The Integrated Effect of Microbial Inoculants and Biochar Types on Soil Biological Properties, and Plant Growth of Lettuce (Lactuca sativa L.)

Numerous reports confirm the positive effect of biochar application on soil properties and plant development. However, the interaction between root-associated beneficial microbes and different types of biochar is not well understood. The objective of this study was to evaluate the plant growth of lettuce after the application of three types of biochar in loamy, sandy soil individually and in combination with plant-beneficial microbes. Furthermore, total microbial activity in rhizosphere soil of lettuce was measured by means of fluorescein diacetate (FDA) hydrolase and enzyme activities linked to carbon, nitrogen, and phosphorus cycling. We used three types of biochar: (i) pyrolysis char from cherry wood (CWBC), (ii) pyrolysis char from wood (WBC), and (iii) pyrolysis char from maize (MBC) at 2% concentration. Our results showed that pyrolysis biochars positively affected plant interaction with microbial inoculants. Plant dry biomass grown on soil amended with MBC in combination with Klebsiella sp. BS13 and Klebsiella sp. BS13 + Talaromyces purpureogenus BS16aPP inoculants was significantly increased by 5.8% and 18%, respectively, compared to the control plants. Comprehensively, interaction analysis showed that the biochar effect on soil enzyme activities involved in N and P cycling depends on the type of microbial inoculant. Microbial strains exhibited plant growth-promoting traits, including the production of indole 3-acetic-acid and hydrogen cyanide and phosphate-solubilizing ability. The effect of microbial inoculant also depends on the biochar type. In summary, these findings provide new insights into the understanding of the interactions between biochar and microbial inoculants, which may affect lettuce growth and development.Peer Reviewe

Microbes for sustainable agriculture: Isolation and identification of beneficial soil- and plant-associated microorganisms

In soil, fungi are effective in the control of pathogens while bacteria can promote growth of plants through secretion of growth-promoting hormones. In this study, beneficial fungi and bacteria were isolated from bulk and rhizosphere soil samples, and from leaves, stems, and roots of romaine lettuce (Lactuca sativa L. var. longifolia) either as epiphytes or endophytes. The isolated microorganisms were tested for their ability to solubilize phosphate. Given the low amount of phosphorus in soil, the ability to acquire this mineral from the soil and share it with its host plants is an important trait that can enhance plant growth. From this study, one bacterium and seven fungal strains were capable of doing this task as evidenced by the clearing zones around colonies in Pikovskayas agar. Isolated soil- and plant-associated fungi were also tested for their ability to inhibit the growth of a plant pathogenic fungus. The dual-culture setups showed 30 of the 53 fungal strains exhibiting antagonistic activities. Of these, nine fungi positively inhibited the growth of Fusarium oxysporum. Identities of the beneficial microorganisms were confirmed through gene sequence analysis. This study showed the potential of soil- and plant- associated microorganisms as plant growth enhancer that can possibly be incorporated in soil amendments