Sago bark (SB) and empty fruit bunch (EFB) are available abundantly as agricultural waste in Sarawak. This study was conducted to investigate the physicochemical characteristics of SB and EFB as composting materials and used as a plant growth medium. The SB and EFB composts were prepared in a separate container by mixing chicken manure as compost accelerator and wood chips as a bulking agent in dry weight equivalent ratio (1:1:1). The maturity and stability of compost in 60-day composting periods were evaluated via physicochemical characterization of the composts in terms of pH, elemental content, total ash content, moisture content and nutrient analyses. The effect of the compost usage as growth medium was assessed towards water spinach and green mustard via seed germination and pot study. After 2 months, the colour of both composts was dark brown with an earthy smell. The acidic pH of the initial composting stage has changed into alkaline pH after 60 days of composting. Total NPK present in the SB and EFB composts were 0.96% and 1.21%, respectively. The germination index (GI) for the studied vegetables was above 100%, while the pot study showed that vegetables in compost media has higher growth compared to the control, after 14 days. SB and EFB are renewable waste which can be used as an excellent compost and able to improve the quality of the soil.
Plant growth-promoting rhizobacteria (PGPR) mediate heavy metal tolerance and improve phytoextraction potential in plants. The present research was conducted to find the potential of bacterial strains in improving the growth and phytoextraction abilities of Brassica nigra (L.) K. Koch. in chromium contaminated soil. In this study, a total of 15 bacterial strains were isolated from heavy metal polluted soil and were screened for their heavy metal tolerance and plant growth promotion potential. The most efficient strain was identified by 16S rRNA gene sequencing and was identified as Bacillus cereus. The isolate also showed the potential to solubilize phosphate and synthesize siderophore, phytohormones (indole acetic acid, cytokinin, and abscisic acid), and osmolyte (proline and sugar) in chromium (Cr+3) supplemented medium. The results of the present study showed that chromium stress has negative effects on seed germination and plant growth in B. nigra while inoculation of B. cereus improved plant growth and reduced chromium toxicity. The increase in seed germination percentage, shoot length, and root length was 28.07%, 35.86%, 19.11% while the fresh and dry biomass of the plant increased by 48.00% and 62.16%, respectively, as compared to the uninoculated/control plants. The photosynthetic pigments were also improved by bacterial inoculation as compared to untreated stress-exposed plants, i.e., increase in chlorophyll a, chlorophyll b, chlorophyll a + b, and carotenoid was d 25.94%, 10.65%, 20.35%, and 44.30%, respectively. Bacterial inoculation also resulted in osmotic adjustment (proline 8.76% and sugar 28.71%) and maintained the membrane stability (51.39%) which was also indicated by reduced malondialdehyde content (59.53% decrease). The antioxidant enzyme activities were also improved to 35.90% (superoxide dismutase), 59.61% (peroxide), and 33.33% (catalase) in inoculated stress-exposed plants as compared to the control plants. B. cereus inoculation also improved the uptake, bioaccumulation, and translocation of Cr in the plant. Data showed that B. cereus also increased Cr content in the root (2.71-fold) and shoot (4.01-fold), its bioaccumulation (2.71-fold in root and 4.03-fold in the shoot) and translocation (40%) was also high in B. nigra. The data revealed that B. cereus is a multifarious PGPR that efficiently tolerates heavy metal ions (Cr+3) and it can be used to enhance the growth and phytoextraction potential of B. nigra in heavy metal contaminated soil.
Matched MeSH terms: Mustard Plant/growth & development