摘要
为探究不同连作条件下烤烟土壤微生物群落结构变化特征及驱动因素,对秦岭腹地商洛地区连作Y1(烤烟种植1 a)、Y2(烤烟连作3 a)、Y3(烤烟连作5 a)和Y4(烤烟连作7 a)4种不同年份的植烟土壤进行了微生物生物量碳、微生物生物量氮、微生物多样性、群落结构变化及驱动因素的分析。结果显示:植烟土壤微生物生物量碳、氮和碳氮比随着种植年限的增加而减少,下降幅度分别为37.16%、20.40%和21.10%。土壤中细菌丰富度和多样性显著减少,其优势菌门为放线菌门、变形菌门、绿弯菌门、酸杆菌门和厚壁菌门,其相对丰度总和占比在80%及以上。在土壤中真菌丰富度显著增加,其优势菌门为子囊菌门、担子菌门和毛霉菌门,其相对丰度总和占比在90%及以上。在Y4连作条件下,土壤有益微生物门水平上相对丰度减少,如厚壁菌门和脱硫菌门,致病微生物门水平上相对丰度增加,如毛霉菌门和壶菌门。长期连作会导致土壤有益微生物相对丰度减少、致病微生物相对丰度增加、土壤微生物生物量碳氮比下降,进而增加烟株病害风险。因此,建立良好的耕作制度或构建微生物群落是缓解或解决连作烟田微生物群落结构失衡的关键技术途径。
连作是指在同一块土地上连续种植同一种作物两茬及以上的栽培措施。连作障碍是指土地连作后,即便有专业人员对作物进行栽培管理,也会出现产质量降低、病虫害加剧的现
微生物群落结构对维持土壤结构、有机物质降解、物质和能量循环等方面起着重要的作
商洛烟区位于秦岭腹地,烟草是当地重要的经济作物,已经有40 a种植历史。近年来由于受土地资源短缺和其他经济作物种植面积影响,烤烟种植出现了十分普遍的连作现象。连作引发的烟叶产量和品质下降等问题日益加重,也是目前我国烟草种植区面临的共性问题。研究表明,土壤细菌是土壤养分循环的重要驱动
试验地位于商洛市洛南县,属于温带季风气候,土壤类型为黄褐土,日照时数1 860 ~ 2 130 h,年平均气温不足12 ℃,无霜期206~210 d,洛南全年≥10 ℃的有效积温不足3 200 ℃,洛南烟草生长期历年均温不足21.5 ℃。该区雨量较为充沛,烟区年平均降雨量688.82 mm,烟草生育期降雨量546.1 mm。海拔、温度、无霜期、积温度和降雨量均满足烤烟的生长发育。
样品采集于2021年烟苗移栽和施肥前,根据当地种烟情况,采集1 a(Y1)、3 a(Y2)、5 a(Y3)和7 a(Y4)4种不同连作年限下的土壤,按照五点取样法取耕作层(0 ~ 20 cm)土壤,将采集的样品按照四分法混合后分为2份,一份去除在杂质后,保存在10 mL无菌离心管中,对土壤进行微生物群落检测;另一份在避光条件下自然风干,进行植烟土壤基础养分分析。
1) 植烟土壤基础养分的测定。土壤有机质、全氮、有效磷、速效钾和pH测定方法参照文献[
2)土壤微生物群落结构测定。采用E.Z.N.A
从
处理 Treatments | 有机质/(g/kg) Organic matter | 全氮/(g/kg) Total nitrogen | 有效磷/(mg/kg) Available phosphorus | 速效钾/(mg/kg) Available potassium | pH |
---|---|---|---|---|---|
Y1 | 17.10±0.265a | 1.11±0.043a | 25.00±0.500a | 177.00±2.646a | 8.1±0.26a |
Y2 | 16.70±0.173a | 0.93±0.026b | 22.30±0.917b | 163.00±4.583b | 7.5±0.26b |
Y3 | 14.60±0.361b | 0.78±0.036c | 13.30±0.173c | 137.00±4.359c | 6.7±0.20c |
Y4 | 13.10±0.265c | 0.66±0.026d | 11.00±1.136c | 102.00±3.606d | 5.6±0.17d |
从
处理 Treatments | 微生物生物量碳/(mg/kg) Microbial biomass carbon | 微生物生物量氮/(mg/kg) Microbial biomass nitrogen | 微生物生物量碳氮比 Microbial biomass carbon tonitrogen ratio |
---|---|---|---|
Y1 | 224.70±4.475a | 17.11±0.140a | 13.13±0.369a |
Y2 | 195.05±4.577b | 16.37±0.230b | 11.91±0.113b |
Y3 | 168.63±3.081c | 14.77±0.189c | 11.41±0.066c |
Y4 | 141.18±1.929d | 13.62±0.085d | 10.36±0.094d |
1)不同连作条件对土壤微生物群落α多样性的影响。对土壤样本进行细菌检测,共获得有效序列752 542条。样品覆盖度在0.97以上,测序数据量合理。依据97%序列相似性对所测序列进行聚类分析,样本平均OTU数为4 117.75(

图1 植烟土壤细菌OTUs(A)和真菌OTUs(B)
Fig.1 Bacterial OTUs (A) and fungal OTUs (B) in tobacco growing soil
项目 Items | 香农指数 Shannon index | 辛普森指数 Simpson index | ACE指数 ACE index | Chao指数 Chao index | 覆盖度 Coverage | |
---|---|---|---|---|---|---|
细菌 Bacteria | Y1 | 6.760±0.089a | 0.004±0.002 1b | 4 242.730±105.853a | 4 233.920±62.613b | 0.975±0.002 4b |
Y2 | 6.600±0.054b | 0.006±0.000 9b | 4 474.210±200.425a | 4 514.430±201.884a | 0.974±0.001 9b | |
Y3 | 6.230±0.045c | 0.010±0.018 8a | 3 768.090±115.982b | 3 769.870±74.742c | 0.975±0.001 8b | |
Y4 | 6.230±0.114c | 0.006±0.0008 b | 3 334.660±31.946c | 3 361.950±86.450d | 0.976±0.003 4a | |
真菌 Fungi | Y1 | 3.120±0.384a | 0.100±0.066 5a | 177.850±14.485c | 177.140±15.597c | 0.999±0.000 1a |
Y2 | 3.080±0.066a | 0.095±0.016 2a | 186.410±5.716bc | 189.570±7.433bc | 0.999±0.000 1a | |
Y3 | 3.130±0.093a | 0.094±0.005 2a | 205.990±13.073ab | 206.810±13.057ab | 0.999±0.000 1b | |
Y4 | 3.020±0.217a | 0.103±0.031 9a | 207.690±6.385a | 212.050±3.564a | 0.999±0.000 1a |
对土壤样本进行真菌检测,共获得有效序列543 208条。样品覆盖度在0.99以上,依据97%序列相似性对所测序列进行聚类分析,样本平均OTU数为226(
2)不同连作条件对土壤微生物群落组成的影响。微生物群落组成测定结果显示,样本中门水平上共获得细菌群落42个(

图2 植烟土壤门水平上细菌相对丰度(A)和真菌相对丰度(B)
Fig.2 Relative abundance of bacteria (A) and fungi (B) at the level of tobacco planting soil gate
所用样本中门水平上共获得真菌群落23个(
3) 土壤基础养分对微生物群落的影响。基于RDA分析研究土壤基础养分与微生物群落之间的关系,结果显示,在不同连作条件下烤烟土壤细菌中,RDA1和RDA2分别解释了36.54%和16.05%细菌群落变量(

图3 土壤基础养分与细菌(A)和真菌(B)群落组成的RDA分析
Fig. 3 RDA analysis of soil basic nutrients and bacterial (A) and fungal (B) community composition
4)不同连作条件下土壤微生物群落线性判别分析。利用LEfSe分析(linear discriminant analysis effect size)筛选出不同连作条件下烤烟土壤中具有显著差异的微生物种类(LDA阈值为2),结果显示,厚壁菌门、甲基孢囊菌门和粘球菌门等菌门在Y1连作条件下显著富集(

图4 植烟土壤细菌(A)和真菌群落(B)LEfSe分析
Fig. 4 LEfSe analysis of bacterial community (A) and fungus (B) in tobacco planting soil
土壤养分含量会随着种植制度、人为调节、土壤类型等条件的不同而产生较大的差
烤烟对土壤酸碱度的适应能力较强,在pH 4~9的土壤环境中均能生
本研究结果表明,连作条件对土壤细菌多样性影响较大,Y1条件下的细菌多样性最高,Y2条件下的细菌丰富度最高,Y3和Y4相比于Y1和Y2连作条件下,细菌丰富度和多样性均显著降低;不同连作条件对土壤真菌多样性影响较小,对真菌丰富度影响较大,其中,Y3和Y4相比于Y1和Y2,真菌丰富度显著增加。连作会导致土壤中微生物群落结构发生变化,与前人研究结果相印
土壤微环境的健康和功能是微生物群落繁殖生长的重要因素,不同的栽培模式对土壤微环境的影响不同,进而改变土壤微生物群落结
烤烟土壤细菌主要在Y1连作条件下富集,包含厚壁菌门、甲基孢囊菌门、粘球菌门、海藻菌门和脱硫菌门等菌门,厚壁菌门主要参与土壤中有机质分解和碳水化合物代
综上,不同连条件下植烟土壤养分和微生物存在差异,随着种植年限的增加,土壤养分逐渐下降,微生物结构失调,细菌多样性和丰富度下降,真菌丰富度增加,土壤中有益菌相对丰度下降,如厚壁菌门和脱硫菌门,致病菌相对丰度增加,如毛霉菌门和壶菌门。因此,建立良好的耕作制度或构建微生物群落是缓解或解决连作烟田微生物群落结构失衡的关键技术途径。
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