<![CDATA[Abstract. Widiarso B, Nuriman M, Afner DDP, Suhaimi. 2026. Soil and water management in tidal rice fields based on irrigation and water quality across land units in Mempawah, West Kalimantan, Indonesia. Asian J Agric 10 (2): g100231. https://doi.org/10.13057/asianjagric/g100231. Tidal rice field management in Indonesia is often applied the same way across different land units. This approach ignores the variations in pyrite depth, which significantly changes how soil and water interact. This study used a comparative land-unit approach to describe soil and water management needs in tidal rice fields of Mempawah District, West Kalimantan, Indonesia. Field surveys at ten locations identified two land units: Sulfaquents with shallow pyrite and Endoaquents with deeper pyrite (>50 cm). We analyzed soil morphology, irrigation water quality, and crop water requirements in a united framework. Sulfaquents needed 13-15% more irrigation during land preparation (221.1-221.7 mm/decade) compared to Endoaquents (187.9-195.1 mm/decade). This difference reflects the role of water in preventing pyrite oxidation. Irrigation water quality differed regardless of land unit. Three out of ten sites exceeded FAO thresholds (EC > 750 µS/cm or SAR > 26). Spearman correlation identified Na⁺ (rs = 0.967) and SAR (rs = 0.939) as the main factors. In contrast, channel discharge showed no clear relationship (rs = -0.231). This indicates that source water and hydrological connectivity are more important than flow volume. The integrated land-unit framework offers a foundation for managing tidal rice fields in a site-specific way.]]>
