Effects of Different Farming Methods and Their Effects on Soil Physicochemical Properties of Guilin Maojian Tea Gardens

In order to further optimize the cultivation and agronomic technology of Guilin Maojian tea gardens, the effects, efficiencies and costs of different farming methods and their effects on the physiochemical properties of tea garden soil were studied through the modification of the test sites with the non-farming land as the control. The results showed that human farming, mini-tiller farming and crawler tractor farming could improve the physical and chemical properties of soil. After farming, the soil had good water retention but low moisture content compared to the control group, while the soil bulk density and hardness value were significantly lower than those of the control, and the porosity of soil was significantly higher than that of contrast. With the passage of time, soil bulk density and hardness value gradually increased after farming, while the porosity of soil decreased gradually. There were great differences in the effects, efficiencies and costs of different farming methods. Crawler tractor had the best and most stable farming effect, and the operation efficiency was 10 times that of human farming while the cost was only 0.39 times of human farming. Therefore, it was feasible to adopt mini-tiller or crawler tractor to carry out mechanical farming of Guilin Maojian tea garden, which provided theoretical references for the soil property improvement using mechanical farming and was favorable for promoting the popularization of farming machines and the acceleration of mechanization of tea gardens. But for tea plantations that are intended to be mechanized, apart from the mechanical and technical personnel to be configured in place, the site conditions, planting modes and mechanical way reservation of tea garden should be planned accordingly. It is recommended to select flat or gentle slope for reclamation, and preference is given to non-sexual tea tree varieties with big line spacing over 180 cm long. Moreover, the main road construction should be more than 3.0 m, and trunk road 2.0 m or above. And isolation ditch and drain should be set between the tea garden and the surrounding mountain forests and farmland.

Colonization of Penicillium oxalicum SL2 in Pb-contaminated paddy soil and its immobilization effect on soil Pb

Penicillium oxalicum SL2(SL2) is a previously screened Pb-tolerant fungus that can promote crops growth. The relationship between SL2 colonization and Pb immobilization was studied to provide a theoretical basis for microbial remediation of Pb-contaminated paddy soil.In this study, green fluorescent protein(GFP) labeled SL2 was inoculated into different Pbcontaminated paddy soils(S1-S6). The Pb extracted from the soil by HNO, EDTA and CaClwere used to characterize the available Pb. The results showed that the colonization of SL2was divided into lag phase(0-7 days), growth phase(7-30 days), and mortality phase(30-90days). SL2 colonized well in sandy soils rich in clay and total phosphorus with initial p H of 4.5-7.0. In addition, SL2 increased soil p H and decreased soil Eh, which was beneficial to immobilize Pb. In different soils, the highest percentages of CaCl-Pb, EDTA-Pb, and HNO3-Pb immobilized by SL2 were 34.34%-40.53%, 17.05%-20.11%, and 7.39%-15.62%, respectively.Pearson correlation analysis showed that the percentages of CaCl-Pb and EDTA-Pb immobilized by SL2 were significantly positively correlated with the number of SL2 during the growth phase. SL2 mainly immobilized Pb in the growth phase and a higher peak number of SL2 was beneficial to the immobilization of Pb.

Unlocking the bacterial contact-dependent antibacterial activity to engineer a biocontrol alliance of two species from natural incompatibility to artificial compatibility

Plant growth-promoting rhizobacteria(PGPR)contain various biocontrol bacteria with broad-spectrum antimicrobial activity,and their single species has been extensively applied to control crop diseases.The development of complex biocontrol community by mixing two or more PGPR members together is a promising strategy to enlarge the efficacy and scope of biocontrol.However,an effective method to assess the natural compatibility of PGPR members has not yet been established to date.Here,we developed such a tool by using the bacterial contactdependent antibacterial activity(CDAA)as a probe.We showed that the CDAA events are common in two-species interactions in the four selected representative PGPRs,represented by the incompatible interaction of Lysobacter enzymogenes strain OH11(OH11)and Lysobacter antibioticus strain OH13(OH13).We further showed that the CDAA between OH11 and OH13 is jointly controlled by a contact-dependent killing device,called the type IV secretion system(T4SS).By deleting the respective T4SS synthesis genes,the T4SS in both strains was co-inactivated and this step unlocked their natural CDAA,resulting in an engineered,compatible mutant alliance that co-displayed antibacterial and antifungal activity.Therefore,this study reveals that releasing bacterial CDAA is effective to rationally engineer the biocontrol community.