Chau Minh Khoi

Assessing pesticide bioavailability in paddy soils is critical for understanding environmental fate and potential food safety implications. This study investigated the desorption and immobilization of isoprothiolane and tricyclazole in a clay- and organic-rich Mekong Delta paddy soil, comparing Tenax and XAD-4 as extraction agents and assessing the effect of biochar amendment, using a two-compartment desorption model. Although both compounds fall below the ISO 16751:2020 criterion for Tenax (log Kow > 3), Tenax and XAD-4 did not differ significantly for the moderately hydrophobic isoprothiolane, whereas for the more polar tricyclazole, Tenax yielded a significantly lower fast-desorbing fraction, despite efficient sorption in matrix-free tests. Both pesticides exhibited high fast-desorbing fractions despite the soil’s high clay and TOC content, consistent with their predominantly neutral form at the soil’s low pH; nevertheless, a considerable slowly desorbing fraction of tricyclazole indicates interactions beyond hydrophobic partitioning. Biochar amendment had compound-specific, opposing effects: it significantly reduced the fast-desorbing fraction of tricyclazole at the applied, above-field concentration, whereas it increased that of isoprothiolane without significantly affecting its remaining fraction in soil. Residues of both fungicides were detected in regional rice grain, but could not be directly linked to the laboratory-derived parameters.

Sustainable agriculture is critical to sustainable development and climate resilience, yet evidence of its multidimensional environmental, social and economic benefits and trade-offs remains limited, especially in regions most vulnerable to climate change. This study addresses this gap in Vietnam’s Mekong Delta (MKD), where decades of intensive rice farming has bolstered rice yields at the expense of environmental quality and farmers’ health. This study presents a multi-criteria analysis (MCA) comparing organic rice (OR) and conventional rice (CR) farming systems in the MKD. We applied a weighted sum model to evaluate the environmental, social and economic performance of the two production systems. The assessment drew on quantitative and qualitative primary data collected through stakeholder engagements and field measurements from Vinh Long province between 2023 and 2025, as part of the OrganoRice project. Overall, OR farming performed cumulatively better (0.663 and 0.695) than CR farming (0.496 and 0.484). OR scores were higher across most sub-criteria, particularly “farmers’ income” and “biodiversity”. However, CR outperformed OR for “rice yield” and “farmers’ workload”. Comparable water and soil quality scores, due to the presence of pesticide residues in both systems, suggest that the environmental performance of OR farming was likely dampened due to cross-contamination from surrounding or upstream non-organic farms. The expansion of OR farming in the MKD has the potential to enhance environmental, social and economic performance of rice production in the region. However, in order to achieve the full scope of these benefits, short-term measures should aim to reduce the financial risks of conversion for farmers, ensure access to affordable organic inputs, increase farmer training, ensure reliable premium contracts for rice producers and support them in accessing organic markets. Longer-term measures must improve irrigation water management and infrastructure to minimise cross-contamination risks. Coordinated marketing campaigns are needed to develop a trusted regional brand for organic rice from the MKD to create new opportunities in international and domestic markets. Moreover, long-term monitoring of post-transition outcomes is important to capture the full impacts of conversion. As OR cultivation continues to expand across the MKD, evidence on its benefits and trade-offs is essential to guide this transition effectively. This study provides that evidence, offering a context-specific, multidimensional evaluation to inform OR policy and practice in the region.

Rice intensification influences soil biodiversity and ecological functioning in paddy ecosystems; however, its effects on soil nematode communities across different rice production systems remain poorly understood in the Vietnamese Mekong Delta (MD). This study evaluated the effects of rice cropping practices in the MD on nematode community composition, trophic structure, functional guilds, diversity, plant-parasitic nematodes (PPN), and soil chemical properties. A total of 91 soil samples were collected from double-rice intensive (RR), triple-rice intensive (RRR), and rice–upland–rice rotational (RUR) systems. Thirty nematode genera were identified, with a total abundance showing high variability, but no significant differences among cropping systems. Community composition differed considerably among systems, with Chronogaster dominating across all systems, particularly under RRR, whereas RUR supported more dominant genera with higher abundances of Tyleptus, Mesodorylaimus, Cephalobus, and Calolaimus. RUR exhibited significantly greater genus richness, and higher abundances of fungivores, omnivores, and higher colonizer–persister groups (cp4–cp5), indicating greater soil food-web complexity and ecological stability. In contrast, RRR was characterized by bacterivore-dominated communities, and increased abundance of cp3 nematodes, suggesting simplified community structures associated with agricultural intensification. Plant-parasitic nematodes remained relatively stable across management systems, despite taxon-specific responses. Soil pH, organic matter, and nitrogen availability were strongly associated with nematode community variation. Therefore, crop diversification through rotational practices enhanced belowground biodiversity, and promoted more sustainable soil ecological functioning in intensive rice production systems.

Rice straw mulching is a soil management practice that influences soil microbial communities. However, its effects on nematode communities under upland rice systems in salt-affected soils remain unclear. This study examined nematode community responses to rice straw mulching at rates of 0, 3.5, 7.0, and 10.5 t ha⁻¹ in paddy fields at two sites, Lieu Tu and Long Phu, in Soc Trang Province, Mekong Delta, Vietnam. A total of 37 and 35 nematode genera were identified in Lieu Tu and Long Phu, respectively. Bacterivores were the dominant group, followed by herbivores. Acrobeloides, Hirschmanniella, Chronogaster, Aporcelaimellus, and Prismatolaimus were prevalent in Long Phu, while Acrobeloides, Prismatolaimus, Hirschmanniella, and Alaimus dominated in Lieu Tu. The highest mulching rate (10.5 t ha⁻¹) increased total nematode abundance, particularly cp1 and cp2 groups in Long Phu, while the application of 7.0 t ha⁻¹ increased the proportion of omnivorous feeders in Lieu Tu. Mulching increased total nematode biomass and metabolic footprints, indicating improved soil fertility. At Long Phu, mulching also increased biodiversity, as reflected by the higher species richness and Shannon–Wiener indices. The highest mulching application rate (10.5 t ha⁻¹) increased the relative abundance of cp2 functional guilds at both sites. Mulching reduced the relative abundance of plant-parasitic nematodes at both sites, and increased cowpea yield from 5.1 to 13.9 t ha⁻¹ and 5.67 to 9.70 t ha⁻¹ at Lieu Tu and Long Phu, respectively. These findings suggest that the rice straw mulching at 10.5 t ha⁻¹ improves soil structure and nematode diversity, thereby supporting agricultural sustainability in salt-affected soils under climate change conditions.

The increasing impacts of water scarcity and salinity intrusion in the Mekong River Delta (MRD) pose significant challenges to sustainable agricultural production, particularly during the dry season. This study evaluated the potential of the Chameleon soil water sensor as a tool to improve irrigation management for upland crops cultivated on former rice fields in the MRD. Three independent trials were conducted: (1) laboratory‐based calibration for the sensor across three common soil textures of the MRD, (2) investigating the use of the Chameleon soil water sensor under varying salinity levels of irrigation water in the greenhouse condition, using beetroot ( Beta vulgaris L.) as a test crop, and (3) the field assessment integrating the sensor with straw mulching for beetroot under real‐world conditions. The results showed that the Chameleon soil water sensor demonstrated consistent sensitivity across sandy, clay loam, and silty clay soils, aligning well with van Genuchten‐modeled soil water retention curves. In greenhouse conditions, sensor‐guided irrigation reduced water use by 45.1%–53.8% compared to the farmer’s daily irrigation practice (the control) treatment across increasing salinity levels (0, 0.5, and 1.0 g L ⁻¹ ) of saline irrigating water, while maintaining comparable beetroot yields (up to 63.2 g pot ⁻¹ ) and significantly improving water use efficiency (WUE), reaching values up to 4.71 kg m ⁻³ . The field trial showed that combining the sensor with mulching stabilized soil moisture, improved chlorophyll content (58.35 SPAD), and reduced total irrigation by over 60% compared to the control. These findings confirm the Chameleon sensor’s potential as a simple and practical tool for precision irrigation. Its integration with mulching offers a promising strategy for water conservation and salinity management in smallholder farming systems in the saline‐affected areas in the MRD and similar environments.

Irrigation water shortages during dry seasons have posed significant challenges to pomelo cultivation in recent years in the Vietnamese Mekong Delta. This study evaluated the effects of organic compost, biochar, and rice straw mulch on soil physicochemical properties and irrigation efficiency in pomelo orchards. A field experiment was conducted from December 2022 to May 2024 using a randomized complete block design with seven treatments and four replications. The treatments included conventional irrigation (control), water‐saving irrigation, and water‐saving irrigation combined with different organic amendments (rice straw mulch, organic compost, and biochar) in various combinations and quantities. Results showed that integrated irrigation and amendment treatments significantly improved soil pH, organic matter, porosity, water holding capacity, and saturated hydraulic conductivity while reducing soil bulk density ( p ≤ 0.05). Notably, water‐saving irrigation combined with rice straw mulch (T3), compost (T4), biochar (T5), compost + biochar (T6), or compost + biochar + rice straw mulch (T7) significantly reduced irrigation water requirements during the dry season compared with conventional irrigation without organic amendments (control treatment). The reduction ranged from 42% to 59% across treatments, with the greatest reduction observed in T7. At the final assessment, T4, T6, and T7 produced significantly higher pomelo yields than T1 and T2, whereas T3 and T5 did not differ significantly from T1. These findings indicate that soil‐moisture‐based irrigation combined with organic amendment packages may improve soil conditions and reduce irrigation requirements in mature pomelo orchards under the nonsaline dry‐season conditions measured at the experimental site.

Vietnam's Mekong River Delta (MRD), where rice is the dominant crop, is increasingly impacted by salinity intrusion, highlighting the need for alternative cropping options. This study evaluated the growth and yield performance of quinoa, beetroot, and maize under three irrigation salinity levels (0, 2 and 4 g/L), with and without rice straw mulch (7 t/ha), in greenhouse conditions representative of the MRD dry season. Agronomic traits, physiological parameters, and changes in soil, including electrical conductivity (ECe), soluble sodium (Sol-Na +), and exchangeable sodium percentage (ESP), were assessed. Results showed that quinoa demonstrated the greatest salinity tolerance, maintaining stable growth and yield under 4 g/L saline irrigation and soil ECe exceeding 15 dS/m. Beetroot's yield was not significantly different under 2 g/L saline irrigation with straw mulching. Maize was highly sensitive to salinity and environmental stress, failing to complete its growth cycle under high heat and humidity, even in non-saline conditions. Across treatments, rice straw mulching significantly reduced soil ECe, Sol-Na + , and ESP, and improved crop performance under saline irrigation. Overall, quinoa and beetroot, especially when combined with mulching, offer promising alternatives for dry-season cropping in saline-prone areas of the MRD. In contrast, maize cultivation requires improved soil and environmental management under such conditions.

Organic rice farming (ORF) can support both climate change mitigation and adaptation. However, a deeper understanding of its specific benefits and challenges is needed. This paper synthesises current knowledge on the potential of ORF to enhance resilience in regions exposed to natural hazards, with particular attention to the climate-vulnerable region of the Mekong Delta (MKD), Vietnam. ORF can deliver multiple benefits: reducing production costs, revitalising degraded and pesticide-contaminated soils, improving water and soil quality, enhancing biodiversity, and contributing to human health and sustainable livelihoods. In the context of MKD, where rice production intersects with acute vulnerability to salinity intrusion, storms, and drought, ORF also presents opportunities for long-term adaptation by improving ecosystem health and reducing socio-ecological vulnerability. Despite these benefits, ORF remains limited in scale and impact due to the lack of integrated, landscape-level implementation strategies. Challenges like chemical contamination, limited access to certified organic inputs, and insufficient institutional and technical support leave many existing ORF initiatives vulnerable and constrain further expansion. To fully realise ORF’s resilience and sustainability potential, more targeted research and policy attention are needed. An integrated governance approach that considers both biophysical and socio-economic dimensions is essential to support a meaningful and scalable transition to organic rice farming in climate-sensitive regions like the MKD.

Organic rice farming (ORF) is can support both climate change mitigation and adaptation. However, a deeper understanding of its specific benefits and challenges is needed. This paper synthesises current knowledge on the potential of ORF to enhance resilience in regions exposed to natural hazards, with particular attention to the climate-vulnerable region of the Mekong Delta (MKD), Vietnam. ORF can deliver multiple benefits: reducing production costs, revitalising degraded and pesticide-contaminated soils, improving water and soil quality, enhancing biodiversity, and contributing to human health and sustainable livelihoods. In the MKD context, where rice production intersects with acute vulnerability to salinity intrusion, storms, and drought, ORF also presents opportunities for long-term adaptation by improving ecosystem health and reducing socio-ecological vulnerability. Despite these benefits, ORF remains limited in scale and impact due to the lack of integrated, landscape-level implementation strategies. Challenges like chemical contamination, limited access to certified organic inputs, and insufficient institutional and technical support leave many existing ORF initiatives vulnerable and constrain further expansion. To fully realise ORF’s resilience and sustainability potential, more targeted research and policy attention are needed. An integrated governance approach that considers both biophysical and socio-economic dimensions is essential to support a meaningful and scalable transition to organic rice farming in climate-sensitive regions like the MKD.