不同连作年限甜瓜种植土壤性质和微生物多样性

Soil properties and microbial diversity in the muskmelon fields after continuous cropping for different years

摘要:

[背景] 连作种植和化肥、农药过量施用导致设施甜瓜土壤质地恶化、病害严重，甜瓜产量和质量下降。[目的] 明确甜瓜连作种植年限对土壤化学性质、土壤酶活性和微生物多样性的影响。[方法] 以甜瓜种植1年、5年和10年的温室耕层土壤为研究对象，采用常规分析方法、土壤酶活测定试剂盒、稀释涂布平板法和Illumina Miseq高通量测序技术分别进行土壤化学性质、酶活性、可培养微生物数量和微生物多样性的测定。[结果] 甜瓜连作种植引起耕层土壤全氮、速效氮、速效磷含量增加和pH值升高。与种植1年土壤相比，连作5年土壤全氮、速效氮、速效磷和pH值分别增加了1.04%、0.56%、6.00%和4.45%，连作10年分别增加了7.25%、6.87%、17.75%和5.60%。土壤速效钾含量随连作年限增加而显著降低，连作10年时降低幅度达12.68%。甜瓜连作种植引起土壤脲酶、碱性磷酸酶、蔗糖酶活性显著降低。连作5年3种酶活性分别降低了2.79%、41.05%和38.81%，连作10年分别降低了23.43%、42.30%和66.21%。过氧化氢酶活性随连作年限增加呈先降低后增加的趋势。甜瓜连作种植导致土壤中细菌和放线菌的数量显著减少，连作5年和10年土壤中细菌、放线菌、真菌数量分别较种植1年减少6.02%、29.32%、32.50%和58.65%、53.17%、33.75%。甜瓜连作使土壤细菌多样性指数降低，细菌中变形菌门（Proteobacteria）、拟杆菌门（Bacteroidetes）等优势菌门及其中的根瘤菌属（Rhizobium）、假单胞菌属（Pseudomonas）、芽孢杆菌属（Bacillus）等有益菌丰度减少；土壤真菌的丰度增加而均一度降低，真菌的子囊菌门（Ascomycota）丰度增加。冗余分析表明，全氮、速效氮、速效磷和pH等土壤性质及鞘脂单胞菌（Sphingomonas）、芽单胞菌（Gemmatimonas）、霉菌属（Mycothermus）等微生物种群与甜瓜连作年限呈正相关。[结论] 设施甜瓜连作导致土壤化学性质和微生物环境恶化，该研究为设施甜瓜连作土壤的修复和甜瓜产业的可持续发展提供参考。

Abstract:

[Background] Muskmelon under protected cultivation faces soil deterioration, serious diseases, and the decline of muskmelon yield and quality as a result of continuous cropping and excessive chemical fertilizer and pesticides application. [Objective] This paper aims to clarify the effect of continuous cropping span of muskmelon on soil chemical properties, enzyme activity, and microbial diversity.[Methods] Topsoil samples were collected from the greenhouses after 1 year, 5 years, and 10 years of continuous muskmelon cropping. Soil chemical properties, enzyme activity, culturable microorganism count, and microbial diversity were determined with conventional methods, enzyme assay kits, dilution-plate method, and Illumina Miseq, respectively.[Results] Continuous cropping increased soil total nitrogen, available nitrogen, available phosphorus, and pH. The total nitrogen, available nitrogen, available phosphorus, and pH in soil after 5 years of continuous cropping were 1.04%, 0.56%, 6.00%, and 4.45% higher than those in soil after one year of planting, respectively, and the corresponding figures for soil after 10 years of continuous cropping were 7.25%, 6.86%, 17.75%, and 5.60%, respectively. However, soil available potassium was reduced significantly with the continuous cropping and the reduction reached 12.68% in soil after 10 years of continuous cropping. Continuous cropping significantly decreased the activity of soil urease, alkaline phosphatase, and sucrase, and the decrease was 2.79%, 41.05%, and 38.81% for soil under 5 years of continuous cropping, respectively, and 23.43%, 42.30% and 66.21% for soil under 10 years of continuous cropping, respectively. However, the activity of catalase reduced first and then rose with the continuous cropping. The counts of bacteria and actinomyces decreased significantly with the continuous cropping. To be specific, the number of bacteria, actinomyces, and fungi was 6.02%, 29.32%, and 32.50% smaller in soil after 5 years of continuous cropping, respectively, and 58.65%, 53.17%, and 33.75% smaller in soil after 10 years of continuous cropping, respectively, than that in soil after one year of planting. Moreover, bacterial diversity was lowered, as manifested by the reduction of the dominant Proteobacteria and Bacteroidetes and the beneficial Rhizobium, Pseudomonas, and Bacillus. The abundance of fungi was increased and the evenness was reduced. Specifically, the abundance of Ascomycota rose. Redundancy analysis indicated that soil total nitrogen, available nitrogen, available phosphorus, and pH and soil Sphingomonas, Gemmatimonas, and Mycothermus were in positive correlation with continuous cropping span. [Conclusion] Continuous cropping of muskmelon resulted in deterioration of soil chemical properties and microbial environment. The study provided a reference for the remediation of soil under continuous muskmelon cropping and sustainable development of muskmelon industry.