Acta Solum

Perbandingan Proses Mineralisasi Karbon dan Nitrogen serta Humifikasi Pada Sistem Pertanian yang Berbeda di Tanah Andisol

Fajar Hidayanto, Retno Tri Purnamasari, Sari Widya Utami, Murni Handayani — Sat, 30 Aug 2025 00:00:00 +0800

The organic farming system has become the choice of most farmers in Indonesia because it has a major impact on agricultural quality and soil fertility. Vegetable farming in Magelang and Semarang Regencies is cultivated on andisol soil which has a relatively high soil fertility level, but farmers still use organic fertilizers to increase the organic matter content of the soil. The organic farming system applies 10 tons ha^-1 of cow manure, 20 liters ha^-1 of liquid fertilizer, and the return of plant residues at each planting season. The conventional farming system with high organic matter applies 7 tons ha^-1 of cow manure, 50 kg ha^-1 of urea, 50 kg ha^-1 of NPK fertilizer, 15 liters ha^-1 of liquid fertilizer, while the conventional farming system with low organic matter applies 3 tons ha^-1 of chicken manure, 50 kg ha^-1 of ZA fertilizer, 50 kg ha^-1 of KCl fertilizer, and 50 kg ha^-1 of NPK fertilizer. Observation variables include pH NaF, C-organic, N-total, C/N ratio, humic acid, fulvic acid and humification rate. Data were analyzed for variety and if different, the method of the smallest significant difference test was continued. The results of the study showed that the organic farming system was more effective in increasing carbon and nitrogen in the soil and accelerating humification, so that nutrients were available more quickly. However, the deeper the soil layer, the mineralization and humification processes will decrease because they are greatly influenced by the availability of organic matter.

Unveiling the BPF9 Isolate as a Potential of Phosphate-Solubilizing Bacteria Through In Vitro Characterization

Tue, 30 Sep 2025 19:32:20 +0800

The increasing demand for food has driven agricultural intensification, particularly through the use of phosphate fertilizers. However, phosphorus uptake efficiency by plants remains low due to its predominance in insoluble forms in the soil. One promising alternative is the use of phosphate-solubilizing bacteria (PSB). This study aimed to evaluate the solubilization potential of the BPF9 isolate through qualitative and quantitative assays, as well as growth curve profiling. The research was conducted at the Soil and Environmental Biotechnology Laboratory, IPB University. Qualitative phosphate solubilization was assessed on Pikovskaya agar by measuring halo zone formation to calculate the solubilization index (SI). Quantitative analysis was carried out using spectrophotometry at 660 nm. The bacterial growth curve was analyzed using the haemocytometer method. Results showed that BPF9 had a solubilization index of 2.0 (moderate category) and was able to solubilize phosphate up to 128.5 ppm, which is considered highly efficient. The growth curve indicated that BPF9 entered the exponential phase at 26 hours and reached its maximum population at 42 hours. These findings indicate that BPF9 possesses strong phosphate-solubilizing capability and stable growth characteristics, making it a promising candidate for biofertilizer development.

Mitigating Heavy Metal Contamination in Agricultural Soils with Biosilica-Humic Acid as Soil Amendment Strategies in Industrial Peripheries

M Ghufron Chakim, Wanti Mindari, Purnomo Edi Sasongko — Tue, 30 Sep 2025 20:20:51 +0800

Soil contamination by heavy metals poses a significant threat to sustainable agriculture, especially in areas adjacent to industrial zones. This study demonstrates that while the initial application of the biosilica-humic acid (BSi-HA) soil amendment did not result in statistically significant changes in soil chemical properties within the first 7 days of incubation, prolonged incubation for 60 days revealed meaningful effects, particularly in reducing heavy metal availability in soil. Significant decreases in iron (Fe) and lead (Pb) concentrations were observed over time, with Fe reductions ranging from 45–67% and Pb reductions between 8–40%. These results are attributed to the synergistic effect of functional groups in BSi-HA—especially the carboxyl (–COOH) and hydroxyl (–OH) groups in humic acid—which exhibit high metal-binding affinity under acidic conditions (pH ~5). Although soil fertility parameters such as C-organic content and cation exchange capacity (CEC) showed a declining trend due to microbial activity during incubation, the ability of BSi-HA to immobilize heavy metals without exceeding safe thresholds highlights its potential as a sustainable soil amendment. Moreover, previous findings indicating reductions of up to 90% for Pb and 76% for Cd in plant tissues further support the efficacy of BSi-HA in mitigating heavy metal contamination in agricultural soils near industrial zones. Further long-term studies are recommended to evaluate BSi-HA's remediation capacity, persistence, and impact on crop yield and food safety. Combining biosilica and humic acid offers a promising, eco-friendly approach for managing heavy metal contamination in soils.

Exploration of Bacteria in Red Chili Plant Soil with Potential as Plant Growth Promoting Rhizobacteria (PGPR)

Miladiarsi Miladiarsi, Muhammad Rizal, Padil Wijaya — Tue, 30 Sep 2025 22:45:22 +0800

Soil fertility depends on the availability of sufficient nutrients for plant absorption. Chemical fertilizers can be used to provide sufficient N and P, but this affects soil health. The presence of rhizobacteria act as biofertilizers by increasing nutrients and altering soil formation, especially in the phosphate and nitrogen cycles. Phosphate-solubilizing and nitrogen-fixing bacteria play a role in increasing soil fertility and improving unstable soil properties. This study aims to identify rhizobacteria that have the potential as PGPR to increase N and P levels in the soil. Soil samples were collected randomly at a depth of 10 cm around chili plant roots. Bacteria were isolated using serial dilution and cultured on Pikovskaya medium. A total of 27 isolates produced clear zones with the highest solubility index and were inoculated on Nitrogen-Free Bromthymol Blue Agar (NFB) to evaluate N fixation through a color change from green to blue, as well as hypersensitivity tests on tobacco plants. Isolates showing the highest P solubility, highest N fixation ability, and no necrosis in tobacco were inoculated into sterile soil to analyze compound changes. Soil N content was measured using the Kjeldahl method, while phosphate levels were analyzed using the Bray I and HCl methods. The results of the study showed that the addition of KE2.15 isolate to the soil after 4 weeks of application increased the total organic N and available P content, making it a potential biofertilizer.

Detection of Arbuscular Mycorrhizal Fungi in the Root of Allium fistulosum Grown in the Fumigated Field

Tue, 30 Sep 2025 23:34:33 +0800

Soil fumigation is important pre-plantation practices to maximize land productivity. Not only effectively eliminate soil pests and pathogens, but this practice also affecting the beneficial soil microbial community including arbuscular mycorrhizal (AM) fungi. The AM fungal community in the roots of Allium fistulosum were studied. The roots have been collected from fumigated and non-fumigated field. The DNA has been extracted, then the fungal LSU ribosomal RNA gene has been amplified and sequenced. Two and three AM fungal OTUs have been detected from fumigated and non-fumigated field, respectively. Decomposer and pathogenic fungi were detected coexist with the AM fungi, suggesting the resilience of these fungi upon fumigation treatment.

Distribution of Soil Physical Characteristics Across Different Slope Gradients in Highland Areas (Tawangmangu, Indonesia) for Potato Crop Development

Tue, 30 Sep 2025 23:56:12 +0800

Tawangmangu District, Indonesia, is located in a highland area with a cool climate and is predominantly composed of Andisol soil types, offering great potential for the development of potato crops (Solanum tuberosum L.). This study aims to examine soil physical properties suitable for potato cultivation, analyze the distribution of these properties across different slope gradients, and identify appropriate soil management strategies for the Tawangmangu area. The research employed a descriptive-exploratory approach, utilizing land map units (LMUs) that were determined through the overlay of soil type maps, rainfall data, slope gradients, and land use. The overlay resulted in 5 LMUs and 25 sampling points. Observed soil physical parameters included texture, porosity, permeability, consistency, effective soil depth, coarse material, and drainage. The land suitability assessment showed that LMUs 1, 2, and 3 were classified as S3-oa, limited by drainage, while LMUs 4 and 5 were classified as S3-oa,rc, limited by both drainage and effective soil depth. Slope gradient significantly affected moisture content (p = 0.022), bulk density (p = 0.037), particle density (p = 0.048), porosity (p = 0.032), effective soil depth (p = 0.001), and coarse material content (p = 0.032). Recommended land management efforts include the addition of organic matter, manual tillage for shallow soils, and the application of eco-drainage techniques to improve soil physical suitability for potato cultivation in Tawangmangu.

Potential of Trace Elements in Volcanic Highlands: Geogenic Sources and Their Implications for Productivity

Imas Masithoh Devangsari, Benito Heru Purwanto — Sun, 05 Oct 2025 08:34:14 +0800

This study investigates the mineralogical composition and trace element potential of volcanic highland soils in Kejajar District, Wonosobo, Central Java, an area that has experienced long-term horticultural intensification. Volcanic Andisols in this region are known for high fertility but also carry risks of trace element accumulation due to complex mineralogy and intensive land use. Bulk powder X-ray diffraction identified feldspar, epidote, apatite, pyrite, and clay minerals, which may release essential (Zn, Cu, Fe, Mn) and toxic (Cd, Pb, As) elements through natural weathering and agricultural activities. Results show that horticultural soils on 9–15% slopes exhibited the highest HCl 25%-extractable P (224.70 mg/100 g). At the same time, shrubland soils also displayed high values (179.74 mg/100 g), indicating contributions from both fertilizer and geogenic sources. Although horticultural soils had higher chemical fertility, the shrubland maintained better physical (bulk density, 0.78 g/cm³) and biological quality (soil respiration, 36.48 mg C/kg/day). Productivity trends further highlight risks: cabbage yields declined by 41% (2020–2023), and potato production dropped by 11% (2017–2021). These findings demonstrate the dual role of geogenic and anthropogenic inputs in shaping soil quality and productivity. Sustainable management requires integrated strategies, including trace element monitoring, pH regulation, organic matter enhancement, and the use of low-contaminant fertilizers, to ensure long-term agroecosystem resilience in volcanic highlands.

Physical and Chemical Characteristics and Classification of Soil in Plantation Land, Bareng Wonosalam, Jombang Regency

Dimas Prabowo Harliando, Dinna Hadi Sholikah, Maroeto Maroeto — Sun, 05 Oct 2025 10:32:20 +0800

Soil is a fundamental factor influencing agricultural productivity, as it determines nutrient availability, water retention, and the long-term sustainability of farming systems. The Bareng Wonosalam District of Jombang Regency is a significant agricultural area with varied topography and intensive land use; however, comprehensive soil characterization in this region remains limited. This study aimed to analyze the physical and chemical characteristics of soils in plantation lands and classify them taxonomically to inform sustainable management. A representative plantation site in Pulosari Dua was selected using land-use and slope overlays. Five soil horizons (Ap, AB, Bt1, Bt2, BC) were described. Samples were analyzed for moisture content, texture, bulk density, pH (H₂O, KCl), electrical conductivity, organic carbon, total nitrogen, available phosphorus (Olsen, Bray), exchangeable cations (K, Na, Ca, Mg), cation exchange capacity (CEC), and base saturation (BS). Results showed moisture content of 6.2–20.8%, bulk density of 1.23–1.52 g/cm³, pH of 5.35–5.99, and organic carbon of 0.77–3.61%. Exchangeable K and Na were low (<0.60 cmol·kg⁻¹), while Ca ranged from 3.69–7.06 cmol·kg⁻¹. Textures were silty clay and clay, with BS of 53.5–117.1% and CEC of 9.15–12.93 cmol·kg⁻¹. The soils were classified as Typic Hapludalfs. Recommended practices include dolomite liming, potassium fertilization, structural amendments, and terracing. These actions are expected to enhance soil fertility, water retention, and plantation productivity by enabling targeted soil amendments, balanced nutrient application, and erosion control measures that directly address the identified limitations.