Pesticide residues in organic vs. conventional rice systems: Management recommendations for Vietnam's Mekong Delta

CONTEXT Intensified paddy rice production in Vietnam, particularly in the Mekong Delta, has led to a significant increase in chemical pesticide use over recent decades, resulting in widespread contamination of agricultural soils and water sources. Vietnam's Mekong Delta, a key region for national rice production and rice exports, holds predominantly smallholder farming with fields typically spanning just 1–2 ha per farmer. This fragmented structure challenges coordinated management and organic certification efforts, while limited data on pesticide use and residues levels challenges system-level evaluations for sustainable transitions. OBJECTIVE This study investigated pesticide application patterns in conventional rice farming across three provinces, An Giang, Đồng Tháp, and Vĩnh Long in the Mekong Delta to assess implications for sustainable organic rice production systems. METHODS Farmer interviews documented pesticide use, while soil and water samples from conventionally and organically managed fields were collected to evaluate contamination levels and potential cross-contamination pathways. RESULTS AND CONCLUSIONS Results showed a wide range of pesticides applied in conventional rice farming, with soil residues reflecting the reported usage. Thus, the detection of compounds not reported by farmers indicated cross-contamination from neighboring land uses. Notably, pesticide residue levels in some organic fields were comparable to those in conventional ones, suggesting contamination via shared water sources or close distance to treated areas. These findings highlight major challenges for organic rice transitions in smallholder dominated landscapes, emphasizing the need for farmer cooperatives, enhanced cooperation, larger buffer zones and stricter spatial separation between conventional and organic fields to reduce pesticide intrusion. SIGNIFICANCE This study provides critical insights and practical recommendations to support farmers and stakeholders throughout the Mekong Delta region to identify effective measures for advancing the transition towards more sustainable rice farming practices.