[Effects of reducing chemical fertilizers combined with organic fertilizers on soil microbial community in litchi orchards].

Organic fertilizer application can replace a part of chemical fertilizer (CF) to improve the quality and efficiency of litchi production. To further explore the soil microbiological mechanism, with 19-year-old 'Feizixiao' litchi trees as the research objects, we examined the effects of two consecutive years of reduced CF applications (average 21.5% of total nutrients) combined with sheep manure (OF) and bio-organic fertilizers (BIO) on soil microbial diversity, community composition and differential microorganisms. The results showed that reducing the application of chemical fertilizers and combining it with the application of sheep manure and bio-organic fertilizer for two consecutive years could significantly improve yield and quality. The average increase of yield in the two years was 23.1% and 39.0%, respectively. Soil organic matter content and pH increased significantly in response to the combination treatments. Compared to that in the chemical fertilizer treatment, the contents of soil available phosphorus, potassium, calcium, magnesium, iron, manganese, copper, and zinc displayed an increasing trend in the combination treatments. The application of organic fertilizer increased the diversity of bacteria and fungi in rhizosphere soil, but not in non-rhizosphere soil. Both treatments significantly changed soil microbial community structure, increased eutrophic bacterial groups such as Bacteroides, Proteobacteria, and Bacillus phylum, and reduced anatrophic bacterial groups such as Acidobacteria and Chloroflexus. Compared with CF, the relative abundances of MND1 under OF and TK10, Gemmatimonas, Pseudolabrys, Trichoderma and Botryotrichum under BIO were significantly increased, which was positively correlated with yield. In conclusion, reducing CF and applying organic ferti-lizer for two consecutive years could effectively improve soil pH and nutrient availability, increase rhizosphere microbial richness and diversity, change soil microbial community structure, and shape microbial communities being more conducive to yield and quality improvement.有机肥替代部分化肥对荔枝生产有提质增效作用。为进一步探讨荔枝土壤微生物学机制,本试验以19年生“妃子笑”荔枝为对象,以化肥处理(CF)为对照,研究2018—2020连续两年减施化肥(平均减施化肥总养分21.5%)配施羊粪(OF)和配施生物有机肥处理(BIO)对土壤微生物多样性、群落组成及差异微生物等的影响,为荔枝科学施肥提供理论指导。结果表明: 与CF相比,连续两年OF和BIO处理均可有效提高荔枝产量和品质,产量平均增幅分别为23.1%和39.0%。土壤有机质含量和pH值均明显提高,土壤有效磷、有效钾、有效钙、有效镁、有效铁、有效锰、有效铜和有效锌含量均有不同程度增加。施用两种有机肥均能提高根际土壤细菌和真菌多样性,对非根际土壤影响不明显,同时改变土壤微生物群落结构,增加拟杆菌门、变形菌门和芽单胞菌门等富营养型细菌类群,减少酸杆菌门、绿弯菌门等贫营养型细菌类群。与CF相比,OF处理下MND1属和BIO处理下TK10属、芽单胞菌属、黄色杆菌属、木霉属、毛匍孢霉属的相对丰度均显著提高,并与产量呈显著正相关关系。综上,在荔枝上连续两年采用有机肥替代部分化肥可有效提高土壤pH值和养分有效性,增加根际土壤微生物丰富度和多样性,改变土壤微生物群落结构,从而形成更有利于产量提高和品质提升的微生物区系。.