The impact of seasonal changes on tidal water quality in acid sulfate soils for rice cultivation and water management strategies in South Kalimantan, Indonesia

Abstract

Abstract Water management is the leading key to success in tidal swamp rice farming of acid sulfate soils toward seasonal and climate changes to increase rice productivity for overcoming the threat of food crisis. This study aimed to assess and know the dynamics of tidal water quality from the dry peak season to the rainy season’s peak and the best practices on tidal water management strategies for rice cultivation in acid sulfate soils. Measurement started from the peak of the dry season to that of the rainy season, carried out every month at the spring and neap tides. The first measurement was conducted in the Ray 5 Channel located 3 km from the Barito River, hourly for 24 hours. The second one was performed every kilometer from the Barito’s Riverbanks up to 8 km during high and low tides. The main parameters measured were pH and electrical conductivity (EC). The results explained that water quality in tidal lands dynamically fluctuated, spatially, and temporally, hourly, daily, and monthly. Spatially, good water quality is only found at locations 0-4km on the water channel from the Barito River. The water quality decreases farther from the estuary channel and towards the rain peak. The best water quality in the channel occurs at the in-situ tide peak, usually for 2-3hours closest to or from the highest tide. However, the water quality is very acidic, with the pH∼3 value often overflowing the land at the height of the rainy season. This research can be used as a guide in water management in acid sulfate soils and other similar locations. Proper management and location-specific and compatible water systems are proposed to ensure good quality water can optimally improve agricultural success in tidal swamps of acid sulfate soils, namely by holding backwater during the dry season, water drain from the swampland in the rainy season, with leaching and flushing at the beginning rain, and closing the floodgates from the poor water quality.