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.

In order to investigate the effect of benzothiadiazole (BTH) and β-aminobutyric acid (BABA) on the resistance of tea plants (Camellia sinensis) to tea geometrid (Ectropis obliqua), three levels each of benzothiadiazole (BTH) and β-aminobutyric acid (BABA) were sprayed on 10-year-old tea plants. Generally PPO and PAL activities increased with low concentrations of BTH and BABA treatments. Quantitative RT-PCR revealed a 1.43 and 2.72-fold increase in PPO gene expression, and 3.26 and 3.99-fold increase in PAL gene expression with 75 mg/L BTH and 400 mg/L BABA respectively. Analysis of hydrolysis of synthetic substrates also revealed that chymotrypsin-like enzyme activity present in larval midgut extracts was not significantly inhibited by BTH and BABA. However, proteinase activity was found to be inversely proportional to the age of tea geometrid. Larvae pupation rate decreased by 8.10, 10.81 and 21.62% when tea geometrid were fed with leaves treated with 25, 50 and 75 mg/L BTH solutions, while 100, 200 and 400 mg/L BABA solutions decreased same by 8.10, 16.21 and 13.51% respectively. Also, larvae development period delayed to 23.33 and 26.33 days with 75 mg/L BTH and 400 mg/L BABA treatments respectively. The results in this study; therefore, suggest that benzothiadiazole (BTH) and β-aminobutyric acid (BABA) play a role in inducing resistance in tea plants to tea geometrid, with the optimal effect achieved at BTH-3 (75 mg/L) and BABA-3 (400 mg/L), respectively.