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Long-Term Balanced Fertilization Decreases Arbuscular Mycorrhizal Fungal Diversity in an Arable Soil in North China Revealed by 454 Pyrosequencing Xiangui Lin,* Youzhi Feng, Huayong Zhang, Ruirui Chen, Junhua Wang, Jiabao Zhang, and Haiyan Chu State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, Jiangsu Province, P.R. China S Supporting Information *
ABSTRACT: A balanced fertilization can increase crop yields partly due to stimulated microbial activities and growths. In this study, we investigated arbuscular mycorrhizal fungi (AMF) in arable soils to determine the optimal practices for an effective fertilization. We used pyrosequencing-based approach to study AMF diversity, as well as their responses to different long-term (>20 years) fertilizations, including OM (organic manure) and mix chemical fertilizers of NP (nitrogen− phosphorus), NK (nitrogen−potassium), and NPK (nitrogen−phosphorus-potassium). Results revealed that 124 998 of 18S rRNA gene fragments were dominated by Glomeromycota with 59 611 sequences, generating 70 operational taxonomic units (OTUs), of which the three largest families were Glomeraceae, Gigasporaceae and Acaulosporaceae. In Control and NK plots, AMF diversity and richness significantly decreased under long-term P fertilizations, such as NP, NPK, and OM. Concomitantly, the AMF community structure shifted. Supported by canonical correspondence analysis, we hereby propose that long-term balanced fertilization, especially P fertilizer with additional N fertilizer, helps the build-up of soil nutrients. Consequently, some AMF community constituents are sacrificed, propelled by the self-regulation of plant-AMF-microbes system, resulting in an agro-ecosystem with a better sustainability. This knowledge would be valuable toward better understandings of AMF community in agro-ecosystem, and long-term ecosystem benefits of the balanced fertilization.
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INTRODUCTION Fertilization, especially a balanced fertilization is an important agricultural practice to increase crop yields. As one of underlying mechanisms, the balanced fertilization, N (nitrogen), P (phosphorus), and K (potassium) present in the fertilizer material, can ameliorate soil microbial properties due to increases in the nutrients availability, and in turn, will lead to the high soil productivity. For example, soil microorganisms have a more efficient metabolism under a balanced fertilization than that under nutrient-deficient fertilization;1 as a consequence, soil microorganisms’ abundance, diversity, and richness are improved under a balanced fertilization.2,3 Microorganisms are key constituents of soil ecosystems and can characterize soil fertility.4 Indeed, He et al. has found that the soil fungal diversity is a good sensitive indicator of soil fertility.2 As one important fungi, arbuscular mycorrhizal fungi (AMF) are ubiquitous soil microorganisms which form a mutualistic symbiosis with the roots of over 80% of all land plants.5 They are beneficial for agricultural crop productivity, because they improve plant nutrition acquisition by supplying mineral nutrients. The uptake of P is most important, at the same time, the uptakes of N, Cu, and Zn may be substantially © 2012 American Chemical Society
enhanced. Besides, AMF play many other roles, such as protection of plants from pathogens,6 improvement of soil structure7 and heavy metal resistance of plants, 8 and suppression of aggressive agricultural weeds.9 Furthermore, AMF community is one of good indicators of soil ecosystem. Recent high-throughput sequencing investigations has revealed that shifts in soil AMF community sensitively mirror the landuse gradient10 and even changes in seasonal temperatures.11 Therefore, we postulate that the knowledge of AMF community responses to different fertilizations could direct us toward a more effective fertilization. For example, changes in AMF community composition and/or diversity could reflect the demand of agricultural soils for certain nutrient. AMF diversity in agro-ecosystems has been extensively studied by culture-independent12−14 and -dependent approaches.15−17 Though these technologies are indispensable approaches for AMF studies, they are still insufficient to uncover its diversity.18 High-throughput sequencing is a Received: Revised: Accepted: Published: 5764
January 19, 2012 April 24, 2012 May 14, 2012 May 14, 2012 dx.doi.org/10.1021/es3001695 | Environ. Sci. Technol. 2012, 46, 5764−5771
Environmental Science & Technology
Article
revolutionizing microbial ecology tool, which can offer sufficient sequencing depth. It reveals microorganism community, diversity, and biogeography that are inaccessible with genetic fingerprinting, clone library, and culture-reliant methods.19 In this study, we applied the high-throughput sequencing technique to investigate AMF community composition in arable soils through shifts in AMF community in response to long-term fertilizer applications. We also wanted to illustrate the ecological function of AMF assemblage in arable soil, both of which would be of great help toward a better understanding of how a balanced fertilization impacts the agroecosystem. For aforementioned purposes, AMF assemblages in arable soils with >20-year different fertilizations (OM (organic manure), fertilizer NP, NK, and NPK as well as control without fertilization) in Fengqiu Agro-Ecological Experimental Station, Institute of Soil Science, Chinese Academy of Sciences were investigated. 124998 of 18S rRNA gene fragments dominated by Glomeromycota with 59611 sequences, generating 70 OTUs, were obtained. The sequence data set allowed us to make exhaustive analyses and comparisons of AMF community structures, richness, and diversities under different long-term fertilizations.
maize was irrigated 1−2 times. The volume of water used for each of irrigation was 900−1200 m3 ha−1. Soil Sampling and DNA Extraction. In September 2010 (at maize harvesting stage), three plots for each of NK, NP, NPK, OM, and Control treatments (total of 15 out of 28 plots) were chosen for soil sampling. Soil samples were collected from 16 points at the depth of 0−15 cm from each plot, and then mixed and homogenized by passing through
