有机无机肥配施模式对氮素淋失的影响

滕 颖，孔凡靖，陈玉成，陈思扬，熊海灵，朱康文，杨志敏

有机无机肥配施模式对氮素淋失的影响

滕 颖1,2，孔凡靖1,2，陈玉成1,2，陈思扬1,2，熊海灵3，朱康文4，杨志敏1,2※

（1. 西南大学资源环境学院，重庆 400716；2. 农村清洁工程重庆市工程研究中心，重庆市生态环境农用地土壤污染风险管控重点实验室，重庆 400716；3. 西南大学电子信息工程学院，重庆 400715；4. 重庆市生态环境科学研究院，重庆 401147）

为了探索农田氮素淋失低风险的有机无机肥配施模式，该研究收集了331个有效农田有机肥化肥配施数据对，分析了施肥总量、施肥结构（有机肥替代比）、施肥时间（基追施）、有机肥种类等因素对氮素淋失的总体影响。结果表明：与单施化肥相比，有机肥配施化肥中氮素总量较低时（N<200 kg/hm2），农田总氮（Total Nitrogen，TN）、硝态氮（NO3--N）淋失分别减少36.77%、65.05%；有机肥替代比高于70%，虽然可减少TN淋失（39.64%），但增加了溶解性有机氮（DON）淋失的风险（15.78%），尤其是动物型有机肥替代化肥使DON淋失增加26.31%；氮肥基施可显著降低TN、NO3--N淋失（43.58%、70.51%，<0.05）。碱性旱地土壤上有机肥配施化肥可有效抑制TN、NO3--N淋失，但增加了26.63%～42.95%的DON淋失。旱地氮素淋失以NO3--N为主，且淋失系数高于水田，提高有机肥替代比可以大幅降低旱地氮素淋失，但增强了DON淋失。因子重要性分析表明：有机肥替代比对TN淋失影响占主导作用，而施氮水平对NO3--N、DON淋失影响更为重要。因此，低施氮量、高替代比动物型有机肥可有效减少碱性旱地土壤氮素淋失。研究结果可为有机肥配施化肥的农田应用提供依据。

肥料；氮素；淋失；有机肥；DON

0 引 言

氮是作物生长的必需元素，施用氮肥在有效增加作物产量的同时，也带来了一系列环境负面影响[1]。研究表明：作物吸收的氮素仅占总氮输出的55%[2]，氮肥的大量使用导致土壤活性氮积累，过量氮素会通过地表径流、地下淋溶、氨挥发、反硝化等途径损失[3]。大量研究发现：中国旱地氮素损失多为20%～50%，水田则多为30%～70%[4]。其中，氮渗流淋失是农业氮素损失的主要途径，Guo等[5]研究发现，在玉米生长季节中，氮淋失约占氮素损失的80%。大量氮素随着降雨或灌溉进入地下水系统后会导致水质恶化、生物多样性丧失[6-7]。

农田化肥的过量施用是导致氮淋失的一个重要原因[8]。目前，有机肥与化肥配施已成为农业施肥常态[9-11]，可显著增加土壤有机质含量，有效提高农产品产量和品质[12]，影响土壤氮素淋失。研究表明：在小麦-玉米轮作系统中，280 kg/hm2（以N计，下同）的施氮总量、30%的猪厩肥替代化肥能够有效抑制土壤总氮（Total Nitrogen，TN）淋失[13]；180 kg/hm2的施氮总量、50%的堆肥替代化肥使得土壤硝态氮（Nitrate Nitrogen，NO3--N）淋失显著降低[14]；但也有研究发现，150 kg/hm2的施氮总量、50%的绿肥替代化肥促进了稻田土壤溶解性有机氮（Dissolved Organic Nitrogen，DON）淋失[15]。尽管前人通过整合分析发现：有机肥（粪便肥、常规商品有机肥）替代比（Substitution Ratio，SR）≤70%时能够有效抑制蔬菜系统TN淋失[16]。Xia等[17]研究也表明：与单施化肥相比，粪便有机肥配施化肥使得TN淋失显著降低了28.9%。但这些试验研究局限于单个作物系统，未考虑施氮水平（Nitrogen Application Level，N）、基追施行为、有机肥种类等施肥行为特征对氮淋失的总体影响。此外，DON作为土壤氮循环中的重要氮库，是土壤中最活跃的化学氮成分[18]。许多研究发现，DON损失占总氮淋失的3%～56%[19-21]，然而，有机肥配施化肥对于DON淋失风险影响并不清楚，使得农业面源污染防控具有不确定性。

为此，本文拟对作物系统中有机肥配施化肥的已有结果进行整合分析，探讨施肥总量、施肥结构（有机肥替代比）、施肥时间（基追施）、有机肥种类、土壤pH、土地利用方式的变化对于氮素淋失（TN、NO3--N、DON）的影响大小与方向，核算不同施肥处理在农业生产中TN、NO3--N、DON的淋失系数，分析有机肥配施化肥对于N素淋失影响的不确定性，以期为优化施肥、减少农田氮素淋失风险提供理论依据。

1 材料与方法

1.1 数据采集

通过业界广泛使用的“中国知网”与“web of science”两个主要数据库检索了截止至2022年1月发表的经同行评议相关论文。在搜索文献时，以下关键词被使用：化肥（Chemical Fertilizer）、有机肥（Organic Fertilizer）、氮淋失（N Leaching）。纳入整合分析中的研究必须满足以下标准：1）分析的数据应为淋溶液氮含量，而不是土壤氮含量。2）研究应具有单施化肥处理（不施用有机肥），因为这是本文的对照处理，同时也应包括有机肥配施化肥或单施有机肥的处理。3）研究中各个施氮处理间应遵循等总氮量原则，且应明确各处理的重复数。4）没有种植作物，缺少有机肥种类、土壤性质（包括pH、有机质）等因素的研究应被舍弃。5）至少有一个目标变量（TN、NO3--N、DON）被量化。6）为避免数据重复，在不同文献中同一研究地点与时间中所观测到的数据只纳入一次。

在提取数据过程中，采用GetData 2.2软件识别图片中的数值；由于部分研究没有报道变量的标准差（Standard Deviation，SD），将给定值的6%～11%作为SD，对应于数据库中各自给定的SD均值[22]，这符合统计学中标准差的一般范围。基于以上标准，总共筛选出35篇经同行评议文章以及331对相关数据对用于整合分析，其中22篇来自web of science，13篇来自CNKI。

1.2 数据分类

在有机肥配施化肥过程中，评估施肥行为（施氮水平、替代比、基追施行为、有机肥种类）、初始土壤pH、土地利用方式等对土壤氮淋失的影响时，为了满足最大程度的组内均质化[23]，做出以下分类。施氮水平分类[16]：低施氮水平（N<200 kg/hm2）、中施氮水平（200 kg/hm2≤N<400 kg/hm2）、高施氮水平（N≥400 kg/hm2）；有机肥替代比分类[16]：低替代比（SR≤30%）、中替代比（30%7.5）；土地利用方式分类：旱地和水田。淋失系数是施氮和不施氮的处理氮淋失差除以施氮总量，以百分比表示。

表1 数据统计描述

1.3 数据分析

有机肥配施化肥对变量（）的影响通过自然对数进行量化，以表示响应比(ln RR)，其计算公式如下[24]：

lnRR=ln(X/X)（1）

式中e与c分别表示变量的处理与对照（单施化肥）的平均值。

为了更好地显示变量的响应大小，采用计算式（（RR-1）×100%）将响应比转化为百分数形式。其中，正百分比变化表示在有机肥配施化肥条件下目标变量增加，反之亦然。

采用Metawin 2.1软件进行随机效应meta分析，加权平均效应值和偏差矫正的95%置信区间是通过bootstrapping过程产生的，其中经过5 000次迭代[16]。如果95%置信区间没有与0相交，则认为有机肥配施化肥对目标变量（）促进或抑制效果显著。通过分类随机效应分析比较了施肥行为、土壤pH、土地利用方式对土壤氮淋失影响的效应大小（以值表示）。经卡方检验<0.05，则认为各组间变量的效应值均数有显著差异。同时运用SPSS 23软件对有机肥配施化肥下氮素淋失（TN、NO3--N、DON）的效应值进行相关性分析；采用Matlab软件依据随机森林模型对施肥行为、土壤pH、土地利用方式等对氮素淋失的影响进行重要性分析。

2 结果与分析

2.1 施肥行为对氮淋失的影响

与单施化肥相比，施肥行为对土壤氮淋失有明显的影响（图1），其中施氮水平对TN、NO3--N、DON淋失均影响显著（<0.05）（图1a）。低施氮水平显著减少了氮淋失，TN、NO3--N淋失分别减少了36.77%、65.05%，而DON淋失的影响效应值具有异质性。同时在中、高施氮水平下，有机肥配施化肥反而增加了DON淋失，增加比例分别为32.94%、24.43%。可能原因是与单施化肥相比，有机肥的施入增加了土壤有机碳含量，改变土壤C/N，微生物将夺取环境中的氮源[25-26]，从而促进土壤氮固持作用，有效抑制NO3--N等无机氮淋失。此外，有机肥自身分解释放的有机氮增加了土壤DON含量，同时DON在土壤中的迁移性较强[27]，随着施氮水平的增加，土壤吸附能力达到饱和，过量的DON可能随降雨或灌溉淋失。

有机肥配施化肥均明显减少了TN、NO3--N淋失（图 1b），同时有机肥替代比对TN淋失影响显著（<0.05），高替代比使得TN淋失显著降低了39.64%，而替代比对NO3--N淋失没有显著差异（=0.37）。这与Wei等[28]研究基本一致，当有机肥替代比大于60%时，TN淋失减少了27%。高替代比能够显著增加土壤团聚体[29]和总有机碳含量，从而刺激微生物活性，增强土壤氮素固定，有效提高氮素利用率[30]。尽管有机肥替代比对于DON淋失没有显著影响，但高替代比使得DON淋失增加了15.78%。这可能是因为高替代比补充了土壤有机碳源[31-32]，促进溶解性有机碳和DON的生成。此外，土壤有机质含量迅速增加，从而阻塞了土壤的吸附位点，促进了溶解性有机质的淋失[33]。

在作物生长中，施肥时间对TN、NO3--N淋失存在显著影响（<0.05）（图1c）。氮肥作基肥一次性施入或以基追施形式在不同时期分次施入均有效抑制TN、NO3--N淋失。且当氮肥全部基施时，TN、NO3--N淋失抑制效果最大，分别减少了43.58%、70.51%。这可能是因为在农业活动中，通常以有机肥作为基肥，无机氮肥作为追肥。同时，有机肥含碳量高，在作物生长初期，有机肥的施入有利于减缓土壤中矿质氮素的累积，从而减少了氮素损失。而氮肥全部作为追肥使得TN、NO3--N淋失的效应值存在较大异质性。氮肥作基肥和追肥分次施入则表现为促进了DON淋失。这可能是因为有机肥施入土壤后，短期内土壤DON含量迅速增加，多次施肥使得DON淋失风险大。

在不同种类有机肥配施下，TN、NO3--N淋失较单施化肥均受到抑制，但组间差异不显著（图1d）。土壤氮素矿化速率受C/N控制[34-35]，与植物秸秆相比，粪肥C/N低[36]，在施入土壤后，氮矿化速率较快，显著增加氮素利用率[16]，从而抑制土壤氮素淋失。有机肥种类对DON淋失变化存在显著影响（<0.05）。其中，动物型有机肥和其他类型有机肥使DON淋失分别增加了26.31%、26.45%。而植物型有机肥对DON淋失效果具有异质性。研究表明[37]：沼液的施用可以促进DON的淋失，而淋失的主要有机成分是黄腐酸、腐殖酸、可溶性微生物副产物等有机化合物。因此施加动物型有机肥后，腐殖酸类有机物可能会随降雨淋滤，导致DON淋失增加。

注：1）LE为低水平；ME为中水平；HE为高水平。2）BF+TF为基追施；BF为全部基施；TF为全部追施。3）AB为动物型；PB为植物型；OT为其他。4）n为数据对个数；P为显著性水平，P<0.05表示各组间变量的效应值均数有显著差异；TN为总氮；NO3--N为硝态氮；DON为溶解性有机氮，下同。

2.2 土壤pH和土地利用方式对氮淋失的影响

在不同初始土壤pH下，与单施化肥相比，有机肥配施化肥均能减少旱地、水田土壤TN、NO3--N淋失（图2）。初始土壤pH对TN淋失影响不显著（=0.33），但对土壤NO3--N淋失存在显著影响（<0.05）。当土壤pH呈中性时，有机肥配施化肥对NO3--N淋失抑制效果最佳，减少了81.52%。初始土壤pH对DON淋失同样存在显著影响（<0.05），初始土壤pH为碱性时，DON淋失增加了42.95%，而在土壤pH呈酸性时，DON淋失存在异质性。土壤酸碱性是影响土壤溶解性有机碳和DON含量的重要因素之一[38-39]。前人也通过整合分析表明[40]：在碱性土壤中，施加有机肥能显著提高土壤DON含量。其原因可能是在高pH条件下，土壤微生物活性增强，促进土壤有机物发生氨化作用，分解形成DON[27]。同时研究表明：随着土壤pH升高，铁铝氧化物和氢氧化物带正电荷性降低，对DON的吸附能力减弱[41]，使得土壤DON更易淋失。

土地利用方式对TN、NO3--N淋失影响不显著（=0.56，=0.61）（图2b），但在旱地中，有机肥配施化肥使DON淋失显著增加了26.63%（<0.05），而水田土壤DON淋失具有异质性。一方面，旱地主要分布在中国北方地区，其积温低于水田，有利于土壤DON的积累[40]；另一方面，微生物活性在旱地中可能受到抑制，从而减少微生物对DON的利用[42]，DON淋失风险增大。而水田土壤含水率高，更多的DON可能随径流损失[43]。同时在淹水条件下，厌氧微生物主要通过反硝化、异养硝化、共反硝化和厌氧氨氧化过程促进N2O、N2排放[44-45]，造成土壤氮素损失。

2.3 氮淋失系数的变化

在不同施肥处理下，高有机肥替代比（70%

注：没有收集到pH为6.5～7.5 DON数据。DL为旱地，PF为水田。

表2 不同有机肥替代比下氮淋失系数

注：SR为有机肥替代比。

Note: SR is organic fertilizer replacement ratio.

2.4 不确定性及重要性分析

化肥的大量投入使得农田氮素通过淋失、气体排放等途径损失，进而造成环境污染。本研究发现，高替代比的动物型有机肥施入碱性旱地土壤促进了DON的淋失（图 3），但有效抑制了土壤总氮淋失。然而，高替代比动物型有机肥对于温室气体排放的贡献并不清楚。尽管相关文献已经报道高有机肥替代化肥会抑制土壤N2O排放，但动物型有机肥抑制效果并不显著，且种类限于粪便和堆肥[17,46]。而高替代比沼液（高水分，低C/N）对于土壤N2O排放的影响未知。此外，前人研究表明高有机肥替代比显著抑制氮素利用率和蔬菜产量[16]。因此，高有机肥替代比对于作物-环境系统的影响需要后续试验进一步权衡。

气候条件、耕作方式及栽培类型等对土壤氮淋失也存在一定影响。土壤氮素淋溶往往随降雨、灌溉发生。研究发现，在蔬菜系统中，水分输入与土壤NO3--N淋失呈微弱正相关[47]。此外，微生物活性在不同环境温度下有所差异，升温可以增加土壤固氮菌和反硝化细菌丰度[48]，这可能改变硝化反硝化速率进而影响土壤氮素淋失。有机肥施用方式可能会间接影响土壤氮素淋失。研究发现，沼液喷施对土壤NO3--N含量影响较小，但采用沼液注施时，高替代比的沼液使得表层土壤NO3--N含量显著提升[49]，进而增加了土壤氮素淋失风险；同时，免耕[50]和模板犁耕[51]能够有效减少土壤氮素淋失。栽培条件往往影响土壤氮素转化。尽管Liu等[16]研究发现，对于蔬菜系统，有机肥配施化肥均有效抑制露天和温室土壤TN淋失，但其对于粮食作物系统和DON淋失的影响具有不确定性。由于数据的缺乏，本研究无法评估气温、耕作方式对于有机肥配施化肥下土壤氮素淋失的影响。

注：“？”指未知。

对施肥行为、土壤pH、土地利用方式等对TN、NO3--N、DON淋失影响的重要性程度进行分析（图4），结果表明，有机肥替代比对于TN淋失的影响占主导作用，而施氮水平对NO3--N、DON淋失影响较替代比更为重要。此外，土壤pH也是有机肥化肥配施下DON淋失的主要影响因素，这可能是因为pH升高会显著增加土壤有机质的溶解度[52]。因此，在农业生产中应针对性采取不同有机肥化肥配施模式，有效降低氮素淋失风险。

注：R2为决定系数。

3 结 论

本文对有机肥化肥配施过程中，施肥行为（施氮水平、替代比、基追施行为、有机肥种类）、初始土壤pH、土地利用方式等因素对氮素淋失的总体影响进行整合分析，主要结论如下：

1）高基施比例与低施氮量（N<200 kg/hm2）能够显著抑制氮素淋失，尤其是NO3--N淋失，即少次适量施氮可以有效降低氮淋失风险，但不一定有益于作物产量。

2）高有机肥替代比（大于70%）能够有效降低水田与旱地氮素淋失总量，显著抑制碱性旱地土壤NO3--N淋失，但促进了溶解性有机氮（Dissolved Organic Nitrogen，DON）淋失，其中，动物型有机肥的施用对DON淋失促进效果更为显著。

3）有机肥化肥配施过程中，减少氮淋失应优先控制有机肥替代比、施氮水平。

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Meta-analysis of the effects of combined application of organic and chemical fertilizers on soil nitrogen leaching

Teng Ying1,2, Kong Fanjing1,2, Chen Yucheng1,2, Chen Siyang1,2, Xiong Hailing3, Zhu Kangwen4, Yang Zhimin1,2※

(1.,,400716,; 2.,,400716,; 3.,,400715; 4.-,401147,)

Nitrogen is one of the most essential elements for crop growth. Nitrogen fertilizer has been widely applied to increase crop yields. At the same time, a large number of negative impacts have posed a great threat to the ecological environment in recent years. Among them, nitrogen leaching can be attributed to the excessive application of chemical fertilizers in farmland. Fortunately, the combined application of organic and chemical fertilizers can be expected to effectively reduce soil nitrogen leaching in normal fertilization during agricultural production at present. Therefore, this study aims to explore the combination application mode of organic and chemical fertilizers with a low risk of nitrogen leaching in farmland. The search terms were selected as chemical fertilizer, organic fertilizer, and nitrogen leaching using the two databases of China National Knowledge Infrastructure (CNKI) and Web of Science. The peer-reviewed and published papers were then obtained up to January 2022. Finally, a total of 35 papers (22 papers from Web of Science, 13 papers from CNKI) and 331 effective data pairs were collected after screening for the combination application of organic and chemical fertilizers in farmland. The target variables were taken as the total nitrogen (TN), nitrate nitrogen (NO3--N), and dissolved organic nitrogen (DON), while the chemical fertilizer was the control. After that, Metawin 2.1 software was used to determine the overall effects of the total amount of fertilization, fertilization structure (organic fertilizer substitution ratio), fertilization time (basic topdressing), and the types of organic fertilizers on the nitrogen leaching, where the chemical fertilizer was as the control. The results showed that there was a significant influence of the above fertilization behavior on nitrogen leaching. Once the total amount of nitrogen was less than 200 kg/hm2, the leaching of TN and NO3--N in farmland decreased by 36.77% and 65.05%, respectively. When the substitution ratio of organic fertilizers was higher than 70%, the TN leaching was reduced by 39.64%, whereas the risk of dissolved DON leaching increased by 15.78%. Especially, there was a 26.31% increase in DON leaching in the application of animal-based organic fertilizers combined with chemical fertilizers. Correspondingly, the application of nitrogen fertilizer significantly reduced the leaching of TN and NO3--N by 43.58% and 70.51%(<0.05), respectively. A certain impact was also found in the soil pH and land use patterns on nitrogen leaching. For example, the combined application of organic and chemical fertilizers on the alkaline dryland soil effectively inhibited the leaching of TN and NO3--N, whereas, there was an increase in the leaching of DON by 26.63%-42.95%. Nitrogen leaching in dryland was dominated by the NO3--N leaching. By contrast, the emission factor (EF) was higher than that in the paddy field. The increasing replacement ratio of organic fertilizers can be expected to greatly reduce the soil nitrogen leaching in dryland, but to enhance the DON leaching. In addition, the Matlab software was used to analyze the importance of factors using the random forest model. Specifically, the replacement ratio of organic fertilizer demonstrated a dominant effect on TN leaching. There was also the more important effect of the nitrogen application level on the NO3--N and DON leaching. Therefore, the low level of nitrogen application and the high substitution ratio of animal-based organic fertilizers can be used to effectively reduce the soil nitrogen leaching loss in the alkaline dryland, compared with the chemical fertilizers only. The finding can provide the practical basis for the combined application of organic and chemical fertilizers in farmland.

fertilizers; nitrogen; leaching; organic fertilizer; DON

10.11975/j.issn.1002-6819.2022.22.009

S146；S157

A

1002-6819(2022)-22-0081-08

滕颖，孔凡靖，陈玉成，等. 有机无机肥配施模式对氮素淋失的影响[J]. 农业工程学报，2022，38(22)：81-88.doi：10.11975/j.issn.1002-6819.2022.22.009 http://www.tcsae.org

Teng Ying, Kong Fanjing, Chen Yucheng, et al. Meta-analysis of the effects of combined application of organic and chemical fertilizers on soil nitrogen leaching[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2022, 38(22): 81-88. (in Chinese with English abstract) doi：10.11975/j.issn.1002-6819.2022.22.009 http://www.tcsae.org

2022-05-10

2022-09-10

重庆市技术创新与应用发展示范专项重点研发项目（cstc2019jscx-gksbX0103）；重庆荣昌农牧高新技术产业研发专项（cstc2020ngzx0010）；重庆市自然科学基金面上项目（CSTB2022NSCQ-MSX0538）

滕颖，研究方向为农业面源污染控制。Email：1351594843@qq.com

杨志敏，副教授，研究方向为农业面源污染控制。Email：bear@swu.edu.cn