Enhancing Soil Health Through Sediment Deposition in Flood-Based Agricultural Systems: Evidence from the Mekong Delta, Vietnam

Sediment deposition in the Vietnamese Mekong Delta (VMD) has declined sharply due to high-dike infrastructure and upstream damming, threatening long-term soil fertility and agroecosystem resilience. This study presents the first integrated assessment of sediment dynamics and soil health across four flood-based and conventional agricultural systems in VMD. We compared sediment accumulation and soil biochemical properties in (1) floating rice–fish farming, (2) lotus–fish farming, (3) natural flooding, and (4) triple-rice cropping systems. Sediment samples (n = 80) and soil samples (n = 35) were collected from 2022 to 2024. We applied principal component analysis (PCA) to identify a minimum data set of soil indicators and used a weighted soil health index (SHI) to evaluate system performance. Nonparametric Kruskal–Wallis tests revealed statistically significant differences in sediment mass, nutrient retention, and soil health among models (p<0.001). The lotus–fish and natural flooding models exhibited 8–15 times greater sediment deposition and SHI values that were 25%–33% higher than those of the triple-rice system, with strong correlations between sediment mass and soil health (R2=0.613). These models also enable reductions of up to 40% in postflood nitrogen and potassium fertilizer requirements. Using PCA and a weighted SHI framework, we highlight that flood-based systems, particularly lotus–fish farming, significantly enhance soil health and reduce fertilizer dependency. Our results support the scaling of sustainable agricultural transitions in line with Vietnam’s Resolution 120 on climate-resilient development in the VMD.