Geostatistics of Soil Organic Carbon over Peatlands with Productive Oil Palm Crops
Yusrizal, Budi Mulyanto, Heru Bagus Pulunggono and Bambang Hendro Trisasongko

Department of Soil Science and Land Resource, Bogor Agricultural University, Jalan Meranti, Dramaga, Bogor 16680, Indonesia
Study Program of Agrotechnology, Faculty of Agriculture, Universitas Teuku Umar, Meureubo, Aceh Barat 23568, Indonesia
Study Program of Smart Agriculture, Faculty of Agriculture, Jalan Meranti, Dramaga, Bogor 16680, Indonesia

Abstract

Tropical peatlands are globally significant carbon sinks, characterized by their high organic matter content and waterlogged conditions that inhibit decomposition. However, widespread conversion of these ecosystems into oil palm plantations has disrupted peat hydrology and accelerated soil organic carbon (SOC) losses, thereby intensifying greenhouse gas emissions and ecological degradation. This study investigates spatial heterogeneity of SOC in Indonesian tropical peatlands cultivated with oil palm using geostatistical modeling. A total of 96 soil samples were collected during the dry season (February 2024), stratified by peat thickness (<3 m and >3 m), sampling depth (0-30 cm and 31-60 cm), and distance from secondary drainage canals (10, 25, 50, 75, 100, and 150 meters). The SOC content was determined using the Walkley-Black wet oxidation method and analyzed spatially using Kriging. SOC concentrations ranged from 29.55% to 60.85%, with elevated mean values in deeper sampling layers (31-60 cm) and areas with peat thickness exceeding 3 meters. Levels of SOC also increased progressively with greater distances from drainage canals, indicating reduced oxidative decomposition in hydrologically stable zones. Empirical semivariogram analysis confirmed strong spatial dependence, and ordinary kriging interpolation demonstrated sufficiency in predictive modeling. Integration of stratified sampling design, peat thickness categorization, and drainage proximity into the spatial model yielded a representative SOC distribution, despite some anomalies. These results highlight the efficacy of geostatistical techniques for capturing SOC variability in peatland ecosystems and provide critical insight for sustainable peatland management, restoration planning, and climate change mitigation

Keywords: Tropical peatlands, Soil organic carbon, Oil palm plantations, Drainage, Kriging

Topic: Topic E: Sustainable Development Goals