傳統和優化施氮對春玉米產量、氨揮發及氮平衡的影響

李欠欠， 李雨繁， 高 強， 李世清， 陳新平， 張福鎖， 劉學軍*

(1 中國農業大學資源與環境學院，北京 100193； 2 吉林農業大學資源與環境學院，吉林長春 130118；3 西北農林科技大學水土保持研究所，陜西楊凌 712100)

傳統和優化施氮對春玉米產量、氨揮發及氮平衡的影響

李欠欠1， 李雨繁2， 高 強2， 李世清3， 陳新平1， 張福鎖1， 劉學軍1*

(1 中國農業大學資源與環境學院，北京 100193； 2 吉林農業大學資源與環境學院，吉林長春 130118；3 西北農林科技大學水土保持研究所，陜西楊凌 712100)

春玉米; 產量; 氮肥利用率；氨揮發; 氮平衡

我國氮肥用量占全球氮肥用量的30%左右[1]。氮肥施入農田土壤后，作物吸收利用率普遍低于50%，大部分損失于環境中，氨揮發是氮肥損失的重要途徑之一[2-3]。進入到大氣中的氨可以沉降方式返回陸地、海洋生態系統[4]，過量的氨沉降可引起生態系統酸化、富營養化、降低生物多樣性等一系列問題； 同時，氨作為空氣中二次顆粒物(如PM2.5)來源的重要組成部分，與人體呼吸系統健康也有密切聯系[5-6]。玉米作為我國的三大糧食作物之一，其種植區域主要分布于我國華北、東北以及西北。目前針對玉米體系的田間氨揮發損失已有研究，但主要集中于華北平原[7-10]。針對東北及西北的春玉米體系氨揮發損失研究很少[11-12]，還需進一步系統研究。此外，由于技術及多處理試驗小區面積等限制，微氣象方法(如梯度擴散法、質量平衡法)對土壤氨揮發測定在我國進行較少[13]。目前國內許多氨揮發研究采用的是簡易密閉箱式法[12]、海綿通氣法[14]等，雖然滿足了小尺度多處理田塊上氨揮發監測，但由于無法考慮自然條件下的風速等氣象條件，通常與氨揮發的實際排放量有一定差異。為此，本研究參考Pacholski等的研究[15-17]，結合自然條件下的風速等氣象條件，采用校正的德爾格氨管法(簡稱DTM法)對東北、西北春玉米季的田間氨揮發開展原位測定，評價春玉米體系的土壤氨揮發通量。此外，通過比較傳統和優化施氮條件下土壤氨揮發通量、春玉米產量以及土壤-春玉米作物系統氮素表觀平衡，以期為春玉米體系氮素優化管理、減少氮素損失及提高氮肥利用率等提供科學依據。

1 材料與方法

1.1 試驗點概況

春玉米田間試驗于2011年分別設在兩個典型的北方春玉米種植區域，為西北的陜西省長武縣(CW)和東北的吉林省梨樹縣(LS)。長武縣位于黃土高原渭北旱塬，35°12′N，107°47′E，海拔1184 m，屬暖溫帶半濕潤易旱氣候區，年均氣溫9.1℃，無霜期171 d，土壤類型為黑壚土，2011年春玉米生育期間的降水量為500 mm；東北的吉林省梨樹縣，地處43°18′N，124°20′E，海拔155 m，屬寒溫帶半濕潤大陸性氣候區，年均氣溫5.8℃，無霜期140 d，土壤類型為黑土，2011年春玉米生育期間的平均降水量為340 mm。兩試驗區的土壤基本理化性狀見表1。

表1 供試土壤(0—20cm)基本理化性狀

1.2 試驗設計

兩試驗點均設3個施氮處理，為不施氮對照，傳統施氮(施氮量長武點為N 250 kg/hm2，梨樹點為N 300 kg/hm2)和優化施氮(兩點均為N 200 kg/hm2)，分別以N0、Ncon、Nopt表示。每處理3次重復，小區面積為40 m2，田間完全隨機排列。兩試驗點具體施肥的方法和時間見表2。所有處理磷肥和鉀肥施用量相同，均為P2O560 kg/hm2、鉀肥K2O 60 kg/hm2，在播種時作基肥一次施入。此外，依照長武當地的管理方式，所有處理均采用半膜覆蓋技術，長武點春玉米種植密度為75000 plant/hm2。梨樹點春玉米種植密度為60000 plant/hm2。

玉米品種均為先玉335，春玉米生長季無灌溉，除草、病蟲害防治等田間管理也均采用當地的傳統方式進行。

表2 試驗期間長武、梨樹點的施肥量與施肥時間

注(Note): 除梨樹點播種期氮肥采用15-15-15氮磷鉀復合肥外，其他氮肥均采用尿素Except seeding time’s N application at LS site conducted as NPK(15-15-15) compound fertilizer, and all the other treatments conducted as urea.

1.3 德爾格氨管法(DTM)氨揮發的原位測定方法

圖1 測定氨揮發的DTM試驗裝置示意圖Fig.1 Experimental set-up of DTM for ammonia volatilization

1.4 氨揮發的計算方法

DTM氨揮發原位測定計算公式為

FNg=V·∣conc.∣·10-6·pNH3·UN·UF·UZ

式中: FNg為氨排放量[N mg/(m2·h)]；V為抽氣的體積(L)；∣conc.∣為氨氣的濃度(μl/L)；pNH3為該溫度氣壓下NH3密度(mg/L)；UN為NH3換算為N的分子量換算因子；UF為表面積換算因子(m2)；UZ為時間換算因子(h)。

經過為氣象學方法校正的DTM氨揮發的計算方法為：

冬季 ln(NH3fluxIHF)=0.444·ln(NH3fluxDTM)+0.590·ln(V2m)

夏季 ln(NH3fluxIHF)=0.456·ln(NH3fluxDTM)+0.745·ln(V2m)-0.280·ln(V0.2m)

式中: NH3fluxIHF表示由IHF微氣象法測定的氨揮發量[N kg/(hm2·h)]；V2m與V0.2m分別表示距地面2 m與0.2 m的風速(m/s)；NH3fluxDTM表示 DTM測定的氨揮發量[N kg/(hm2·h)]。

通過DTM進行原位測定，結合氣象數據(以風速為主)，校正為微氣象學(IHF)下的氨揮發通量。由于該監測方法已和IHF微氣象學法進行了校驗，所得結果接近于IHF法，而且具有操作簡便的特點，無需將氨采集后再進行實驗室分析。 因此該方法在進行多個處理的田間氨揮發測定中具有明顯的優勢。有關此DTM法的詳細介紹可參考文獻[13,15-17]。

2 結果與分析

2.1 春玉米產量、吸氮量及氮肥利用率

2.2 春玉米生長季氨揮發的動態變化及累積量

表3 不同施肥處理下長武和梨樹點春玉米產量、吸氮量和氮素利用率

注(Note): 籽粒產量是指包括14%含水量的玉米產量，地上生物量是指籽粒、棒芯和秸稈的干物質總量The grain yield denotes air dry grain yield with 14% moisture and the shoot biomass refers to total dry matter yield of grain, cobs and straw . 氮素利用率(ANR%)=(施肥區氮吸收-對照區氮吸收)/氮肥施用量×100, ANR% =(N uptake in fertilized treatment-N uptake in unfertilized treatment)/N applied in fertilized treatment×100. 同列數據后不同字母表示處理間差異達5%顯著水平 Values followed by different letters in a column are significant among treatments at the 5% level.

圖2 追肥期長武(a)和梨樹(b)春玉米田間氨揮發動態Fig.2 Rate of NH3 losses in Changwu county(a) and Lishu county(b) spring maize field with top-dressing fertilization[注(Note)： 箭頭表示降雨Arrows denote rainfall events.]

圖3 追肥期長武(a)和梨樹(b)春玉米田間氨揮發累積量Fig.3 Cumulative NH3 losses at Changwu county(a) and Lishu county(b) sites during N top-dressing of spring maize

2.3 春玉米生長季的氮素平衡

3 討論與結論

3.1 氮肥的玉米產量效應與節氮潛力

3.2 玉米季的氮肥氨揮發損失特征

表4 不同施肥處理下長武和梨樹春玉米田間氮的表觀平衡

注(Note): 氮礦化=(對照區吸氮量-播前對照區0—1 m土壤無機氮量+收獲后對照區0—1 m土壤無機氮殘留量) N mineralization= N uptake from control-initial 0-1 m soil Nmin in the control + residual 0-1 m soil Nmin in the control

3.3 氮素優化對土壤-玉米體系氮素平衡的影響

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Effect of conventional and optimized nitrogen fertilization on spring maize yield, ammonia volatilization and nitrogen balance in soil-maize system

LI Qian-qian1, LI Yu-fan2, GAO Qiang2, LI Shi-qing2, CHEN Xin-ping1, ZHANG Fu-suo1, LIU Xue-jun1*

(1CollegeofResourceandEnvironmentScience,ChinaAgriculturalUniversity,Beijing100193,China;2CollegeofResourceandEnvironmentScience,JilinAgriculturalUniversity,Changchun130118,China;3InstituteofSoilandWaterConservation,NorthwestA&FUniversity,Yangling712100,China))

【Objectives】 Two field experiments were conducted in spring maize at Changwu county(CW) of Shaanxi province and Lishu county(LS) of Jinlin province, to compare the effects of optimized and conventional N fertilization on crop yield, NH3volatilization, and N balance in soil-spring maize system. The objective of the paper was to quantify the N saving potential and NH3mitigation potential in spring maize under optimization N fertilization. 【Methods】 NH3volatilization was monitoredinsituwith a Dr?ger-Tube Method(DTM), which was corrected by a micrometeorological flux method in previous work. Three N treatments: CK(no N application), Ncon(conventional N fertilizer, N 250 kg/hm2at CW and N 300 kg/hm2at LS) and Nopt(optimized N fertilization, N 200 kg/hm2), were designed at the two sites. 【Results】 Except CK treatment(7.9 t/hm2at CW and 3.8 t/hm2at LS), no significant difference of maize yield between Ncon and Nopt was found at both sites(10.6-10.8 t/hm2at CW and 9.5-9.6 t/hm2at LS). In contrast, apparent N recovery was significantly higher in Nopt(44.3%-44.5%) than in Ncon(33.6%-36.4%). Compared with Ncon, apparent N recovery increased by 8.1 percentage points and 10.7 percentage points in Nopt at CW and LS, respectively. No obvious NH3loss was detected during the basal fertilization period with uniformly incorporated fertilizer into soil, combined with later precipitation at both sites. However substantial NH3volatilization, accounting for 16%-22% of N applied, was found at the two sites during N top-dressing period. Reduced N application of N 30 kg/hm2(CW) and N 100 kg/hm2(LS) could significantly reduce NH3volatilization(N 8 kg/hm2at CW and N 15 kg/hm2at LS). Calculated N balance results showed regional difference for N surplus and apparent N loss between CW and LS sites. For apparent N mineralization, N 97 kg/hm2was observed at CW site, while only N 16 kg/hm2at LS site. The Nopt significantly decreased N surplus N 48-88 kg/hm2compared with Ncon. At CW, about 46% of N surplus was as 0-1 m residual soil N, and 54% of N surplus lost to environment, and NH3volatilization accounted for 15%-30% of total N loss. At LS, about 65% N surplus existed as 0-1 m residual soil N, 35% of N surplus lost to environment, and NH3volatilization accounted for 54%-75% of total N loss. Nearly N 140 kg/hm2of residual soil N in Ncon treatment at LS, while parts of residual soil N may be lost due to N leaching and/or nitrification/denitrification. Compared with Ncon, the Nopt treatment significantly decreased N 30-40 kg/hm2of N loss. The N loss results also showed large amounts of N unaccounted for(other N loss) was not NH3loss but a considerable amount of N leaching, and/or denitrification. 【Conclusions】 Out results reveal that there is a N saving potential of N 50-100 kg/hm2or 20%-33% of conventional N rate in major spring maize production area of China without yield loss but significant less N loss to the environment.

spring maize; grain yield; N recovery; ammonia volatilization; apparent N balance

2014-02-17 接受日期： 2014-05-09

國家自然科學基金項目(41071151) 資助。

李欠欠 (1984—)， 女， 江蘇徐州人， 博士研究生， 主要從事植物營養與肥料方面的研究。E-mail: cute_lq@163.com * 通信作者 E-mail: liu310@cau.edu.cn

S513.062； S153.6+1

A

1008-505X(2015)03-0571-09