Correlation and path analysis of Tobacco (Nicotiana tabacum L.) yield vs root traits and relative water content as affected by Azotobacter, mycorrhizal symbiosis and biochar application under dry-land farming conditions

In recent years, the excessive consumption of chemical fertilizers in combination with increasing production costs has led to the destruction of soil, water and biological resources (Gebhardt et al., 2017). Hence, in order to reduce the traces of chemical fertilizers in the environment and maximize the economic use of fertilizers, biofertilizers are considered to be a promising alternative approach to maintain and impr ove agroecosystems (Gao et al., 2020). These biofertilizers are mainly based on beneficial microorganisms which have the effect of enhancing soil fertility and plant growth by increasing the number and biological activity of useful microorganisms in the rhizosphere (Gao et al., 2020). Arbuscular mycorrhizal fungi (AMF) are the most effective microbial symbiotic organisms for improving the growth and yield of the majority (90%) of plants (Ardakani et al., 2009; Ahanger et al., 2014; Tarnabi et al., 2019). The symbiotic relationship between plants and mycorrhizal constitutes a link between the biotic and the geochemical portions of the ecosystem, and such a relationship may be © 2021 Institute of Agrophysics, Polish Academy of Sciences R. MESBAH et al. 320 considered to be a bridge connecting the root with the surrounding soil microhabitats (Larsen et al., 2017). Inoculating soil with AMF results in the formation of more constant masses and significantly higher extra-radical hyphal mycelium than the non-AMF-treated soils (Samarbakhsh et al., 2009; Syamsiyah et al., 2018). In low moisture conditions in the soil, the available water for plants is limited (Dai, 2012). Hence, all plant physiological processes such as cell turgidity, photosynthetic processes, growth of the root, tissue and organs are influenced (Sheteiwy et al., 2021). AMF can enhance plant tolerance to various environmental stresses by improving the acquisition of mineral nutrients and water (Baum et al., 2015) and it can also affect the water balance of both amply watered and droughtstressed host plants (Sheteiwy et al., 2021). Moreover, AMF improves the physical and chemical properties of the soil, and in particular, the soil structure. Additionally, AMF symbiosis enhanced the activity of soil microbial enzymes (El-Sawah et al., 2021). The plant growth-promoting rhizobacteria (PGPR) was used for the first time at the end of the 1970s in many key ecosystem processes, in such forms as bio-fertilizers and bio-pesticides (Gao et al., 2020). Recent studies have reported that bio-fertilizers can promote plant growth through nitrogen fixation, phytohormone, phosphate (P), and potassium solubilization (Bashan and de-Bashan, 2005). To reduce the harmful effects of agrochemicals with regard to tobacco leaf quality, the use of biofertilizers and nature-based compounds such as biochar are becoming established as essential agroecological practices for plant production. Biochar is a carbon-rich material obtained by pyrolysis using various biomasses (Major et al., 2010; Soliman et al., 2020). The positive effects of biochar application in improving plant growth are manifested in multiple forms, including the enhancement of the uptake and transport of nutrients (Mehari et al., 2015). Biochar enhances soil properties (soil physicochemical characteristics like pH, CEC, soil structure), water holding capacity and immobilizes soil environmental pollutants (Abbas et al., 2017; Moosavi et al., 2020). However, the properties of biochar are closely related to its physical and chemical properties. In recent times, biochar has been developed to improve crop production as an environmentally friendly solution to reduce water scarcity problems (Oppong Danso