Mercury (Hg) is a toxic trace element that can cause serious environmental problems. The main source of Hg contamination to soil across Indonesia is artisanal and small-scale gold mining (ASGM) and strategies to manage or remove Hg from soil are needed. This study isolated Hg-resistant endophytic bacteria from indigenous local grasses (Cynodon dactylon and Eleusine indica) growing in Hg-contaminated soils to identify potential inoculants that could increase plant growth and mercury uptake for phytoremediation. Grass samples were collected from an ASGM location on Lombok Island. The grass samples (both, root and shoot) were surface sterilized, aseptically mashed, and serially diluted with 0.9% sodium chloride (v/v) and an aliquot of the extracted bacteria was cultured on Nutrient Agar across a range of HgCl₂ concentration from 0 to 1000 mg/L. Thirteen bacterial isolates were tested for their ability to detoxify Hg, Hg bioaccumulation, indole acetic acid (IAA) production, ammonium production, and siderophore production. Five of thirteen isolates were Hg-resistant and survived on a medium containing 250 mg/L HgCl₂. One isolate from each of E. indica and C. dactylon showed complete Hg detoxification. The greatest Hg bioaccumulation was 85.04%. The highest expressed IAA and ammonium concentration was 13.17 mg/L and 2.58 mg/L respectively. Based on 16S rDNA sequence similarity, the two isolates with the greatest potential as inoculants (CD6 and EI6) were identified as Jeotgalicoccus huakuii (isolated from C. dactylon) and Bacillus amyloliquefaciens (isolated from E. indica) and could be used as inoculum for phytoremediation of Hg-contaminated soil in future studies.

Mercury (Hg)-contaminated soil remediation has become an urgent necessity due to its harmful effect on the environment and living organisms. The use of plant-endophyte partnership for phytoremediation demonstrates an excellent opportunity for cleaning heavy metal contaminated soil. This study...

Nutrient management in coffee-based agroforestry systems plays a critical role in soil nitrogen (N) cycling, but has not been well documented. The objective of this study was to evaluate the effect of coffee canopy management and fertilization on soil N dynamics. This study used a randomized complete block design (2 × 3 × 2) with four replications. There were three factors: 1) coffee canopy management (T1: Pruned, T2: Unpruned), 2) fertilizer type (O: Organic, I: Inorganic; M: 50% Organic + 50% Inorganic), and 3) fertilizer dose (D1: low, D2: medium, D3: high). Soil N dynamic indicators (i.e., total N, ammonium (NH₄⁺), nitrate (NO₃⁻), net N-NH₄⁺, net N-NO₃⁻, soil microbial biomass N) were measured at two soil sampling depths (0–20 cm and 20–40 cm). Results showed that pruning increased soil total N and microbial biomass N (MBN) by 10–56% relative to unpruned coffee trees. In contrast, the unpruned coffee canopy had 15–345% higher NH₄⁺, NO₃⁻, net N-NH₄⁺, net N-NO₃⁻, and microbial biomass N concentration than pruned coffee. Mixed fertilizer application increased NO₃⁻ and net N-NH₄⁺ accumulation by 5–15% relative to inorganic and organic fertilizers. In addition, medium to high dose fertilization led to a 19–86% higher net N-NO₃⁻ concentration and microbial biomass N as compared to low dose fertilization. The treatment of no pruning and mixed fertilizer at low to medium doses was the optimal management strategy to maintain soil available N, while pruning combined with organic fertilizer has the potential to improve soil total N and MBN.

Volcanic eruptions cause large-scale damage and leave piles of volcanic material that destroy plants, agricultural lands, animals, and soil microorganisms, decreasing soil fertility. Therefore, it is necessary to accelerate soil fertility recovery in post-volcanic eruption areas to resume...

Coffee agroforestry has become a land use system that provides both ecological and economic benefits, so it is managed in various ways. Pruning and fertilizer management is a combination that is applied for optimal production. However, understanding the effect of combined management on soil...

Plant growth-promoting endophytic bacteria can potentially improve the biomass production of Hg-accumulating grasses, resulting in improved Hg extraction from contaminated soils. This study aimed to analyze the effect of inoculation of Hg-resistant endophytic bacteria (i) Jeotgalicoccus huakuii (B1) and (ii) Bacillus amyloliquefaciens (B2), as single and consortium inoculant, on biomass production and Hg bioaccumulation of Bermuda grass (R1) and Indian goosegrass (R2) planted as monoculture and mixed cropping. The grass seeds were surface-sterilized before the inoculation. Both inoculated seeds with B1 and B2 (treatments) and uninoculated seeds were sown separately in sterilized sand. Grass seedlings of both treatments and control were replanted in the washed and sterilized sand medium, spiked with HgCl₂ (100 mg kg⁻¹). A subset of grass was harvested at 0, 4, 6, and 10 weeks after planting to measure biomass production and Hg bioaccumulation. The results showed that bacterial inoculation enhanced the grass biomass by 52.68% and Hg bioaccumulation by 47.76%. Mercury residue of Hg-spiked sand treated with the bacterial consortium was reduced by 80%. This suggests that endophytic bacteria can improve grass biomass production and enhance Hg bioaccumulation in grass biomass. Graphical Abstract