马铃薯连作栽培对土壤微生物多样性的影响

为阐明马铃薯连作对土壤微生物群落结构和功能多样性的影响,揭示马铃薯连作障碍机制,本试验采用BIOLOG技术结合丛枝菌根真菌(AMF)形态学鉴定方法,就连作0(迎茬)、2 a、4 a、6 a、10 a的马铃薯田块土壤进行研究。结果表明:土壤养分含量随马铃薯连作年限增加有一定程度下降,其中,连作10 a马铃薯根际土壤的全磷、速效磷、速效钾和碱解氮与连作4 a相比分别下降61.32%、26.86%、26.87%和17.24%,但没有明显的养分亏缺和不均衡现象。土壤微生物群落结构发生了较大变化,放线菌、真菌数量显著随连作年限的延长先增加后减少,呈单峰型变化趋势;细菌数量随连作年限的延长呈逐步减少趋势,但差异不显著。连作4~6 a土壤微生物群落依然有较强的功能多样性,培养120 h后,连作6 a较迎茬AWCD值提高3.89%;群落组成中随连作年限的延长以碳水化合物、氨基酸类为碳源的微生物类群代谢能力明显下降,但代谢功能多样性趋于一致。连作马铃薯土壤AM真菌优势种发生改变,迎茬土壤为沙漠球囊霉(Glomus deserticola),连作2 a土壤为扭形球囊霉(Glomus delhiense)和福摩萨球囊霉(Glomus formosanum),连作10 a土壤为球泡球囊霉(Glomus globiferum)。多元分析结果表明,土壤微生物结构与功能多样性、AM真菌多样性变化受土壤p H、全磷含量、放线菌数量、细菌数量及土壤中以碳水化合物、氨基酸类等为碳源基质的微生物类群影响。说明长期连作栽培会影响土壤真菌、放线菌的数量,使真菌群落中AM真菌种的多样性显著下降,优势种发生改变,打破了微生物群落结构与功能平衡,引起土壤微生物群落结构与功能的失调。

Effects of continuous potato cropping on the diversity of soil microorganisms

Alternative cropping (0 year of potato cultivation), and 2, 4, 6, 10 years of continuous monoculture of potato were studied to explain the mechanism of continuous cropping obstacles by using combined BIOLOG and morphological identification techniques of arbuscular mycorrhizal fungi (AMF). The results showed that soil nutrients contents decreased with increasing number of continuous potato cropping years after 4 years continuous cropping. Compared with 4 years continuous potato cropping, 10 years continuous potato cropping decreased soil total phosphorus, available phosphorus, available potassium and available nitrogen respectively by 61.32%, 26.86%, 26.87% and 17.24%. However, no obvious nutrient deficiency or imbalance was noted in the experiment. Soil microbial community structure also changed significantly. The amounts of actinomyces and fungi increased in the first few years and later dropped significantly. The amount of bacteria gradually decreased with increasing number of years of continuous potato cropping, but no significantly changed. Microbial functional diversity of soil microbial community was still strong under 4 6 years of continuous potato cropping. Compared with alternative cropping (0 years), average well color development (AWCD) increased by 3.89% under 6 years of continuous potato cropping. The metabolism ability of soil microbial community using carbohydrate and amino acids as sources of carbon obviously decreased, but metabolism ability diversity tended to unanimous with the extension of continuous potato cropping years. The dominant AMF species changed from Glomus deserticola under alternative cropping (0 years) to G. delhiense and G. formosanum under 2 years of continuous potato cropping, and to G. globiferum under 10 years of continuous potato cropping. Multivariate analysis showed that the diversity of soil microbial structure and function, and AMF diversity were affected by soil pH, total phosphorus, amounts of actynomycetes and bacteria, and soil microbial groups using carbohydrate and amino acids as sources of carbon substrate. It was therefore concluded that continuous potato cropping decreased not only fungi and actinomycetes population but also AMF diversity. The dominant AMF species also changed and soil microbial structure diversity performance was inconsistent with function diversity. There was functional and structural disorder of soil microbial communities under continuous potato cropping.