| dc.description.abstract | Limited land resources have led to gradual expansion of land use from productive lands to less productive or marginal lands. One of the marginal land types utilized for food crop production is acid sulfate soils. Acid sulfate soils are formed through oxidation of pyrite, which produces sulfuric acid resulting in a drastic decline in soil pH. These soils are characterized by low soil fertility, including acidic to very acidic pH, low phosphorus availability due to fixation by aluminum and iron, and low total nitrogen content. These characteristics indicate that rice cultivation on acid sulfate soils requires special management practices to achieve optimal yields. Land suitability analysis is essential to identify the potential for rice cultivation on acid sulfate soils. Problems associated with acid sulfate soils can be identified at an early stage through mapping the spatial distribution of pyrite depth. Agricultural planning in site-specific areas also requires actual land use data. The potential of acid sulfate soils, which are classified as marginal lands, needs to be further evaluated, particularly regarding their recommendation as intensive paddy fields that can support sustainable food security.This study was conducted from May to June 2024 in Sungai Kakap District, Kubu Raya Regency, West Kalimantan, Indonesia. Soil sample analyses were carried out at the Soil Laboratory of Tanjungpura University. The materials used included chemical reagents for field and laboratory soil analyses. Spatial and secondary data consisted of: (1) The Indonesian Topographic Map (RBI); (2) Landsat 9 imagery from 2024; (3) Climate data (rainfall and average temperature); and (4) Soil maps. Observation points for pyrite depth determination were selected using an overlay technique of several base maps, under the Area of Interest (AOI) map, resulting in a total of 64 observation points. Spatial distribution analysis of pyrite depth was performed using Ordinary Kriging (OK) prediction method. Analysis of actual land availability was conducted using Landsat 9 imagery and a machine learning approach, namely Support Vector Machine (SVM). Soil samples for land suitability analysis were collected from each representative soil profile of the Land Mapping Unit (LMU). Land suitability evaluation was performed through a matching process using SPKL 2.1, while the economic feasibility of farming activities was evaluated based on B/C Ratio and R/C Ratio. Spatial distribution pattern of pyrite in the study area showed that very shallow to shallow pyrite layers were predominantly found in areas close to major rivers and coastal zones, while moderate to deep pyrite layers gradually occurred farther inland, increasing with distance from the sea and large rivers. Actual land suitability evaluation at three observation points were classified as S3-nr/xs, N-xs, and S3-rc/nr, whereas potential land suitability after improvement measures increased to S2-xs, S3-xs, and S1, respectively. Areas characterized by very shallow to shallow pyrite distribution patterns were classified as not suitable (N), while areas with moderate to deep pyrite distribution patterns were classified as marginally suitable (S3). The presence of pyrite at very shallow to shallow soil layers significantly affected the extent of land available for rice cultivation. Total land area available for rice cultivation was 21860 ha out of the total study area. Priority I, dominated by soils with deep pyrite layers, covered an area of 5073 ha (23,21%) and had a land suitability class of S3–rc/nr, with the potential to improve to S1 through drainage system management. These methods can be adopted to address drainage limitation factors and also function effectively as climate-smart agriculture practices. Priority II, dominated by soils with shallow pyrite layers, covered an area of 11346 ha (51,90%) and had a suitability class of S3–nr/xs, with the potential to improve to S2–xs through fertilizer and lime application. Priority III, dominated by soils with very shallow pyrite layers, covered an area of 5441 ha (24,89%) and had a suitability class of N–xs, with the potential to improve to S3–xs through groundwater level management. Tidal lowland rice cultivation shows relatively high economic viability, characterized by a B/C ratio of 1,50 and an R/C Ratio of 2.50, as well as a productivity level of 2.9 t ha?¹, relative to the region's optimum productivity of 3,1 t ha-1 in Kubu Raya Regency. | |
