环境科学  2025, Vol. 46 Issue (4): 2621-2628   PDF    
长期施用有机肥和化肥对黑土N2O排放的影响
王昊1,2, 胡荣桂2, 林杉2, 高洪军3, 徐明岗1, 张文菊1, 邬磊1     
1. 中国农业科学院农业资源与农业区划研究所, 北方干旱半干旱耕地高效利用全国重点实验室, 北京 100081;
2. 华中农业大学资源与环境学院, 武汉 430072;
3. 吉林省农业科学院农业资源与环境研究所, 长春 130119
摘要: 东北黑土区作为我国重要的粮食生产基地, 近年来面临着土壤退化、肥力下降和粮食减产等诸多问题.优化施肥管理是维持或提升土壤肥力的一种重要措施, 但不合理的肥料施用会促使养分损失和N2O等温室气体排放, 导致土壤退化和环境污染.为探明黑土N2O排放对长期施用有机肥和化肥的响应及关键控制因素, 采集吉林公主岭黑土长期定位试验(32 a)的施用有机肥主处理(M0, 不施有机肥;M1, 低量有机肥;M2, 高量有机肥)和施用化肥副处理(CK, 不施肥;N, 化学氮肥;NPK, 化学氮磷钾肥)共计9个处理(即每个施用有机肥水平下包含3个化肥施用水平)的表层土壤样品(0~20 cm), 进行室内恒温恒湿培养(65%田间持水量25℃下培养21 d), 并测定N2O排放通量和土壤物理化学生物学性质.研究结果表明, 长期施用有机肥和化肥显著增加了黑土N2O排放.与M0CK处理[(0.25±0.01)mg·kg-1, 以N计, 下同]相比, 单施有机肥处理N2O累计排放量显著提高了361%~456%[M1CK和M2CK处理分别为(1.17±0.02)mg·kg-1和(1.41±0.02)mg·kg-1], 且N2O排放随着有机肥施用量增加显著增强.与M0CK处理相比, 单施化肥处理N2O累计排放量显著提高了96%~236%[M0N和M0NPK处理分别为(0.49±0.01)mg·kg-1和(0.84±0.03)mg·kg-1], 且平衡施用化肥处理N2O排放提升幅度明显高于单施氮肥处理.在M1和M2条件下, 化肥施用对N2O排放的影响程度减弱, 说明有机肥施用缓解了化肥对N2O排放的影响.单施有机肥显著提高了土壤及团聚体有机碳(SOC)和总氮(TN)、土壤微生物量碳氮含量, 有机肥配施进一步提高土壤及团聚体SOC和TN含量.Pearson相关及路径分析结果表明, N2O排放与土壤碳氮组分及微生物量碳氮含量显著正相关, 长期施用有机肥和化肥主要通过影响土壤碳氮组分, 改变微生物量和底物有效性调控N2O排放.综上所述, 施用有机肥通过增加土壤可利用碳氮库以及微生物生物量碳氮显著促进了N2O排放.有机肥施用缓解了化肥对N2O排放的促进作用, 在施用化肥时应适量配施有机肥, 以平衡肥力提升与氮素损失及温室气体排放的综合效应.
关键词: 长期施肥      碳氮组分      N2O      土壤团聚体      偏最小二乘法路径分析模型(PLS-PM)     
Effects of Long-term Application of Organic and Chemical Fertilizers on N2O Emissions from Black Soils
WANG Hao1,2 , HU Rong-gui2 , LIN Shan2 , GAO Hong-jun3 , XU Ming-gang1 , ZHANG Wen-ju1 , WU Lei1     
1. National Key Laboratory of Efficient Utilization of Arid and Semi-arid Farmland in North China, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China;
2. College of Resources and Environment, Huazhong Agricultural University, Wuhan 430072, China;
3. Institute of Agricultural Resources and Environment, Jilin Academy of Agricultural Sciences, Changchun 130119, China
Abstract: As an important grain production area in China, the Northeast Black Soil Region has experienced many problems, such as soil degradation, fertility decline, and grain yield reduction, in recent years. Optimizing fertilizer management is an important measure to maintain and enhance soil fertility. However, improper fertilizer application could aggravate nutrient losses and greenhouse gas N2O emissions, thus leading to soil degradation and environmental pollution. The objectives of the present study were to investigate the response of N2O emission from black soil to long-term application of organic and chemical fertilizers and the key controlling factors. Soil samples (0-20 cm) were collected from a total of nine treatments, including organic fertilizer as the primary treatment (M0- no organic fertilizer; M1- low organic fertilizer; M2- high organic fertilizer) and chemical fertilizer as the secondary treatment (CK- no fertilizer; N- chemical nitrogen fertilizer; NPK- chemical nitrogen, phosphorus, and potassium fertilizer), in a long-term experiment (32 years) on the black soil of Gongzhuling, Jilin Province. The soil samples were incubated at 25℃ with 65% field water holding capacity for 21 days, and N2O emission and soil physico-chemical biological properties were determined. The results showed that long-term application of organic and chemical fertilizers notably increased N2O emissions from black soil. Compared to those from the M0CK treatment [(0.25±0.01) mg·kg-1, in terms of N, the same as below], the cumulative N2O emissions from the only organic fertilizer treatment significantly increased by 361%-456% [(1.17±0.02) mg·kg-1 and (1.41±0.02) mg·kg-1 for the M1CK and M2CK treatments, respectively]. Furthermore, the N2O emissions strongly increased with increasing organic fertilizer application amounts. Cumulative N2O emissions were significantly higher in the chemical fertilizer treatments by 96%-236% [(0.49±0.01) mg·kg-1 and (0.84±0.03) mg·kg-1 for the M0N and M0NPK treatments, respectively] compared to those in the M0CK treatments. Moreover, the increased N2O emissions due to fertilizers application were significantly larger in the M0NPK relative to M0N treatments. The positive effects of chemical fertilizer application on N2O emission decreased under organic fertilizer amendments (M1 and M2), indicating that organic fertilizer application alleviated increased N2O emission because of chemical fertilization. The application of organic fertilizers significantly increased bulk soil, aggregate organic carbon (SOC), total nitrogen (TN), and soil microbial carbon and nitrogen contents. The application of organic combined with chemical fertilizers further increased SOC and TN contents in bulk soil and aggregates. Pearson correlation and path model analyses showed that the N2O emission was positively correlated with soil carbon and nitrogen fractions and microbial carbon and nitrogen contents among organic and chemical fertilizer treatments. Long-term application of organic and chemical fertilizers strongly regulated N2O emissions via affecting the distribution of carbon and nitrogen contents in soil fractions and changing microbial biomass and substrate availability. In conclusion, the application of organic fertilizers could significantly facilitate N2O emission by increasing the available soil carbon and nitrogen pools as well as microbial carbon and nitrogen contents. The application of organic fertilizers mitigated the positive effects of chemical fertilizers on N2O emissions. Appropriate amounts of organic fertilizers should be used when applying chemical fertilizers, in order to balance the comprehensive effects of fertility improvement with nitrogen loss and greenhouse gas emissions.
Key words: long-term fertilizer application      carbon and nitrogen fractions      N2O      soil aggregates      partial least squares path modeling(PLS-PM)     

我国东北黑土区土壤质地疏松、肥力和生产力高, 是重要的商品粮基地, 素有“粮仓”之称, 粮食商品率高达60%以上, 为全国提供1/3的商品粮[1].然而, 高强度黑土地利用和大量肥料施用在增加粮食产量的同时, 也加速了养分流失和温室气体排放等, 引起水体污染和全球气候变化等一系列环境问题.N2O是仅次于CO2和CH4的第三大温室气体, 百年增温潜势是CO2的298倍[2].农田土壤是N2O的重要排放源, 对全球N2O排放的贡献率为60%左右[3]. 因此, 如何提高氮肥利用率以及减少N2O排放一直备受关注[4].

长期施肥改变土壤生物化学性质, 从而影响N2O排放.土壤N2O一般是由微生物硝化和反硝化过程产生[5, 6]. 硝化过程是在有氧环境中微生物通过合成氨单加氧酶和羟胺酶将氨氧化为NO2--N或NO3--N, 并伴随N2O产生[7].反硝化过程是在缺氧条件下, NO3-作为电子受体在一系列反硝化酶作用下最终还原为N2O和N2[8].黑土土壤有机碳和氮磷养分含量高, 有利于促进硝化和反硝化过程进行[9].肥料种类、用量、施肥方式以及施肥时间都会影响土壤N2O排放.一般情况下, 土壤N2O排放量随氮肥用量的增加而增加[10]. 在农业管理过程中, 有机肥替代化肥被视为一种提高土壤肥力和缓解环境恶化的可持续措施[11].董玉红等[12]采用不同种类肥料进行田间试验发现, 与单纯施用化肥相比, 化肥配合有机肥施用促进N2O排放, 而秸秆还田降低了N2O排放.陈哲等[13]研究表明有机肥与化肥配施处理N2O累计排放量显著高于单施化肥处理, 主要原因是有机肥施用维持了土壤NH4+-N持续供给, 进而增加N2O排放.Ding等[14]通过田间试验, 发现有机肥代替化学氮肥施用有效降低了农田N2O排放. Shang等[15]分析表明, 2004~2014年我国农业土壤N2O年排放量增幅比1990至2003年显著减缓, 但黑土区N2O排放却呈现明显增加趋势[16].近阶段东北地区正积极展开一系列举措, 以提高土壤碳储量.然而最新研究发现, 土壤固碳的气候缓解作用可能随着N2O排放增加而减弱[17].

现阶段对黑土N2O排放的主要影响因素研究大多集中在土壤不同温度[18]和水分条件下[19], 而不同长期施肥下黑土N2O排放的响应规律及其关键控制因素仍然不清楚. 为明确长期不同施肥措施下黑土N2O排放特征, 本研究依托吉林公主岭黑土长期定位试验平台, 结合室内控制实验, 分析长期施用有机肥和化肥条件下黑土N2O排放特征及土壤物理化学生物学性质, 阐明黑土N2O排放对长期施用有机肥和化肥的响应关系, 以期为黑土固碳减排措施制定和农业可持续发展提供理论依据.

1 材料与方法 1.1 定位试验和样品采集

本研究土壤样品采自国家黑土肥力与肥料效益监测基地, 本试验点位于吉林省公主岭市(东经124°48′34″, 北纬43°30′23″).本试验始建于1980年.试验基地地势平坦, 海拔220 m, 年均气温4~5℃, 无霜期125~140 d, 有效积温2 600~3 000℃, 年降水量450~600 mm, 年蒸发量1 200~1 600 mm, 年日照时数2 500~2 700 h.土壤类型为典型的中层黑土, 种植制度为一年一熟玉米作物.本试验开始时土壤的基本性质如下:ω(有机碳)为16.12 g·kg-1ω(全氮)为1.90 g·kg-1ω(全磷)为1.39 g·kg-1ω(全钾)为22.1 g·kg-1ω(速效磷)为27.0 mg·kg-1ω(速效钾)为190 mg·kg-1ω(碱解氮)为114 mg·kg-1和pH值为7.6.

本长期试验为裂区设计, 小区按照国家土壤肥力长期定位试验监测标准统一设置, 每个试验小区面积为100 m2(20 m×5 m), 无重复, 随机排列.本研究选取其中3个主处理[不同有机肥(猪粪)施用量]以及每个主处理下设置3个副处理(化肥配施)共计9个处理. 3个有机肥施用水平分别为不施有机肥(M0);年施有机肥30 t·hm-2(M1, 低量有机肥水平);年施有机肥60 t·hm-2(M2, 高量有机肥水平).副处理为不施化肥对照(CK);施N 150 kg·hm-2(N);施N 150 kg·hm-2、P2O5 75 kg·hm-2和K2O 75 kg·hm-2(NPK)(见表 1).有机肥作底肥, 磷、钾和1/3氮肥作基肥随播种同时施入, 其余2/3氮肥于拔节期追施.有机肥中有机碳含量为9%~13%, 全氮含量为0.66%~0.87%.于2012年11月玉米收获后, 采集各处理小区表层土壤(0~20 cm).在每个小区采用“S”形布点, 随机取8点充分混合作为1份样品, 各小区采集3组平行样品.土样样品预处理完成后混匀分为3份.取2份通过10目筛网, 其中1份低温冰箱内储存用于测定土壤微生物量碳氮、可溶性碳氮和团聚体组成, 另1份用于室内培养.一份土样室内风干后分别过100目筛网, 用于测定土壤有机质和全氮含量.

表 1 不同施肥处理下化肥和有机肥年施用量 Table 1 Annual application amounts of chemical and organic fertilizers under different fertilizer treatments

1.2 室内培养实验

室内培养实验土壤样品采自上述监测基地, 采用室内密闭培养法测定N2O排放通量.称取100 g土壤样品置于500 mL培养瓶中, 利用去离子水将土壤水分调节为60%田间持水量, 在25℃条件下预培养7 d.预培养结束后, 利用配有气体采样的橡胶塞密封培养瓶瓶口, 继续保持60%田间持水量在同温下培养21 d, 使用注射器在顶部采气, 每次采气均需多次推拉以混匀气体. 共采集13次(依次为培养实验进行的第1、2、5、6、7、8、9、12、16、17、18、20和21 d).整个培养期内均需维持土壤含水量为60%田间持水量, 每个处理设置3个重复.气体采集后使用气相色谱仪(Agilent 7890A, Agilent Ltd., USA)分析气体样品浓度, 通过气体的浓度随密闭时间变化计算N2O排放通量.

N2O排放通量和累计排放量的计算公式[20]如下:

式中, F为N2O排放通量[以N计, mg·(kg·d)-1];ρ为标准状态下N2O-N的密度;V为培养瓶中气体的有效空间体积(m3);W为培养瓶内的烘干土重(kg);T为培养温度(℃);ΔCt为在特定时间内气体浓度变化速率;α为N2O换算到N的转化因子;E为N2O累计排放量(mg·kg-1);ti+1-ti为第ii+1次采样的时间间隔(d);n为观测期间总测定次数.

1.3 土壤生物化学性质测定

土壤有机碳(SOC)采用重铬酸钾外加热法[21]测定:称取过0.15 mm孔径筛的风干土样0.10~0.50 g于试管中, 加入5 mL 0.80 mol·L-1的K2CrO7, 再加入5 mL浓H2SO4, 充分摇匀, 放入升温至185~190℃的油浴锅中, 控制温度为170~180℃, 待试管中液体沸腾发生气泡时开始计时, 煮沸5 min, 拿出试管, 冷却后将试管内混合液倒入250 mL容量瓶中, 用0.2 mol·L-1 Fe2SO4滴定.采用元素分析仪(EA3000)测定土样全氮含量[22].土壤微生物量碳(SMBC)和氮(SMBN)采用氯仿熏蒸K2SO4浸提法[23]测定:土样熏蒸后用50 mL 0.5 mol·L-1的K2SO4振荡浸提30 min.将混合液过滤, 用TOC分析仪(Multi N/C 3100)测定, 熏蒸组碳、氮与未熏蒸组碳、氮的差值分别除以系数0.45和0.54即为土样微生物生物量碳、氮含量.未熏蒸组的浸提的碳、氮含量即为土壤可溶性碳、氮.

土壤团聚体分级采用干筛法, 具体步骤如下:称取20 g过2 mm筛的新鲜土壤样品放在250 μm和53 μm的套筛上, 底部放有托盘, 置于干筛振动仪分离30 min, 分离后计算各粒级百分数.采用重铬酸钾外加热法和元素分析仪(EA3000)分别测定各粒径团聚体中SOC和TN含量.

1.4 数据处理

本文所用数据使用Origin Pro 2021制图.使用SPSS 22.0进行数据分析, 单因素方差分析(One-way ANOVA)基于LSD法检验不同处理之间差异性(LSD, α=0.05), 通过Pearson相关性分析N2O排放与土壤性质的相关性, 使用Smart PLS 3.0进行偏最小二乘法路径分析(PLS-PM).图中数据均为平均值±标准差.

2 结果与分析 2.1 有机肥和化肥施用对黑土N2O排放的影响

有机肥和化肥施用及其交互作用显著影响黑土N2O排放(图 1).相较于M0CK处理, 单施有机肥处理N2O累计排放量显著提高了361%~456%[M1CK和M2CK处理N2O累计排放量分别为(1.17±0.02)mg·kg-1和(1.41±0.02)mg·kg-1].N2O排放随着有机肥施用量增加显著增强(图 1).在不添加有机肥(M0)条件下, 与CK处理相比[0.25±0.01)mg·kg-1], 施化肥处理N2O累计排放量显著提高了96%~236%[N和NPK处理分别为(0.49±0.01)mg·kg-1和(0.84±0.03)mg·kg-1].在配施低量有机肥(M1)条件下, 不同化肥处理间N2O累计排放量差异减小, 但NPK处理显著高于CK处理.而在配施高量有机肥(M2)条件下, CK处理与施用化肥处理间无显著差异.施用有机肥后, 化肥施用对N2O排放的影响减弱, 说明有机肥施用缓解了化肥对黑土N2O排放的促进作用.

M0、M1和M2分别表示不施有机肥、施用低量和高量有机肥;不同小写字母表示同一有机肥处理下不同化肥处理的差异性(P < 0.05), 不同大写字母表示不同有机肥处理的差异性(P < 0.05) 图 1 施用有机肥和化肥对黑土N2O排放的影响 Fig. 1 Effects of organic and chemical fertilizer application on N2O emission from black soil

2.2 有机肥和化肥施用对黑土化学生物学性质的影响

有机肥、化肥以及两者的交互作用均显著影响土壤团聚体SOC和TN含量(图 2).相较于M0CK处理[ω(SOC)为(17.48±0.69)g·kg-1], 单施有机肥处理[M1CK和M2CK的ω(SOC)分别为(26.25±0.81)g·kg-1和(30.87±0.51)g·kg-1], 原状土SOC含量提高50%~77%, 3种粒径团聚体(< 0.053、0.035~0.25和0.25~2 mm)分别提高了21%~57%、48%~86%和67%~102%[图 2(a)].单施化肥处理间原状土ω(SOC)无显著差异[M0N和M0NPK的分别为(17.7±0.07)g·kg-1和(18.12±0.08)g·kg-1].配施有机肥提高了SOC含量, 且随有机肥施用量增加而增加. 单施有机肥显著提升原状土和3种粒径团聚体TN含量[图 2(b)].相较于对照组, 单独施用化肥对土壤TN的提升作用不明显.有机肥显著影响土壤C/N[图 2(c)].

不同小写字母表示同一粒径下各处理间的差异性(P < 0.05) 图 2 施用有机肥和化肥对土壤团聚体有机碳(SOC)、全氮(TN)和碳氮比(C/N)的影响 Fig. 2 Effects of organic and chemical fertilizer application on soil organic carbon (SOC), total nitrogen (TN), and carbon to nitrogen ratio (C/N) in aggregate fractions

有机肥和化肥施用及其交互作用均显著影响了土壤DOC、DON、MBC和MBN等生物化学性质(图 3).与不施有机肥处理相比, 单施低量和高量有机肥处理DOC含量提高了181%~301%[图 3(a)].单施N和NPK处理DOC含量相较于CK处理提高了26%~47%.各有机肥配施下DON含量均表现为:NPK > N > CK[图 3(b)].与M0CK相比, 单施低量和高量有机肥处理DOC含量显著提高了345%~630% [M1CK和M2CK的ω(DOC)分别为(37.99±0.68)mg·kg-1和(62.3±2.6)mg·kg-1], MBC含量提高了40%~93%[M1CK和M2CK的ω(MBC)分别为(376.11±8.25)mg·kg-1和(519.19±6.56)mg·kg-1] [图 3(c)].化肥施用对土壤MBC含量无显著影响.在不施有机肥(M0)条件下, CK、N和NPK处理间MBN含量无显著差异, 配施有机肥后, 3组处理出现了显著性差异[图 3(d)].与M0CK相比, M2CK处理的MBN含量[(79.43±5.03)mg·kg-1]提高了64%.有机肥施用显著提高了土壤NH4+-N和NO3--N含量.

不同小写字母表示同一有机肥处理下不同化肥处理间的差异性(P < 0.05), 不同大写字母表示不同有机肥处理间的差异性(P < 0.05) 图 3 施用有机肥和化肥对土壤可溶性有机碳(DOC)、可溶性有机氮(DON)、微生物生物量碳(MBC)、微生物生物量氮(MBN)、铵态氮(NH4+-N)和硝态氮(NO3--N)的影响 Fig. 3 Effects of organic and chemical fertilizer application on dissolved organic carbon (DOC), dissolved organic nitrogen (DON), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), ammonium (NH4+-N), and nitrate (NO3--N) in bulk soil

2.3 N2O排放与土壤化学生物学性质的关系

相关性分析结果表明, 不同有机肥和化肥处理下N2O累计排放量与土壤碳氮组分及微生物量碳氮含量均显著正相关(图 4).路径分析模型解释了79%的N2O排放变化(图 5).施肥引起的土壤碳氮组分和微生物量含量增加显著促进了N2O排放(P < 0.05).微生物生物量碳含量是N2O排放的主要影响因素(路径系数为0.635).有机肥和化肥施用通过引起土壤碳氮组分含量变化调控N2O排放.土壤碳组分通过影响土壤氮组分变化调控N2O排放(路径系数分别为0.985和0.431, P < 0.05), 也通过影响微生物碳含量进而调控N2O排放(路径系数分别为0.888和0.635, P < 0.05).

1.SOC原状土, 2.SOC < 0.053 mm, 3.SOC0.053~0.25 mm, 4.SOC0.25~2 mm, 5.DOC, 6.TN原状土, 7.TN < 0.053 mm, 8.TN0.053~0.25 mm, 9.TN0.25~2 mm, 10.DON, 11.NH4+-N, 12.NO3--N, 13.MBC, 14.MBN;黑色和红色表示原状土和3种粒径下的碳组分和氮组分, 绿色表示原状土的MBC和MBN;扇形大小表示各指标与N2O排放的相关性, 0.0~1.0为相关性系数大小;*、**和***分别表示在P < 0.05、P < 0.01和P < 0.001水平显著相关 图 4 N2O与土壤生物化学性质之间的关系 Fig. 4 Relationship between N2O emission and soil biochemical properties

单个箭头表示一个变量对另一个变量的直接影响;箭头上的数字为标准化路径系数, 虚线箭头表示不显著, 箭头粗细表示路径系数大小;*表示P < 0.05, ***表示P < 0.001 图 5 基于路径模型分析N2O排放的主要控制因素 Fig. 5 Main controlling factors of N2O emission analyzed using the path model

3 讨论 3.1 有机肥和化肥施用对黑土N2O排放的影响

施用有机肥和化肥及其交互作用均显著影响黑土N2O排放.本研究中M2CK处理N2O累计排放量是M1CK处理的1.2倍, M0CK处理的5.6倍(图 1). M2CK处理的SOC、TN、DON和DOC都显著高于M1CK和M0CK处理. 有机肥料中含有大量碳氮, 施入土中后刺激了参与硝化和反硝化过程的微生物呼吸和代谢过程[24, 25], 降低了土壤含氧量, 为反硝化过程提供了厌氧环境, 促进反硝化介导的N2O产生[26].本研究中M2CK处理MBC、MBN含量和N2O排放显著高于其他处理.随着有机肥施用量增加, 可利用的碳氮增加, 微生物活性增强[27, 28].土壤氮素作为微生物硝化和反硝化过程的底物, 氮肥施用会促进硝化和反硝化过程及N2O排放[29], 这解释了本研究中随着有机肥施用量增加, N2O排放增强.

施用化肥处理N2O累计排放量显著高于CK处理且表现为:NPK > N > CK, NPK和N处理TN和DON含量高于CK处理.大量研究表明, 施用氮肥是土壤N2O排放最直接的影响因素[30].施用氮肥提高了矿质氮含量, 微生物可直接利用化肥提供的矿质氮, 从而显著增加土壤N2O排放[31].平衡施肥DON含量高于CK与N处理, 这是因为增加了作物产量, 使得进入土壤的根系残叶等增加, 从而提高了土壤微生物活性, 增加了N2O排放[32].也有研究表明当肥料施用提供的氮素量超过作物和土壤微生物的需求时, 多余的氮也可能通过硝化和反硝化过程产生N2O, 进而导致了大量的N2O排放[33].

配施有机肥处理进一步促进了N2O排放.配施有机肥处理MBC含量与DOC含量高于其余处理.微生物可以代谢被矿化和硝化的氮素[34], 化肥和有机肥中的氮都能为硝化作用提供氮底物, 缓解了微生物氮限制[35], 增强了N2O排放.本研究中配施有机肥显著提高了土壤C/N, 促进了微生物硝化作用, NH4+-N和NO3--N升高, 土壤N2O排放增加. Yang等[36]的研究表明, 与单施猪粪相比, 有机肥与化肥混合施用在施肥后短时间内显著提高反硝化和N2O排放速率, 这与本研究结果一致.此外, 唐占明等[37]基于田间试验认为NH4+-N和NO3--N含量与N2O排放有关, 这与本研究发现的N2O排放只与NH4+-N含量有关, 与NO3--N含量无关有所差异. 这是因为在田间条件下, 施肥会影响表层土壤的水热条件使得环境因子变化从而导致结果产生差异.也有室内培养实验表明, 配施有机肥后NH4+-N含量是影响N2O排放的主要因素, 这与本研究的结果相同[38, 39].

3.2 黑土N2O排放的主要控制因素

Pearson分析结果表明, 不同施肥处理间黑土N2O累计排放量与土壤碳氮组分及微生物生物量碳氮显著正相关(图 4).N2O排放与原状土及团聚体SOC均呈现极显著相关关系, 这主要是因为土壤有机质为硝化作用和反硝化作用提供了反应底物, 是调控N2O排放的重要因子[40].路径分析模型结果进一步表明土壤碳组分含量通过影响氮组分和MBC进而调控N2O排放(图 5). 土壤有机质在分解过程中不仅能为土壤硝化和反硝化微生物提供氮源, 而且还能为微生物代谢活动提供能量来源.如果C/N比过大, 会导致其分解过程中微生物吸收同化无机氮, 使土壤中的无机氮含量下降, 降低硝化速率, 减少N2O排放[41].本研究长期施肥土壤中N2O排放与DOC和DON含量显著相关, 两者直接或间接影响了N2O排放.DOC作为微生物呼吸底物消耗土壤孔隙中的O2, 在土壤局部形成厌氧微域, 有利于反硝化作用介导的N2O产生过程[42]. NO3-、NO2-和NH4+等氮组分可以被微生物利用产生N2O[43].MBC和MBN含量高一定程度上代表了参与硝化和反硝化的微生物较多[44].相关性和路径分析模型表明N2O排放与MBC和MBN也显著相关, 较高的MBC显著促进N2O排放, 这与朱津宏等[45]研究的结果一致.

本研究是基于室内培养实验进行, 仍需基于田间定位试验进一步研究长期施用有机肥和化肥如何影响N2O排放.今后研究应拓展不同田间管理措施结合不同环境因子(如温度和水分)进行田间试验, 以明确长期施用有机肥和化肥对土壤养分及N2O排放的长期影响及其调控机制.

4 结论

(1)长期施用有机肥和化肥显著增加了黑土N2O排放.配施有机肥减弱了化肥对N2O排放的促进作用.在施用化肥时应适量配施有机肥, 以平衡肥力提升与氮素损失及温室气体排放的综合效应.

(2)在长期施肥条件下, 土壤碳氮组分和微生物生物量碳含量是影响N2O排放的主要因素, 长期施用有机肥和化肥主要通过影响土壤可利用碳氮库和微生物活性, 调控黑土N2O排放.

参考文献
[1] 李发东, 岳泽伟. 加强东北黑土地保护, 实现粮食安全与固碳增汇协同发展[J]. 中国发展, 2021, 21(6): 66-70.
Li F D, Yue Z W. Strengthening the protection of black land in northeast China and realizing coordinated development of food security and carbon sequestrationand carbon sink increase[J]. China Development, 2021, 21(6): 66-70.
[2] 宋毅, 张璐, 韩天富, 等. 长期施肥下红壤玉米关键生育期氧化亚氮排放差异及其影响因素[J]. 植物营养与肥料学报, 2023, 29(10): 1794-1804.
Song Y, Zhang L, Han T F, et al. Red soil N2O emission difference caused by fertilizers and other factors at the key growth stages of maize[J]. Journal of Plant Nutrition and Fertilizers, 2023, 29(10): 1794-1804. DOI:10.11674/zwyf.2023082
[3] Ding T, Ning Y D, Zhang Y. Estimation of greenhouse gas emissions in China 1990-2013[J]. Greenhouse Gases: Science and Technology, 2017, 7(6): 1097-1115.
[4] 颜晓元, 夏龙龙, 遆超普. 面向作物产量和环境双赢的氮肥施用策略[J]. 中国科学院院刊, 2018, 33(2): 177-183.
Yan X Y, Xia L L, Di C P. Win-win nitrogen management practices for improving crop yield and environmental sustainability[J]. Bulletin of Chinese Academy of Sciences, 2018, 33(2): 177-183.
[5] Jung M Y, Well R, Min D, et al. Isotopic signatures of N2O produced by ammonia-oxidizing archaea from soils[J]. The ISME Journal, 2014, 8(5): 1115-1125.
[6] Tenuta M, Gao X P, Tiessen K H D, et al. Placement and nitrogen source effects on N2O emissions for canola production in Manitoba[J]. Agronomy Journal, 2023, 115(5): 2369-2383.
[7] Han B B, Yao Y Z, Liu B, et al. Relative importance between nitrification and denitrification to N2O from a global perspective[J]. Global Change Biology, 2024, 30(1). DOI:10.1111/gcb.17082
[8] Song Y Q, Wu D M, Ju X T, et al. Nitrite stimulates HONO and NOx but not N2O emissions in Chinese agricultural soils during nitrification[J]. Science of the Total Environment, 2023, 902. DOI:10.1016/j.scitotenv.2023.166451
[9] Chen Z M, Ding W X, Xu Y H, et al. Importance of heterotrophic nitrification and dissimilatory nitrate reduction to ammonium in a cropland soil: Evidences from a 15N tracing study to literature synthesis[J]. Soil Biology and Biochemistry, 2015, 91: 65-75.
[10] 靳帅, 史永晖, 叶桂香, 等. 基于DNDC模型的秸秆还田量与氮肥的耦合效应对夏玉米农田N2O排放的影响研究[J]. 山东农业科学, 2016, 48(2): 68-73.
Jin S, Shi Y H, Ye G X, et al. Study on coupling effect of straw returning and nitrogen fertilizer on N2O emission in summer corn field based on DNDC model[J]. Shandong Agricultural Sciences, 2016, 48(2): 68-73.
[11] Muller A, Schader C, Scialabba N E H, et al. Strategies for feeding the world more sustainably with organic agriculture[J]. Nature Communications, 2017, 8(1). DOI:10.1038/s41467-017-01410-w
[12] 董玉红, 欧阳竹, 李运生, 等. 不同施肥方式对农田土壤CO2和N2O排放的影响[J]. 中国土壤与肥料, 2007(4): 34-39.
Dong Y H, Ouyang Z, Li Y S, et al. Influence of different fertilization on CO2 and N2O fluxes from agricultural soil[J]. Soil and Fertilizer Sciences in China, 2007(4): 34-39.
[13] 陈哲, 陈媛媛, 高霁, 等. 不同施肥措施对黄河上游灌区油葵田土壤N2O排放的影响[J]. 应用生态学报, 2015, 26(1): 129-139.
Chen Z, Chen Y Y, Gao Q, et al. Effects of different fertilization measures on N2O emission in oil sunflower field in irrigation area of upper Yellow River[J]. Chinese Journal of Applied Ecology, 2015, 26(1): 129-139.
[14] Ding W X, Luo J F, Li J, et al. Effect of long-term compost and inorganic fertilizer application on background N2O and fertilizer-induced N2O emissions from an intensively cultivated soil[J]. Science of the Total Environment, 2013, 465: 115-124.
[15] Shang Z Y, Zhou F, Smith P, et al. Weakened growth of cropland-N2O emissions in China associated with nationwide policy interventions[J]. Global Change Biology, 2019, 25(11): 3706-3719.
[16] Bai J S, Qiu S J, Jin L, et al. Quantifying soil N pools and N2O emissions after application of chemical fertilizer and straw to a typical chernozem soil[J]. Biology and Fertility of Soils, 2020, 56(3): 319-329.
[17] Guenet B, Gabrielle B, Chenu C, et al. Can N2O emissions offset the benefits from soil organic carbon storage?[J]. Global Change Biology, 2020, 27(2): 237-256.
[18] 张楠, 苗淑杰, 乔云发, 等. 东北农田黑土N2O排放研究进展[J]. 土壤学报, 2022, 59(4): 899-909.
Zhang N, Miao S J, Qiao Y F, et al. N2O emissions from black soils in northeast China[J]. Acta Pedologica Sinica, 2022, 59(4): 899-909.
[19] 王蕾, 董彦宏, 王连峰. 不同水分含量下黑土氧化亚氮排放差异[J]. 大连交通大学学报, 2021, 42(5): 84-88.
Wang L, Dong Y H, Wang L F. Difference of nitrous oxide emission in black soil under different water content[J]. Journal of Dalian Jiaotong University, 2021, 42(5): 84-88.
[20] Zheng X H, Wang M X, Wang Y S, et al. Impacts of soil moisture on nitrous oxide emission from croplands: a case study on the rice-based agro-ecosystem in Southeast China[J]. Chemosphere - Global Change Science, 2000, 2(2): 207-224.
[21] Liu X, Ma J, Ma Z W, et al. Soil nutrient contents and stoichiometry as affected by land-use in an agro-pastoral region of northwest China[J]. CATENA, 2017, 150: 146-153.
[22] Valjavec M B, Čarni A, Žlindra D, et al. Soil organic carbon stock capacity in karst dolines under different land uses[J]. CATENA, 2022, 218. DOI:10.1016/j.catena.2022.106548
[23] 陈国潮. 土壤微生物量测定方法现状及其在红壤上的应用[J]. 土壤通报, 1999, 30(6): 284-287.
[24] Wu Y F, Gao X P, Kuang W N, et al. Long-Term fertilization increased nitrous oxide emissions from croplands reclaimed from desert[J]. Atmosphere, 2022, 13(11). DOI:10.3390/atmos13111897
[25] 杜梦寅, 袁建钰, 李广, 等. 有机-无机肥配施对黄土高原半干旱区农田土壤N2O排放的影响[J]. 干旱地区农业研究, 2023, 41(3): 186-194.
Du M Y, Yuan J Y, Li G, et al. Effects of combined organic-inorganic fertilizer application on soil N2O emissions from farmland in the semi-arid area of the Loess Plateau[J]. Agricultural Research in the Arid Areas, 2023, 41(3): 186-194.
[26] Xia F, Mei K, Xu Y, et al. Response of N2O emission to manure application in field trials of agricultural soils across the globe[J]. Science of the Total Environment, 2020, 733. DOI:10.1016/j.scitotenv.2020.139390
[27] Zhou Y Z, Zhang Y Y, Tian D, et al. The influence of straw returning on N2O emissions from a maize-wheat field in the North China Plain[J]. Science of the Total Environment, 2017, 584-585: 935-941.
[28] 杨叶华, 黄兴成, 朱华清, 等. 长期有机与无机肥配施的黄壤稻田土壤细菌群落结构特征[J]. 植物营养与肥料学报, 2022, 28(6): 984-992.
Yang Y H, Huang X C, Zhu H Q, et al. Bacterial community structure and composition under long-term combined application of organic and inorganic fertilizers in a yellow paddy soil[J]. Journal of Plant Nutrition and Fertilizers, 2022, 28(6): 984-992.
[29] Li Z L, Zeng Z Q, Song Z P, et al. Vital roles of soil microbes in driving terrestrial nitrogen immobilization[J]. Global change biology, 2021, 27(9): 1848-1858.
[30] Stehfest E, Bouwman L. N2O and NO emission from agricultural fields and soils under natural vegetation: summarizing available measurement data and modeling of global annual emissions[J]. Nutrient Cycling in Agroecosystems, 2006, 74(3): 207-228.
[31] 何志龙, 周维, 田亚男, 等. 中亚热带丘陵区茶园和林地土壤春季N2O排放及其影响因素[J]. 农业环境科学学报, 2016, 35(6): 1210-1217.
He Z L, Zhou W, Tian Y N, et al. Nitrous oxide emission and its impact factors in tea garden and woodland soils in subtropical hilly region of China during spring season[J]. Journal of Agro-Environment Science, 2016, 35(6): 1210-1217.
[32] Stein L Y. Insights into the physiology of ammonia-oxidizing microorganisms[J]. Current Opinion in Chemical Biology, 2019, 49: 9-15.
[33] Lin S, Iqbal J, Hu R G, et al. Nitrous oxide emissions from yellow brown soil as affected by incorporation of crop residues with different carbon-to-nitrogen ratios: A case study in central China[J]. Archives of Environmental Contamination and Toxicology, 2013, 65(2): 183-192.
[34] Hei Z W, Peng Y T, Hao S L, et al. Full substitution of chemical fertilizer by organic manure decreases soil N2O emissions driven by ammonia oxidizers and gross nitrogen transformations[J]. Global Change Biology, 2023, 29(24): 7117-7130.
[35] Jung J Y, Lal R, Ussiri D A N. Changes in CO2, 13C abundance, inorganic nitrogen, β-glucosidase, and oxidative enzyme activities of soil during the decomposition of switchgrass root carbon as affected by inorganic nitrogen additions[J]. Biology and Fertility of Soils, 2011, 47(7): 801-813.
[36] Yang X M, Drury C F, Reynolds W D, et al. Interactive effects of composts and liquid pig manure with added nitrate on soil carbon dioxide and nitrous oxide emissions from soil under aerobic and anaerobic conditions[J]. Canadian Journal of Soil Science, 2003, 83(4): 343-352.
[37] 唐占明, 刘杏认, 张晴雯, 等. 对比研究生物炭和秸秆对麦玉轮作系统N2O排放的影响[J]. 环境科学, 2021, 42(3): 1569-1580.
Tang Z M, Liu X R, Zhang Q W, et al. Effects of biochar and straw on soil N2O emission from a wheat maize rotation system[J]. Environmental Science, 2021, 42(3): 1569-1580.
[38] Zheng X B, Cong P, Singh B P, et al. Fertilizer nitrogen substitution using biochar-loaded ammonium-nitrogen reduces nitrous oxide emissions by regulating nitrous oxide-reducing bacteria[J]. Environmental Technology & Innovation, 2024, 33. DOI:10.1016/j.eti.2023.103487
[39] Liyanage T D P, Maeda M, Somura H, et al. Nitrous oxide and carbon dioxide emissions from two types of soil amended with manure compost at different ammonium nitrogen rates[J]. Soil Science and Plant Nutrition, 2022, 68(4): 473-490.
[40] 陈召月, 段巍巍. 旱地农田N2O、CO2排放主要影响因素及减排措施研究进展[J]. 现代农业科技, 2020(24): 140-142.
Chen Z Y, Duan W W. Research progress on main influencing factors and emission reduction measures of N2O and CO2 from Dryland Farmland[J]. Modern Agricultural Science and Technology, 2020(24): 140-142.
[41] 张振贤, 华珞, 尹逊霄, 等. 农田土壤N2O的发生机制及其主要影响因素[J]. 首都师范大学学报(自然科学版), 2005, 26(3): 114-120.
Zhang Z X, Hua L, Yin X X, et al. Nitrous oxide emission from agricultural soil and some influence factors[J]. Journal of Capital Normal University (Natural Sciences Edition), 2005, 26(3): 114-120.
[42] Punshon S, Moore R M. Nitrous oxide production and consumption in a eutrophic coastal embayment[J]. Marine Chemistry, 2004, 91(1-4): 37-51.
[43] 毕智超, 张浩轩, 房歌, 等. 不同配比有机无机肥料对菜地N2O排放的影响[J]. 植物营养与肥料学报, 2017, 23(1): 154-161.
Bi Z C, Zhang H X, Fang G, et al. Effects of combined organic and inorganic fertilizers on N2O emissions in intensified vegetable field[J]. Journal of Plant Nutrition and Fertiliser, 2017, 23(1): 154-161.
[44] Farooq M S, Uzair M, Maqbool Z, et al. Improving nitrogen use efficiency in aerobic rice based on insights into the ecophysiology of archaeal and bacterial ammonia oxidizers[J]. Frontiers in Plant Science, 2022, 13. DOI:10.3389/fpls.2022.913204
[45] 朱津宏, 熊若男, 杨思琪, 等. 接种氧化亚氮(N2O)还原细菌YSQ030对复垦土壤N2O排放和氮循环关键功能基因的影响[J]. 南京信息工程大学学报, 2024, 16(3): 416-427.
Zhu J H, Xiong R N, Yang S Q, et al. Effects of inoculation with N2O-reducing bacteria YSQ030 on soil N2O emission and key functional genes involved in nitrogen cycling in reclaimed soil[J]. Journal of Nanjing University of Information Science & Technology, 2024, 16(3): 416-427.