Malaysian Society of Soil Science

Abstract
Assessing soil properties across different forest types is a critical aspect of silviculture. This study aimed to investigate the variations in the characteristics of yellow-brown ferralitic soil beneath the canopy of tropical semi-moist evergreen closed forests subjected to varying intensities of selective logging in the Hoa Binh Hydropower Reservoir area, Hoa Binh Province, Vietnam. Twelve 1000 m² plots representing rich, medium, poor, and mixed wood–bamboo forests were sampled. At each plot, soil sample was collected at two depths from five random points along an S-shaped transect, then composited by depth for physical and chemical analysis. The results showed that: (1) The characteristics of yellow-brown ferralitic soil varied significantly based on the forest types. Soil water content was higher in the rich and medium forests compared to the poor and mixed wood-bamboo forests. Soil clay content progressively increased from the rich forest to the poor forest, with the lowest levels found in the mixed wood-bamboo forest. Conversely, soil silt content tended to increase with forest degradation, while soil sand content decreased significantly as degradation intensified. (2) An increase in stand timber volume is linked to a decrease in soil bulk density and particle density. In contrast, it is associated with higher levels of soil pHKCl, as well as greater concentrations of soil organic matter, organic carbon and essential nutrients such as total nitrogen, phosphorus, and potassium. (3) Organic matter content in yellow-brown ferralitic soil was most strongly influenced by standing tree volume, followed by soil pHKCl, microbial community, and water content. The findings of this study not only contribute to a deeper understanding of soil dynamics under the influence of logging but also offer a scientific basis for the development of silvicultural practices and sustainable forest management strategies.

Abstract
Tomato (Solanum lycopersicum L.) production often relies heavily on chemical nitrogen (N) fertilizers, raising concerns about costs, sustainability, and soil health. Plant growth-promoting bacteria (PGPB) represent a promising alternative that may reduce fertilizer inputs while maintaining fruit yield and quality. This study was undertaken to investigate the influence of two PGPB strains, Bacillus tequilensis (UPMRB9) and Bacillus subtilis (UPMB10), applied under different N levels on tomato performance and soil enzymatic activity. A glasshouse experiment was arranged in a completely randomized design with nine treatments, combining bacterial inoculation and three N application rates (0, 50, and 100% of the recommended dose). Inoculated plants consistently performed better than the uninoculated control, with significant improvements in yield attributes (flower number, fruit number, fruit set, and fruit weight) and fruit quality traits. The combination of UPMRB9 with 50% of the recommended N rate (UPMRB9N50) produced the greatest effects, increasing fruit yield by 27.27%, lycopene content by 12.16%, antioxidant activity by 26.96%, and soil microbial activity by 11.14% compared with the full N dose without inoculation. Higher total soluble solids (5.15 °Brix) were also recorded in UPMRB9N50-treated plants, reflecting better fruit quality. Overall, the findings suggest that microbial inoculation, particularly with UPMRB9, can reduce N fertilizer use by almost 50% while still enhancing tomato yield and fruit quality. Such results provide important preliminary evidence for adopting PGPB as a viable strategy to reduce chemical fertilizer dependency and promote more sustainable tomato production.

Abstract
Mangroves are highly productive blue carbon (C) ecosystems with an exceptional capacity to store organic C in soils. Soil organic C storage in these systems is recognized as a key component of the global C cycle and an important natural mechanism for climate change mitigation. Nonetheless, knowledge of how soil C dynamics vary with forest development in mangrove plantations remains limited. To address this gap, the current study quantified changes in soil C stocks along a forest age sequence of Rhizophora apiculata Blume plantations in the Kien Vang coastal area, Ca Mau Province, Vietnam, through systematic field surveys. The results revealed that: (1) Soil C content and stocks significantly increased with the developing forest age. (2) Soil C concentration and storage significantly decreased with increasing of soil depth along forest age. (3) The stocks of total soil organic C (SCs) increased from 94.97 Mg C ha^-1 to 224.75 Mg C ha^-1, during forest development. SCs exhibited obvious surface aggregation, with more than 70% of SCs occurring in the soil of 0–40 cm depth, underscoring the pivotal role of surface soils in C sequestration. (4) Based on the random forest regression analysis, soil salinity, total nitrogen, and stand density were identified as the key factors regulating variations in SCs across forest age development, accounting for 15.3%, 13.4%, and 11.8% of the variation, respectively. These findings highlight the vital role of R. apiculata mangrove plantations as effective C sinks and underscore their contribution to global climate change mitigation efforts and sustainable forest management strategies for improved soil health.

Abstract
Rice production has recently declined, primarily due to reduced soil fertility and the high cost of synthetic fertilizers. This necessitated exploring greener alternatives, such as silicate-solubilizing bacteria (SSB), which are vital for enhancing soil fertility by making silicate available for plant use. The objectives of this study are to screen selected bacteria from culture collections for silicate- solubilizing properties, characterize them for silicate-solubilizing properties, and evaluate the effect of silicate-solubilizing bacteria on rice growth and yield. The study was laid out in an RCBD with 2 silicate sources (Calcium Silicate and Kaolinite) and 3 bacterial strains (UPMC1341, UPMC1446, and UPMC383), with B0 serving as a negative control. An 8-treatment combination and a total of 24 experimental units were supplied with silicates, inoculated with 3 SSBs on day one, and re-inoculated at 55 days after transplanting (DAP). In the results, bacterial strains, most importantly UPMC1446, significantly increased plant height and the number of tillers (29 ± 2.08). UPMC1341 also increased the number of panicles/plant and the number of spikelets/panicle, 36±2.34, 211±2.25,respectively, in combination with Kaolinite. This research highlighted the efficacy of SSBs, most importantly UPMC1446 and UPMC1341, in solubilizing insoluble silicate, thereby enhancing rice growth and yield, particularly when supplied with kaolinite.

Abstract
This study assessed soil quality differences between five uniformly aged fruit orchards and an adjacent arboretum reference by applying the Tropical Soil Quality Index (TSQI), which integrates physical, chemical, and biological indicators. The arboretum, which has remained undisturbed relative to orchard management, was used as the benchmark for evaluating current soil condition after long term cultivation in orchard plots. Composite topsoil (0–30 cm) sampling was conducted by dividing each field into nine areas and combining five auger subsamples per area, with separate handling for microbial biomass analysis. Measured soil properties included texture, coarse fragments, bulk density, organic matter proxies (total carbon and total nitrogen), cation exchange capacity, exchangeable bases, available phosphorus, soil pH, exchangeable aluminium, microbial biomass carbon, and microbial biomass nitrogen. These were analysed using Analysis of Variance and TSQI scoring. The results showed clear differences between land uses, with the arboretum exhibiting lower bulk density than orchard soils. Chemical indicators also distinguished the arboretum, where organic matter related fertility indicators were higher (organic matter, total carbon, total nitrogen, cation exchange capacity) than in orchards. The arboretum also had a lower C/N ratio compared to the orchards. Nutrient patterns varied across sites with available phosphorus lowest in the arboretum while all sites remained within a deficient range, and exchangeable magnesium sufficient only in the arboretum but low in most orchards, despite exchangeable potassium being within a sufficient range across plots. Available phosphorus was lowest in the arboretum, although all sites were phosphorus-deficient. Exchangeable magnesium was sufficient only in the arboretum, while potassium levels were adequate across all plots. Soil pH and exchangeable aluminium were similar, with the arboretum showing slightly higher acidity and aluminium content. Biological indicators showed difference from the organic matter pattern, with microbial biomass carbon highest in one orchard soil and lowest in the arboretum, while microbial biomass nitrogen peaked in the arboretum and was lowest in another orchard. Soil quality was further assessed using the TSQI, which integrated multiple indicators into a single comparative framework. The arboretum recorded a higher index score (63.64%) than the fruit orchards (50.00%), primarily due to its greater total carbon, total nitrogen, and exchangeable magnesium, suggesting that rebuilding organic matter linked nutrient retention and alleviating magnesium limitation are central leverage points for improving orchard soil function under sustained management. These findings indicate that long-term conversion of forest land to fruit orchards, combined with intensive management practices, has gradually improved soil quality, with orchard soils approaching the benchmark condition represented by the arboretum. The results also confirm that the TSQI is a sensitive and effective tool for assessing soil condition in tropical agroecosystems and detecting changes driven by management over time.

Abstract
The prolonged overuse of inorganic fertilizers has raised environmental concerns, prompting the search for alternative nutrient management strategies that can maintain crop productivity. Vermicompost (VC) and vermicompost leachate (VCL) show promise as organic nutrient sources; however, their effectiveness under field conditions for medicinal crops remains inadequately documented. This study evaluated the effects of VC and VCL on the growth performance, soil properties, and nutrient assimilation of Clinacanthus nutans, a high-value medicinal herb with antiviral, wound-healing and anticancer agent. A field experiment was conducted using a randomized complete block design (RCBD) with four treatments: (T1) control; (T2) recommended rate of chemical fertilizer; (T3) vermicompost (15 t ha^-1); and (T4) an integrated treatment combining 50% chemical fertilizer with foliar VCL (2 mL L⁻¹). Results indicated that the full CF treatment produced the highest biomass, whereas T4 achieved statistically comparable yields despite a 50% reduction in synthetic fertilizer input. Vermicompost significantly enhanced soil organic carbon and potassium availability but exhibited a slower nitrogen release. The T4 treatment also reduced soil alkalinity while promoting greater nutrient accumulation. Correlation analysis showed that plant nutrient concentrations, particularly nitrogen and potassium, were more closely associated with growth and biomass accumulation than total soil nutrient levels. These findings demonstrate that combining reduced chemical fertilization with vermicompost leachate represents a viable and bio- economic strategy for sustainable cultivation of C. nutans without compromising yield.

Malaysia sits at the centre of an important conversation on plantation sustainability, biomass utilization, and climate aligned land management. Among the many options being discussed, biochar derived from oil palm residues has emerged as a particularly compelling candidate. The country generates a large and continuous stream of oil palm biomass, including empty fruit bunch, palm kernel shell, mesocarp fibre, trunk, and frond residues (Hwong et al., 2022; Karam et al., 2022; Tugiman et al., 2024). This creates a clear opportunity to convert an abundant by product into a carbon rich material with possible value for soil improvement and climate mitigation.

The topic is not new, but it is increasingly timely. Existing studies have shown that biochar produced from oil palm residues may improve selected soil chemical properties, nutrient retention, and seedling performance (Alarefee et al., 2023; Cheng et al., 2025). Biochar derived from empty fruit bunch and palm kernel shell has shown promise in improving soil conditions and nutrient uptake in nursery and seedling-based studies. Palm kernel shell biochar has also been reported to possess physicochemical properties associated with relatively high carbon stability. Collectively, these findings support the view that oil palm residue biochar deserves serious consideration within Malaysia's broader sustainability agenda.

Yet this is also where caution is needed. Much of the available evidence remains concentrated in biochar production studies, laboratory characterization, greenhouse or nursery trials, and relatively short-term assessments of soil response. These are useful contributions, but they do not yet establish whether oil palm residue biochar can consistently and durably enhance soil carbon sequestration under field conditions in mature Malaysian plantation systems. That distinction matters. A material may appear promising in controlled settings while still falling short as a scalable carbon management strategy once field variability, soil differences, operational constraints, and system wide trade-offs are considered.

Despite the growing interest in biochar as a sustainable solution for soil improvement and carbon sequestration, significant research and technological gaps remain in the areas of biochar production, biomass conversion efficiency, and scalable carbon-focused innovations. Many current studies focus on laboratory-scale outcomes, while practical implementation at field and industrial levels is still limited. There is also insufficient integration between biomass waste management, optimized pyrolysis technologies, and long-term carbon stability assessments. Addressing these gaps is crucial to unlock the full potential of biochar as a climate mitigation tool, particularly in regions with abundant agricultural residues (Kong et al., 2014; Kong et al., 2019). Advancing research in biomass conversion pathways and developing innovative carbon-focused technologies can enhance the value chain of biochar, transforming organic waste into high-value carbon products while simultaneously contributing to soil health, circular bioeconomy development, and global carbon reduction strategies.

This gap should now be treated as a priority research question. What is needed is not more enthusiasm alone, but stronger field-based validation. Long term studies in representative Malaysian plantation environments are required to monitor soil organic carbon dynamics, greenhouse gas fluxes, nutrient interactions, and agronomic performance over time. Comparative evaluation across feedstocks such as empty fruit bunch and palm kernel shell, across soil types, and across application rates would be especially valuable. Core indicators should include soil organic carbon, bulk density, pH, cation exchange capacity, nutrient availability, and carbon related fractions, together with practical measures of plant response and nutrient uptake.

If biochar is to be discussed as a credible climate aligned intervention, the assessment must extend beyond plot level measurements. Life cycle assessment and techno economic analysis are essential to capture the wider implications of feedstock sourcing, conversion energy, transport, field application, and eventual scaling. Only through this more integrated approach can the true environmental value of oil palm residue biochar be judged with confidence.

Oil palm residue biochar should not be framed merely as a waste management option or an agronomic amendment. It may represent a broader circular strategy in which plantation biomass is redirected toward soil rehabilitation, nutrient efficiency, and carbon management. Whether that promise holds under realistic Malaysian conditions remains an open question, and it is precisely that question which now deserves disciplined, well-designed investigation.

The path forward is therefore clear. The field must move from plausible potential to demonstrated performance. Malaysia is particularly well placed to lead this effort because of the scale of its biomass resource, the relevance of the plantation context, and the growing need for climate responsive land management strategies. A focused research agenda on oil palm residue biochar could make an important contribution, but only if it is grounded in robust field evidence and systems level evaluation.

Referrence:

• Alarefee HA, Ishak CF, Othman R, Karam DS, 2023. Effectiveness of mixing poultry litter compost with rice husk biochar in mitigating ammonia volatilization and carbon dioxide emission. Journal of Environmental Management. 329, Article ID 117051.
• Cheng X, Onn CC, Othman F, Abdullah R, Guo W, Gunn PFE & Yue L. 2025. Impact of biochars on CO₂ emissions and physic chemical properties in Malaysian tropical soils. Journal of Environmental Sciences. 158, 84-97.
• Hwong CN, Sim SF, Kho LK, The YA, Harrold LD, Chua KH & Zainal NH. 2022. Effects of biochar from oil palm biomass on soil properties and growth performance of oil palm seedlings. Journal of Sustainability Science and Management. 17(4): 183-200.
• Karam DS, Nagabovanalli P, Rajoo KS, Ishak CF, Abdu, Rosli Z, Muharam FM, Zulperi D, 2022. An overview on the preparation of rice husk biochar, factors affecting its properties, and its agriculture application. Journal of the Saudi Society of Agricultural Sciences. 21(3), 149-159.
• Kong S-H, Loh S-K, Bachmann RT, Rahim SA & Salimon J. 2014. Biochar from oil palm biomass and its potential and challenges. Renewable and Sustainable Energy Reviews. 39, 729-739.
• Kong S-H, Loh SK, Bachmann RT, Zainal H, Cheong KY. 2019. Palm kernel shell biochar production, characteristics and carbon sequestration potential. Journal of Oil Palm Research. 31(3), 508-520.
• Tugiman ET, Yusoff MZM, Hassan MA, Samad MYA, Farid MAA, Shirai Y. 2024. Assessing the efficacy of utilizing biochar derived from oil palm biomass as a planting medium for promoting the growth and development of oil palm seedlings. Biocatalysis and Agricultural Biotechnology. 58, Article ID 103203.

Abstract
Land degradation caused by unsustainable cultivation practices remains a critical constraint to agricultural productivity in tropical highland regions. This study investigates the effects of various integrated agricultural land–use patterns on soil erosion, runoff, and land productivity in a tropical highland watershed of Southeast Asia. A field experiment and socio–economic survey was conducted from October 2024 to April 2025 using a Randomized Block Design comprising five treatments: (T1) cabbage–chili–tobacco, (T2) maize–upland rice, (T3) maize–kidney bean, (T4) coffee–elephant grass, and (T5) pine forest. Erosion and surface runoff were measured to assess soil loss and water regulation performance under different land–use types. The results showed that the T1 produced the highest erosion rate (25.15 t ha^–1 yr^–1), while T5 recorded the lowest (3.89 t ha^–1 yr^–1). All systems, however, exceeded the tolerable erosion threshold for Ultisols(11.21 t ha^–1 yr^–1), indicating the need for improved soil conservation measures. Land allocation modeling revealed that an optimal land–use configuration, comprising 37% mixed agroforestry, 20.8% annual crops, and 5.7% grasslands, maximized income while minimizing soil loss. The findings underscore the importance of diversified and conservation– oriented land–use planning for achieving sustainable agricultural production and watershed resilience in tropical highland environments.

Abstract
Spent coffee grounds (SCG) represent a growing waste stream with potential for agricultural valorization, yet their direct soil application is limited by phytotoxic compounds. This study evaluated the physico-chemical properties and agronomic effectiveness of SCG compost enriched with biochar and agricultural residues. Four formulations were composted over 91 days: SCG (Heap 1), SCG with rice husk biochar (Heap 2), SCG with rice husk biochar and empty fruit bunches (Heap 3), and SCG with palm kernel shell biochar (Heap 4). Temperature, pH, weight loss, lead (Pb) concentration, germination index (GI), root elongation, and leaf cell wall thickness of maize (Zea mays L.) were assessed. Heap 3 exhibited the highest thermophilic activity (p = 0.0029 vs. Heap 1) and GI (95.3%). Biochar-amended treatments stabilized pH near neutrality, whereas SCG alone remained acidic. Linear regression confirmed significant weight reduction across all treatments (p < 0.001), with biochar enhancing mass retention. Lead (Pb) concentrations declined to undetectable levels by day 91 in all heaps. Root elongation was significantly greater in biochar-amended composts (6.46–7.50 cm) compared to SCG alone (4.48 cm; p < 0.001). Transmission electron microscopy revealed that Heap 4 significantly increased maize leaf cell wall thickness relative to the control (mean difference = 0.201 µm, p = 0.001). These findings demonstrate that biochar-enriched SCG composting produces mature, non-phytotoxic amendments that enhance maize seedling vigor and leaf structural development.