Overuse of chemical fertilizers to maintain tea production has caused many adverse effects in tea plantations and largely hampers the sustainable development of the tea industry. Applying bio-organic fertilizer (BOF) to achieve the goal of sustainable agriculture has become popular because of its advantages, such as its pollution-free nature, considerable amount of beneficial microbes and soil-friendly organic materials. However, the effects of BOF application on tea plantation soil remain an open question. Herein, we carried out a 3-year pot experiment with four treatments, including control without fertilization (CK), 100% chemical fertilizer (CF), 50% chemical fertilizer +50% BOF (CFOF) and 100% BOF (OF), to explore the effects of BOF application on soil fertility and bacterial community in tea plantations. The results showed that BOF application could increase soil fertility in both bulk and rhizosphere soils and improve the biomass of tea leaves. In addition, the nutrient level change caused by BOF application significantly changed bacterial community diversity and composition and accounted for 74.91% of the community variation. CFOF and OF treatments significantly increased the bacterial Chao1 and Shannon indices compared to CF treatment (p < 0.05). Moreover, bacterial community composition was dominated by Betaproteobacteria (46.88%), Acidobacteria (11.29%), Alphaproteobacteria (9.69%) and Gammaproteobacteria (9.59%). BOF application increased the relative abundance of Alphaproteobacteria, Acidobacteria, Deltaproteobacteria and planctomycetes and decreased the relative abundance of Betaproteobacteria (p < 0.05). Furthermore, bacterial function prediction revealed that BOF application improved the N and C cycling processes and enhanced the co-occurrence network complexity in the bulk soils. Bacterial community functions and co-occurrence networks in the rhizosphere did not show similar results, indicating that rhizosphere bacterial communities were more affected by the rhizosphere effect than BOF application. All these findings verified our hypothesis that applying BOF in tea plantations could increase the biomass of tea plants by improving soil fertility and influencing the soil bacterial function groups. In summary, we suggested that BOF application could be a promising way to achieve the sustainable development of the tea industry.

Crop coefficient (K_c) is one of the most significant parameters for crop water demand prediction and irrigation scheduling. However, there is a lack of knowledge about water vapor and K_c in tea plantation ecosystems. This study explored and determined the actual evapotranspiration (ET_c) and K_c of two cultivars of tea (Camellia sinensis), clone variety Baiye1 (BY1) and Longjing43 (LJ43), based on lysimeter data. An estimation was made for both for ET_c and adjusted ET_c, and the corresponding K_c and adjusted K_c. The results showed that the adjusted ET_c and K_c values revealed a minor fluctuation when compared to the ET_c and K_c values during the experimental period, which indicated that the adjusted ET_c and K_c values were more precise and practical to field conditions. The average adjusted K_c values were 0.71 (range of 0.43–1.02) for BY1 and 0.84 (range of 0.48–1.22) for LJ43. Additionally, heavy pruning can decrease ET_c and K_c values, possibly due to the lower level of LAI after pruning. Moreover, it is clearly manifested that BY1 consistently had lower ET_c and K_c values than those of LJ43 because of plant growth status differences between BY1 and LJ43. Overall, our study proposed a reliable reference of K_c in tea plantation, and illuminated the effects of pruning and plant growth differences on K_c, which could provide a strong basis for precise irrigation in tea plantations in a subtropical climate.

Although annual return of litter occurs in tea (Camellia sinensis L.) plantations, the level of soil organic carbon (SOC) therein remains relatively low. The exact impacts of pruned litter on soil and its association with SOC accumulation in tea plantations remain unclear. In this study, we prepared ¹³C-labeled tea plant material and incubated it with soils collected at a tea plantation. Carbon dioxide (CO₂) efflux and its sources were measured and distinguished based on the ¹³C isotopic method. Soil microbial community and the utilization of litter C were assessed by phospholipid fatty acid (PLFA) analysis combined with a stable isotope probing (SIP) technique. Litter incorporation initially significantly increased CO₂ efflux. The majority of CO₂ production (>90%) arose from native SOC mineralization, which was reflected by a strong positive priming effect (PE) that decreased over time. During the incubation period, β-glucosidase activity significantly decreased in both the control and litter-amended soil. A significant difference in the microbial community was observed between control and litter-amended soil, in which litter incorporation significantly increased the biomass of each microbial group relative to control soil. Based on PLFA-SIP, 78% of the C incorporated into individual microbes was derived from native SOC, while only 22% was derived from litter. Additionally, partial least squares regression path modeling (PLS-PM) revealed that the microbes associated with native SOC mineralization directly affected the changes in SOC (ΔC_SOC+litter), whereas microbes related to litter degradation exhibited an indirect effect on ΔC_SOC+litter by affecting β-glucosidase activity under litter incorporation. Taken together, SOC accumulated less in the tea plantation system despite the annual return of pruned litter to the field.

The application of shaking during the withering process has been shown to significantly enhance the floral aroma of black tea. However, prior to this study, there was limited research on the effects of shaking combined with other withering treatments on the aroma components of black tea. In this study, the aroma attributes of black teas processed with shaking combinations of yellow-light or high-temperature withering (YLS, HTS, and HYS) were evaluated through sensory evaluation, and the volatile composition and identification of key aroma compounds in black teas and in-process withered tea leaves were analyzed by gas chromatography–mass spectrometry (GC-MS). The results indicated that black teas subjected to different shaking combinations exhibited a distinct floral aroma with higher volatile compound content, with the YLS treatment showing the most significant aroma improvement. Eight volatile compounds with relative odor activity values (rOAV) > 1 were identified from 53 differential volatile compounds in black tea under different shaking combinations as the most important contributors to aroma quality. Linalool, trans-β-Ionone, α-cedrene, and nonanal were identified as key floral volatiles with high rOAVs. Their concentrations in YLS were notably higher compared to those in S, both in withered tea leaves (with the exception of trans-β-Ionone) and in the final dry black teas, suggesting that there may be a synergistic effect between the yellow-light withering and the shaking process in enhancing these key floral compounds. Overall, this study found that shaking combined with yellow-light withering can improve the aroma composition and quality of black tea, providing a theoretical basis and practical guidance for the production and optimization of high-aroma black tea.

In order to achieve sustainable development of the tea industry in China, it is necessary to reduce the use of chemical fertiliser rationally. With conventional fertilisation (CF) treatment as the control, five different chemical fertiliser-reduced regimes, including tea-specific formula fertiliser (T1), T1 + acidification amendment (T2), organic substitution based on T1 (T3), urea formaldehyde slow-release fertiliser (T4) and carbon-based organic fertiliser (T5), were conducted and evaluated on a green tea plantation from 2018 to 2021. The results showed that the spring tea yield of T1–T5 increased by 4.65–28.67%, while the free amino acids, tea polyphenols and sensory evaluation scores did not remarkably decrease. In addition, the T1–T5 treatments had a slight effect on soil acidification mitigation (except T2) and maintained the essential nutrients for tea production. Nutrient use efficiency improved, with agronomic efficiency (AE) increasing by 0.01–0.08 kg kg⁻¹, shoot nutrient use efficiency (NUE) by 0.14–0.70% and partial factor productivity (PFP) by 0.05–0.18 kg kg⁻¹. The net economic benefits also improved, with T1 showing a 135.28% increase, followed by T3 (67.53%), T2 (48.65%), T4 (38.07%) and T5 (33.35%). Overall, our results indicated that the T1 treatment could maintain the tea yield and quality while reducing the chemical fertiliser input and maximising the net economic benefit and AE.