Mapping the spatial distribution of pyrite and evaluating soil and water properties in idle swamp land: A strategy to promote sustainable paddy field establishment and prevent land degradation

[Display omitted] •New pyrite mapping plays a crucial role for soil zonation management in swamp land.•Integrated management of pyrite, soil, water, and nutrients can support rice cultivation.•Swamp lands have low bearing capacity and are susceptible to subsidence.•Soils develop from alluvium with low pyrite overlying coastal sediment with high pyrite.•Significant Al and SO4 increased while pH decreased from inlet to water canal networks. The idle swamp land of the former mega rice project in Indonesia has the potential for development of paddy field as a response to the global food crisis. Mapping of pyrite (FeS2) in swamp land as the key driver of soil degradation and poor water quality has not been made to establish a strategy for sustainable paddy field practices. The objective of the study was to assess the spatial distribution of pyrite (FeS2) through detailed mapping, and to evaluate soil and water properties associated with the adverse effects of pyrite. Detailed conventional pyrite mapping with a grid system at 1:10,000 scale, covering a large area of 26,588 ha, had been made. A comprehensive analysis of soil chemical, physical and mineralogical properties, pyrite content, and water properties was conducted. The detailed pyrite mapping showed that spatial distribution of pyrite was delineated into six depth classes, in the order of decreasing extent: P3-moderately deep (>50–75 cm) > P4-deep (>75–100 cm) ≫ P5-very deep (>100–150 cm) > P2-shallow (>25–50 cm) > P6-exceptionally deep (>150 cm) > P1-very shallow (0–25 cm). These pyrite classes allow zonation management strategy of soils and water table into different depths to avoid pyrite oxidation and its harmful effect. Soils have limited easily weathered minerals ( tertiary > quaternary > pyrite collector), as well as the increased Al and SO4 ions suggests the decrease in quality throughout the canal network. We propose the management strategy for the sustainable establishment of paddy field in pyritic swamp areas including: (i) performing detailed mapping of pyrite classes to guide depth-based pyrite zonation to control water tab