Plant-parasitic nematodes associated with dragon fruit have not previously been reported in Vietnam, nor has their impact on crop productivity been documented. In July 2023, a survey was conducted in dragon fruit orchards across southern Vietnam. A total of 60 soil and 60 root samples were collected from Tien Giang and Long An provinces. Plant-parasitic nematodes were identified from both soil and root samples, and notably, the cactus cyst nematode was detected in 100

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.

Predatory and omnivorous nematodes are known as potential biological control agents for root-knot nematodes (RKN). However, it is still unclear whether free-living nematodes (FLN) communities, including microbial-feeding nematodes, contribute to RKN suppression. To evaluate their contribution, a pot experiment was conducted using soils containing either 1) microbes or 2) microbes and FLN. After six weeks of green pepper growth, we analysed the level of Meloidogyne incognita infection and the bacterial community with next-generation sequencing (NOS). The same analysis was conducted after an additional 1-month incubation. Meloidogyne incognita densities were significantly lower in soils with FLN than in those with microbes only. Moreover, M. incognita multiplication was suppressed even in the absence of predators and omnivores, highlighting the importance of microbial-feeding nematodes. NOS results showed that some bacterial genera had a significant negative correlation with M. incognita density, suggesting that bacterivores altered bacterial communities to promote microbial suppression of M. incognita.

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.

Root-lesion nematodes (Pratylenchus spp.) significantly inhibit sugarcane growth and are prevalent in Okinawa, Japan. However, no synthetic nematicide is currently registered for ratoon sugarcanes under Japanese regulations. Furthermore, there is a potential risk that nematicide use could harm non-target free-living nematodes, which may contribute to soil health and fertility. To address these challenges, we investigated the nematicidal efficacy of the insecticide fipronil, which interferes with GABA receptors, against root-lesion nematodes, aiming to improve yield and quality in ratoon sugarcane. Simultaneously, we assessed its potential side-effects on the non-target free-living nematode community. We first determined an appropriate dose of fipronil to control rootlesion nematodes in ratoon canes in pot trials. We then conducted multi-year field experiments to assess a yield response to fipronil treatment and its side-effects on the soil nematode community using metabarcoding analysis with next-generation sequencing. Fipronil treatment significantly decreased root-lesion nematodes in ratoon cane roots (42-51 % to control) three months after application, resulting in significant increases in yield by 4-20 % and Brix value by 2-3 %. Impact of fipronil on the abundance of soil nematodes and their community structure was negligible, as revealed by metabarcoding analysis. Diversity indices, functional metrics, and maturity index showed no significant difference between treatments. Furthermore, principal component analysis and differential abundance testing (ANCOM-BC) showed no dominant and impacted nematode taxon due to fipronil treatment. Our findings suggest that fipronil (0.3 kg a.i./ha) is appropriate to control root-lesion nematodes in ratoon sugarcane, providing yield increase without evident side-effects on the overall non-target nematode community.

In Vietnam, Si accumulator crops like rice and maize crops are commonly rotated, but rice straw is often removed for animal feed. This study assessed whether rice straw mulch could improve soil available Si and maize growth. A field experiment was conducted over three years in two fields with different soil Si levels. Four rice straw mulch levels (0, 3.5, 7, and 10.5 t ha⁻1) were applied during the maize growing season (Feb–Apr), and repeated for three years. In the 3rd year, soil samples were analyzed for available Si (phosphate buffer extraction) and Si fractions (CaCl2-Si, acetic acid-Si, H2O2-Si, oxalate-Si, and NaOH-Si). Maize yield and Si, N, P, K, and Na uptake were also evaluated. At the lower available Si field, rice straw mulch significantly increased the phosphate buffer-Si, CaCl2-Si and H2O2-Si in soil two weeks after sowing whereas the higher available Si field showed no differences among treatments. In contrast, the Si concentration in maize stems and leaves increased notably in the higher rice straw treatments at both sites. Furthermore, a negative correlation was found between Si and Na concentrations in the maize stems and leaves, suggesting that Si may play a role in mitigating Na uptake and reducing Na toxicity. This study demonstrated that the application of 7 and 10.5 t ha⁻1crop⁻1 of rice straw to fields with low available Si may enhance the soil Si availability, and improve Si, N, P, K uptake and tolerance to salt stress.

Agricultural P loss is a major contributor to surface water eutrophication. However, the effects of repeated applications of biochar and compost on potential risk of P loss in salt-affected acidic soils remain unclear. A field experiment was set up in two salt-affected acidic paddy fields with a different level of soil available P in Vietnamese Mekong Delta. Each site had four treatments: i) three rice crops per year (RRR), ii) two rice crops rotated with fallow (FRR), iii) FRR plus compost (FRR + Comp), iv) FRR plus biochar (FRR + BC). Soil samples were collected after two years of rice cultivation in RRR (crop sixth) and P adsorption–desorption parameters and Olsen P were determined for each soil sample. The Langmuir maximum adsorption capacity (Qmax) and degree of P saturation (DPS) were calculated. The risk of P loss was estimated using the equation: P concentration in leachate (mg L−1) = 0.0323 × ln(DPS) + 0.128. Biochar and compost amendments did not alter Qmax at either site. By contrast, the amount of P desorption and the DPS were significantly higher in FRR + BC than in FRR, indicating a greater potential risk of P loss. Nevertheless, estimated P concentrations in leachates from biochar-amended soil were up to 0.03 mg L−1 at both sites, well below the Vietnamese surface water quality threshold of 0.1 mg L−1. These findings suggest that biochar and compost can be applied to salt-affected acidic paddy soils without causing significant environmental P losses, provided that DPS is monitored and managed.

In Myanmar, the application of both nitrogen-based chemical fertilizers and biofertilizers is limited and this low input has caused poor agricultural yields. The present study aimed to isolate indigenous endospore-forming nitrogen-fixing bacteria (EFNFB) and examine their potential for co-inoculation with agricultural waste. A total of 387 isolates were obtained from 42 different soil samples in the central dry zone of Myanmar using nitrogen-free Rennie medium. Nitrogen-fixing activity (NFA) assessed with the acetylene reduction assay was positive in 102 isolates. A phylogenetic ana-lysis based on 16S rRNA sequences identified 25 different species, including the genera Paenibacillus, Priestia, Bacillus, Brevibacillus, Sporolactobacillus, Niallia, and Neobacillus. Among these genera, Paenibacillus spp. was the predominant genus, comprising 51 isolates (64%) across 16 different species (64%) that were prevalent in soils rotated with rice and pulses. Paenibacillus spp. showed different NFA levels in Rennie medium. Eleven species belonging to different genera had not been previously documented as nitrogen-fixing bacteria. NFA levels were evaluated in soil inoculated with EFNFB and rice straw or mung bean residue. The results obtained demonstrated that NFA levels were dependent on isolates and the type of agricultural waste. NFA in soil was significantly increased by inoculations with some isolates, suggesting their potential as biofertilizers. The inoculation of Priestia aryabhattai S10 with rice straw or mung bean resulted in significantly higher NFA levels in soil. These results indicate the potential of EFNFB as biofertilizer inoculants in Myanmar.

Microbial carbon use efficiency (CUE) is an essential indicator of soil organic carbon (SOC) dynamics. The high yield (Y)-resource acquisition (A)-stress tolerance (S) life strategy framework was used to assess microbial adaptation and its impact on CUE in response to soil environment and nutrient availability. Topsoil (0-15 cm) was collected from a 36-year experimental field of Andosol in Japan with six fertilizer treatments: no application, inorganic PK, NK, NPK, compost, and NPK with compost (NPKCM) to elucidate the effects of nutrient availability and environmental changes caused by fertilization on CUE. Soil chemical properties, microbial biomass and community structure, and extracellular enzyme activities (EEAs) were measured. Microbial nutrient limitation and CUE were assessed using enzyme stoichiometry (CUEst), and structural equation modeling (SEM) tested the conjecture that microbial nutrient limitation, mainly P-limitation, reduces CUEst through changes in bacterial community structures and EEAs. Results showed higher CUEst in NPK-treated soils (NPK: 0.37, NPKCM: 0.32) compared to P-deficient soils (Ctrl: 0.19, NK: 0.22). Increased P availability and reduced DOC:AP and IN:AP ratios in NPK-treated soils favored a shift of dominant bacterial strategies from A-strategists (including Alphaproteobacteria, Vicinamibacterales, and AD3) to Y-strategists (including Bacteroidota, Verrucomicrobiota, Blastocatellales, Bryobacterales, and Ktedonobacterales). SEM revealed that increased soil C and P availability alleviated microbial P limitation, enhancing CUEst directly and via reducing C-acquiring EEAs and altering microbial strategies. Overall, NPK fertilization may be an optimal strategy for enhancing SOC sequestration by improving microbial CUE in Andosols, emphasizing the trade-off between nutrient acquisition and energy conservation.

This study aimed to assess the co-incorporation of mung bean residue and rice husk biochar with reduced NPK fertilizer rates on rice yield and nutrient uptake in the subsequent rice crop. A field experiment was conducted in five treatments (T1 to T5). In the spring–summer (SS) of 2023, rice was cultivated and its straw was burned (T1), while mung bean was cultivated and its residue was incorporated (T2 to T5). In the next summer–autumn crop (SA), rice was cultivated with different levels of inorganic fertilizers. T1 was added with the conventional fertilizer (95 kg N, 45 kg P2O5, and 35 kg K2O ha−1). T2 included the same amount of NPK fertilizer as T1 with mung bean incorporation. In T3 to T5, rice husk biochar was amended at a rate of 10 Mg ha−1 before SA. In T3, inorganic fertilizers were reduced by 30% of N and 50% of P2O5 and K2O; in T4, by 15% of N, 30% of P2O5 and K2O; and in T5, by 15% of N only. The rice grain yield was 26.6–35.3% significantly higher in T3, T4, and T5 compared to T1. P accumulation in straw and grain was significantly higher in T3, T4, and T5 than in T1. Furthermore, K accumulation in grain was markedly higher in T3, T4, and T5. No significant differences were observed in any of the soil chemical properties among treatments at harvest in SA. This study highlights that the combination of residue incorporation and biochar may substitute a part of chemical fertilizers and contribute to more sustainable rice production.

Phosphorus fertilizer is indispensable in agricultural production. In this study, we focused on pig slurry-treated foamed glass (FGpig), a porous material made of waste glass. Our objective was to evaluate the effect of FGpig as a P fertilizer on different plants compared to that of a conventional P fertilizer, calcium superphosphate (CSP). The percentage of available P, which consists of Truog P, was 91.6% in CSP, while it ranged from 6.5% to 20.8% in FGpig, depending on the lot. Komatsuna and wheat were fertilized with FGpig or CSP at the same rate of total P and with urea and potassium sulfate and grown in a glasshouse. In two times repeated experiments, the dry weight of the komatsuna shoot in FGpig was greater by 413% and 2140% in FGpig than in control (no P fertilizer). The dry weight of wheat shoot was also greater by 96.6% and 87.8% in FGpig than in control. In addition, the dry weights of komatsuna and wheat shoot in FGpig were comparable and slightly lower (from 80% to 120% and 70% to 80%, respectively) to those in CSP (100%). These results suggested that FGpig had a P fertilizer effect in spite of the low available P content. Two-way ANOVA analysis showed that the P accumulation by komatsuna shoot was significantly higher in FGpig than in CSP, while P accumulation by wheat was significantly lower in FGpig than in CSP. When foamed glass without P enrichment (FG) was used as a soil amendment with CSP, P accumulation in the komatsuna shoot was significantly greater in CSP+FG by 20.2% than in CSP. These results suggest that FGpig is a promising material for recycling P in pig slurry. FG without P enrichment and with a high amount of available Si might have a potential to increase P accumulation.

Background and aims In Vietnam, Si accumulator crops like rice and maize crops are commonly rotated, in which rice straw is often removed for animal feed. It was assessed whether rice straw mulch could improve soil available Si and maize growth. Methods A field experiment was conducted over three years in two fields with low and high soil Si. Four rice straw mulch rates (0, 3.5, 7, and 10.5 t ha⁻¹) were applied during the maize growing season (Feb–Apr), and the same treatments were repeated for three years. In the 3rd year, soil samples were analyzed for available Si by phosphate buffer extraction and Si fractions, including CaCl2-Si, acetic acid-Si, H2O2-Si, oxalate-Si, and NaOH-Si. Maize yield and Si, N, P, K, and Na uptake were analyzed to evaluate the effects of soil Si availability on maize growth. Results At the lower available Si field, rice straw mulch significantly increased the phosphate buffer-Si, CaCl2-Si and H2O2-Si in soil two weeks after sowing whereas the higher available Si field showed no differences among treatments. In contrast, the Si concentration in maize stems and leaves increased notably in the higher rice straw treatments at both sites. Furthermore, a negative correlation was found between Si and Na concentrations in the maize stems and leaves. Conclusion This study demonstrated that the application of 7 and 10.5 t ha⁻¹crop⁻¹ of rice straw to fields with low available Si may enhance the soil Si availability, and improve Si, N, P, K uptake and tolerance to salt stress.

Forest mycorrhizal type and soil acidity strongly influence soil nitrogen (N) availability. Arbuscular mycorrhizal pure cedar plantations are expected to exhibit higher soil mineral N availability than ectomycorrhizal (ECM) forests, particularly under low soil acidity. We hypothesized that mixing ECM-associated tree species into such pure cedar plantations would reduce soil mineral N, ultimately lowering the risk of nitrate leaching, in sites with relatively low soil acidity. We investigated belowground microbial communities and N cycling across three microhabitats—roots, rhizosphere soils, and bulk soils—in six forest ecosystems with varying ECM tree abundance and soil acidity. These included pure cedar plantations, cedar plantations mixed with ECM-associated trees, and ECM-dominated forests, located at two types of sites differing in soil acidity (low acidity: pH > 5, high acidity: pH < 5) but both characterized by relatively low mineral soil C to N ratios. Higher ECM fungal abundance and higher soil acidity were associated with lower abundance of ammonia-oxidizing archaea (AOA) and lower nitrate content. Notably, ECM fungi appeared to suppress AOA abundance independently of ECM-mediated soil acidification. Moreover, competitive interactions between ECM fungi and AOA may suppress nitrate N contents in low acidity sites. Meanwhile, cedar trees appeared to exhibit a relatively high capacity for nitrate uptake, as evidenced by a negative rhizosphere effect on nitrate. Mixing ECM-associated tree species into pure cedar plantations could help mitigate nitrate leaching risks by reducing AOA abundance through enhancing ECM fungal activity, while simultaneously taking advantage of the cedar trees’ high nitrate uptake capacity, especially under low soil acidity.

Although biochar is widely used in agriculture, its effects on nutrient leaching remain inconsistent due to differences in biochar types, nutrient forms, soil types, and prior soil management. This study investigated the effects of rice husk biochar on leachate quality and soil properties in a clay loam Andosol managed with green manure. Pot experiments were conducted using soils without biochar or mung bean (control) and with mung bean grown under different rates of rice husk biochar application at 0, 1, 2, 5, 10, and 30 Mg ha-1, namely, B0, B1, B2, B5, B10, and B30, respectively. Mung bean was grown for 1 month and then incorporated into the soil. Leaching was simulated by applying 4.4 mm of water at 8, 10, and 12 weeks after incorporation, and the leachates were analyzed for chemical properties. Compared to B0, leachate from B10 and B30 showed increases in soluble K by 38% and 88%, available P by 55% and 123%, and soluble Si by 128% and 245%, respectively. Conversely, rice husk biochar reduced NO3- by 30.4% and 70.3%, and NH4+ by 20.8% and 27.8% in B10 and B30, respectively, indicating reduced nitrogen leaching. 12 weeks after incorporation, biochar-amended soils showed increased levels of soluble and exchangeable K, as well as available Si and P, with increasing application rates. Biochar application also enhanced exchangeable Ca in soil, although not in leachate. The biochar application rate was positively correlated with soil properties (K, P, Si, total C and total N) and nutrient concentrations in leachates (K, P, and Si), while negatively correlated with inorganic N in both soil and leachates. Rice husk biochar increased capillary water retention in the pF range of 2.2–3.0, with a minimum of 5 Mg ha-1 required to improve water retention. We highlighted that rice husk biochar provided available nutrients like Si, K, and P, while reducing N loss.

Faunal-mediated nutrient cycling, especially N mineralization, has the potential to make a significant contribution to nutrient supply to crop plants in production systems involving e.g. green manure cover crops. We investigated the effects of enchytraeids on N mineralization from mung bean residues in microcosm experiments using an organically-farmed soil with an inherently large population of enchytraeids. Enchytraeids promoted N mineralization by 23% after a distinct lag of between four and 12 weeks, concomitant with a substantial increase in population size followed by an almost complete collapse. Nitrogen release from the necromass would have contributed a small but significant fraction of the N mineralized, and the result suggested the presence of other mechanisms. Enchytraeids suppressed nematode populations, while did not affect the mean weight diameter (MWD) of soil aggregates, although mung bean residues increased MWD. We conclude that enchytraeids have potential to play significant roles in mediating N supply to crops but matching supply-and-demand periods may be challenging.

This study examined the accelerated degradation of poly(caprolactone) films using two types of lignin derivatives. The degradation of poly(caprolactone) films was unaffected by the lignin-derivative-capped hydroxy groups, indicating the participation of radicals from phenolic hydroxy groups in lignin derivatives for accelerating the degradation of films. Furthermore, the role of lignin radicals in relation to polymer degradation changed as per the mechanism of polymer decomposition, e.g., the degradation of poly(ethylene carbonate) films was suppressed by feeding lignin derivatives because of the back biting type decomposition nature of poly(ethylene carbonate), which differs from the radical-mediated addition/cleavage type decomposition nature of poly(caprolactone). These results provide an approach of designing bio-degradative materials from lignin, a natural phenolic polymer.

A novel approach, i.e. mung bean was grown in paddy soil for 1 month as a pre-rice crop, which is a short but a feasible period applicable to the current intensive rice monoculture cropping system in the Vietnamese Mekong Delta. This study aimed to assess how short-term growth of green manure and its incorporation combined with rice husk or its ash impact the soil quality of sandy loam soil and silty clay soil. Four treatments, viz. soil without mung bean (control), soil plus mung bean incorporation, soil plus mung bean and rice husk of 10 Mg ha-1, and soil plus mung bean and rice husk ash of 5 Mg ha-1, were established. Different soil parameters were determined to evaluate their initial effects after incubating for 60 days. In both soils, the incorporation of mung bean significantly increased beta-glucosidase, acid phosphatase, and urease activities, as well as C mineralization compared with control. Soil labile C was increased by 15-50% by incorporation of mung bean, irrespective of the application of rice husk or its ash, compared to that in control. The highest total C and available N were found in mung bean combined with rice husk followed by mung bean with rice husk ash, only mung bean, and control. Sandy loam soil with a lower exchangeable K level showed significant improvements in the exchangeable K content with rice husk and its ash amendments. Therefore, these practices, short-term green manure planting, could offer benefits to farmers for enhancing soil quality such as enzyme activities in the intensive paddy cultivation.

BACKGROUNDThe root-knot nematode (RKN), Meloidogyne incognita, affects food production globally and nematicides, such as fosthiazate and fluopyram, are frequently used in Japan to control damage caused by RKN. In aboveground pests, the emergence of a population with developed resistance is frequently found after the continuous use of the same pesticides; however, there are few studies on changes in the sensitivity of plant-parasitic nematodes, including RKN, to nematicides. RESULTS We compared the sensitivity of two populations of M. incognita to fosthiazate and fluopyram, one population with a history of exposure to fosthiazate and 1,3-dichloropropene (Ibaraki population) and the other without nematicide use for decades (Aichi population). A concentration of fosthiazate and fluopyram causing 50% mortality at 24 h post-treatment (LC50) was markedly higher in the Ibaraki population (5.4 and 2.3 mg L-1) than in the Aichi population (0.024 and 0.011 mg L-1 in fosthiazate and fluopyram, respectively), indicating the low sensitivity of the Ibaraki population to fosthiazate and fluopyram. Experiments using different enzyme inhibitors indicated the involvement of acetylcholinesterase (AChE), which is the target of fosthiazate, and glutathione S-transferase (GST), a typical enzyme related to detoxification, in the low sensitivity mechanism. The activity of AChE was 33-fold higher in the Ibaraki population than in the Aichi population and there were many differences in their nucleotide sequences. In addition, the gene expression level of GST was 239-fold higher in the Ibaraki population than in the Aichi population. CONCLUSIONThese results revealed differences in the sensitivity to nematicides among RKN populations. Two factors were identified as related to the mechanism of low sensitivity in the Ibaraki population. This is the first report showing the difference in the sensitivity to fluopyram between populations of M. incognita. (c) 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Green soybean (edamame), an early-harvested soybean, is a popular vegetable in Asia and is recognised as a healthy vegetable in the other parts of the world. In Japan, edamame yield has gradually decreased over the last 30 years, despite similar cultivation areas. Damage caused by the soybean cyst nematode (SCN), Heterodera glycines, is one of the main causes. We surveyed the distribution of SCN in different locations and found a wide distribution of SCN across Japan. Different control measures are available, such as chemical control using fumigants or a granular type of nematicide, solarisation, and rotation with non-host crops. We are developing a new type of biological control method, which comprises short-term field cultivation and soil incorporation of mung bean. This method not only decreases the SCN density in soil but also mitigates soil erosion and nitrate leaching. For future SCN control it is essential to establish an environmentally friendly management strategy.