Fuyuan Peng

Rational application of organic and chemical fertilizers is beneficial to improve crop yield and quality. However, the effect of combining these fertilizers on bacterial community structure and metabolic functions remains unclear, especially in reddish paddy soil. In the present study, absolute quantification 16S rRNA amplicon sequencing technology (AQS) was used to study the responses of soil bacterial community composition and its absolute abundance to environmental factors under different application ratios of organic and chemical fertilisers for two consecutive years in reddish paddy soil. The results showed that replacing the chemical fertiliser with organic fertiliser significantly increased the total nitrogen (TN), total potassium, hydrolysed nitrogen, and soil organic carbon (SOC), and significantly decreased the soil bulk density. These effects were more prominent in the treatment with 60% of organic fertilizer (60M). More importantly, AQS revealed that different fertilization treatments non-significantly affected soil bacterial diversity (Shannon) and richness (Chao1) but significantly changed the composition and abundance of bacterial communities. SOC, TN, and available potassium were the key factors shaping bacterial community structure under different fertilization regimes. The bacterial absolute abundance in the 60M treatment was 25.30% and 56.58% higher than that in the NPK and 30M treatments, respectively. Functional prediction analysis with PICRUSt2 revealed that the 60M treatment increased the abundance of species involved in xenobiotic biodegradation and metabolism, amino acid metabolism, and lipid metabolism, and further improved metabolic functions to a certain degree.

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.