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The spatial heterogeneity of potentially toxic elements (PTEs) in a typical green tea-producing area in Zhejiang was investigated with application of geostatistics. The positive matrix factorization (PMF) was conducted for analysis of pollution sources and risk assessment of the soil of the tea garden. The results revealed that 93.52% of the study area did not exceed the PTEs risk screening value in the soil pollution risk control standard of agricultural land. The results of the spatial heterogeneity analysis showed that Cd and Pb had moderate spatial auto-correlation, exhibiting similar spatial distribution patterns. The high-value locations were distributed in the southeast of the study area, while low-value locations were distributed in the southwest of the study area. The Cr, As, and Hg had strong spatial auto-correlation, while Cr and As had similar spatial distribution patterns whose high-value areas and low-value areas were concentrated in the west and center of the study area, respectively. The Cd, Pb, and As originated from the agricultural source, transportation source, and industrial source, respectively, while Cr and Hg were from the natural source on the basis of the results of the PMF model. The results of a potential ecological risk assessment revealed that five PTEs in the study area were of low potential risk. The single-factor ecological risk ranking was Cd > As > Hg > Cr > Pb. The overall ecological risk in the study area was slight. The human health risk model indicates that there was a non-carcinogenic risk for children in the study area, and the high-value area was concentrated in the northwest of the study area. It is concluded that emphasis shall be given to excessive Cd caused by agricultural sources in the southeast of the study area, and control and monitoring will be strengthened in the northwestern part of the study area. The relevant measures for prevention of soil pollution must be conducted.

Selenium (Se)-enriched tea is a well-regarded natural beverage that is often consumed for its Se supplementation benefits. However, the production of this tea, particularly in Se-abundant tea plantations, is challenging due to soil acidification. Therefore, this study aimed to investigate the effects of changes in Se under acidified soil conditions. Eight tea plantation soil monitoring sites in Southern Jiangsu were first selected. Simulated acid rain experiments and experiments with different acidification methods were designed and soil pH, as well as various Al-ion and Se-ion concentrations were systematically determined. The data were analyzed using R statistical software, and a correlation analysis was carried out. The results indicated that as the pH value dropped, exchangeable selenium (Exc-Se) and residual selenium (Res-Se) were transformed into acid-soluble selenium (Fmo-Se) and manganese oxide selenium (Om-Se). As the pH increased, exchange state aluminum (Alex) and water-soluble aluminum (Alw) decreased, Fmo-Se and Om-Se declined, and Exc-Se and Res-Se increased, a phenomenon attributed to the weakened substitution of Se ions by Al ions. In the simulated acid rain experiment, P1 compared to the control (CK), the pH value of the YJW tea plantation decreased by 0.13, Exc-Se decreased by 4 ug mg−1, Res-Se decreased by 54.65 ug kg−1, Fmo-Se increased by 2.78 ug mg−1, and Om-Se increased by 5.94 ug mg−1 while Alex increased by 28.53 mg kg−1. The decrease in pH led to an increase in the content of Alex and Alw, which further resulted in the conversion of Exc-Se to Fmo-Se and Om-Se. In various acidification experiments, compared with CK, the pH value of T6 decreased by 0.23, Exc-Se content decreased by 8.35 ug kg−1, Res-Se content decreased by 40.62 ug kg−1, and Fmo-Se content increased by 15.52 ug kg−1 while Alex increased by 33.67 mg kg−1, Alw increased by 1.7 mg kg−1, and Alh decreased by 573.89 mg kg−1. Acidification can trigger the conversion of Exc-Se to Fmo-Se and Om-Se, while the content of available Se may decrease due to the complexation interplay between Alex and Exc-Se. This study provides a theoretical basis for solving the problem of Se-enriched in tea caused by soil acidification.

The application of biochar is one of the promising management practices to alleviate soil acidification and improve soil fertility. However, it has been found to reduce the content of ammonium nitrogen (NH4+−N) in the soil, which is the most important form of nitrogen (N) for tea tree growth. To investigate the response of soil NH4+−N content to the combined application of biochar and pruned tea plant litter, a pot trial was performed with three treatments: control (CK); biochar (BC); biochar + tea plant litter (BC + L). Soil chemistry properties and ammonification rates were determined, and the microbial community composition was analyzed by high-throughput sequencing. The results showed that the NH4+−N content in BC + L treatment was 1.7–9.5 fold higher than CK and BC treatments after 15 days of application, with no difference in the proportion of ammonia oxidation phyla such as Nitrospirae. The proportion of soil fungus Ascomycota was strongly correlated with the content of soil available nitrogen (p = 0.032), and the relationship was well described by a linear equation (R2 = 0.876, p = 0.01). Further redundancy analysis revealed that soil pH, soil organic carbon (SOC), the ratio of SOC to total nitrogen and the ratio of SOC to alkaline hydrolyzable nitrogen appeared to be important factors influencing the separation of BC + L from CK and BC groups. In summary, the addition of biochar and pruned tea plant litter alters soil properties and may influence the composition of microorganisms with various trophic groups, thus affecting ecosystem function. Our results also highlight the importance of returning pruned materials with biochar application in tea plantation ecosystems.

Biofertilizers have been suggested as alternatives to synthetic fertilizers, which could reduce soil degradation brought on by excessive chemical fertilization and have an impact on the bacterial diversity and community in the soil. The diversity and community of soil bacteria in tea plantations treated with wheat straw compost have, however, received relatively little attention. In this research, a two-year field trial was run to examine the effects of applying wheat straw compost on the characteristics of the soil and the quality of the tea. We also used high-throughput sequencing to investigate the response of the soil bacterial community, and Spearman’s rank correlation was used to estimate the relationship between the soil bacterial community, soil characteristics, and tea quality. It was noticed that applying chemical fertilizer along with compost increased the fertility of the soil and the quality of the tea. Based on a two-year thorough data analysis, the T4 treatment (compost fertilizers 15,000 kg ha−1 + chemical fertilizers 1050 kg ha−1, chemical fertilizer reduction 30%) was determined to be the best group. The diversity and community makeup of soil bacteria were impacted by fertilization management. After the initial compost replacement, soils with compost had a greater bacterial richness than soils with inorganic fertilizers. After the second compost substitution, PCoA analysis revealed that compost fertilizer could be easily differentiated from chemical fertilizer. In 2019, Proteobacteria, Actinobacteria, Acidobacteria, Bacteroidetes, and Patescibacteria were the most prevalent bacterial phyla. In 2020, Firmicutes and Chloroflexi overtook Bacteroidetes and Patescibacteria as the two major bacterial phyla. In addition to increasing the diversity of soil bacteria and having an impact on the bacterial population, the application of wheat straw compost mixed with chemical fertilizers can also control the soil’s characteristics and the quality of the tea produced in tea plantations. So, as a fertilization way with less environmental impact, wheat straw compost fertilization can be used in tea plantations.

Abstract Background Cow manure is not only an agricultural waste, but also an organic fertilizer resource. The application of organic fertilizer is a feasible practice to mitigate the soil degradation caused by overuse of chemical fertilizers, which can affect the bacterial diversity and community composition in soils. However, to our knowledge, the information about the soil bacterial diversity and composition in tea plantation applied with cow manure fertilization was limited. In this study, we performed one field trial to research the response of the soil bacterial community to cow manure fertilization compared with urea fertilization using the high-throughput sequencing technique of 16S rRNA genes, and analyzed the relationship between the soil bacterial community and soil characteristics during different tea-picking seasons using the Spearman’s rank correlation analysis. Results The results showed that the soil bacterial communities were dominated by Proteobacteria, Bacteroidetes, Acidobacteria and Actinobacteria across all tea-picking seasons. Therein, there were significant differences of bacterial communities in soils with cow manure fertilization (CMF) and urea fertilization (UF) in three seasons: the relative abundance of Bacteroidetes in CMF was significantly higher than that in UF and CK in spring, and the relative abundance of Proteobacteria and Bacteroidetes in CMF was significantly higher than that in UF and CK in autumn. So, the distribution of the dominant phyla was mainly affected by cow manure fertilization. The diversity of bacterial communities in soils with cow manure fertilization was higher than that in soils with urea fertilization, and was the highest in summer. Moreover, soil pH, OM and AK were important environmental properties affecting the soil bacterial community structure in tea plantation. Conclusions Although different fertilizers and seasons affect the diversity and structure of soil microorganisms, the application of cow manure can not only improve the diversity of soil bacteria, but also effectively regulate the structure of soil bacterial community in tea plantation. So, cow manure fertilization is more suitable for tea plantation.

Abstract Background Different mulches have variable effects on soil physicochemical characteristics, bacterial and fungal communities and ecosystem functions. However, the information about soil microbial diversity, community structure and ecosystem function in tea plantation under different mulching patterns was limited. In this study, we investigated bacterial and fungal communities of tea plantation soils under polyethylene film and peanut hull mulching using high-throughput 16S rRNA and ITS rDNA gene Illumina sequencing. Results The results showed that the dominant bacterial phyla were Proteobacteria, Actinobacteria, Acidobacteria and Chloroflexi, and the dominant fungal phyla were Ascomycota, Mortierellomycota and Basidiomycota in all samples, but different mulching patterns affected the distribution of microbial communities. At the phylum level, the relative abundance of Nitrospirae in peanut hull mulching soils (3.24%) was significantly higher than that in polyethylene film mulching soils (1.21%) in bacterial communities, and the relative abundances of Mortierellomycota and Basidiomycota in peanut hull mulching soils (33.72, 21.93%) was significantly higher than that in polyethylene film mulching soils (14.88, 6.53%) in fungal communities. Peanut hull mulching increased the diversity of fungal communities in 0–20 cm soils and the diversity of bacterial communities in 20–40 cm soils. At the microbial functional level, there was an enrichment of bacterial functional features, including amino acid transport and metabolism and energy production and conversion, and there was an enrichment of fungal functional features, including undefined saprotrophs, plant pathogens and soils aprotrophs. Conclusions Unique distributions of bacterial and fungal communities were observed in soils under organic mulching. Thus, we believe that the organic mulching has a positive regulatory effect on the soil bacterial and fungal communities and ecosystem functions, and so, is more suitable for tea plantation.