Crop Research Institute, Hunan Academy of Agricultural Sciences, Changsha, China.
Yangtze Normal University, Chongqing, China.
BMC Microbiol. 2022 Feb 15;22(1):57. doi: 10.1186/s12866-022-02468-3.
Soybean-corn intercropping is widely practised by farmers in Southwest China. Although rhizosphere microorganisms are important in nutrient cycling processes, the differences in rhizosphere microbial communities between intercropped soybean and corn and their monoculture are poorly known. Additionally, the effects of cadmium (Cd) pollution on these differences have not been examined. Therefore, a field experiment was conducted in Cd-polluted soil to determine the effects of monocultures and soybean-corn intercropping systems on Cd concentrations in plants, on rhizosphere bacterial communities, soil nutrients and Cd availability. Plants and soils were examined five times in the growing season, and Illumina sequencing of 16S rRNA genes was used to analyze the rhizosphere bacterial communities.
Intercropping did not alter Cd concentrations in corn and soybean, but changed soil available Cd (ACd) concentrations and caused different effects in the rhizosphere soils of the two crop species. However, there was little difference in bacterial community diversity for the same crop species under the two planting modes. Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria and Firmicutes were the dominant phyla in the soybean and corn rhizospheres. In ecological networks of bacterial communities, intercropping soybean (IS) had more module hubs and connectors, whereas intercropped corn (IC) had fewer module hubs and connectors than those of corresponding monoculture crops. Soil organic matter (SOM) was the key factor affecting soybean rhizosphere bacterial communities, whereas available nutrients (N, P, K) were the key factors affecting those in corn rhizosphere. During the cropping season, the concentration of soil available phosphorus (AP) in the intercropped soybean-corn was significantly higher than that in corresponding monocultures. In addition, the soil available potassium (AK) concentration was higher in intercropped soybean than that in monocropped soybean.
Intercropped soybean-corn lead to an increase in the AP concentration during the growing season, and although crop absorption of Cd was not affected in the Cd-contaminated soil, soil ACd concentration was affected. Intercropped soybean-corn also affected the soil physicochemical properties and rhizosphere bacterial community structure. Thus, intercropped soybean-corn was a key factor in determining changes in microbial community composition and networks. These results provide a basic ecological framework for soil microbial function in Cd-contaminated soil.
在中国西南地区，农民广泛实行大豆-玉米间作。虽然根际微生物在养分循环过程中很重要，但大豆和玉米间作与其单作之间的根际微生物群落差异尚不清楚。此外，尚未研究镉（Cd）污染对这些差异的影响。因此，在 Cd 污染土壤中进行了田间试验，以确定单作和大豆-玉米间作系统对植物中 Cd 浓度、根际细菌群落、土壤养分和 Cd 有效性的影响。在生长季节中对植物和土壤进行了五次检查，并使用 16S rRNA 基因的 Illumina 测序分析根际细菌群落。
间作并没有改变玉米和大豆中的 Cd 浓度，但改变了土壤有效 Cd（ACd）浓度，并对两种作物的根际土壤产生了不同的影响。然而，在两种种植模式下，同一作物的细菌群落多样性差异不大。变形菌门、绿弯菌门、酸杆菌门、放线菌门和厚壁菌门是大豆和玉米根际的优势门。在细菌群落的生态网络中，间作大豆（IS）的模块枢纽和连接器较多，而间作玉米（IC）的模块枢纽和连接器较少。土壤有机质（SOM）是影响大豆根际细菌群落的关键因素，而有效养分（N、P、K）是影响玉米根际细菌群落的关键因素。在种植季节，间作大豆-玉米土壤有效磷（AP）浓度明显高于相应单作。此外，间作大豆的土壤有效钾（AK）浓度高于单作大豆。
间作大豆-玉米导致生长季节 AP 浓度增加，尽管在 Cd 污染土壤中作物对 Cd 的吸收没有受到影响，但土壤 ACd 浓度受到了影响。间作大豆-玉米还影响土壤理化性质和根际细菌群落结构。因此，间作大豆-玉米是决定微生物群落组成和网络变化的关键因素。这些结果为 Cd 污染土壤中土壤微生物功能提供了基本的生态框架。
