Sediment properties in flood-based farming systems in the Vietnamese upstream Mekong Delta

The Mekong Delta is a flood-based agricultural landscape the agricultural productivity of which strongly depends on sediment deposition.This study aimed to evaluate the quantity and quality of flood-borne sediments across three areas in Tinh Bien district, An Giang province, including upstream, behind the Melaleuca forest, and downstream.This study compared the quantity and quality of sediments deposited in the fields with flood-based farming models: ratoon rice with natural fish storage (RR-NFS), ratoon rice with fish farming (RR-FF), and lotus with fish farming (L-FF); whereas natural flood fields (NF) were used as control fields.Field sampling was conducted from September to November 2024 (within 78 days).The deposited sediments were collected using net sediment traps.The sediments were analyzed for mass and quality parameters, including texture, pH, electrical conductivity (EC), organic matter (OM), total nitrogen (TN), ammonium (NH 4 + -N), nitrate (NO 3 -N), total phosphorus (TP), available phosphorus (P₂O₅), and total and exchangeable potassium (TK and K₂O).Results showed that sediment deposition was highest at upstream (5.81 ± 1.70 g/m²×d), moderate at downstream (4.34 ± 0.76 g/m²×d), and lowest at behind the Melaleuca forest (3.55 ± 0.28 g/m²×d).The level of sediment deposition in fields of flood-based farming models was significantly lower than that in natural floodplain fields.Sediments were consistently classified as clay loam, dominated by clay (~60%), moderate silt (~33%), and low sand (