甘蓝、菜豆和玉米不同轮作组合对淡褐土细菌群落和作物产量的影响

为研究不同连作、轮作组合对土壤细菌群落和作物产量的影响,选择北方旱地常见种植作物甘蓝(C)、菜豆(B)和玉米(M),以3种作物轮作下甘蓝-玉米-甘蓝(CMC)、菜豆-玉米-甘蓝(BMC)、甘蓝-甘蓝-甘蓝(CCC)、甘蓝-玉米-菜豆(CMB)、菜豆-玉米-菜豆(BMB)、菜豆-菜豆-菜豆(BBB)、甘蓝-甘蓝-玉米(CCM)、甘蓝-菜豆-玉米(CBM)、菜豆-菜豆-玉米(BBM)、菜豆-甘蓝-玉米(BCM)共10种轮作组合为对象,利用IlluminaHiSeq高通量测序平台,基于16S rRNA基因序列扩增子测序,研究10种轮作模式下耕层土壤细菌群落结构和多样性的变化,分析其不同变化对作物产量的影响。结果表明:各处理间细菌OTU数目差异较小,丰富度间没有差异;前茬种植作物为甘蓝时,CCC处理特有OTU数为2,BMC处理特有OTU数为1;前茬种植作物为菜豆时,BBB处理无特有OTU,CMB处理轮作特有OTU数为1;前茬种植作物为玉米时,CCM、CBM、BCM处理均有1个特有OTU。BCM处理的土壤细菌丰富度指数(Ace指数和Chao1指数)显著低于CCC处理,但CCC、BCM处理与其余处理间无显著差异;与CCC处理相比,BCM处理的Ace指数降低了2.6%,Chao1指数降低了2.5%。CMC、BMC、CCC、BMB、CCM、BBM处理的土壤细菌多样性指数(Shannon指数)较CBM处理显著提高了3.3%~3.6%。与连作相比,CBM处理土壤细菌相对丰度和群落结构变化最大,BCM处理次之;与CCC处理相比,轮作能够降低土壤细菌丰富度和土壤细菌多样性。CMB和BMB处理细菌优势门(相对丰度>10%)为变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)、拟杆菌门(Bacteroidetes),其余处理细菌优势门为变形菌门、酸杆菌门、拟杆菌门、厚壁菌门(Firmicutes);各处理相对丰度最大的门是变形菌门(25.0%~31.1%)。与连作相比,CBM处理显著降低酸杆菌门、绿弯菌门、放线菌门相对丰度,显著提高拟杆菌门相对丰度。属水平相对丰度聚类热图显示,CMC、BBB、CCM处理与BMC、BBM、BCM处理土壤细菌群落相似性较高,CCC、CMB、BMB处理与CMC、BMC、BBB、CCM、BBM、BCM处理群落相似性次之,CBM处理与其余9种处理细菌群落差异最大。前茬种植作物相同时,各处理产量均无显著差异,其中CMC、BMB、BBM处理产量最高。综合而言,菜豆-菜豆-玉米为最优轮作组合。

Effects of different crop rotation combinations of cabbage, kidney bean, and maize on bacterial community and crop yield in light brown soil

Soil bacterial community and crop yield are affected by different combinations of continuous cropping and rotation. Cabbage(C), kidney bean(B), and maize(M) commonly grown in northern dry land were selected and used for this study. The experiment comprises a total of ten crop rotation combinations under three crop rotations:CMC, BMC, CCC, CMB, BMB, BBB, CCM, CBM, BBM, and BCM. Illumina HiSeq high-throughput sequencing and physicochemical test methods were used to study the changes in bacterial community structure and diversity in topsoil under the ten cropping rotation modes. To provide basis for rational crop rotation of cabbage, kidney bean, and maize in semiarid region of light brown soil, the effects of different changes on crop yield were analyzed. The results showed that there was a little difference in the OTUs and there was no difference in the richness of bacteria. The OTUs specific to CCC treatment was two, while the OTUs specific to BMC, CMB, CCM, CBM, and BCM treatment was one. The richness index of soil bacteria in BCM treatment was significantly lower than that in CCC treatment. Compared with that of CCC treatment, Ace index of BCM treatment decreased by 2.6%, while Chao1 index decreased by 2.5%. The shannon index of soil bacteria in CMC, BMC, CCC, BMB, CCM, and BBM treatments was significantly higher than that in CBM treatments by 3.3%~3.6%. Compared with those in continuous cropping treatment, the changes in relative abundance and community structure of bacteria in CBM treatment were the largest, followed by BCM treatment. Compared with CCC treatment, crop rotation reduced richness and diversity of soil bacteria. Proteobacteria, Acidobacteria, and Bacteroidetes were the dominant phyla in CMB and BMB treatments. The dominant phyla in other treatments were Proteobacteria, Acidobacteria, Bacteroidetes, and Firmicutes. Proteobacteria was the phylum with the largest relative abundance in each treatment. Compared with those of soil bacteria under continuous cropping, the relative abundance and community structure of soil bacteria under CBM treatment changed the most. It significantly reduced the relative abundance of Proteobacteria, Chloroflexi, and Actinobacteria but increased the relative abundance of Bacteroidetes. Abundance cluster heatmap of bacteria at genus level showed that CMC, BBB, and CCM treatments were more similar to BMC, BBM, and BCM treatments in terms of soil bacterial community, followed by CCC, CMB, and BMB treatments with CMC, BMC, BBB, CCM, BBM, and BCM treatments. CBM treatment had the greatest difference in bacterial communities compared with the remaining nine treatments. Although, there was no significant change in crop yield, CMC, BMB and BBM treatments had the highest yield. In general, kidney bean-kidney bean-maize was the best crop rotation combination.