Abstract: To study the effects of intercropping walnut in karst area on rhizosphere soil nutrients and microecological environment, this research selected four different planting modes of walnut in the northwest Guangxi karst area as experimental subjects. The modes included intercropping walnut with mulberry(H-SS), walnut with Mahonia fortunei(H-SD), walnut with corn(H-YM), and monoculture walnuts(H-D). The physicochemical properties and microbial characteristics of the walnut rhizosphere and non-rhizosphere soils under different planting modes were analyzed using laboratory chemical experiments and Illumina Hiseq PE300 high-throughput sequencing technology. The results were as follows:(1)The walnut rhizosphere soils of different modes exhibited different degrees of enrichment in total nitrogen(TN), total phosphorus(TP), total potassium(TK), available phosphorus(AP), soil organic carbon(SOC), and exchangeable calcium, while available nitrogen(AN)showed a deficiency. Among them, H-SS showed significant enrichment effects on TN, TP, and SOC, while H-YM demonstrated the best enrichment effects on AP, AK, and exchangeable calcium.(2)Sucrase activity, microbial biomass carbon and nitrogen, and bacteria all exhibited significant rhizosphere effects, with H-YM showing the highest sucrase activity, phosphatase activity, and microbial biomass carbon. However, intercropping modes reduced the rhizosphere effects of microbial biomass nitrogen and bacteria.(3)Under the three intercropping modes, the Shannon index of rhizosphere soil bacteria was higher than that of monoculture walnuts.(4)Intercropping could enhance the diversity of rhizosphere soil bacteria. Moreover, the diversity of rhizosphere soil microorganisms was mainly influenced by nutrients, while non-rhizosphere soil was primarily affected by enzyme activities. In conclusion, intercropping can increase the enrichment ratio of rhizosphere nutrients, enhance soil enzyme activities, and promote microbial proliferation. Among the four different planting modes, H-SS shows significant enrichment effects on TN, TP, and SOC in rhizosphere soil, and it also has the highest soil bacterial content. H-YM exhibits better enrichment effects on AP, AK, and exchangeable calcium in rhizosphere soil. Therefore, in practical production, intercropping with mulberry or corn can be chosen based on local farming practices to optimize land use and improve ecological benefits. This study is of great significance for the development of sustainable agriculture in the northwest Guangxi karst area and provides a scientific basis for agricultural production and ecological conservation in similar ecological environments. Additionally, this research offers new ideas and methods for promoting agricultural modernization and facilitating the rational utilization of land resources and improvements in the ecological environment in karst area.

Key words: karst area, walnut, intercropping, soil nutrients, microbial characteristics, rhizosphere effect

摘要： 为探究喀斯特地区间套种核桃对根际土壤养分及微生态环境的影响,该研究以桂西北喀斯特地区间套种核桃-桑树(H-SS)、核桃-十大功劳(H-SD)、核桃-玉米(H-YM)以及核桃单种(H-D)的核桃根际和非根际土壤为试验对象,基于室内化学实验和Illumina Hiseq PE300高通量测序技术,分析不同种植模式下核桃根际与非根际土壤理化性质和微生物特征。结果表明:(1)不同模式核桃根际土壤对全氮(TN)、全磷(TP)、全钾(TK)、速效磷(AP)、土壤有机碳(SOC)和交换性钙主要表现为不同程度的富集作用,对速效氮(AN)有亏缺现象。H-SS对TN、TP和SOC富集作用明显,H-YM富集AP、速效钾(AK)和交换性钙的效果最佳。(2)蔗糖酶活性、微生物量碳、氮及细菌均出现明显的根际效应,H-YM的蔗糖酶活性、磷酸酶活性和微生物量碳最高,但间套种模式降低了微生物量氮和细菌的根际效应。(3)3种间套种模式下根际土壤细菌Shannon指数均高于核桃单种。(4)根际土壤微生物多样性主要受养分影响,非根际主要受酶活性影响。综上认为,间套种能够提高根际养分富集率、增强土壤酶活性、促进微生物增殖。此中,H-SS根际土壤对TN、TP和SOC的富集作用明显,其土壤细菌含量也最高; H-YM根际土壤富集AP、AK和交换性钙的效果更佳。在实际生产中可根据当地经营习俗选择桑树或玉米进行间套种。

关键词: 喀斯特地区, 核桃, 间套种, 土壤养分, 微生物特征, 根际效应