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University of Delaware (2019)

Plant-growth promoting rhizobacteria increase soil water retention by changing soil physical and hydraulic properties

Zeng, Saiqi

Titre : Plant-growth promoting rhizobacteria increase soil water retention by changing soil physical and hydraulic properties

Auteur : Zeng, Saiqi

Université de soutenance  : University of Delaware

Grade : Master of Science in Plant and Soil Sciences 2019

Résumé partiel
The growing global population and food consumption is challenging agriculture for higher productivity. Water is a key factor limiting crop yield in (semi-) arid regions, in this case, increasing water use efficiency is of great importance. The plant growth promoting rhizobacteria (PGPR) could potentially increase agricultural productivity in (semi-) arid regions as its beneficial effects on enhancing plant drought stress tolerance, which has been increasingly documented in the literature. However, most of previous researches have focused on PGPR-root interactions, less is known about PGPR’s effects on physiochemical and hydrological properties in rhizospheric soil that may also contribute to plant drought stress tolerance. This study aimed to investigate changes in soil physical and hydraulic properties induced by Bacillus subtilis FB17, a generalist PGPR that has been commercialized (named as UD1022) for its ability to benefit plant growth and disease protection. In this study, soil water retention curves (SWRC) and water evaporation in soils with various textures (i.e., pure sand, sandy soil, and clay) as influenced by UD1022 were measured using HYPROP. In addition, X-ray and neutron radiography/tomography, an in-situ, non-destructive imaging technique were used to image water movement in UD1022-treated and control soil samples during evaporation. Results from both HYPROP and radiography imaging experiments showed that all UD1022-treated soils held more water and had reduced conductivity and cumulative evaporation compared to their corresponding controls. Analyses the HYPROP results combined with neutron radiography and SEM imaging revealed two potential mechanisms responsible for the changes in hydraulic properties and soil evaporation upon UD1022 treatment : (1) EPS alter the structure of soil matrix and connectivity of pore spaces and (2) EPS modify the physicochemical properties of water (surface tension and viscosity).

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