Journal of Tropical Soils
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Soil Organic Carbon in Typic Hapluderts on Different Slopes and Land Uses
No full textOrganic carbon is a key component in the carbon cycle and plays a crucial role in determining soil quality. This research aimed to determine the soil organic carbon content on different slopes and land uses in Candirejo Village, Semin District, Gunungkidul Regency. Soil samples were taken by creating soil mini-pits to collect two samples in ten locations based on soil color differences as well as from the plow layer at depths of 0-10 cm and 10-20 cm. A field work was conducted using a survey method on the Typic Hapluderts with varying slopes and land uses. Soil analysis were: organic carbon using the Walkley and Black method, soil texture using the pipette method, soil bulk density using the volumetric ring method, pH H2O using the potentiometric method, and soil color using the Munsell method. The results indicated that soil organic carbon levels varied across different slopes and land uses. Average organic carbon content on flat slopes was 1,64% (low), on gentle slopes it was 1,21% (low), while the land uses content from highest to lowest was in forests 2,19% (medium), in shrublands 1,55% (low), in settlements 1,31%, in dry lands 1,20% (low), and in paddy soils 0,86% (very low). Slope did not significantly influence soil organic carbon levels. However, land use significantly influences soil organic carbon levels, resulting in significant differences in soil organic carbon content. Soil color coordinate L* (lightness) is linearly negatively correlated with soil organic-C with a value of r = 0,641. Soil organic carbon showed a strong and significant relationship with soil color coordinate L* (lightness). Higher soil organic carbon content led to lower L* values, indicating darker soil color.Keywords: Land use, organic carbon, slope, Typic Hapludert
Flux of Nutrient Leaching from Ultisol of Pineapple Plantation Ameliorated with FABA and Compost and Its Implications on Fertilizer Management
No full textABSTRACTUltisol is a weathered tropical soil order with low fertility status. It is also prone to nutrient leaching processes. Plantation area of PT. Great Giant Pineapple (PT GGP), which is dominated by Ultisol, has been intensively cultivated for pineapple in rotation with banana and cassava for decades.  This study aims to evaluate the effects of FABA+compost amelioration on nutrient leaching from Ultisol of PT GGP area and its fertilizer management implications. A nutrient leaching simulation through percolation experimentation had been conducted using soil samples of 0-20 cm layer taken from the pineapple-cultivated field plots 9 months after the treatment application or one month before the plant regenerative-phase forcing step was done. Percolations were done every 7 days with 170 mL aquadest 0,75 kg-1 soil for 35 days experimental period, which was equivalent to the monthly-average of the six wet-months’ rainfall in the study area. The amelioration evaluated reduced significantly the soil nutrients leached in terms of tmax, total flux, and flux proportion. The band-application of 25 ton.ha-1 FABA+compost gave the best results. The NO3 and K leaching flux proportions, however, were still high. It is suggested to consider the use of controlled release fertilizers to reduce the nutrient leaching flux.Keywords: fertilizer management, flux proportion, percolation, total flux, tma
ENHANCING THE SANDY SOIL NITROGEN CONTENT OF THE SAMAS COASTAL AREA USING ANAEROBIC DIGESTION SLUDGE DERIVED FROM PALM OIL MILL EFFLUENT
No full textSandy coastal soils, characterized by poor fertility and low nitrogen (N) content, present significant challenges for sustainable agriculture. This study investigates the potential of anaerobic digestion (AD) sludge derived from palm oil mill effluent (POME) as an organic amendment to enhance soil N in Samas Beach’s degraded sandy soils. Using a completely randomized design (CRD), six digestate application rates (0–800 mL/kg soil) were tested over a 30-day incubation period. Results demonstrated a strong linear dose-response relationship (R² = 0.995), with the highest treatment (A5: 800 mL/kg) increasing soil N by 140% (0.005% to 0.012%) compared to the control. The Kjeldahl method confirmed efficient mineralization of organic N into plant-available NH₄⺠and NO₃â», supported by microbial activity from cow dung inoculum. Tukey’s HSD test revealed all treatments significantly improved N content (p < 0.05), with 400 mL/kg (A4) identified as the optimal rate—balancing efficacy (0.011% N) with economic and environmental practicality. This study highlights POME-derived sludge as a cost-effective, sustainable alternative to synthetic fertilizers for rehabilitating coastal soils, aligning with circular economy principles by valorizing agro-industrial waste
Distribution of Soil organic carbon of volcanic soil along elevation gradient on Kaba Volcano Bengkulu Province
No full textClimate change is a global issue primarily driven by increased carbon dioxide levels in the atmosphere. Numerous studies have been conducted to reduce carbon dioxide emissions as a strategy to mitigate its effects. Soils, particularly volcanic soils, are known to store significant amounts of carbon - second only to deep-sea reservoirs. This study aims to investigate the soil organic carbon content distribution of volcanic soils along elevation gradient on Kaba Volcano in Bengkulu Province, Indonesia. Nine soil samples, both disturbed and undisturbed, were collected at a depth of 10 cm from three locations at different elevations: the foothill (1360–1380 m a.s.l.), hillside (1610–1620 m a.s.l.), and hilltop (1930–1940 m a.s.l.). Undisturbed samples were collected using a 70-mm core cylinder to determine soil bulk density, while disturbed samples were taken with a shovel and analyzed for soil organic carbon, pH, and particle size distribution (sand, silt, and clay). The results showed that the hillside samples had the highest soil organic carbon content, while the hilltop samples had the lowest. Correspondingly, the lowest soil pH was observed at the hillside, and the highest bulk density was found at the hilltop. Particle size analysis revealed that sand and clay content at the hillside were similar to those at the foothill and both were higher than those at the hilltop. The lower soil organic carbon at the hilltop may be attributed to drier conditions and reduced vegetation cover compared to the foothill and hillside
MODEL OF THE RELATIONSHIP BETWEEN SELECTED THE SOIL PHYSICAL PROPERTIES OF OIL PALM SOIL
No full textSoil, water, and plants are interrelated elements in agricultural production. An in-depth understanding of the characteristics and interactions of these three aspects is essential in effective agricultural system management. The study aims to examine the relationship of soil capacity to hold water to different levels of land slope and identify the physical characteristics of the soil that affect it. The research was conducted in a community oil palm plantation in Talang Tengah I Village, Pondok Kubang District, Central Bengkulu Regency, Bengkulu Province. The method used was a survey with purposive sampling at five different slope levels, namely flat (0-8%), sloping (8-15%), slightly steep (15-25%), steep (25-45%), and very steep (45-100%). The data was statistically analyzed using the Partial Least Squares Structural Equation Modelling (PLS-SEM) method with WarpPLS 7.0 software. The results showed that slope had a significant effect on various soil physical characteristics and soil water holding capacity. The steeper the slope, there is a decrease in soil permeability, total pore space, and C-Organic soil, and an increase in soil volume weight, which results in a decrease in soil water holding capacity. The resulting model shows the agreement in describing the relationship between variables, where slope affects organic matter, sand %, and permeability, and then volume weight affects total pore space and permeability, which in turn effects the soil’s capacity to hold water
Change of Sandy Soil Chemical Properties with Azolla microphylla and Quail Manure
No full textUncontrolled land conversion reduces the available land for plant cultivation. The alternative used for rice cultivation is marginal land, such as sandy soil. However, several constraints led to very low productivity, so it needs proper management, such as adding organic matter. This study aimed to determine changes in the chemical properties of sandy soil treated with Azolla microphylla and quail manure. The pot research was carried out in the Greenhouse of the Faculty of Agriculture, Universitas Sebelas Maret, using a factorial Completely Randomized Design (CRD) with two factors. The first factor consisted of four levels of Azolla microphylla (AM),i.e., (0, 50,100, and 150 Mg ha-1). The second factor was three-level quail manure (QM ), i.e., (0, 20, 40 Mg ha-1). Fresh Azolla microphylla and quail manure were incubated for 14 days under anaerobic conditions. The results showed that applying Azolla microphylla, with or without quail manure, significantly improved the chemical properties of sandy soil. The addition of Azolla microphylla (100 Mg ha-1) with quail manure (40 Mg ha-1) increased organic C, Cation exchange capacity (CEC), available-P, Ammonium, Nitrate, exchangeable-K, Ca, electrical conductivity (EC), and redox potential (Eh)
Spatial Distribution of Soil Properties and Soil Fertility Status in the Paddy Rice Field of Oransbari
Full text linkSoil properties and soil fertility status of paddy rice fields are considered important factors related to the yield and production of rice; therefore it is essential to understand those properties across the farm. The objectives of this research is to quantify the soil properties and soil fertility status of paddy-rice soil and their spatial variability in Oransbari. Forty-two composite soil samples (0-30 cm) were taken across paddy rice fields and analyzed for soil chemical properties and fertility status. Geostatistical analysis and ordinary kriging interpolation methods were used to quantify soil variability and its fertility status across the farm. The results showed that total soil Nitrogen ranges from 0.11% to 0.17%), organic-C (1.47-6.94%), C/N ratio (11-47), total-P (13-99 mg 100 g-1), available-P (30-227 mg kg-1), total-K (27-54 mg 100 g-1), soil pH (5.83-6.93), base saturation (70-100%), and CEC is 30.51-51.23 me 100 g-1. The spatial variability of all soil characteristics exhibited medium and fit the stable model, except for available Phosphorus and Potassium. Most rice paddy fields in Oransbari showed high soil fertility status, which indicated that high-yield rice production can be achieved for this region, however, land management factors should be considered for sustainable land use
Integrating Soil Properties and Vegetation Indices for Modeling Potato Productivity
No full textGlobal potato production reached approximately 383 million metric tons in 2025, with Indonesia contributing around 1.22 million metric tons (0.32% of global output). However, the sustainability of Indonesia’s potato production is increasingly threatened by soil quality degradation in key growing regions. Existing predictive studies have primarily focused on soil chemical properties, with limited incorporation of remote sensing technologies. This study investigates the potential of Unmanned Aerial Vehicle (UAV) as a high-resolution, non-destructive tool for estimating potato yield using vegetation index transformations. Utilizing a split-plot experimental design across elevation gradients, we integrated soil properties with UAV-derived vegetation indices—Visible Atmospherically Resistant Index (VARI), Green Leaf Index (GLI), and Normalized Green-Red Difference Index (NGRDI). Results reveal that total nitrogen, base saturation, and bulk density significantly influence yield variability, and can be accurately estimated using NGRDI, GLI, and a modified GLI (GLI CS), respectively. A multiple linear regression model was developed to predict potato yield = 24.22 + 7.26(NGRDI) + 9.87(GLI) + 28.42(GLI CS). This research demonstrates the efficacy of UAV-based spectral analysis in improving yield-prediction models, offering a scalable, precise approach for sustainable potato cultivation. Future work should incorporate machine learning to improve model robustness and assess applicability across varied agro-ecological contexts
The Influence of Organic and Inorganic Amendments on Phosphorus Chemistry in Two Acidic Soils of Southwestern Ghana
Full text linkA study in southwestern Ghana compared the effects of organic and inorganic additives on P availability and related factors in two acidic soils, Ankasa and Abenia. Different amounts of P as KH2PO4 were applied: 0.067 g kg-1 for Abenia and 0.041 g kg-1 for Ankasa. Soil samples were treated with cow dung, Chromolaena odorata, and poultry droppings for six weeks to increase standard P requirement and neutralize exchangeable Aluminum. Data analysis was performed using GenStat (version 14). An analysis of variance (ANOVA) was conducted for the soil amendments, followed by Tukey’s comparison test at a 5% significance level to identify significant differences among the soil amendments. The result showed that higher rates of organic amendments significantly increased pH, available P (Bray 1 and NaHCO3-P), NaOH-P, and reduced exchangeable Al concentration. Poultry droppings and cow dung impact notably improved soil quality. At the same time, CaCO3 had similar effects on soil pH. However, it did not significantly affect P availability or NaOH-extractable P. CaSO4 and CaCO3 had minimal impact on phosphorus distribution, suggesting that altering pH or exchangeable Al does not necessarily change P fractions. Poultry droppings, rich in P, could be a potential alternative to lime in enhancing P availability and reducing soil acidity
Application of Rice-Husk Biochar to Coarse-Textured Ultisols and the Effects on Soil Fertility Indicators at Different Amendment-to-Sampling Intervals
Full text linkThe low fertility status of the highly weathered tropical soils offers the opportunity to study the potential and optimum application rate of biochar as an organic soil amendment, especially for the dominant coarse-textured Ultisols. Despite the relatively fast mineralisation of organics in these soils and the need to synchronise nutrient release crops critical stages of nutrient requirement, the time corresponding to peak effects of biochar remains unclear. The effects of rice-husk biochar (RHB) on the soil fertility of sandy-loam Ultisols at 0, 7.5, 15, 30, and 60 Mg ha-1 equivalents in 2-kg soils were assessed at 0, 2, 4, 8, and 12 weeks of incubation (WOI). Treatments were prepared in batches to enable concurrent sampling for all five incubation intervals. The RHB enhanced soil fertility across the incubation intervals, with optimal rates as 15 Mg ha-1 for soil pH and 30 - 60 Mg ha-1 for macronutrients availability. Relative to the its non-application, RHB increased soil pH-H2O, total N, available P, exchangeable bases, exchangeable acidity, apparent CEC and base saturation by 4-30%, 43-100%, 30-202%, 13-240%, 14-675%, 21-126% and 7-82%, respectively. Soil pH tended to decrease after, while available P progressively decreased before 8 WOI, when treatment effects were generally most pronounced. At an all-encompassing optimal rate range of 30-60 Mg ha-1, RHB could reduce soil acidity and enhance the macronutrient status of coarse-textured Ultisols over at least 12 weeks, soil fertility restoration effects of which are likely to be most pronounced around 8 weeks