Tolerance of green manures associated with microbial inoculants in soil with tebuthiuron

Author(s)

Victor Hugo Cruz

• Document type: Master's Dissertation
• Press: Ilha Solteira. 2023-03-20.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Engenharia. Ilha Solteira
• Defense date: 2023-02-23
• Advisor: Paulo Renato Matos Lopes

Abstract

The aim of this research was to evaluate the tolerance and capacity of phytoremediation of velvet bean (Mucuna pruriens L. cv. Pruriens) and jack bean (Canavalia ensiformis L.) associated with microbial inoculants in soil with the herbicide tebuthiuron. The research was carried out between September/2021 and March/2022, under completely randomized design, in a triple factorial scheme, with seven replicates, resulting in 126 experimental units. The following factors were considered: (1º) Tebuthiuron: absence or recommended dose (TBT); (2º) Microbial inoculant: absence, liquid (Liq) or solid (Sol); (3º) Plants: absence, velvet bean (MP) or jack bean (CE). Sunn hemp (Crotalaria juncea) was used as sentinel species. Throughout the experimental period, plant height and dry biomass were evaluated. The ecotoxicological potential of the soil samples was also evaluated temporally throughout of the lettuce seed germination index. The dry biomass data were evaluated using analysis of variance (ANOVA at 5% probability) and comparison of average test (Tukey at 5% probability). For the elaboration of the Gompertz non-linear model, the data of plant height and dry biomass were evaluated (MP, CE and sunn hemp), and the germination index of lettuce were used. Statistical analyses were performed using R, GraphPad Prism and Microsoft Excel® 2019 software. In the long term, natural attenuation can gradually dissipate the herbicide tebuthiuron from the soil, and this is noticeable in the ecotoxicological bioassays, as satisfactory results were obtained in the final germination index (0.96) and growth speed (k=0.0314). M. pruriens was tolerant to the herbicide tebuthiuron due to its rapid establishment (k = 0.109) when compared to C. ensiformis (k = 0.069). Furthermore, this species can be considered a phytoremediator of the herbicide tebuthiuron due to the results obtained in C. juncea cultivation (specific growth rate = 0.0330; dry biomass: 3.52 g) and ecotoxicological bioassays (growth velocity = 0.0632) when compared to treatments with C. ensiformis. Consequently, the results showed that C. ensiformis has greater dependence on bioaugmentation than M. pruriens. Thus, to note that the phytotoxic effect on C. juncea was reduced in CE + Liq/Sol + TBT (CE + Liq + TBT = 6.27 g > CE + Sol + TBT = 6.21 g), and better plant performance of L. sativa was observed in CE + Sol + TBT (k = 0.0480) and CE +Liq + TBT (k = 0.0422). Therefore, the findings of this research show that the cultivation of potential phytoremediators associated with bioaugmentation can reduce the antagonistic effects of the herbicide tebuthiuron in the ecosystem, whether edaphic or aquatic. (AU)

• FAPESP's process: 21/01884-6 - Phytoremediation of soil with tebuthiuron associated with microbial inoculants
• Grantee: Victor Hugo Cruz
• Support Opportunities: Scholarships in Brazil - Master