Monoculture and intensive fertiliser use in the cultivation of Robusta coffee (Coffea canephora var. Robusta) and black pepper (Piper nigrum L.) have led to soil degradation and increased disease pressure in Vietnam's Central Highlands. To identify key factors driving soilborne diseases and threatening sustainable production, a soil and root survey was conducted across three provinces: Gia Lai, Dak Lak, and Dak Nong. Soils were characterised by high clay content (51.2-62.0 %), moderate silt (35.5-46.0 %), and low sand (2.5-2.8 %), with a notably low cation exchange capacity (7.72-8.04 cmolckg-1). The soils were strongly acidic, with average pH values of 4.51 in coffee farms and 5.45 in pepper farms. Despite sufficient levels of nitrogen (N), phosphorus (P), and potassium (K), soilborne pathogens were widespread. Fusarium spp. were detected in all samples, Phytophthora spp. in 64-76 % of black pepper farms, and plant-parasitic nematodes in 67-84 % of farms, with Meloidogyne spp. predominant. Fusarium density increased with soil acidity in coffee plantations. In coffee, nematode density was positively correlated with N input, while in black pepper, N was negatively correlated with Phytophthora. Organic matter and available K were negatively associated with Fusarium in coffee but positively with Phytophthora in black pepper. These findings underscore the need for integrated management of nutrients and pathogens to sustain perennial crop production in the region.

Vietnam is the world's leading exporter of Robusta coffee and black pepper. However, the widespread use of intensive cultivation practices has contributed to progressive soil acidification and an increasing incidence of soilborne diseases, threatening the long-term sustainability of these high-value crops. This study evaluated the short-term effects of applying coffee huskderived biochar (2.5 t ha(-1)) on soil quality, pathogen suppression, and crop performance in acidic soils of coffee and black pepper farms in Gia Lai province. Over the course of 1 year, key soil physicochemical and biological properties, soilborne pathogen populations, and crop yields were monitored. The overall impact of biochar at this application rate was limited, and most differences between treated and untreated plots were not statistically significant (p < 0.05). The study found that biochar application could lead to slight and promising improvements in soil conditions, including modest increases in nutrient availability, soil pH, and arbuscular mycorrhizal colonisation of plant roots. Reductions in specific pathogen populations, particularly plant-parasitic nematodes and Phytophthora spp., were also observed. These findings suggest that while biochar holds promise as a sustainable soil amendment, it requires more time than a single season to deliver substantial agronomic benefits. Additionally, future research should explore higher or repeated application rates, assess medium- and long-term effects, and investigate how biochar can be integrated with complementary biological or ecological soil management strategies to enhance its effectiveness in improving soil health and reducing disease pressure in perennial cropping systems.

Context Vietnam is the global leading producer of robusta coffee and black pepper. However, expanding coffee and pepper cultivation and intensive farming practices have led to soil acidification and increased pest and pathogen pressures. Agricultural liming applications could sustainably alleviate acidification, modify soil physicochemical parameters, restore microbial ecosystems, and suppress soil pathogens.Aims To address this issue, field trials were conducted in Gia Lai province in acidic soil within coffee and pepper plantations.Methods Two treatments were applied: 2.5 t ha-1 of dolomite lime and a no-lime control. The trials assessed soil chemical and biological properties, soilborne pests and diseases, and crop yield.Key results The results indicated no significant yield differences between the lime-treated and control crops. However, application of lime effectively raised soil pH by around 0.5 units for coffee and 0.4 units for pepper, compared to the free-lime treatment. In contrast, soil pH in the control plots decreased by 0.3 units (6.8%) for coffee and 0.2 units (3.8%) for pepper plantations compared to the pre-application values. In coffee plantations, lime application led to significant enhancements in organic matter and exchangeable K+, Ca2+, and Mg2+ by 17.4%, 26.1%, 103.6%, and 243.7%, respectively. It also decreased exchangeable Fe3+ and Al3+ by 9.7% and 30.3%, respectively, compared to the control. Additionally, lime application significantly improved root mycorrhization by arbuscular mycorrhizal fungi. In pepper farms, liming considerably improved available NH4+ and NO3- and exchangeable Ca2+ and Mg2+ by 7.5%, 9.8%, 35.1%, and 132.8%, respectively. Exchangeable Fe3+ and Al3+ decreased by 29.8% and 29.0%, respectively. However, for both commodities, no positive effects of liming were observed for populations of pathogenic fungi, oomycetes, and nematodes.Conclusions Lime had positive effects on soil chemical properties and colonisation by arbuscular mycorrhizal fungi but did not significantly affect soilborne pathogens and crop yield.Implications Sustainable soil acidity mitigation and improvement of soil fertility could be undertaken by annual lime application. Alternative practices, including biological and ecological approaches, should be explored in conjunction with the use of lime.

Rice husk (RH) is a major agro-waste in rice-producing countries and its management is a serious concern. RH biochar (RHB) is generally used for soil amelioration; however, its functionality can be further enhanced by tailoring its properties to meet specific requirements of crops. Herein, we report that the conversion of RHB to its nanoform (hereafter termed as NRB) and employing surface engineering could enable its use as a slow-release carrier for the delivery of micronutrients to plants. We used Zn, a key plant micronutrient, to study its effect in rice seedling growth. The results showed that the Zn loaded functionalized biochar (Zn-FRB) contributed to the enhanced root and shoot growth of rice compared to that of NRB. Zn-FRB at a high concentration (100 mu g mL-1) showed similar to 11% increase in the soluble protein content. Zn-FRB (30 and 200 mu g mL-1) also showed reduction in antioxidative enzyme activity (CAT and APX) compared to that of NRB suggesting an imperative role of Zn in protecting against oxidative damage of membrane lipids. Zn-FRB application caused a change in expression of Zn homeostasis genes and phloem transporter gene and increased their transcript levels as revealed by qPCR studies. According to these results, Zn-FRB was found to be more effective than NRB in enhancing plant growth, reducing oxidative damage and transportation of Zn. These results suggest the potential of this approach as a new slow delivery system of micronutrients to plants.

A microcosm experiment was performed to investigate the interactive effects of heavy metals, soil conditioners (biochar and compost), and plant on petroleum hydrocarbon (PHC)-degrading bacteria and its resultant rhizodegradation of long-chain PHCs in soils. Two levels of heavy metal contamination (50 mg/kg and 100 mg/kg for each of Cu, Ni and Zn) and three soil amendment treatments (biochar treatment, compost treatment, and biochar-compost co-treatment) were set. Comparison was made between the vegetated soils and the unvegetated counterparts and between the soils with different levels of heavy metal contamination under vegetation conditions. Plant growth consistently increased the abundance of bacterial PHC-degraders in the soils co-contaminated by PHCs and heavy metals. Elevated levels of heavy metal contamination adversely affected the growth of the plant and bacterial PHC-degraders. It also caused alteration in the structure of the PHC-degrading bacterial communities. Soil amendments enhanced plant and microbial growth. However, the enhanced effect varied among the different treatments with the performance in the following decreasing order: combined biochar and compost > compost > biochar. Plant growth and soil amendments all resulted in increased soil-borne dissolved organic compounds, which in turn caused an increase in the abundance of PHC-degrading bacterial genera and thus the rate of rhizodegradation of the long-chain PHCs in the soils co-contaminated by heavy metals. The research findings have implications for developing treatment strategies to cost-effectively remediate co-contaminated soils with PHCs and heavy metals.

Robusta coffee, a vital cash crop for Vietnamese smallholders, significantly contributes to the national economy. Vietnam is the largest exporter of Robusta coffee, supplying 53

In Northern Vietnam, farmers are converting significant areas of their allocated rice paddy fields into organic tea plantations to increase and diversify their income. Our previous study indicated that as tea soil is strongly acidic, suitable solutions such as lime application can help to mitigate soil acidity. However, to date, the impact of these strategies on soil chemical properties, soil biodiversity and crop productivity in tea farming has not been thoroughly investigated. This study examined how liming affects soil chemical and biological indicators using amplicon Illumina sequencing analyses, and crop productivity in organic tea farming with different land use histories. Nine months after applying lime, soil pH increased by 0.4 units, soil organic matter content by 0.28 %, and P availability by 23.1 mg/100 g while soil exchangeable Al and Mn were reduced. The abundance and composition of macrofauna in soil and organic mulch were altered by lime addition but were not significantly correlated to land use history. Liming also enhanced tea root mycorrhization by native arbuscular mycorrhizal fungi (AMF) and tea yield, regardless of land use history. Despite this, the relative abundance and composition of soil bacteria, fungi, and AMF showed a significant response to land use history rather than liming. This study provides valuable insights into how soil liming and land use history affect tea soil food webs, plant growth, and tea organic yields, and suggests that liming could be an effective strategy to improve acidic soils, restore soil biodiversity in these soils, and sustain crop productivity in this tropical region.

In this study, inexpensive earth-abundant catalyst of Co/TiO2 is coupled with a low-temperature modification approach to enhance NH3 adsorption capacity on wheat straw (WS). The highest NH3 uptake achieved is 111.9 mg/g, with 80.8 % retention even after 3 h of desorption. Mechanistic investigation indicates that the enhanced adsorption capacity stems from Co/TiO2, which facilitates generation of reactive oxygen species, leading improved ultra-micropore structure that enhances the interaction between NH3 and oxygen-containing functional groups through a trapping effect. The robust stability of adsorbed NH3 is attributed to the formation of amides or amines. Incorporation of only 1 wt% WS-Co to urea-fertilized alkaline soil reduced NH3 volatilization by 83.1 %. The significant effect is primarily attributed to the excellent adsorption capacity of WS-Co, rather than alterations in the relative abundance of the microbial community. These findings present a novel approach for development of effective fertiliser additive to mitigate NH3 volatilization from alkaline soil.

Foot rot disease caused by Phytophthora capsici is one of the most destructive diseases of black pepper in Vietnam and worldwide. However, other oomycete species such as P. tropicalis and Pythium deliense reported as serious threats to black pepper in India have also been recorded on this plant. The population of oomycetes occurring in black pepper plantations in Vietnam and their pathogenicity have not been investigated in the last decade. To this end, two hundred fifteen oomycete isolates were collected from the root rots and rhizospheric soil of black pepper in the Central Highlands and the Southeast region of Vietnam. Of these, 23 isolates were representatively chosen based on their origin and morphology for DNA sequence analysis of the internal transcribed spacer region, then 11 isolates were further selected for the translation elongation factor 1-alpha and the beta-tubulin gene analyses. Morphology and molecular analyses indicated that P. capsici, P. cinnamomi, P. heveae, P. nicotianae, P. parvispora, P. tropicalis, Phytopythium vexans, and a new species candidate Phytopythium sp. were identified among oomycete isolates. Of these, P. capsici and P. tropicalis could be the prevalent species in black pepper plantations in studied areas. The inoculation tests demonstrated that P. capsici, P. nicotianae and P. tropicalis were pathogenic on both leaves and roots of black pepper. Phytopythium vexans was pathogenic on root only. Meanwhile, P. cinnamomi, P. heveae, P. parvispora and Phytopythium sp. were non-pathogenic.

Tea is a very important cash crop in Vietnam as it provides crucial income and employment for farmers in poor rural areas. Unfortunately, the dominance of long-term, conventional tea cultivation has caused severe soil health degradation and environmental pollution. At the same time, as tea production may provide a better net income compared with other annual crops such as rice and vegetables, farmers have been converting parts of their allocated land to cultivate tea plants. Little is known about the benefit of agroecological management as an alternative to conventional tea management practices, and thus, there is a need to understand how it can improve tea yields, quality and the livelihoods of the farmers. Conducted in Northern Vietnam from 2019 to 2022, this study examined the impacts of agroecological tea management practices on soil health indicators, tea yield and quality, and net income of tea farmers. We showed that agroecological management practices significantly enhanced soil organic matter by 0.8% and soil pH by 0.5 units on average. Conversely, conventional management based on chemical fertilizer applications, significantly increased soil total nitrogen by 0.15%-0.2%. No significant differences were observed between soil texture and other soil chemical characteristics. Soil biological parameters were also significantly higher in agroecological tea soil and root samples than in conventional tea plots. Average AMF frequency and intensity of the agroecological tea roots were 98% and 37%, respectively, compared with 73% and 15% of the conventional tea roots. Likewise, soil macrofauna and mesofauna abundance in the agroecological tea plantations was 76 individuals/m(2) and 101 individuals/100 g fresh soil on average, respectively, while that of conventional tea farms were 34 and 63 individuals/100 g fresh soil, respectively. Interestingly, a comparison between the converted and nonconverted lands did not show any significant effect of the conversion on soil physicochemical and biological characteristics, apart from tea root AMF colonization. Conventional tea management consistently resulted in higher tea yield and yield components, even though the differences were not always statistically significant. Despite lower tea yields, agroecological tea adopters earned around USD 8400 ha/year more than the farmers still practicing conventional management. This study shows that it is economically and environmentally more sustainable to produce organic tea than conventional tea, and our results should encourage more farmers to adopt such agroecological practices in Northern Vietnam.

Microbial communities play a vital role in nitrogen (N) removal in constructed wetlands (CWs). However, the lack of studies on microbial characteristics of wetland systems designed to treat stormwater demonstrates the importance of comprehensive investigation on microbial response to wetland fluctuations. Moreover, the observed inconsistency in N removal, and detected links between microbial shifts and wetland water level fluctuations is an area of research interest perculiar to stormwater applications. This study surveyed nearly 150 publications to provide a summary and evaluation of N removal efficiency in different types of CWs where microbial communities and their behavior have been correlated to regulating factors. Factors such as flow regime, plants, and physico-chemical properties (e.g., temperature, dissolved oxygen, pH, and nitrogen concentration) were found to significantly influence microbial diversity and composition. Although many studies have analyzed microbial N removal, a majority conducted their studies in bioretention systems. Accordingly, some of the microbial pathways in CWs designed for stormwater treatment have not been investigated. As such, it is suggested that pathways, such as dissimilatory nitrate reduction to ammonium (DNRA) and comammox activity and their changes over dry-wet cycles in stormwater constructed wetlands be investigated. This information could assist engineers to take advantage of the presence of other N transforming communities which could improve microbial diversity within wetland systems. Moreover, it is recommended to track microbial functional genes and their changes over wetland water fluctuation to develop an ecosystem with conditions favorable for microbial pathways with higher N removal potential. In conclusion, the findings of the current literature review reinforce the importance of stormwater runoff treatment and the implementation of new design strategies that are able to enhance microbial activity and diversity leading to a better treatment outcome.

Arbuscular mycorrhizal fungi (AMF) and beneficial bacteria are found naturally associated with most terrestrial plant roots. While it is now well known that bacteria colonize AMF and can form aggregates and biofilms, little is known about how interactions between bacterial communities and AMF take place under both in situ and in vitro conditions. We investigated the impact of inoculation with AMF-associated bacteria (AABs) of AMF by in vitro recreation of the interaction on synthetic growth media in a two-compartment Petri plate system. The inoculated AABs were found to be associated with the mycorrhizal co-culture and were found to migrate along growing AMF hyphae and to be associated with the spore surface. AABs differentially influenced the growth of the AMF and their functional capability demonstrated by analysis of phosphate solubilization, nitrogen fixation, and biofilm formation. We have thus characterized these important interactions adding to a further understanding of the synergistic relationship between the two cross-kingdom microbial partners. • An in vitro assay was utilized to recreate functional biofilms with AMF-associated bacteria. • AMF-associated bacteria formed a biofilm and enhanced sporulation of Rhizophagus irregularis. • AMF–bacterial interactions through biofilm formation influence the functional capability of both partners.

Tea is one of the world’s most consumed beverages and an important crop of many developing countries. Intensive tea cultivation has negative impacts on soil health properties and the environment. While soil acidification in tea plantations is a known severe issue, there is a lack of literature analysis of the ways in which soil acidification affects soil health, tea productivity and the environment, and suitable methods to control this issue. Here, we review the mechanisms of tea soil acidification and consequences, the potential of common agricultural wastes for ameliorating soil acidity and enhancing soil health and crop productivity, as well as reducing environmental pollution under tea cultivation. We show that intensive application of mineral nitrogen is the main cause of soil acidification in tea plantations, while tea plants also play a part in accelerating tea soil acidity. Agricultural waste and byproducts have a great potential to correct soil acidity, and to enhance soil health, tea productivity and quality. These soil amendments also have drawbacks such as metal and pathogen pollution, and supplementary costs.

Glyphosate-based foliar spray herbicides are the most common method for urban weed control due to their broad-spectrum and efficacy for burndown applications. As interest in glyphosate alternatives has increased in recent years, this project assessed the efficacy of the following non-glyphosate-based alternative weed management strategies: glufosinate, imazapyr, MCPA + dicamba, prodiamine, pine oil, clove oil, nonanoic acid, acetic acid + hydrochloric acid and steam against untreated (negative) controls and glyphosate-treated sites. Across all four seasonal treatments (winter, spring, summer and autumn), glyphosate and glufosinate reduced weed coverage (>65% after 4 and 12 weeks); imazapyr reduced weed coverage by >80% after 12 weeks; and steam reduced weed coverage by >80% after 4 weeks, and after 12 weeks showed to reduce weed coverage by >20% after the second application. The MCPA + dicamba, prodiamine, pine oil, clove oil, nonanoic acid and acetic acid + hydrochloric acid treatments had mixed impacts on weed coverage. Minimal alterations to soil physicochemical properties were observed across the two sites for all treatments. Assessment of impacts the different weed management strategies had on arthropod and microbial relative abundance showed minimal alterations; with only steam observed to reduce relative microbial abundance. Glufosinate, imazapyr and steam may be considered alternatives to glyphosate for reducing weed coverage but may not be as effective or have undesirable off-target effects. Overall, glyphosate provided the most consistent weed reduction at both sites over 12 weeks, without any recorded negative off-target or soil biota impacts.