Earthworm activity optimized the rhizosphere bacterial community structure and further alleviated the yield loss in continuous cropping lily (Lilium lancifolium Thunb.)

Yaoxiong Lu,Wei Li,Jiamin Zhou,Peng Gao,Yunsheng Wang,Liangying Dai,Xinwei Cui,Fuyuan Peng

doi:10.1038/s41598-021-99597-y

Abstract

The soil microbial community plays a vital role in the biogeochemical cycles of bioelements and maintaining healthy soil conditions in agricultural ecosystems. However, how the soil microbial community responds to mitigation measures for continuous cropping obstacles remains largely unknown. Here we examined the impact of quicklime (QL), chemical fungicide (CF), inoculation with earthworm (IE), and a biocontrol agent (BA) on the soil microbial community structure, and the effects toward alleviating crop yield decline in lily. High-throughput sequencing of the 16S rRNA gene from the lily rhizosphere after 3 years of continuous cropping was performed using the Illumina MiSeq platform. The results showed that Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria, Chloroflexi and Gemmatimonadetes were the dominant bacterial phyla, with a total relative abundance of 86.15–91.59%. On the other hand, Betaproteobacteriales, Rhizobiales, Myxococcales, Gemmatimonadales, Xanthomonadales, and Micropepsales were the dominant orders with a relative abundance of 28.23–37.89%. The hydrogen ion concentration (pH) and available phosphorus (AP) were the key factors affecting the structure and diversity of the bacterial community. The yield of continuous cropping lily with using similar treatments decreased yearly for the leaf blight, but that of IE was significantly (p < 0.05) higher than with the other treatments in the same year, which were 17.9%, 18.54%, and 15.69% higher than that of blank control (CK) over 3 years. In addition, IE significantly (p < 0.05) increased organic matter (OM), available nitrogen (AN), AP, and available potassium (AK) content in the lily rhizosphere soil, optimized the structure and diversity of the rhizosphere bacterial community, and increased the abundance of several beneficial bacterial taxa, including Rhizobiales, Myxococcales, Streptomycetales and Pseudomonadales. Therefore, enriching the number of earthworms in fields could effectively optimize the bacterial community structure of the lily rhizosphere soil, promote the circulation and release in soil nutrients and consequently alleviate the loss of continuous cropping lily yield.

Highlights

The soil microbial community plays a vital role in the biogeochemical cycles of bioelements and maintaining healthy soil conditions in agricultural ecosystems
The responses of the soil microbial community were investigated for continuous cropping lily (Lilium lancifolium Thunb.) for 3 years when the mitigation measures were applied for continuous cropping obstacles
In order to reveal the effects of different treatments on the yield from continuous cropping, lily was planted continuously from 2015 to 2018 and treated with five different ways: blank control (CK), quicklime (QL), chemical fungicide (CF), inoculation with earthworms (IE), and a biocontrol agent (BA)

Summary

Introduction

The soil microbial community plays a vital role in the biogeochemical cycles of bioelements and maintaining healthy soil conditions in agricultural ecosystems. These chemical compounds are usually secreted by the roots or produced by the decomposition of root residues, which tend to cause a direct rhizosphere microorganisms s election[6,7] and lead to a soil microbial community structure imbalance[8], to be the main cause of continuous cropping obstacles These will subsequently result in decreasing of the diversity and richness indices of bacterial c ommunity[9]. In contrast chemical methods include the use of trifloxystrobin, carbendazim, mancozeb, thiram and c hlorothalonil[14,15], and biological methods include using biocontrol b acteria[16], biological organic fertilizer[17], and earthworm activities (wormcast)[18,19] All of these treatments are beneficial for optimizing the microbial community structure of continuous cropping soils, and adjust the unfavorable factors affecting plant growth and directly inhibiting the rapid growth of soil fungi. Soil properties, and the rhizosphere bacterial community were investigated to provide a theoretical basis for exploring an efficient cultivation technique for continuous cropping lily

Methods

Results

Discussion

Conclusion