Rice Systems Research Articles

Impact of Crop Residue, Nutrients, and Soil Moisture on Methane Emissions from Soil under Long-Term Conservation Tillage

Greenhouse gas emissions from agricultural production systems are a major area of concern in mitigating climate change. Therefore, a study was conducted to investigate the effects of crop residue, nutrient management, and soil moisture on methane (CH4) emissions from maize, rice, soybean, and wheat production systems. In this study, incubation experiments were conducted with four residue types (maize, rice, soybean, wheat), seven nutrient management treatments {N0P0K0 (no nutrients), N0PK, N100PK, N150PK, N100PK + manure@ 5 Mg ha−1, N100PK + biochar@ 5 Mg ha−1, N150PK+ biochar@ 5 Mg ha−1}, and two soil moisture levels (80% FC, and 60% FC). The results of this study indicated that interactive effects of residue type, nutrient management, and soil moisture significantly affected methane (CH4) fluxes. After 87 days of incubation, the treatment receiving rice residue with N100PK at 60% FC had the highest cumulative CH4 mitigation of −19.4 µg C kg−1 soil, and the highest emission of CH4 was observed in wheat residue application with N0PK at 80% FC (+12.93 µg C kg−1 soil). Nutrient management had mixed effects on CH4 emissions across residue and soil moisture levels in the following order: N150PK > N0PK > N150PK + biochar > N0P0K0 > N100PK + manure > N100PK + biochar > N100PK. Decreasing soil moisture from 80% FC to 60% FC reduced methane emissions across all residue types and nutrient treatments. Wheat and maize residues exhibited the highest carbon mineralization rates, followed by rice and soybean residues. Nutrient inputs generally decreased residue carbon mineralization. The regression analysis indicated that soil moisture and residue C mineralization were the two dominant predictor variables that estimated 31% of soil methane fluxes in Vertisols. The results of this study show the complexity of methane dynamics and emphasize the importance of integrated crop, nutrient, and soil moisture (irrigation) management strategies that need to be developed to minimize methane emissions from agricultural production systems to mitigate climate change.

Assessment of florpyrauxifen-benzyl in water-seeded rice systems as affected by application timing

Florpyrauxifen-benzyl (FPB) is a novel auxin mimic rice herbicide used to control selected grasses, sedges, and broadleaves. Field experiments were conducted in 2020–2022 to 1) characterize the effects of FPB on rice crop safety and weed control when applied alone or in a mixture, 2) determine the FPB application timing to optimize smallflower umbrella sedge (SMF) control, and 3) evaluate the effect of late season application on rice flower sterility. In the first study, FPB was applied alone at 15, 30, and 60 g ai ha−1 and in mixture with bispyribac-sodium, penoxsulam, and propanil. FPB applied alone at 30 g ha−1 at 4–5-leaf (LF) rice stage controlled more than 80% of watergrasses, ricefield bulrush, and SMF and more than 99% of all broadleaf weeds at 28 days after treatment (DAT). The mixture treatments of FPB plus bispyribac-sodium applied at maximum use rate had the greatest grass weed control whereas, FPB plus propanil at the maximum use rate provided the greatest sedge control. In the second study, FPB at 40 g ha−1 was applied at 1-LF, 10-, 15-, 20-, and 25-cm tall SMF, where treatments controlled 95%, 86%, 89%, 87%, and 85% of SMF at 42 DAT, respectively. In the third study, FPB at 40 and 80 g ha−1 rate was applied at rice panicle initiation (PI) and 50% flowering (FL) growth stages. While the weed control was more than 90% at 42 DAT for all applications, the FL stage application caused 26% and 35% rice panicle blanking at 40 and 80 g ha−1 rate, respectively. This research suggests, the window of FPB application should be from 2-LF rice to rice PI stage to ensure crop safety and highest weed control.

Internet of things-based rice field irrigation evaporation monitoring system

The urgency for efficient irrigation in Indonesia’s agriculture sector, particularly in paddy fields, is evident. However, existing methods for monitoring water levels are antiquated, often requiring manual measurements with a ruler. This research introduces a comprehensive “monitoring system for light intensity and water temperature as an analysis of evaporation for rice irrigation based on the internet of things”. The system integrates various sensors an anemometer for wind speed, an ultrasonic sensor for water level, a DS18B20 waterproof sensor for water temperature, and a GY-8511 sensor for sunlight intensity. All data are collected by an Arduino Mega controller, connected to an ESP32 for transmitting the readings to the Blynk app and an I2C 20×4 liquid crystal display (LCD) screen. The control mechanism employs a closed-loop system with a direct current (DC) motor actuator to operate the water gate, which can also be manually controlled via a cellphone. The system effectively meets daily evapotranspiration requirements of 1.44 mm, with optimal conditions yielding water levels of 3 cm, water temperatures of 38.53 °C, sunlight intensity of 4.59 mW/cm², and wind speed of 0.21 m/s.

Inhibition of Pre-Emergent Herbicide on Weedy Rice under Flooded and Saturated Soil Conditions in Rice

Weedy rice poses a formidable challenge in rice cultivation due to its genetic similarity to cultivated rice, making selective herbicides less effective in controlling it without causing harm to the cultivated rice. The potential use of pre-emergent herbicides before rice sowing to inhibit emergence and growth of weedy rice seedlings in the soil remain unknown. Thus, this study aimed to evaluate the responses of weedy rice towards selected pre-emergent herbicides under different soil water conditions and to identify the optimal timing for rice seed sowing following the application of pre-emergent herbicide to the soil under glasshouse conditions. The results showed that oxadiazon and pretilachlor at 500 g ai ha-1 exhibited higher reductions in weedy rice density and dry weight compared to those given by pendimethalin. Under saturated soil conditions, oxadiazon demonstrated 79 and 80% reductions whereas pretilachlor gave 50 and 59% reductions in weedy rice density and dry weight, respectively. By contrast, under flooded soil conditions both oxadiazon and pretilachlor resulted in complete inhibition of weedy rice. The study showed that delaying rice seed sowing for at least six days after application of pretilachlor or oxadiazon effectively minimized phytotoxic effects on rice. These findings provide valuable insights on the impact of soil water conditions when applying pretilachlor and oxadiazon for effective weedy rice control in direct-seeded rice systems.

Impact of IPM practices on microbial population and disease development in transplanted and direct-seeded rice.

Integrated pest management (IPM) is a comprehensive approach to managing diseases, focusing on combining various strategies to reduce pathogen populations effectively and in an environmentally conscious way. We investigated the effects of IPM on beneficial microbial populations and its relationship with pathogen populations in both direct-seeded rice (DSR) and transplanted rice (TR) systems. This study demonstrates that IPM practices have significantly higher populations of beneficial microbes, such as Trichoderma harzianum and Pseudomonas fluorescens, and lower level of the pathogen Fusarium verticillioides compared to non-IPM (farmer practices). The average mean population of T. harzianum was 6.38 × 103 CFU/g in IPM compared to 3.22 × 103 CFU/g in non-IPM during 2019 in TR at Bambawad. P. fluorescens mean population in 2019 was significantly higher in IPM (4.67 × 103 CFU/g) than in non-IPM (3.82 × 103 CFU/g) at the Karnal location in DSR. The F. verticillioides populations were significantly lower in IPM fields (9.46 × 103 CFU/g) compared to non-IPM fields (11.48 × 103 CFU/g) during 2017 at Haridwar in TR. Over three years, a significant increase in the populations of beneficial microbes in IPM plots was observed in all three locations of both TR and DSR, highlighting the sustainable impact of IPM practices. Disease dynamics analysis revealed that IPM effectively managed key diseases in both DSR and TR systems, with significant correlations between microbial density and disease severity. A significant positive correlation was recorded between F. verticillioides population and bakanae incidence at all three locations. Sheath blight incidence was negatively correlated with P. fluorescens population in both TR and DSR. In DSR, bacterial blight and brown spot diseases are reduced with the increased population of T. harzianum. Bioagents T. harzianum and P. fluorescens reduced disease incidence, underscoring the role of beneficial microbes in disease suppression and their importance for sustainable production using IPM practices.

Identifying a sustainable rice-based cropping system via on-farm evaluation of grain yield, carbon sequestration capacity and carbon footprints in Central China

ContextRice-based cropping system is a major anthropogenic source of direct greenhouse gases (GHG) emissions, agricultural inputs also produces numerous indirect GHG emissions and environmental problems. Identification of rice cropping systems with lower GHG emissions and higher grain yields is of great significance to ensure food security while minimizing agricultural carbon footprint (CF). ObjectiveThis study aimed to identify the optimal rice-based cropping system with lower greenhouse effects and comparable annual yield in central China. MethodsUsed life cycle assessment, a two-year field experiment was performed to evaluate the direct and indirect GHG emissions, CF, and carbon sequestration capacity in the six rice-based cropping systems widely used in central China, which consisted of fallow-early rice-late rice, rapeseed-early rice-late rice, fallow-ratoon rice, rapeseed-ratoon rice (RRaR), fallow-middle rice, and rapeseed-middle rice. ResultsThe results showed that compared with the three systems with fallow season, the three systems with rapeseed had lower annual CH4 emissions. The two systems with ratoon rice had lower annual indirect and direct GHG emissions than the two systems with double rice. The three systems with rapeseed had higher annual biomass, grain yields, and fixed carbon in biomass and significantly lower CF than the three systems with fallow season, and RRaR had the highest value of fixed carbon in biomass. The systems with ratoon rice had lower average CF than those systems with double rice. CH4 emissions from paddy fields were the primary source of total annual GHG and the main component of CF. Compared with the three systems with fallow season, the three systems with rapeseed had significantly higher annual carbon sequestration capacity based on net ecosystem production (NEP). Ratoon rice systems had higher average NEP than double- and middle-rice systems. RRaR had the lowest CF per unit yield and highest NEP among all the six systems. ConclusionsThe results indicated that appropriate rice-based cropping systems may alleviate the greenhouse effect via reducing GHG emissions and enhancing paddy NEP, RRaR could achieve relatively higher annual grain yield and carbon sequestration capacity as well as lower CF. SignificanceThis study highlight conversion of double rice and middle rice systems to RRaR may help improve grain yield and mitigate greenhouse effect. The findings may provide a theoretical basis for selection of sustainable development of rice based cropping systems in central China.

Edaphic Factors Modulating Phosphorus Availability in Lowland Rice Systems, Nigeria

ABSTRACT The low rice production level in Africa is attributed to poor soil fertility despite the potential for rice cultivation in the inland valleys. This study was conducted to evaluate soil characteristics in some lowlands that have been continuously and intensively used for rice production for over two decades in southwestern Nigeria. Soil physical, chemical, and mineralogical properties, as well as phosphorus sorption characteristics, were assessed in soil samples collected from diagnostic horizons of profiles in six benchmark soils. The results show kaolinite, quartz, potassium(K)-feldspars, and mixed-layered smectite as the predominant minerals. The iron oxide fractions indicate that the soils are at varying degrees of development where the soils at the advanced stage of development are predominantly rich in kaolinite and quartz with a high concentration of total pedogenic iron oxide and generally low in soil fertility. Soil phosphorus buffering capacity is low and varies inversely with pH, confirming the deficiency of phosphorus at low pH. Short-range-order (SRO) iron (Fe) oxides show a strong affinity for phosphorus and this is stronger at lower soil horizons and mediated by some redoxomorphic reactions. The SRO iron oxide concentration has more influence on phosphorus retention in soils rather than the absolute concentration of iron oxides. The study concludes that SRO Fe oxides and soil pH are the major edaphic factors playing a prominent role in phosphorus retention and availability in the wetland soils rather than the clay minerals.

Five years of conservation tillage and weed management in a rice-chickpea rotation of northern Gangetic Plains of India: Weed growth, yield benefits and economic profitability

Cropping system diversification of cereal-cereal systems with alternative systems preferably with pulses/legumes is demand of time across the globe for sustenance of natural resources and climate resilience. Rice-chickpea has been advocated as a futuristic cropping system in rice ecologies of South Asia for diversification of dominating rice-wheat system. However, the long-term sustainability of this system with respect to weed severity/growth, crop/system productivity, profitability, and yield stability under variable tillage, crop residues, and weed management practices has not been studied elaborately. Hence, present study was undertaken for five consecutive years in split-plot design with four tillage and residue management practices in main plot (conventional and zero tillage with and without residues), and three weed control practices (pre + post emergence herbicides and manual weeding) in sub-plot. Conservation tillage system comprising zero-tilled (ZT) direct seeded rice (ZTDSR) - ZT chickpea with rice residue retention (ZTDSR-ZTC+RR) led to the lower weed density in chickpea (by 10 %) and system (by 7 %) than conventional-tilled (CT) puddled transplanted rice - CT chickpea without residues (PTR-CTC-R; farmer practice). Among weed management practices, pendimethalin 1 kg a.i. ha−1 – metsulfuron-methyl + chlorimuron ethyl (ready-mix) 4 g a.i. ha−1 in rice and oxyfluorfen 150 g a.i. ha−1 – propaquizafop 100 g a.i. ha−1 in chickpea decreased the weed density in system by 14–22 % (p < 0.05) than pendimethalin + one hand weeding. The best weed management practice (pendimethalin – metsulfuron-methyl + chlorimuron ethyl) had significantly total weed density rice (by 7 %) and system (by 10 %) than current recommendation of the Indo-Gangetic Plains region (pendimethalin - bispyribac-sodium). It suggested that rotation of bispyribac-sodium with metsulfuron-methyl+chlorimuron ethyl (mixture herbicide) could reduce weed density and increase yield over time. Mean of five years indicated a non-significant yield difference among conservation and conventional tillage systems in rice. However, conservation tillage practice (ZTDSR-ZTC+RR) had 10 % higher chickpea yield and 4 % higher system yield (five years mean) over the PTR-CTC-R (p < 0.05). Further, conservation tillage comprising ZT in both crops in system with added residues (ZTDSR-ZTC+RR) resulted in an economic benefit of INR 22,000 than the conventional tillage in both crops without residues (PTR-CTC-R). Moreover, five years sustainable yield index was 16 % higher in ZTDSR-ZTC+RR system than conventional-tilled rice-chickpea system. Thus, conservation tillage with suitable pre- + post- emergence herbicides such as pendimethalin – metsulfuron-methyl + chlorimuron ethyl in rice and oxyfluorfen – propaquizafop in chickpea can reduce the weed density and enhance the crop and system productivity over time than conventional tillage. This system can also sustain the yields of component crops and system in long-run with higher yield stability over conventional tillage without residues. This system can be adopted in the cereal-cereal based cropping system of rice ecologies to diversify the system and to reverse the weed infestation and yield decline.

Adoption Pattern of Direct-Seeded Rice Systems in Three South Asian Countries during COVID-19 and Thereafter

Adoption Pattern of Direct-Seeded Rice Systems in Three South Asian Countries during COVID-19 and Thereafter

Effects of Straw and Fertilizer Managements on Nitrogen Loss in Rice Cultivation in Taihu Lake Basin

Nitrogen loss from rice systems is an important source of agricultural non-point source pollution. Many studies revolve around reducing the rate of nitrogen fertilizer application. However, studies examining the characteristics of nitrogen loss in multiple loss paths （runoff, leaching, and lateral seepage） under different straw and fertilizer managements are lacking. Therefore, a study was carried out based on a rice field planted for more than 20 years with straw continuously returned to the field for more than 5 years in Taihu lake basin. The effects of straw and fertilizer managements on nitrogen loss in different paths during the whole growth period of rice were studied. Moreover, straw and fertilizer managements were evaluated by their production suitability and environmental friendliness based on crop yield, nitrogen use efficiency, and nitrogen loss. The results showed that straw removal from the field increased the response sensitivity of nitrogen accumulation in plant tissue to nitrogen application. The nitrogen loss in the rice season was 9-17 kg·hm-2, accounting for 5%-7% of the nitrogen application rate. Straw removal increased the risk of nitrogen loss when soaking water discharged. Straw returning could decrease the nitrogen loss by more than 15%, though the effect of straw on nitrogen loss via lateral seepage was not clear. Furthermore, the suitable substitution of organic fertilizer （30% in this study） could respectively reduce the amount of nitrogen loss via runoff, leaching, and lateral seepage by 16%, 26%, and 37% compared with the fertilizer application under the same nitrogen gradient. In conclusion, the implementation of straw returning and fertilizer type optimization measures effectively reduced the nitrogen loss for unit weight of rice production and realized the balance between agricultural production and environmental protection.

Hydrologic variability governs GHG emissions in rice-based cropping systems of Eastern India

Reducing methane (CH4) emissions is increasingly recognized as an urgent greenhouse gas mitigation priority for avoiding ecosystem ‘tipping points’ that will accelerate global warming. Agricultural systems, namely ruminant livestock and rice cultivation are dominant sources of CH4 emissions. Efforts to reduce methane from rice typically focus on water management strategies that implicitly assume that irrigated rice systems are consistently flooded and that farmers exert a high level of control over the field water balance. In India most rice is cultivated during the monsoon season and hydrologic variability is common, particularly in the Eastern Gangetic Plains (EGP) where high but variable rainfall, shallow groundwater, and subtle differences in topography interact to create complex mosaics of field water conditions. Here, we characterize the hydrologic variability of monsoon season rice fields (n = 207) in the Indian EGP (‘Eastern India’) across two contrasting climate years (2021, 2022) and use the Denitrification Decomposition (DNDC) model to estimate GHG emissions for the observed hydrologic conditions. Five distinct clusters of field hydrology patterns were evident in each year, but cluster characteristics were not stable across years. In 2021, average GHG emissions (8.14 mt CO2-eq ha−1) were twice as high as in 2022 (3.81 mt CO2-eq ha−1). Importantly, intra-annual variability between fields was also high, underlining the need to characterize representative emission distributions across the landscape and across seasons to appropriately target GHG mitigation strategies and generate accurate baseline values. Simulation results were also analyzed to identify main drivers of emissions, with readily identified factors such as flooding period and hydrologic interactions with crop residues and nitrogen management practices emerging as important. These insights provide a foundation for understanding landscape variability in GHG emissions from rice in Eastern India and suggest priorities for mitigation that honor the hydrologic complexity of the region.

Joint utilization of Chinese milk vetch and lime materials mitigates soil cadmium risk and improves soil health in a double-cropping rice system

Cadmium (Cd) in paddy soil poses significant risks to humans due to its strong biological migration and toxicity. Chinese milk vetch (MV) is commonly used as green manure in the paddy fields of southern China and its potential to decrease the availability of Cd has been identified. Nevertheless, the effects of MV combined with lime materials (lime, L; limestone, LS) on Cd availability, soil properties, enzyme activity and comprehensive benefits are still not fully understood in double-cropping rice system. A field study was conducted to investigate these changes. The results indicated that all treatments notably decreased soil available Cd (Avail-Cd) by 19.3–44.3% and 14.9–43.1% during early and late rice, compared with CK. Moreover, the Cd fractions transformed to more stable forms. Compared to CK, all treatments reduced brown rice Cd content by 34.6–64.2% and 12.7–52.5% during the two periods. Furthermore, the translocation factors root to shoot, as well as shoot to brown rice, decreased. The combination led to improvements in soil properties, soil enzyme activity. Meantime, Cd in iron-manganese plaque (IMP) decreased by 31.9–51.1% and 29.0–42.7% respectively during two periods in amendments treatments. Soil pH and DOC were more important factors for Cd bioavailability than other properties. Additionally, rice Cd uptake was positively correlated with Cd in IMP. Enzyme activity exhibited a negative correlation with soil active Cd. Partial Least Squares Path Model (PLS-PM) indicated that the mitigation of Cd pollution helped to improve soil enzyme activity. Grey correlation analysis (GRA) indicated that MVLS showed the best comprehensive benefits in soil-plant system. Overall, the combination of MV and lime materials could reduce Cd availability, enhance soil properties and enzyme activity. And this could be strengthened by the combination. These findings will provide valuable insights for Cd-contaminated soil remediation.

Rotary Tillage Plus Mechanical Transplanting Practices Increased Rice Yields with Lower CH4 Emission in a Single Cropping Rice System

As the main contributor to greenhouse gas (GHG) in paddy soil, information on methane (CH4) emission characteristics under different tillage and cultivation practices are limited. A five-year field trial was conducted from 2019 in a single-cropping rice system in Taihu Lake region, east of China. The experiment had a completely randomized block design, and the treatments included rotary tillage plus rice dry direct seeding (RD), rotary tillage plus rice mechanical transplanting (RT), and plowing tillage plus rice mechanical transplanting (PT). We determined the rice yield, GHG emission, soil traits, and methanogens and methanotrophs in 2022 and 2023. The results revealed that PT and RT significantly increased rice yield compared to RD, whereas PT simultaneously increased CH4 emissions. The year-averaged cumulative CH4 emissions in PT were increased by 38.5% and 61.4% higher than RT and RD, respectively. Meanwhile, yield-scaled global warming potentials (GWPs) in RT and RD were lower than those in PT. Tillage and cultivation practices shifted mcrA and pmoA abundances, and PT significantly decreased pmoA abundance. The community structure and diversity of the methanogens and methanotrophs were not significantly affected. Structural equation model analyses illustrated that CH4 emissions were regulated by mcrA and pmoA directly, which in turn, regulated by soil carbon and nitrogen. Overall, rotary tillage plus mechanism transplanting was a feasible agronomic technology in a single-cropping rice system in Taihu Lake region, exhibiting higher and more stable rice productivity, accompanied with lower CH4 emissions and yield-scaled GWP.

Effects of unbalanced fertilizer use on system productivity and profitability under rice‐based cropping systems: Evidence from Eastern Gangetic Plain

AbstractUnbalanced nutrient supply is one of the key causes of yield gaps and low farming profitability which impact food insecurity globally. However, the effects of an unbalanced nutrient supply on rice yields and farming profitability have not been quantified for diverse rice‐based cropping systems. To explore the effects, 412 respondents (mostly smallholder farmers) were surveyed in 2019 for the rice crops in three fully rice‐based cropping systems in four agro‐ecological zones of Bangladesh. Two robust estimation approaches namely propensity score matching and endogenous switching regression approaches were used to quantify the effects of unbalanced fertilizer use. The results show that about 68% of farmers in the study areas used unbalanced (over‐doses or under‐doses) nutrient rates relative to government‐endorsed recommendations. Adoption of recommended fertilizer rates was influenced by education, amount of organic manure used, off‐farm income, crop farming‐related training, organizational membership and lack of soil testing tendency. The findings also indicate that adopters of recommended nutrient rates received almost 16% and 46% higher system rice yield and system net return, respectively, relative to non‐adopters. However, based on our research findings, formulation and implementation of effective agricultural policies like effective extension services, strengthening soil testing facilities, increasing organizational membership and targeted awareness programmes could motivate smallholder rice farmers towards adoption of recommended nutrient rates. Adoption of recommended fertilizer rates can significantly enhance crop yields and farming profitability which can boost food security and rural livelihoods in the Eastern Gangetic Plain.

Evaluation of integrated threshing and drying design concepts for paddy rice using analytical hierarchy process

Threshing and drying are two major postharvest activities that contribute significantly to postharvest losses for small and medium-scale rice farmers, leading to food insecurity and hunger in Sub-Saharan Africa. Developing an appropriate system for threshing and drying needs urgent attention. The objective of the study involved the use of Analytical Hierarchy Process (AHP) for evaluation and selection of the best option among four design concepts for development and fabrication. The four design concepts shortlisted were: (1) batch flow biomass-powered manual threshing and drying system, (2) recirculating diesel-powered mobile threshing and drying system, (3) mechanized threshing with solar drying batch system, and (4) tractor-powered recirculating continues flow integrated system. For the MCAHP analysis, 17 attributes were proposed and divided into five main criteria. The evaluation of the main criteria showed that cost had the highest score, followed by performance, safety, ease of installation and operation, and manufacturability, with a global score of 0.560, 0.202, 0.108, 0.083 and 0.048, respectively. It was observed that design concept two received the highest weighted score of 0.35 and was selected as the design concept to proceed with. The consistency ratios of the main criteria and attributes were all less than 0.1, which is the allowable limit of inconsistency. In conclusion, concept 2 was selected as the best design for developing an integrated threshing and drying system for paddy rice and is recommended for development, fabrication, evaluation and optimisation. Int. J. Agril. Res. Innov. Tech. 14(1): 30-44, June 2024

Nutrient status and soil fertility index as a basis for sustainable rice field management in Madiun Regency, Indonesia

&lt;p&gt;Agricultural development, specifically for crops, contributes significantly to national development. However, problems with water and low soil fertility are obstacles to this development. This study evaluated the nutritional status and soil fertility index as the basis for determining the direction of rice field management in Madiun Regency, East Java, Indonesia. The research method was conducted by surveying the soil characteristics followed by laboratory analysis. Soil samples were collected using stratified proportional sampling from 19 land units with 31 samples. The soil fertility index was determined using a principal component analysis test and calculated by dividing the weights by the minimum soil fertility index indicators. The study results show that the nutritional status of total N in the study area is low to high (0.13%–0.59%) and total P is very low to very high (12.18–73.66 ppm), whereas the status of exchangeable K is very low to very high (0.01–0.67 cmol.kg&lt;sup&gt;−&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;), Cation Exchange Capacity is low to high (12.8–36.0 cmol.kg&lt;sup&gt;−&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;), and organic carbon is low to very high (1.98%–6.54%). The soil fertility index ranges from medium to extremely high. The influential indicators are total P, total N, exchangeable K, and organic carbon. It is recommended that the rice field management system implement a “sustainable agricultural intensification” system that combines the two systems “intensification” and “sustainable agroecosystem.” This system still uses proportional inorganic and organic fertilizers (manure, compost, and agricultural waste).&lt;/p&gt;

&lt;span&gt;Assessing the impact of land-use/land-cover change on provisioning ecosystem services in the Long Xuyen Quadrangle from 2000 to 2021&lt;/span&gt;

Changes in land use/land cover (LULC) have a significant impact on the changes in ecosystem service values. This study aims to assess the impacts of LULC changes on provisioning ecosystem services (pES) in the Long Xuyen Quadrangle region (LXQ) from 2000 to 2021. Using Landsat 5 TM and Landsat 8 OLI imagery, this study analyzes the normalized difference vegetation index (NDVI) time series using MODIS imagery to monitor and evaluate the impacts of LULC changes in the LXQ region. Additionally, interviews with farmers were conducted to estimate the ecosystem service values of different rice cultivation models. The research results in the creation of LULC maps for the LXQ in 2000 and 2021, with relatively high reliability, including overall accuracy (OA) of 83.18% (K = 0.772) and 94.26% (K = 0.9284), respectively. The main LULC change observed in the LXQ region from 2000 to 2021 is the conversion from wetlands to double-cropped rice and triple-cropped rice systems. The study identified an area of 54,667.722 ha (26.24%) where wetlands were converted to double-cropped rice, and an area of 36,779.633 ha (17.65%) where wetlands were converted to triple-cropped rice. Furthermore, the estimated ecosystem service values after the conversion from wetlands to triple-cropped rice were approximately 122,504,931 VND/ha/year, and for double-cropped rice, it was approximately 87,772,604.88 VND/ha/year. The research findings indicate that wetland agriculturalization, including double-cropped rice and triple-cropped rice, has affected the ecosystem service provision in the LXQ region. These research results provide significant considerations for future comprehensive valuation of ecosystem service values in the LXQ, Vietnamese MD.

Nitrogen scavenging by winter fallow weeds and its availability to rice crops

Weedy fallow presents a promising strategy for nitrogen (N) scavenging and reducing N losses from croplands. The study aimed to (1) reassess the N scavenging potential of winter fallow weeds, specifically foxtail grasses, within rice cropping systems and (2) determine the availability of N scavenged by winter fallow weeds in rice paddies to rice crops. A two-year on-farm investigation (2022 and 2023), a one-year 15N-tracing microplot experiment (2021), and a two-year field experiment (2022 and 2023) were conducted in Hunan Province, China. The on-farm investigation revealed that winter fallow weeds scavenged on average 10.6 g N m–2 in 2022 and 10.9 g N m–2 in 2023. In the 15N-tracing microplot experiment, a 24 % average recovery efficiency of N from winter fallow weeds, applied in conjunction with two rice varieties and two urea-N application rates, was observed. The field experiment showed that total N uptake by rice plants and grain yield of rice crops were linearly and quadratically related to the total N application rate (the sum of N in applied winter fallow weeds and urea), respectively, in both 2022 and 2023. These findings highlight the potential of winter fallow weeds in rice paddies to scavenge N effectively and reveal this scavenged N to be highly available to rice crops. This study offers insights into the dual advantages of winter fallow weeds within rice cropping systems, shedding light on their environmental benefits as well as their positive agronomic outcomes.

Geochemical characterization of heavy metals in the soil rice system and risk assessment for human health

ABSTRACT The ingestion of heavy metals in agricultural soils by the population has implications for human health. The research demonstrate that the concentration of Cd in the soil exceeded the national background level, with 62% of soil samples surpassing the Chinese soil screening value. Furthermore, 42% of the analyzed rice grains exhibited Cd levels that surpassed the established standard. Notably, there was no significant association between the concentration of Cd in soil and rice. The bio-effectiveness of heavy metals was enhanced in soils with low pH, and residue state was the main storage form for heavy metals. Cd exhibited a different distribution pattern compared to other heavy metals. Human health risk assessment revealed that children in the study area were at greater risk, particularly due to non-carcinogenic and carcinogenic effects of Cd. These findings provide valuable insights for the development of strategies to remediate heavy metal contamination in similar areas..

Effects of Long-Term Fertilizer Managements on Soil Organic Carbon Mineralization Under the Double-Cropping Rice System in Southern China

ABSTRACT Soil organic carbon (SOC) plays an important role in maintaining or increasing soil fertility and quality in paddy field, but there is limited information about how SOC mineralization responds to different fertilizer managements under the double-cropping rice system in southern China. Therefore, this study was designed to explore changes in SOC content, soil enzyme activities, SOC mineralization at 0–10 cm and 10–20 cm layers, and its relationship with long-term fertilizer managements in a double-cropping rice system of southern China. The experiment included four fertilizer treatments: chemical fertilizer alone (CF), rice straw and chemical fertilizer (RS+F), 30% organic manure and 70% chemical fertilizer (OM+F), and without fertilizer input as a control (Con). These results showed that SOC and labile organic carbon contents at 0–10 cm and 10–20 cm layers in paddy field with RS+F and OM+F treatments were increased, compared to CF and Con treatments. Compared with Con treatment, SOC mineralization rate and accumulation with CF, RS+F, and OM+F treatments were increased. SOC accumulation and potential mineralization at 0–10 cm and 10–20 cm layers with RS+F and OM+F treatments were increased, compared with CF and Con treatments. SOC mineralization rate and accumulation at 0–10 cm layer with CF, RS+F, OM+F, and Con treatments were higher than that of 10–20 cm layer. These results indicated that soil invertase, cellulose and urease activities in paddy field with RS+F and OM+F treatments were significantly higher than that of CF and Con treatments. There was a significant positive relationship between SOC accumulation and SOC content, soil invertase, cellulose, urease activities but were significant negative correlated with soil pH, bulk density. As a result, these were beneficial practices for improving SOC content and SOC mineralization in a double-cropping rice field of southern China by combined application of rice residue or organic matter with chemical fertilizer managements.