Background and aims

Maintaining sustainable high yield and soil fertility is the key to cultivate perennial alfalfa grassland. However, little is known about the effects of rhizosphere microbes on soil fertility and alfalfa yield in different planting years and regimes.

Methods

We sampled 10 alfalfa fields to investigate the rhizosphere soil microbial community and yields in monoculture and rotation systems in different planting years.

Results

The alfalfa yield in monoculture was significantly declined (P < 0.05) starting in 6 yr. Wheat-corn-alfalfa rotation generated higher (P < 0.05) soil fertility index and alfalfa yield than wheat-alfalfa rotation and 2 yr alfalfa monoculture. The alfalfa yield significantly (R² = 0.583, P < 0.001) increased with soil fertility. Significant differences were observed for bacteria (R_ANOSIM = 0.955, P = 0.001) and fungal (R_ANOSIM = 0.889, P = 0.001) communities in different planting years and regimes. Different ecological processes dominated bacterial and fungal communities assembly. Blastococcus and Massilia were important biomarkers, which had a significant (P < 0.05) positive correlation with alfalfa yield. PLS-PM analysis identified that planting regimes had positive impacts on alfalfa yield through edaphic variables, microbial genera and fungal community composition. Conversely, planting years had negative effects on alfalfa yield by indirectly regulating fungal genera and community composition through fungal community assembly.

Conclusions

This study could help improve our understanding of the role and importance of rhizosphere soil microbial changes in regulating farmland soil processes and crop productivity.

中文翻译：

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群落组装通过调节不同种植年份和制度的根际土壤微生物群落组成与紫花苜蓿生产相关

背景和目标

保持可持续的高产和土壤肥力是培育多年生苜蓿草草地的关键。然而，在不同种植年份和制度下，根际微生物对土壤肥力和苜蓿产量的影响知之甚少。

方法

我们对 10 个紫花苜蓿田进行了抽样调查，以调查不同种植年份单作和轮作系统的根际土壤微生物群落和产量。

结果

从 6 年开始，单作苜蓿产量显着下降（P  < 0.05）。小麦-玉米-苜蓿轮作产生的 土壤肥力指数和苜蓿产量高于小麦-苜蓿轮作和2年苜蓿单作。 苜蓿产量随着土壤肥力的增加而显着增加（R ²  = 0.583, P < 0.001）。 在不同种植年份和制度下，细菌 (R _ANOSIM  = 0.955, P  = 0.001) 和真菌 (R _ANOSIM  = 0.889, P = 0.001) 群落存在显着差异。不同的生态过程主导了细菌和真菌群落的组装。芽球菌和Massilia是重要的生物标志物， 与苜蓿产量呈显着（ P < 0.05）正相关。PLS-PM 分析发现，种植制度通过土壤变量、微生物属和真菌群落组成对紫花苜蓿产量产生积极影响。相反，种植年限通过真菌群落组装间接调节真菌属和群落组成，从而对苜蓿产量产生负面影响。

结论

这项研究有助于加深我们对根际土壤微生物变化在调节农田土壤过程和作物生产力中的作用和重要性的理解。