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All Journal Journal of Degraded and Mining Lands Management
Hermawan, Mega Kartika
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Agriculture, Biological Sciences & Forestry Biochemistry, Genetics & Molecular Biology

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Extraction and characterization of humic acid from low-rank coal mined reserves in South Sumatra and its application on red chili (Capsicum annuum L.) in fertilizer exhausted soil Hermawan, Mega Kartika; Sofyan, Emma Trinurani; Sudirja, Rija; Nurbaity, Anne
Journal of Degraded and Mining Lands Management Vol. 12 No. 4 (2025)
Publisher : Brawijaya University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15243/jdmlm.2025.124.8065

Abstract

Intensive use of inorganic fertilizers has led to soil degradation, decreased productivity, and increased greenhouse gas emissions. Humic acid (HA) offers a sustainable solution by improving soil health and nutrient uptake while reducing dependence on chemical inputs. However, commercial HA from leonardite is expensive and rarely available in Indonesia. This study aimed to develop a high-quality and cost-effective HA product from low-rank coal (LRC) mined in South Sumatra. Given LRC’s low calorific value and high organic content, it presents an underutilized but promising HA source. A descriptive quantitative approach was used, starting with LRC selection and modified extraction to obtain HA. Laboratory-scale characterization revealed that locally sourced HA shares many functional groups with commercial leonardite-based HA. Hydrofluoric acid pretreatment significantly increased HA yield from 26.3% to 44%. A field trial was conducted on degraded soil overused with inorganic fertilizers, using a completely randomized block design with five treatments and five replications. Red chili (Capsicum annuum L.) was selected because of its high economic value. Data were analyzed using ANOVA at a significance level of 5%. The results showed that the combination of HA derived from LRC with low phosphate fertilizer (150 kg ha-1 SP-36 + 27 kg ha-1 HA) significantly increased plant height, fruit yield, and soil P availability, resulting in a yield of more than 28 t ha-1. These findings demonstrate the potential of LRC as a sustainable HA source to restore degraded soils and increase crop productivity in Indonesia.
Path analysis of “new” humic acid derived from water hyacinth on phosphorus dynamics in P-deficient Inceptisols and chili response under intensive cultivation Sofyan, Emma Trinurani; Hermawan, Mega Kartika; Sudirja, Rija; Nurbaity, Anne; Fitriatin, Betty Natalie; Mulyani, Oviyanti; Setiawati, Mieke Rochimi; Djuansah, Muhamad Rahman
Journal of Degraded and Mining Lands Management Vol. 13 No. 1 (2026)
Publisher : Brawijaya University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15243/jdmlm.2026.131.9669

Abstract

Phosphorus (P) deficiency in intensively cultivated Inceptisols is a persistent problem, not only because of low P reserves but also because of ongoing soil degradation, which reduces fertilizer use efficiency and is characteristic of degraded soils. This study aimed to develop a “new” humic acid from water hyacinth biomass (WHL) through accelerated aerobic decomposition using lignocellulolytic microorganisms and to evaluate its effectiveness in improving soil P dynamics and chili growth responses. The experiment was conducted on P-deficient Inceptisols of the Jatinangor series characterized by low P availability and high metal content. Water hyacinth collected from local reservoirs and rivers was aerobically decomposed with selected microbial starters to enhance humification. WHL was applied in combination with inorganic P fertilizer (SP-36), and its effects on soil P availability, phosphorus dynamics, and chili pepper growth and yield were evaluated using path analysis. The results showed that WHL significantly improved P dynamics mainly through an indirect mechanism involving increased P availability and reduced P fixation, thereby improving chili growth and yield. Application of WHL at a rate of 30 kg ha?¹ combined with SP-36 at a rate of 250 kg ha?¹ produced responses comparable to those obtained with commercial humic acid. These findings indicate that WHL has strong potential as a renewable and cost-effective alternative source of humic acid to improve phosphorus efficiency, restore soil chemical function, and reduce dependence on inorganic P fertilizers in degraded Inceptisols under intensive cultivation.
Path analysis of phosphorus dynamics and chili response to low rank coal-derived humic acid in P-deficient Inceptisols Hermawan, Mega Kartika; Sofyan, Emma Trinurani; Sudirja, Rija; Nurbaity, Anne; Fitriatin, Betty Natalie; Mulyani, Oviyanti; Setiawati, Mieke Rochimi; Djuansah, Muhamad Rahman
Journal of Degraded and Mining Lands Management Vol. 13 No. 2 (2026)
Publisher : Brawijaya University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15243/jdmlm.2026.132.9893

Abstract

Jatinangor Inceptisols are formed from volcanic material with a high concentration of iron oxide and a low concentration of phosphorus (P), which leads to high rates of P fixation and low P fertilization efficiency. The situation is exacerbated by intensive agricultural practices. This research was conducted to assess the effect of humic acid derived from low rank coal (AHL) as a soil conditioner in enhancing P availability and chili response in P-deficient Inceptisols. The experiment was conducted in the greenhouse of the Soil Chemistry and Plant Nutrition Laboratory at Universitas Padjadjaran. AHL treatments were combined with various doses of SP-36 fertilizer to evaluate their direct and indirect effects on soil chemical properties, phosphate-solubilizing bacteria (PSB) populations, P uptake, and plant responses. The results showed that AHL application did not cause metal toxicity symptoms and significantly increased potential P, available P, cation exchange capacity (CEC), and total PSB populations. The best results were obtained with a combination of AHL at 30 kg ha?¹ and SP-36 at 125 kg ha?¹, which optimally enhanced P dynamics and chili yields. AHL was proven to reduce the need for inorganic P fertilizer by up to 50% without compromising chili yield or quality. These findings indicate that AHL has great potential to be developed as a locally sourced soil conditioner to support sustainable agriculture and the use of more environmentally friendly low-rank coal.
Co-Authors Anne Nurbaity Betty Natalie Fitriatin Djuansah, Muhamad Rahman Emma Trinurani Sofyan Mieke Rochimi Setiawati Oviyanti Mulyani Rija Sudirja