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.

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.

Abstract
The mismanagement of dairy cattle manure under tropical conditions contributes to odor pollution, nutrient loss, and environmental degradation. This study evaluated the individual and combined effects of wood vinegar (pyroligneous acid), rice husk biochar, and a microbial inoculant comprising Bacillus licheniformis, Bacillus megaterium, and Lactobacillus acidophilus on odor reduction, composting kinetics, and the physicochemical and microbiological quality of dairy manure compost in Ho Chi Minh City, Vietnam. A two-phase experimental design was employed: Phase 1 screened concentration– response relationships between each amendment and odor intensity using a trained sensory panel (VDI 3882-1 scale, 0–6), and Phase 2 assessed composting performance at the optimal concentrations identified — wood vinegar at 1:40 (v/v), rice husk biochar at 5% (w/w), and microbial inoculant at 2% (v/v) – over six weeks. All amendments exhibited concentration-dependent odor reduction. The combined treatment produced the greatest improvements in organic matter content (56.11%), humic acid (17.14%), total nitrogen (19.57%), and available phosphorus expressed as P₂O₅ (11.63%), and reduced compost maturation time to four weeks compared with six weeks for the unamended control. The resulting compost met multiple quality thresholds of the Vietnamese national standard for microbial organic fertilisers (TCVN 7185:2002). These findings demonstrate that this bio-based amendment system offers a low-cost, scalable approach to sustainable dairy manure management under tropical conditions.

Abstract
Cassava (Manihot esculenta Crantz) is an important food crop widely cultivated worldwide and critical in addressing food security. Optimising plant spacing is essential for improving yield and agronomic performance in tropical soils. This study evaluated the effect of different plant spacings on growth and yields using the Markona variety. The experiment consisted of five spacings: T1 (0.50×1.50 m), T2 (0.75×1.50 m), T3 (1.00×1.50 m), T4 (1.25×1.50 m) and T5 (1.50×1.50 m), corresponding to plant densities of 13 333 plants ha^-1, 8 888 plants ha^-1, 6 666 plants ha^-1, 5 333 plants ha^-1 and 4 444 plants ha^-1, respectively. Growth parameters measured included plant height, girth circumference, leaves number per plant, chlorophyll content (SPAD unit) and root fresh weight yield. Results showed that plant spacing did not significantly affect plant height, girth circumference, leaves number per plant, and chlorophyll content. Root yield was greater at plant spacings between 0.75 m and 1.25 m, while yield was lower at 0.50 m and 1.50 m. The highest yield at 14.59 t/ha was obtained at the 1.25 m spacing and was significantly higher than T1 and T5. These findings highlight the importance of appropriate plant spacing in maximising cassava productivity under land constraint and provide useful agronomic guidance that may be applied to other cassava varieties.

Abstract
The extensive application of the fungicide zole over last few decades has led to its accumulation as a toxic residue in agricultural soils and plants. To mitigate its environmental impact and to maintain soil and plant health, optimization of its dosage is essential. The present study aims to examine the role of fungicide zole in conjunction with non-polar and neutral amino acid, namely glycine as a soil additive for the growth of wheat. The experiment is done to explore the growth of wheat plants (Triticum aestivum) at varying concentration of fungicide zole in terms of seed germination, number of leaves grown, shoot and root length of the wheat plants while the glycine concentration was held constant. To assess the results on wheat plant development and nutrient uptake, the experiment includes five different combinations in a randomized block design (RBD) in three sets of replications. Each set was labelled as S1 (0.1M glycine and 0% fungicide zole/kg soil), S2 (0.1M glycine and 2% fungicide zole/ kg soil), S3 (0.1M glycine and 4% fungicide zole/kg soil), S4 (0.1M glycine and 6% fungicide zole/kg soil) and S5 (0.1M glycine and 8% fungicide zole/kg soil). The integrated use of fungicide zole and glycine significantly increases the micro and macronutrients (N, Na, Mg, Ca, Cr, Fe, Co, Ni, Zn and Cu) of the wheat plant and reduces the concentration of toxic elements such as cadmium and lead. The number of leaves, seed germination, root and shoot length show maximum growth at S5. Reduced soil pH and increased electrical conductivity improve micro and marco-nutrient solubility. improve seed germination, and biomass accumulation. The finding of this study also indicates that fungicide–amino acid amendments are effective soil conditioners that improve soil fertility and nutrient uptake in wheat plants, although careful dosage optimization is necessary to balance crop protection with nutrient bioavailability.

Abstract
Insufficient supplies of potassium (K⁺) in acidic sapric soils impedes pineapple growth and development, fruit quality attributes, and yield. Clinoptilolite zeolite was incorporated in the MD2 pineapple fertilization programme to evaluate this mineral's effectiveness to improve peat soils' K⁺ availability and pineapple productivity. Field studies with two MD2 pineapple seasons and laboratory leaching column experiments were utilized to determine K⁺ availability in drained sapric soils with the following treatments: (i) four rates of clinoptilolite at 25, 60, 75, and 100% incorporated with compound NPK 30:1:32 fertilizer, (ii) standard pineapple fertilization (NPK 30:1:32), and (iii) untreated soils. Clinoptilolite amended sapric soils improved K⁺ availability due to the absorption of K⁺ ions onto clinoptilolite's lattices and surface frameworks via ion exchange and mass transport. Co- application of clinoptilolite (100%) and NPK 30:1:32 was more effective in improving peat K⁺ availability, whereas clinoptilolite fertilization at rates of 25 to 100% improved soil pH (pH: 4.27 – 5.62), increased pineapple K uptake and use efficiency, and yield (2.42–2.66 kg/fruit or 92.0–101.1 t/ha) due to the ability of clinoptilolite to regulate soil exchangeable K⁺ ions for optimum MD2 plant uptake compared with standard pineapple fertilization (1.50–1.76 kg/fruit or 57.0–66.9 t/ha). The recommended clinoptilolite fertilization (25% zeolite + NPK 30:1:32) at the vegetative (3- and 6- months plant age) and flower induction (9 months plant age) phase provides alternative agronomic management for pineapple growers to improve peat soil productivity without compromising MD2 yield production.

Abstract
A field experiment was conducted with the objective of enhancing the grain yield of Kharif rice by substituting soil-applied potassium with nano-potassium. The result revealed that significantly highest mean total chlorophyll content (3.5 Mg/g), potassium content of leaves (2.61%), root length (16.4 cm) root volume (20.22 cc), plant height (116 cm), panicle length (22.2cm), panicles/hill (7.1), spikelet/panicle (119), filled grains/panicle (92) and test weight (25.4gm) was recorded with T5 [100% of soil test dose (STD)+ Twice foliar spray of Nano K at 14 and 28 days after transplanting (DAT)]. This treatment (T5) also recorded the highest grain yield of 2570 kg/ha and straw yield of 3469 kg/ha as compared to T2 (Nitrogen and phosphorus were applied as per 100% of STD) having the grain and straw yield of 2494 and 3367 kg/ha respectively. Similarly, the grain and straw yield of 2421 and 3178 kg/ha was recorded with T6 (100% STD for N&P + 75% STD for K + twice foliar spray of nano-K at 14 and 28 DAT) which was not significantly lower than that of T2. The highest K content (0.48% in grain, 2.35% in straw) and K uptake (12.22 kg/ha in grain, 81.5 kg/ha in straw) was recorded with T5 which was not significantly higher than that of T6. The grain and straw yields were not significantly reduced with T6, indicated that reduction of soil-applied potassium by 25% was effectively managed with twice foliar application of nano-K without sacrificing yield.

Abstract
Forests play a central role in terrestrial ecosystems by regulating hydrological and climatic cycles, preserving biodiversity, and providing environmental ecosystem services. Soil, a limited and non- renewable resource, is essential for plant production, carbon sequestration, regulation of biogeochemical cycles, and maintenance of edaphic fertility. However, its degradation, particularly in arid and semi-arid regions, poses a major environmental challenge, linked to climate change through a vicious cycle of greenhouse gas emissions and vulnerability to extreme events. Ecological restoration approaches are emerging as key tools, with forest restoration recognized for curbing biodiversity loss, enhancing climatic resilience, and improving soil quality. This study evaluates the potential of spent mushroom substrate (SMC), an organic amendment derived from agricultural waste rich in nutrients, to restore degraded forest soils. The objective is to analyze its impact on the physical and chemical properties of the soil, as well as on ecological restoration processes, by comparing the responses of monospecific and mixed forest stands one year after application. The results show significant improvements: increases in organic carbon, total nitrogen, organic matter, moisture, electrical conductivity, water retention, and porosity; decreases in pH, C/N ratio, bulk density, and permeability. These changes enhance nutrient availability and soil structure, promoting plant recovery. Spent mushroom substrate appears as a promising tool for the ecological restoration of degraded forest soils, improving edaphic health and forest resilience, while aligning with circular economy principles.

Abstract
Open-field burning of agricultural residues remains a common practice in Indonesian farming systems and contributes to environmental degradation. Converting these biomasses into biochar using a simple instrument is likely to benefit smallholder farmers in semi-arid tropical regions. This study characterises biochar produced in Lombok Island from four locally abundant feedstocks (Rice Husk (RH), Corn Cob (CC), Coconut Fibre (CF), Tobacco Stem (TS)). Analysis by SEM, BET, FTIR, and XRD shows these biochars have different properties as a function of feedstock type and pyrolysis conditions. SEM revealed varying porous structures; CC had the widest pores. BET showed that TS biochar had the highest surface area (17.08 m² g^-1) and the longest pyrolysis time (59 min), whereas CC had the lowest surface area (5.74 m² g^-1) and the shortest pyrolysis time (14 min). FTIR analysis revealed that all biochars share key functional groups (-OH, C=C, C-H) but also exhibit feedstock- specific traits. RH and CC are rich in silica (Si-O-Si), CF contains complex oxygen groups, and TS has a stable aromatic structure. These findings suggest that RH biochar is suited for inorganic adsorption and as a silica soil amendment, CC for organic molecule adsorption, and CF/TS biochars for long-term soil carbon sinks and CEC enhancement. This work provides practical guidance for selecting biochar types for agricultural and environmental applications.