长期施肥对农田土壤真菌的影响

不合理施肥所引发的土壤环境问题逐渐成为制约我国农业可持续发展的重要因素之一,而土壤真菌作为一类重要的土壤微生物,研究施肥措施对真菌群落的影响对促进农业生产具有重要意义。本研究以有20年历史的长期定位试验田为研究对象,利用末端限制性片段长度多态性分析技术,对长期定位施肥农田生态系统中不同施肥方式对土壤真菌群落的影响以及时间变化规律进行了系统研究。长期施肥定位试验包括EM堆肥(EM)、传统堆肥(OF)、化肥(CF)和不施肥(CK)处理。主要研究结果如下:在0~20 cm土层,施肥处理对土壤真菌多样性有显著影响,Shannon-Weiner多样性指数为2.64~3.53,Simpson集中性指数为0.03~0.08;EM和OF处理的Shannon-Weiner多样性指数均显著高于CF和CK;在3月、6月和10月,EM和OF处理与CF和CK处理相比,有较高的真菌多样性;Simpson集中性指数最高的是3月的CK处理,最低的是10月的EM和OF处理。冗余分析结果表明,土壤pH、有机质、总氮、有效磷和有效钾等对真菌影响显著。因此,长期施用有机肥与化肥相比可以提高土壤真菌多样性,改变其群落结构;与化肥处理相比,施用EM堆肥,不仅可以保持土壤可持续利用性,同时改善0~20 cm土层土壤真菌的生存环境;3种施肥处理对土壤真菌群落结构影响程度由强到弱:EMOFCF。

Effects of long-term fertilization on soil fungi

Fungi are critical for the decomposition of terrestrial organic matter and subsequent global carbon cycle. High microbial diversity is essential for efficient nutrient recycling in soils. To investigate the impacts of different application modes of fertilizers on fungal communities, a long-term fertilization experiment (of over 20 years of continuous fertilizer treatments) was conducted in North China. Soil samples were collected from 4 treatments: effective microorganisms compost (EM), traditional compost (OF), chemical fertilizer (CF) and unfertilized control (CK) from March to October in 2012. The T-RFLP analysis, which is a polymerase chain reaction (PCR)-fingerprinting method commonly used for comparative microbial community analysis, was used to analyze the soil samples. Because of differences in T-RFLP patterns, a series of analyses - diversity index analysis, principal component analysis (PCA) and redundancy analysis (RDA) - was used to further determine soil fungal diversity in different treatments. Several multi-variate statistical approaches were used to interpret and compare the changes in T-RFLP fingerprints derived from different communities. Then the principal component analysis (PCA) and redundancy analysis (RDA) were particularly used in determining the trends in T-RFLP data. The results showed that fungal community structures in EM and OF were different from those in CK and CF. The ranges of Shannon-Weiner diversity index and the Simpson index in the samples were 2.64-3.53 and 0.03-0.08, respectively, under fertilzation treatments. While the highest Shannon-Weiner diversity index was in October and at the 0-20 cm soil layer under OF and EM treatments, the lowest was in March and at the 0-20 cm soil layer under CK treatment. Also while the highest Simpson index was in March and at the 0-20 cm soil layer under CK treatment, the lowest was in October and at the 0-20 cm soil layer under OF and EM treatments. Based on the comprehensive evaluation indexes of fungal community using PCA of T-RFs peak area and Shannon-Weiner index, fungal community was higher in EM and OF than in CF and CK treatments. The high fungal diversities in EM and OF treatments occurred in March, June and October. PCA analysis indicated that soil fungi under EM, OF, CF and CK treatments formed independent community structures. The communities were adaptable to own specific soil environments to form the dominant population. Redundancy analysis showed that fungal community composition was significantly influenced by soil pH, organic matter, total nitrogen, available phosphorus and available potassium. The above findings contributed significantly to the understanding of the specific changes in soil fungal diversity and fungal community in response to different fertilization treatments. The addition of different organic fertilizers improved a range of soil properties related with microbial activities after 19 years of treatment. Also fungi community became more diverse after application of organic fertilizer. It was concluded that organic fertilizer application was best strategy for increasing diversity of soil fungi.