Purpose

Fallowing is an improvement process aimed at promoting the soil health and the sustainability of cultivated land. How it affects the soil health-related abiotic properties and microbial community composition under different levels of cadmium (Cd) contamination is not well known.

Materials and methods

This study involved applying consistent fallowing practices to paddy soils of low and high Cd content, in order to examine changes in the soil Cd, nutrient, and microbial community using a high-throughput sequencing method.

Results and discussion

Fallowing significantly decreased available Cd and phosphorus (P) content, but increased ammonium nitrogen (N) on lightly contaminated plots, whereas only P variables changed significantly for heavily contaminated plots. Furthermore, fallowing significantly decreased bacterial Shannon diversity on lightly contaminated plots and altered bacterial community composition on heavily contaminated plots, but it had no impact on archaeal or fungal communities, indicating that bacteria are more sensitive to fallowing than archaea and fungi. Specifically, fallowing significantly promoted some copiotrophic bacteria (Alphaproteobacteria and Betaproteobacteria) but suppressed some oligotrophic taxa (Chloroflexi phylum and OTU5837 belonging to the phylum Acidobacteria) on highly contaminated plots. Interestingly, the soil microbial community in the lightly contaminated plots was mainly affected by soil pH, C, and N properties, whereas on heavily contaminated plots, it was largely influenced by soil Cd and P variables.

Conclusions

Overall, these findings showed that fallowing significantly improved soil N availability but decreased Cd availability in lightly contaminated conditions, while shifts in microbial community composition under heavily contaminated conditions may indirectly enhance soil nutrient availability and reduce available Cd. These findings highlight the significance of fallowing to promote the health and the sustainability of Cd-contaminated cultivated land.

中文翻译：

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休耕后土壤有效镉和细菌群落的变化取决于污染水平

目的

休耕是一种改善过程，旨在促进土壤健康和耕地的可持续性。在不同水平的镉（Cd）污染下，它如何影响与土壤健康相关的非生物特性和微生物群落组成，这一点尚不清楚。

材料和方法

这项研究涉及对低和高Cd含量的稻田应用一致的休耕方法，以便使用高通量测序方法检查土壤Cd，养分和微生物群落的变化。

结果与讨论

休耕显着降低了轻度污染土地上的有效镉和磷（P）含量，但增加了铵态氮（N），而重度污染土地上只有P变量发生了显着变化。此外，在轻度污染的土地上，休耕显着降低了细菌的香农多样性，在重度污染的土地上改变了细菌群落的组成，但对古细菌或真菌群落没有影响，表明细菌比古细菌和真菌对休耕更为敏感。具体而言，休耕显着促进了一些嗜营养细菌（α变形细菌和Beta变形细菌），但抑制了一些贫营养类群（Chloroflexi phylum和OTU5837属于该门）酸性细菌）在高度污染的地块上。有趣的是，轻度污染区的土壤微生物群落主要受土壤pH，C和N性质的影响，而重度污染区的土壤微生物群落主要受土壤Cd和P变量的影响。

结论

总体而言，这些发现表明，在轻度污染的条件下，休耕可显着改善土壤氮素的利用率，但降低了Cd的利用率，而在重度污染的条件下，微生物群落组成的变化可能间接增加土壤养分的利用率，并降低了Cd的利用率。这些发现突出了休耕对促进镉污染的耕地的健康和可持续性的重要性。