Asian Soil Research Journal

Monitoring and Prioritizing Control Solutions for Land Subsidence in Khonj Plain, Iran: An Integrated Approach of SBAS Time Series Analysis and AHP Model

Mehdi Safari Namivandi — 2026-06-27

Land subsidence is a critical environmental hazard in arid and semi-arid regions, primarily associated with excessive groundwater extraction. Khonj Plain, in southern Fars Province, Iran, has experienced a marked decline in groundwater levels due to intensive agricultural activities in recent years. However, no comprehensive study has monitored the subsidence rate or identified critical hotspots in this plain. This study aimed to prepare a land subsidence map of Khonj Plain using the SBAS time-series method and 21 Sentinel-1 radar images acquired from January 2020 to January 2022, and to identify and prioritise effective control solutions using the Analytic Hierarchy Process (AHP) based on the opinions of 20 experts. The results showed subsidence ranging from 31 to 218 mm during the two-year period, with an average annual subsidence rate in critical areas exceeding 109 mm/year. The highest rates of vertical displacement were concentrated in two main areas: south of Khonj city and between Dehno and Hosseinabad villages. These areas coincide with Quaternary alluvial deposits with thick fine-grained sediments and intensive agricultural land use. The AHP results indicated that hydrology had the highest cluster weight (0.42), followed by agriculture (0.27), economic (0.19), and management (0.12). Among individual solutions, banning new well drilling and sealing illegal wells (H2) and utilising groundwater resources in balance with recharge (H1) ranked highest, with weights of 0.143 and 0.126, respectively. The findings provide a scientific basis for water resources management and land-use planning to control and mitigate land subsidence in Khonj Plain.

The Ameliorative Effects of Foliar Amino Acid Applications on Tomato (Solanum lycopersicum L.) Growth and Pigment Content under Salinity Stress

Fatma Kaplan — 2026-06-30

Salinity can restrict tomato growth, particularly under arid and semi-arid growing conditions. This greenhouse pot experiment evaluated whether foliar application of a commercial amino acid (AA) mixture could improve growth and pigment responses of tomato (Solanum lycopersicum L. cv. Falcon) exposed to 100 mM NaCl. Six treatments were arranged in a completely randomised design with four replications: control, 100 mM NaCl, 100 ppm AA, 200 ppm AA, NaCl+100 ppm AA, and NaCl+200 ppm AA. Treatments were applied weekly for seven weeks, after which plant height, fresh and dry weights, root length, chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid contents were measured. Salt stress significantly reduced plant height and root length relative to the control. Foliar AA application modified plant responses, with the 200 ppm dose generally performing better than 100 ppm under salinity. The NaCl+200 ppm AA treatment produced higher plant height, plant fresh weight, plant dry weight, and root length than NaCl alone. Pigment variables showed numerical differences among treatments, but these differences were not statistically significant. Correlation analysis, principal component analysis, and radar chart evaluation indicated treatment-dependent relationships among growth and pigment parameters. Overall, foliar application of 200 ppm AA may support vegetative growth of tomato under 100 mM NaCl, although further validation is required to clarify pigment-related and physiological mechanisms.

Quantitative Study of Saprophytic and Cellulose-Decomposing Microorganisms in Mountain Meadow, Soddy Meadow, Alluvial-Carbonate, and Meadow Brown Soils of Eastern Georgia

Ketevan Mamulashvili — 2026-07-01

Microorganisms play a particularly important role in the biological activity of soils, as they are responsible for the transformation of organic matter, humus formation, and minerals mobilization. Georgia is distinguished by exceptional soil diversity, and nearly all major soil types except tropical soils are represented within its territory. The aim of the present study was to investigate the microflora of different soil types of Eastern Georgia — mountain meadow, soddy mountain meadow, alluvial-carbonate, and meadow brown soils; in particular to study the content of saprophytic and among them cellulose-decomposing microorganisms in relation to soil type. The study employed widely accepted modern microbiological methods. Sampling was carried out using the Waksman’s envelope method. Microbial groups were studied using the dilution method. Meat-peptone agar (MPA) was used for cultivating saprophytic bacteria, while Imshenetsky-Solntseva’s and Czapek’s media were used for cellulose-decomposing microorganisms. The number of saprophytic bacteria was determined by the direct counting method, whereas cellulose-decomposing microorganisms were quantified using McCready’s table. For microorganisms identification were studied: structural features of colonies (shape, size, spore formation, motility, colony morphology); nutritional characteristics; utilization and transformation of chemical compounds; metabolic products; response to oxygen, temperature, and acidity; and genetic characteristics. In all soil types, saprophytic bacteria belonged to the genus Bacillus, while cellulose-decomposing bacteria belonged to the genus Cellulomonas. Three genera of cellulose-decomposing fungi were identified in the soils: Aspergillus, Penicillium, and Fusarium. The maximum total number of microorganisms was observed in alluvial-carbonate soil. Mountain meadow and meadow brown soils were distinguished by greater morphological diversity of microorganisms. The largest number of saprophytic bacteria was recorded in alluvial-carbonate soil. Cellulose-decomposing microorganisms dominated in meadow brown soil. The obtained results indicate that the studied soils of Eastern Georgia are characterized by high microbial activity and a well-developed cellulose-decomposing microflora. Near-neutral pH, moderate moisture, and the presence of organic matter create favorable conditions for the functioning of both bacteria and fungi, which play an important role in organic matter mineralization and biogeochemical cycles in soils.

Evaluation and Health Risk Assessment of Heavy Metals Contamination in Agricultural Soil of Onna River Basin, Nigeria

Samuel Akpan Nta — 2026-07-17

Background: Heavy metal contamination of agricultural soils can impair soil quality, affect crop productivity, and pose ecological and human health risks through multiple exposure pathways. Assessing metal concentrations and associated contamination and risk indices is therefore essential for supporting evidence-based soil management and environmental protection.

Aims: This study assessed the levels of contamination and associated health risks of selected heavy metals, including Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn, in agricultural soil from the Onna River Basin Development Authority, Onna, Akwa Ibom State, Nigeria.

Place and Duration of Study: The study was conducted at the Onna River Basin Development Authority, Onna, Akwa Ibom State, Nigeria, in November 2024.

Methodology: Soil samples were collected at depths of 0–15 cm and 15–30 cm using a 1 m auger and analysed in the laboratory using standard methods. Heavy metal contamination was assessed using the contamination factor (CF), degree of contamination (CD), pollution load index (PLI), and geo-accumulation index (I-geo). The assessment also included the potential ecological risk index and non-carcinogenic and carcinogenic health risk estimates.

Results: Metal concentrations were higher at the 0–15 cm depth than at the 15–30 cm depth. Cu, Ni, Pb, and Zn were below the stated target values for uncontaminated soil. Cd concentrations at 0–15 cm and 15–30 cm were 1.063 and 0.847 mg/kg, respectively, both exceeding the stated target value of 0.8 mg/kg. The farmer reported the use of NPK+ 12 12 17 2 fertiliser, poultry manure, and herbicide on the field during the preceding 7 years. The CF values for Cu, Pb, Zn, and Ni indicated low contamination, whereas those for Cd indicated moderate contamination at both depths. The I-geo values for all assessed metals were below 1, corresponding to the uncontaminated-to-moderately-contaminated category. The hazard index (HI) values were below 1 for adults and children. Most lifetime cancer risk estimates were within the stated acceptable range of 1 × 10^-6–1 × 10^-4_{; however,} the estimated ingestion risk for children at 0–15 cm was in the 10^-2 range. Inhalation risks were in the 10^-9–10^-10 range and were regarded as negligible.

Conclusion: Cd concentrations at both sampling depths exceeded the stated target value for uncontaminated soil and therefore require attention in the management of the agricultural site.

Heavy Metal Presence in Roadside Soils along Major Highways in Igboora, Oyo State, Nigeria

N. O. Olla — 2026-07-20

This study assessed the concentrations and spatial distribution of selected heavy metals in roadside soils along major highways in Igboora, Oyo State, Nigeria. Soil samples were collected from three highway locations: Abeokuta–Igboora–Iseyin Highway, Igboora–Idere–Igangan Road, and OYSCATECH main road. At each location, samples were obtained at 0, 20, and 40 m from the road edge and from two soil depths, 0–20 and 20–40 cm. The concentrations of lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn), chromium (Cr), and nickel (Ni) were determined using atomic absorption spectroscopy after acid digestion. Soil pH and organic carbon were also measured. Data were subjected to an analysis of variance, and treatment means were separated using Duncan’s Multiple Range Test at the 5% probability level. The results showed significant differences in soil properties and heavy metal concentrations among highway locations, sampling distances, and soil depths. Soil pH ranged from slightly acidic to near-neutral, while organic carbon varied significantly across locations, distances, and depths. Zinc was the most abundant metal in the roadside soils, with the highest concentration of 499.15 mg kg⁻¹ recorded at a distance of 0 m and a depth of 0–20 cm along the Abeokuta–Igboora–Iseyin Highway. In general, most metal concentrations were higher near the road edge and declined with increasing distance from the highway. Surface soils also contained higher concentrations of most metals than subsoil samples, except for Pb, which showed relatively higher accumulation at a depth of 20–40 cm. The findings indicate that roadside soils in the study area contain measurable levels of traffic-associated heavy metals, particularly close to highway margins. Based on international soil quality guidelines, the soils showed low to moderate contamination. Zinc was the principal contaminant; cadmium and copper showed moderate enrichment, while lead, chromium, and nickel remained within acceptable limits. Continued monitoring and a 40 m roadside cultivation buffer were recommended.