,可计算得出当季化肥氮表观损失率为32.0%~ 39.2%,这部分化肥氮可能损失到环境或迁移至深层土壤。本研究结果(
本研究表明,残留化肥氮在后续生长季的损失较少,这与Sebilo等[
在长期不施氮的稻麦轮作农田中,土壤残留化肥氮在后续17年间向后季作物累积贡献了12.2%~15.8%的初始标记氮肥,显著增加了氮肥的累积利用率。土壤残留化肥氮主要被表层土壤(0~20 cm)固持而较少进入深层土壤,即使在施氮17年后,表层土壤残留化肥氮量仍占总残留化肥氮量的73.5%~78.5%。施入的氮肥共有36.3%~39.9%损失至环境中,其中绝大部分损失发生在施肥当季,残留化肥氮在后续作物生长季的损失较小。因此,通过合理的农田管理措施减少氮肥当季损失,保留更多氮于土壤中,可有效提高氮肥累积利用率,提高作物产量。
Nawaz A, Farooq M, Nadeem F, et al. Rice-wheat cropping systems in South Asia: issues, options and opportunities[J]. Crop and Pasture Science, 2019, 70(5): 395-427.
Zhao X, Zhou Y, Wang S Q, et al. Nitrogen balance in a highly fertilized rice-wheat double-cropping system in southern China[J]. Soil Science Society of America Journal, 2012, 76(3): 1068-1078.
Ma S Y, Hou J Y, Wang Y Y, et al. Research progress on efficient utilization of inorganic nitrogen in rice and wheat rotation system[J]. Chinese Journal of Soil Science, 2021, 52(6): 1496-1504.
马尚宇, 侯君佑, 王艳艳, 等. 稻麦轮作系统无机氮肥高效利用研究进展[J]. 土壤通报, 2021, 52(6): 1496-1504.
Li P F, Li X K, Hou W F, et al. Studying the fate and recovery efficiency of controlled release urea in paddy soil using 15N tracer technique[J]. Scientia Agricultura Sinica, 2018, 51(20): 3961-3971.
李鹏飞, 李小坤, 侯文峰, 等. 应用15N示踪技术研究控释尿素在稻田中的去向及利用率[J]. 中国农业科学, 2018, 51(20): 3961-3971.
Fan P F, Liu W M, Yang Y, et al. Quantitative study on nitrogen fate and residual effect of double cropping rice fields in Hunan[J]. Journal of Southern Agriculture, 2021, 52(1): 45-54.
樊鹏飞, 刘伟民, 杨勇, 等. 湖南双季稻田氮素去向及残效定量研究[J]. 南方农业学报, 2021, 52(1): 45-54.
Macdonald A J, Poulton P R, Stockdale E A, et al. The fate of residual 15N-labelled fertilizer in arable soils: its availability to subsequent crops and retention in soil[J]. Plant and Soil, 2002, 246(1): 123-137.
Wang Z H, Li S X, Wang X N, et al. Nitrate nitrogen residue and leaching in dryland soil and influence factors[J]. Soils, 2006, 38(6): 676-681.
王朝辉, 李生秀, 王西娜, 等. 旱地土壤硝态氮残留淋溶及影响因素研究[J]. 土壤, 2006, 38(6): 676-681.
Sebilo M, Mayer B, Nicolardot B, et al. Long-term fate of nitrate fertilizer in agricultural soils[J]. Proceedings of the National Academy of Sciences of the United States of America, 2013, 110(45): 18185-18189.
Dang T H, Cai G X, Guo S L, et al. Study on nitrogen efficiencies of dry land wheat by 15N labeled fertilizer[J]. Acta Agriculturae Nucleatae Sinica, 2003, 17(4): 280-285.
党廷辉, 蔡贵信, 郭胜利, 等. 用15N标记肥料研究旱地冬小麦氮肥利用率与去向[J]. 核农学报, 2003, 17(4): 280-285.
Dong X X, Liu X Y, Ren C L, et al. Fate and residual effect of fertilizer nitrogen under winter wheat-summer maize rotation in North China Plain in meadow cinnamon soils[J]. Scientia Agricultura Sinica, 2012, 45(11): 2209-2216.
董娴娴, 刘新宇, 任翠莲, 等. 潮褐土冬小麦-夏玉米轮作体系氮肥后效及去向研究[J]. 中国农业科学, 2012, 45(11): 2209-2216.
Jia S L, Wang X B, Yang Y M, et al. Fate of labeled urea-15N as basal and topdressing applications in an irrigated wheat-maize rotation system in North China Plain: I winter wheat[J]. Nutrient Cycling in Agroecosystems, 2011, 90(3): 331-346.
Ju X T, Liu X J, Pan J R, et al. Fate of 15N-labeled urea under a winter wheat-summer maize rotation on the North China Plain[J]. Pedosphere, 2007, 17(1): 52-61.
Tian Y H, Yin B, He F Y, et al. Recovery by crop and loss of nitrogen fertilizer applied in rice season in Taihu Lake region[J]. Plant Nutrition and Fertilizer Science, 2009, 15(1): 55-61.
田玉华, 尹斌, 贺发云, 等. 太湖地区水稻季氮肥的作物回收和损失研究[J]. 植物营养与肥料学报, 2009, 15(1): 55-61.
Huang D M, Zhu P L, Gao J H. Residual effects of organic and inorganic fertilizer nitrogen in paddy field and dryland[J]. Science in China Series B, 1982, 12(10): 907-912.
黄东迈, 朱培立, 高家骅. 有机、无机态肥料氮在水田和旱地的残留效应[J]. 中国科学(B辑化学生物学农学医学地学), 1982, 12(10): 907-912.
Ju X T, Pan J R, Liu X J, et al. Study on the fate of nitrogen fertilizer in winter wheat/summer maize rotation system in Beijing suburban[J]. Plant Nutrition and Fertitizer Science, 2003, 9(3): 264-270.
巨晓棠, 潘家荣, 刘学军, 等. 北京郊区冬小麦/夏玉米轮作体系中氮肥去向研究[J]. 植物营养与肥料学报, 2003, 9(3): 264-270.
Hart P B S, Powlson D S, Poulton P R, et al. The avalibility of the nitrogen in the crop residues of winter-wheat to subsequent crops[J]. Journal of Agricultural Science, 1993, 121: 355-362.
Liu X J, Ai Y W, Zhang F S, et al. Crop production, nitrogen recovery and water use efficiency in rice-wheat rotation as affected by non-flooded mulching cultivation(NFMC)[J]. Nutrient Cycling in Agroecosystems, 2005, 71(3): 289-299.
Smith C J, Chalk P M. The residual value of fertiliser N in crop sequences: An appraisal of 60 years of research using 15N tracer[J]. Field Crops Research, 2018, 217: 66-74.
Frick H, Oberson A, Cormann, M. et al. Similar distribution of 15N labeled cattle slurry and mineral fertilizer in soil after one year[J]. Nutrient Cycling in Agroecosystems, 2022, https://doi.org/10.1007/s10705-022-10205-5.
Wang X N, Wang Z H, Li H, et al. Dynamics and availability to crops of residual fertilizer nitrogen in upland soil[J]. Acta Pedologica Sinica, 2016, 53(5): 1202-1212.
王西娜, 王朝辉, 李华, 等. 旱地土壤中残留肥料氮的动向及作物有效性[J]. 土壤学报, 2016, 53(5): 1202-1212.
Yan X Y, Ti C P, Vitousek P, et al. Fertilizer nitrogen recovery efficiencies in crop production systems of China with and without consideration of the residual effect of nitrogen[J]. Environmental Research Letters, 2014, 9(9): 095002.
Ju X T, Xing G X, Chen X P, et al. Reducing environmental risk by improving N management in intensive Chinese agricultural systems[J]. Proceedings of the National Academy of Sciences of the United States of America, 2009, 106(9): 3041-3046.
Xie Y X. Nitrogen originating from environment in paddy ecosystem under anthropogenic influences[D]. Nanjing: Institute of Soil Science, Chinese Academy of Sciences, 2006.
谢迎新. 人为影响下稻田生态系统环境来源氮解析[D] 南京: 中国科学院南京土壤研究所, 2006.
Niu Y, Niu Y, Wang L J, et al. Comparative study on nitrogen and phosphorus characteristics of atmospheric wet deposition in Lake Taihu from 2009 to 2018[J]. Research of Environmental Sciences, 2020, 33(1): 122-129.
牛勇, 牛远, 王琳杰, 等. 2009-2018年太湖大气湿沉降氮磷特征对比研究[J]. 环境科学研究, 2020, 33(1): 122-129.
Cui J, Zhou J, Peng Y, et al. Atmospheric wet deposition of nitrogen and sulfur in the agroecosystem in developing and developed areas of Southeastern China[J]. Atmospheric Environment, 2014, 89: 102-108.
Zhu J X, He N P, Wang Q F, et al. The composition, spatial patterns, and influencing factors of atmospheric wet nitrogen deposition in Chinese terrestrial ecosystems[J]. Science of the Total Environment, 2015, 511: 777-785.
Ti C P, Gao B, Luo Y X, et al. Dry deposition of N has a major impact on surface water quality in the Taihu Lake region in southeast China[J]. Atmospheric Environment, 2018, 190: 1-9.
Chen X, Wang Y H, Ye C, et al. Atmospheric nitrogen deposition associated with the eutrophication of Taihu Lake[J]. Journal of Chemistry, 2018: 4017107.
Xu Z B, Yang Y, Bian L, et al. Dry and wet atmospheric deposition of nitrogen and phosphorus in Taihu Lake[J]. Environmental Monitoring and Forewarning, 2019, 11(4): 37-42.
许志波, 杨仪, 卞莉, 等. 太湖大气氮、磷干湿沉降特征[J]. 环境监控与预警, 2019, 11(4): 37-42.
Zhu Z L, Wen Q X. Soil nitrogen in China[M]. Nanjing: Jiangsu Science and Technology Press, 1992.
朱兆良, 文启孝. 中国土壤氮素[M]. 南京: 江苏科学技术出版社, 1992.
Yang B G, Cai S Y, Liu Y J, et al. Soil nitrogen supply and retention capacity determine the effect and utilization rate of nitrogen fertilizer in paddy field[J]. Acta Pedologica Sinica, 2021, DOI: 10.11766/trxb202104070181.
杨秉庚, 蔡思源, 刘宇娟, 等. 土壤供保氮能力决定稻田氮肥增产效果和利用率[J]. 土壤学报, 2021, DOI: 10.11766/trxb202104070181.
Chen Z M, Wang H Y, Liu X W, et al. The effect of N fertilizer placement on the fate of urea-15N and yield of winter wheat in southeast China[J]. PLoS One, 2016, 11(4): e0153701. .
Yao S H, Zhang B, Hu F, et al. Fate of nitrogen fertilizer in paddy fields different in cultivation history and slope position in a red soil region[J]. Soils, 2007, 39(4): 582-588.
尧水红, 张斌, 胡锋, 等. 不同利用年限不同坡位的红壤水稻田化肥氮去向[J]. 土壤, 2007, 39(4): 582-588.
Yan X Y, Zhou W. Groundwater nitrate removal through denitrification under farmland in Yangtze River Delta[J]. Acta Pedologica Sinica, 2019, 56(2): 350-362.
颜晓元, 周伟. 长江三角洲农田地下水反硝化对硝酸盐的去除作用[J]. 土壤学报, 2019, 56(2): 350-362.
Ju X T. The concept and meanings of nitrogen fertilizer availability ratio-Disscussing misunderstanding of traditional nitrogen use efficiency[J]. Acta Pedologica Sinica, 2014, 51(5): 921-933.
巨晓棠. 氮肥有效率的概念及意义——兼论对传统氮肥利用率的理解误区[J]. 土壤学报, 2014, 51(5): 921-933.
Wang L, Zhao X, Gao J, et al. Effects of fertilizer types on nitrogen and phosphorous loss from rice-wheat rotation system in the Taihu Lake region of China[J]. Agriculture, Ecosystems & Environment, 2019, 285: 106605.
Zhang M, Tian Y H, Zhao M, et al. The assessment of nitrate leaching in a rice-wheat rotation system using an improved agronomic practice aimed to increase rice crop yields[J]. Agriculture, Ecosystems & Environment, 2017, 241: 100-109.
Zhao X, Yan X Y, Xie Y X, et al. Use of nitrogen isotope to determine fertilizer- and soil-derived ammonia volatilization in a rice/wheat rotation system[J]. Journal of Agricutural and Food Chemistry, 2016, 64(15): 3017-3024.