In the Vietnamese Mekong Delta, soil quality and crop yield are steadily declining under rice monocultures with three crops per year. The objective of this study was to evaluate the medium-term effects of rotating rice with upland crops and adding organic amendments on rice yield, and to relate this to soil quality. A field trial with split-plot design including two factors and three replicates was carried out from 2017 to 2020, over the course of nine consecutive cropping seasons. Crop rotations and organic amendments were applied as main-plot and subplot factors, respectively. The rotations were (1) rice–rice–rice (R–R–R), (2) soybean–rice–rice (So–R–R), and (3) sesame–rice–rice (Se–R–R), while organic amendment treatments included (i) no amendment (NO-AM), (ii) compost of rice straw and cow manure (RS+CM), and (iii) sugarcane compost (SGC); the composts were applied at a rate of 2.0 t ha⁻¹. The rotation cycle started with the so-called spring–summer (SS) season, followed by the summer–autumn (SA) season and ending with the winter–spring (WS) season. Rice yield significantly (p < 0.05) increased under organic amendments after nine growing seasons (2019–2020 WS), with an increment of 5.1% for RS+CM (7.07 ton/ha) and 6.1% for SGC (7.14 ton/ha). Contrary to our expectation, rotations with upland crops did not significantly increase rice yield. Rice yield significantly and positively correlated with an integrated soil quality index–SQI (r = 0.85) for the topsoil (0–15 cm), but not for the subsoil (15–30 cm). The increased availability of soil nutrients (Si and marginally also P) and improved soil physical properties probably induced by organic amendments, along with other soil properties under study, cumulatively attributed to enhanced rice yield. Repeated organic amendments thus becomes an effective management practice in improving soil quality under rice-based systems and could be applied to sustain rice yield in rice-producing regions with similar soil types and climatic conditions. Use of a SQI involving several soil quality indicators enables us to quantify the overall importance of soil fertility for rice yield versus other factors, and it provides an effective means of quantifying the integrated effect of improved management. Moreover, integrating a wide range of soil quality indicators in a SQI ensures its applicability across diverse settings, including different crop rotations and various soil types.

Uneven fruit ripening (UFR) is currently causing a decrease in the quality and value of “Ri 6” durian fruit. The soil moisture and nutrient (K, Ca, and Mg) levels present during the fruit development stage are the two main factors affecting UFR in durian fruit. However, measurements that can be used to determine the decrease in the UFR rate of durian remain unknown. Therefore, this study sought to evaluate the impact of plastic mulching (PM) and polyhalite fertilizer (PH) on improving the UFR rate and quality of durian fruit. A field study was conducted at three different durian orchards in the Vietnamese Mekong Delta (VMD) throughout two seasons (2022–2023 and 2023–2024). We used PM a month before fruit harvesting, combined with PH applied during the fruit development stage. Four treatments were used: (T1) control; (T2) PM, plastic mulching a month before durian fruit harvesting; (T3) PH, polyhalite fertilizer application (3 kg tree⁻¹ year⁻¹); and (T4) PM + PH, polyhalite fertilizer application (3 kg tree⁻¹ year⁻¹) and plastic mulching a month before durian fruit harvesting. The farmer’s fertilization practice (450 g N–450 g P–450 g K per tree⁻¹ during the fruit development period) was used in all treatments. Parameters such as soil physicochemical properties, fruit quality, and leaf mineral nutrient concentration were investigated at the harvesting stage. The results show that using PM + PH decreased soil moisture (>15%) but increased the concentrations of K, Mg, and Ca in both soil and durian leaves, thereby reducing the UFR rate (>80%) compared with the control. Additionally, applying PM + PH increased the aril proportion (>18%) and total soluble solids (approximately 5%) in durian fruit in comparison with the control. In conclusion, combining PM and PH improved the UFR rate and durian fruit quality. Therefore, we recommend that farmers apply these methods to their durian orchards to decrease physiological disorders and enhance fruit quality, thus contributing to achieving sustainable durian production in the VMD.

The application of organic substrates can affect soil respiration, dehydrogenase (DH‐ase) activity, dissolved organic carbon (DOC), and humic acid (HA) fractions. This study aimed to evaluate the effects of five organic substrates in the organic fractions of degraded alluvial soil, acid sulfate soil, and sandy soils and the physicochemical properties of the soil. Soil samples were amended at a rate of 5 tons ha⁻¹ with (1) water hyacinth compost, (2) sugarcane filter cake compost, (3) biogas sludge‐rice straw compost, (4) vermicompost, and (5) sludge. The results showed that soil respiration and DH‐ase activity increased rapidly within the first 5 days of incubation, while the concentrations of DOC and HA decreased throughout the incubation period. The highest respiration and DH‐ase activity occurred after the application of vermicompost. DOC was found to be the highest in soils amended with sugarcane. The highest concentration of HA was observed with the application of sugarcane residues, regardless of the type of soil. The application of water hyacinth and biogas sludge stimulated cumulative HA only in the acid sulfate soil, while vermicompost improved HA only in the degraded soil. The largest stimulation in respiration and DH‐ase activity was observed in degraded and sandy soils, regardless of the type of amendment. In the acid sulfate soil (3.7 mg·C·g⁻¹), larger amounts of DOC and HA were observed than in both degraded (1.7 mg·C·g⁻¹) and sandy soils (1 mg·C·g⁻¹). However, DH‐ase activity was the lowest in acid sulfate soil.

This study investigated the effect of upland crop rotation on soil bacterial community in bulk soil and rice straw residues in the alluvial soils. Soil samples and rice straw residues in two crop rotation models including triple rice and rice‐upland crops were collected for incubation under anaerobic and aerobic conditions. Data were analyzed from Denaturing Gradient Gel Electrophoresis band patterns. The results showed that the composition and diversity of communities colonizing the rice straw residues differed from those inhabiting the bulk soil. The bacterial community composition and diversity were only moderately affected by rice straw residues in the bulk soil. Especially, this study indicated that the composition of the bacterial community associated with the bulk soil and rice straw residues was dynamic in two incubation conditions (aerobic or anaerobic) and the different crop rotation models. The findings of this study demonstrated that the bacterial diversity was not affected by the difference in continuous paddy rice cultivation compared to the upland crop rotation system.

In the Vietnamese Mekong delta, soil quality and crop yield are steadily declining under rice monocultures with three crops per year. The objective of this study was to evaluate the medium-term effects of rotating rice with upland crops and adding organic amendments on rice yield and relate it to soil quality. A field trial with split-plot design including two factors and three replicates was carried out from 2017 to 2020, over the course of nine consecutive cropping seasons. Crop rotations and organic amendments were applied as main-plot and subplot factors, respectively. The rotations were: 1) rice–rice–rice (R–R–R), 2) soybean–rice–rice (So–R–R), and 3) sesame–rice–rice (Se–R–R), while organic amendment treatments included: i) no amendment (NO-AM); ii) compost of rice straw and cow manure (RS+CM), and iii) sugarcane compost (SGC); the composts were applied at a rate of 2.0 t ha-1. The rotation cycle started with the so-called spring–summer (SS), followed by summer–autumn (SA) and ended with the winter–spring (WS) season. Rice yield significantly (P < 0.05) increased by organic amendments after nine growing seasons (2019–2020 WS), with an increment of 5.1% for RS+CM (7.07 ton/ha) and 6.1% for SGC (7.14 ton/ha). Contrary to our expectation, rotations with upland crops did not significantly increase rice yield. Rice yield significantly and positively correlated with an integrated soil quality index SQI (r = 0.86) for the topsoil (0–15 cm), but not for the subsoil (15–30 cm). The increased availability of soil nutrients (Si and marginally also P) and improved soil physical properties probably induced by organic amendments, along with other soil properties under study, cumulatively attributed to enhanced rice yield. Use of a SQI involving several soil quality indicators enables to overall quantify the importance of soil fertility for rice yield versus other factors and it provides an effective means of quantifying the integrated effect of improved management. Moreover, integrating a wide range of soil quality indicators in a SQI ensures its applicability across diverse settings, including different crop rotations and various soil types.

Nghiên cứu được thực hiện nhằm đánh giá hiệu quả của SLAKES, trong việc xác định và đánh giá độ bền kết cấu của đất nông nghiệp. Kết quả đánh giá cho thấy, trên hai nhóm đất được khảo sát, chỉ số Slakes có mối tương quan thuận rất chặt chẽ với chỉ số SI (Stability index) – chỉ số độ bền kết cấu đất, được xác định bằng phương pháp rây khô – ướt. Bên cạnh đó, khi đối sánh chỉ số Slakes với các chỉ số chất lượng đất khác như pH, EC, thành phần cơ giới, dung trọng và độ xốp, phương pháp SLAKES thể hiện tiềm năng phản ánh sự thay đổi chất lượng đất giữa các mô hình canh tác, trong đó sự biến động về chất lượng đất chủ yếu liên quan đến tác động của các biện pháp quản lý đất và đặc điểm thổ nhưỡng tại các địa điểm nghiên cứu. Nhìn chung, phương pháp xác định độ bền kết cấu đất trên ứng dụng SLAKES có tiềm năng trở thành một giải pháp thay thế hiệu quả về chi phí, thời gian và thiết bị đơn giản so với phương pháp truyền thống hiện đang được sử dụng, góp phần đánh giá nhanh chất lượng đất.