Objectives The aims of the study were to understand the effects of different organic fertilizers on fungal community structure and functional groups in tobacco-planting soil, so as to provide scientific basis for guiding the rational fertilizer application and alleviating continuous cropping obstacles and soil-borne diseases.
Methods Five local main organic materials were used to make the tested composts, and tobacco cultivar Yun87 was selected as experimental crop for a field experiment in Fujina Province. The six treatments included chemical fertilizer control (CK), chicken manure (T1), sesame cake (T2), rapeseed cake (T3), cow dung (T4) and rice straw (T5). All the treatments were adjusted to the same NPK input ratio and amount using chemical fertilizers. Illumine high-throughput sequencing and FUNGuild were employed to determine soil fungal community structure, diversity, composition and community function under the six treatments.
Results Combined UPGMA clustering analysis with principal coordinate analysis (PCoA), the treatments of T5, T4 and T1 had greater impact on soil fungal community structure in the vigorous growth period of tobacco, and the T2 and T3 treatments had greater effect in the mature period. Compared with CK, the proportion of saprophytic fungi in T2, T3 and T5 treatments were increased significantly by 262.0%, 64.0% and 198.0%, respectively. Among them, the proportion of saprophytic fungi of rice straw treatment exceeded the proportion of pathological nutritive fungi and became the dominant fungal community. The proportion of symbiotic fungi in T1, T2 and T4 treatments was increased significantly by 80.0%, 320.0% and 85.71%, respectively. T1, T2 and T4 treatments respectively increased the relative abundance of plant pathogens Monographella (408.98%), Microidium (93.63%) and Gibberella (559.22%).
Conclusions Application of all the tested five organic fertilizers could increase the ratio of soil saprophytic fungi and symbiotic fungi, which is beneficial to create a stable and health soil ecosystem. The effects of changing soil fungal community structure are different among the organic fertilizers and in different tobacco growing stages. Rice straw has the highest superiority in reducing the risk of soil-borne diseases in long-term tobacco rice rotation and improves soil fertility, followed by chicken manure and rapeseed cake compost; sesame cake and cow dung compost could increase the proportion of saprophytic fungi and symbiotic fungi as well, but have the risks of Fusarium graminearum and tobacco root rot in tobacco rice rotation system.
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