Intermittent Irrigation Research Articles

Investigating the effects of various irrigation methods on bacterial communities in paddy soil

Different irrigation methods can impact the micro-ecological environment of paddy soil, affecting crop growth. This study focuses on County A, a key grain production area on China’s East Coast, where 20 plots each of intermittent and flood irrigation were selected and labeled as Group I and Group F, respectively. Soil's basic physicochemical properties and heavy metal content were measured in the laboratory, and high-throughput sequencing was used to analyze soil bacterial communities. The study evaluated the impact mechanisms of different irrigation methods on these bacterial communities. Results indicate: (1) Intermittent irrigation significantly increased bacterial richness, evenness, and diversity, enhancing microbial community diversity and stability. (2) Intermittent irrigation notably raised the abundance of 9 bacterial genera (e.g., Nitrospira, H16) while reducing the abundance of 7 genera (e.g., Geobacter, Sphingomonas). (3) The soil environment in Group I was stable, with bacterial communities influenced by SMC, pH, and Cu; Group F was affected by multiple environmental factors. Intermittent irrigation provides a stable environment that supports bacterial diversity and abundance, contributing to a richer community structure. (4) Intermittent irrigation optimizes moisture, significantly enhancing bacterial functions such as energy production, cell wall biosynthesis, repair, and signal transduction. These findings suggest that intermittent irrigation improves bacterial community stability and diversity, which is crucial for enhancing the overall quality of paddy fields.

Intermittent Drip Irrigation Soil Wet Front Prediction Model and Effective Water Storage Analysis

The depth and width of drip infiltration play a critical role in designing effective irrigation strategies. However, existing models primarily focus on continuous irrigation and fail to predict wetting patterns under intermittent drip irrigation. This study developed an infiltration model to estimate soil moisture depth and width under intermittent drip irrigation and identified strategies that enhance effective water storage. Indoor soil box simulations were conducted, with continuous drip irrigation as the control. Results showed that intermittent irrigation increased infiltration width and reduced depth, maximizing water storage efficiency. We recommend adopting an intermittent irrigation system with 1.5 h of irrigation followed by a 0.5 h interval, repeated four times. This system increased effective water storage by up to 16.23% compared to continuous irrigation. The proposed method is suitable for sandy loam farmland in southern Xinjiang and can significantly improve water use efficiency in arid regions.

Robotic Hepatic Parenchymal Transection Techniques: A Choice Between Imperfect Tools.

Regardless of approach, safe and effective parenchymal transection is critical for hepatectomies.1 In robotic surgery, this can be accomplished via several methods. The authors highlight some of the more common tools and techniques used to transect the liver. The Vessel Sealer Extend is a console-controlled device with bipolar energy, mechanical cutting, full-wristed articulation, and grasping abilities that allow it to replicate the clamp-crush technique while sealing small vessels. However, the jaw is bulky and suboptimal for firm/fibrotic livers.2,3 The Synchroseal shares many features of the Vessel Sealer Extend but has thinner jaws, making it easier to advance in firm livers, and lacks a cutting blade, relying instead on a cut electrode to divide tissue. Proteinaceous char can accumulate on the jaws, impairing its effectiveness, but intermittent irrigation can mitigate this. The robotic Harmonic Scalpel coagulates, transects, and precisely dissects parenchyma. However, it is limited in length and lacks wristed articulation.4,5 Ultrasonic surgical aspiratory devices allow for precise, atraumatic dissection around vasculobiliary structures, but no robotic-integrated versions currently exist. Therefore, application of this technology in robotic surgery requires an experienced bedside assistant operating the laparoscopic version while the console surgeon uses robotic instruments to coagulate, clip, and divide larger structures.6-9 The dual bipolar technique is useful for spot coagulation and dissection but has limited transection ability.10 It often is an adjunct to other transection techniques.11-13 Several methods exist for robotic parenchymal transection, and although none are perfect, they can be combined for safe and effective transection.

What influences interruption of continuous renal replacement therapy in intensive care unit patients: A review with meta-analysis on outcome variables.

Evidence suggests that 8%-10% of ICU patients receive renal replacement therapy. However, there is a high rate of unplanned CRRT interruption, ranging between 17% and 74%. Studies on unplanned interruption of CRRT mainly focused on the retrospective investigation of related risk factors and conclusions have been diverse. This article aims to clarify the main influencing factors related to unplanned interruption of continuous renal replacement therapy (CRRT) in adult patients in intensive care units (ICUs). A literature review and meta-analysis were undertaken. Following the application of the Newcastle-Ottawa Scale (NOS), a total of 15 articles were included in a total of 2132 patients who underwent 3690 CRRT procedures and 2181 unplanned interruption times. The methodological guideline of a scoping review was applied for the evidence synthesis while applying the meta-analysis quantitative methodological guideline to identify and clarify main influencing factors related to unplanned interruption of CRRT. The reporting Prisma Protocol was followed. Longer filter life and prothrombin activation time, higher red blood cell count, greater transmembrane pressure, faster blood flow rate, intermittent saline irrigation, lower creatinine level, low prothrombin activity and pre-dilution are factors identified to potentially affect unplanned CRRT in ICU patients. Available evidence suggests four clinical challenges associated with unplanned CRRT interruption, namely: (a) effects of red blood cell count, filter life, cross-mode pressure, blood flow velocity, prothrombin activity and activated partial thrombin time on unplanned interruption; (b) influence of dilution mode on unplanned interruption; (c) influence of intermittent saline irrigation on unplanned interruption; (d) influence of Scr level on unplanned interruption. The potential to increase the ability to better manage unplanned CRRT in ICUs has been identified in this article and constitutes a relevant potential health care management contribution that can be implemented by nurses.

Meta-analysis of GHG emissions stimulated by crop residue return in paddy fields: Strategies for mitigation

The stimulating impact of crop residue return on greenhouse gas (GHG) emissions from paddy fields have been widely accepted, while the influence of site environmental and human factors on the simulating degree remains unclear. Here, we performed a meta-analysis to assess the GHG emissions affected by residue return, and its mitigation potential combined with key factors in paddy fields. Drawing upon 1047 observation sets of CH4 and N2O emissions from 155 peer-reviewed publications we found that residue return to paddy fields caused an average increase of 73% CH4 emissions and 14% in N2O emissions. Utilizing meta-analytical models, we identified pH as the most significant driver modulating GHG emissions, followed by soil organic matter (SOC) and total nitrogen. In alkaline soils, combining straw return with intermittent irrigation (285.2%) or mid-season drainage (118.9%) significantly reduced CH4 emissions compared to continuous flooding (1201.9%). Additionally, pairing straw return with higher nitrogen inputs (above 150 kg N ha−1) improved soil N2O uptake by −11.5%. In acid and neutral soils, straw carbonization achieved soil CH4 negative emissions (from −2.9% to −39.3%), but the long-term effects remained unclear. Reduced drainage frequency mitigates N2O emissions but may increase CH4 emissions. To efficiently mitigate GHG emissions, we proposed low-carbon schemes for acid or neutral soils based on specific SOC content: For soils with SOC content <10 g kg−1, prioritize nitrogen input control with rates not exceeding 174 kg N ha−1. For soils with SOC content >10 g kg−1, prioritize adjusting the type of straw. Our study underscores the significance of site-specific factors in modulating GHG emissions. Efficient GHG mitigation can be achieved by combining residue return with other agronomic measures tailored to different soil conditions.

Rice yield and water productivity in response to water-saving irrigation practices in China: A meta-analysis

Various water-saving irrigation (WSI) practices (e.g., dry cultivation, intermittent irrigation, controlled irrigation, shallow-wet irrigation, and rain-gathering irrigation) have been applied to rice cultivation mitigate water scarcity in China. However, in previous studies, these WSI practices have shown different water savings and yield increases, mainly due to different application conditions. A meta-analysis was applied to investigate the responses of the actual evapotranspiration (ETact), irrigation water (IW), rice yield (Y), and water productivity (WP) to WSI practices in different conditions, and 956 data sets were selected from 108 published papers. The results showed that, compared to traditional flood irrigation, rain-gathering irrigation decreased ETact and IW by 25.41 % and 55.7 % respectively, and increased WP greatly by 14.26 % while having a slight decrease in Y. Except for dry cultivation, all WSI practices increased WP by 4.72–14.26 % compared to traditional flood irrigation. The effects of different soil qualities on rice water consumption and production vary; medium soils with high organic content and a pH below 6.5 are better for rice growth. As for rice seasons, WSI practices had the least impact on ETact in middle rice, with an average reduction of 5.84 %, followed by early rice (–12.66 %) and late rice (–18.81 %). Higher mean annual temperature and more precipitation led to more Y under WSI practices. Differences in the effects of mean annual temperature and mean annual precipitation on WP were not significant. Our meta-analysis provides more insight into the effects of water-saving irrigation practices on rice water consumption, yield, and water productivity at various experimental sites. In general, there is considerable variation in the responses of Y and WP to different water-saving irrigation practices, and more evaluation of aspects such as rice seasons, soil properties, and meteorological conditions is needed for optimizing WSI in practice.

Vulnerability and risk analysis of climate change Impacts on rice production (Oryza sativa L.) in Majalengka regency

Climate change, especially temperature and rainfall shifting can be a threat to the agricultural sector, i.e., the decrease in rice yields in Majalengka Regency as the West Java rice production center. As an anticipatory measure to deal with that problem, a study is needed regarding the level of hazard, vulnerability and risk of climate change impacts in Majalengka Regency. This research aims to identify climate change and examine the level of hazzard, vulnerability and risk of the impact of climate change on rice production in each sub-district in Majalengka Regency. The method used in this research is descriptive quantitative. The data used in the analysis of the level of hazard, vulnerability and risk of climate change include temperature, rainfall, production, productivity, planting area, harvested area and farmers' socio-economic data obtained from Statistics Indonesia; Meteorology, Climatology, and Geophysical Agency; Agriculture Office of Majalengka Regency and other relevant sources, while farmer interview data were used in analyzing strategic adaptation options. The results of the study stated that areas with a very high potential risk of decreasing rice production (Risk Index or RI &gt; 0.80) were in Kertajati District; the risk level of rice production in the high category (RI 0.61-0.80) was in Bantarujeg and Ligung Districts. Meanwhile, areas with a very high level of risk of decreasing rice productivity (IR) &gt; 0.80) are in Bantarujeg District; high-risk level (IR 0.61-0.80) was in the Districts of Lemahsugih, Malausma, Argapura, Kertajati, Jatipuh and Ligung. The adaptation efforts that can be made to reduce the risk of decreasing rice production are the use of superior seeds, crop rotation, intermittent irrigation systems, acceleration of land preparation by mechanization, application of the jajar legowo cropping system, and integrated pest management measures.

Higher rice productivity and lower paddy nitrogen loss with optimized irrigation and fertilization practices in a rice-upland system

Intermittent irrigation and controlled-release fertilizers are considered effective practices for rice growth; however, their combined effects on nitrogen (N) loss from intensified agricultural lands remain unclear. Here, a two-year field experiment was conducted using two irrigation regimens (flooded irrigation, FI; controlled irrigation, CI) and two fertilizer types (conventional urea, CU, split applied; controlled-release blend fertilizer, CRBF, one-time basal applied) to investigate their effects on N turnover in rice upland systems. The results demonstrated that CI not only saved 56.7 % of irrigation water compared to FI but also increased rice yield (5.3 %) and N use efficiency (7.8 %). The significant reduction in water input and soil water content for the CI led to lower N leaching (47.5 %) and N runoff (20.2 %) than for the FI. In contrast, N2O emissions increased by 27.8 % under CI compared with FI. CRBF reduced NH3 volatilization by 18.8 % and improved N use efficiency by 14.0 %, due to decreased N diffusion from the soil to surface water compared to CU. However, the N runoff of the CRBF was 23.8 % greater than that of the CU. The CI-CRBF improved the rice yield by 6.3 % and decreased N loss (22.3 %) by reducing NH3 volatilization (21.4 %) and N leaching (46.9 %). The findings suggest CI-CRBF to be an eco-friendly and lightly simplified pattern in rice upland systems, with higher rice productivity and lower paddy N loss.

Sprinkler irrigation: An efficient and eco-friendly approach to produce safe rice

Rice is the most widely grown and consumed cereal globally. It is the primary source of sustenance for half of the world's population and may remain so for future generations. However, rice cultivation is currently considered environmentally unfriendly due to its high use of irrigation water, significant emissions of greenhouse gases, and bioaccumulation of arsenic in the grain. These concerns are attributed to the global use of continuous flooding as irrigation method. To address this issue, replacing continuous flooding with intermittent sprinkler irrigation can result in significant water savings while maintaining the same product yield. This method also offers further agronomic benefits. Moreover, this method can reduce the bioaccumulation of toxic elements and greenhouse gas emissions. In particular, sprinkler irrigation can produce healthy rice from plants grown in soils contaminated with arsenic and cadmium. It can also help minimize the concentration of many other toxic elements in rice or tune the levels of trace elements, such as selenium or iron as required.

Seedbed management, transplanting methods and irrigation regimes influence the growth, productivity and economics of summer rice (Oryza sativa L.)

A field experiment was conducted during the rabi (winter) seasons of 2017–2018 and 2018–2019 at the Central Research Farm under Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India, to study the effects of planting techniques, irrigation regimes, and nursery bed management on the growth, yield, nutrient dynamics, water productivity, and economics of summer rice (cv. Shatabdi) production. The experiment was performed in a strip-split plot design with twelve treatment combinations, which were replicated three times. The design consisted of two types of transplanted rice establishment methods (viz., puddled transplanted rice (PTR) and nonpuddled transplanted rice (NPTR)) allocated to the main plot, three irrigation regimes (three-day intervals; six-day intervals; nine-day intervals) allocated to the subplot, and two nursery bed management practices (conventional seedbed and improved seedbed) allocated to the subplot. Higher growth attributes, such as plant height, tiller count, biomass, and LAI, were found under nonpuddled conditions at the time of harvesting. Similarly, a three-day irrigation interval and improved seedlings led to better growth traits. The yield attributes and yield varied nonsignificantly among the crop establishment methods. However, the lowest irrigation intervals accounted for 53.78% and 43.02% greater grain yield than did the nine-day intervals in two consecutive years, respectively, and produced statistically similar yields with six-day intervals. The percentage of seedlings transplanted from improved seedbeds was 4.01 and 4.13% greater than that from conventional seedlings. A similar trend was observed for both input and irrigation water productivity, except that the nine-day irrigation interval resulted in significantly greater water productivity than did the other intervals. The treatment consisted of nonpuddled transplanted rice along with six six-day irrigation intervals and improved seedbed management, resulting in the highest net return and benefit:cost ratio due to the low production cost. Thus, it can be concluded that transplanting seedlings into nonpuddled soil from an improved seedbed with intermittent irrigation might be the most judicious and recommended in terms of productivity as well as profitability for summer rice production.

Water-saving irrigation mitigates methane emissions from paddy fields: The role of iron

Iron (Fe) and methane (CH4) emissions play crucial roles in the carbon cycling of paddy field ecosystems. However, little is known about the effect and mechanism of Fe transformation on the CH4 emission from paddy fields, especially with different water management methods. In this study, the dynamic changes in CH4 emissions and different forms of Fe and soil organic carbon content were observed in paddy fields under flooded irrigation (FI) and water-saving irrigation (WSI) (including intermittent irrigation (II) and controlled irrigation (CI)). In addition, the structural equation model was used to clarify the response relationship between CH4 emissions and Fe ions in paddy fields. The results indicate that the cumulative CH4 emissions under WSI were reduced by 29.03–61.29%. The reasons are as follows (i) WSI increased the oxidation ability of Fe to CH4 by increasing the soil ferric iron (Fe3+) content in paddy fields; (ii) WSI could reduce the substrate utilization by methanogens by transforming the Fe oxide forms to increase the binding capacity of Fe to dissolved organic carbon, which reduced the CH4 production. In addition, compared with II, CI had higher soil Fe3+ content, Fe-bound organic carbon content, and lower acetate content, so it had lower CH4 production capacity. In summary, WSI promotes the direct oxidation of CH4 by Fe3+ in paddy fields and indirectly reduces CH4 production by facilitating the combination of Fe oxides with the substrates. These findings deepen our understanding of the mechanisms of CH4 emission in paddy fields and provide new insights for research on carbon sequestration and emission reduction in paddy field ecosystems.

The Effect of Intermittent Subsurface Drip Irrigation on Soil Water Distribution

The Effect of Intermittent Subsurface Drip Irrigation on Soil Water Distribution

Water productivity and yield characteristics of transplanted rice in puddled soil under drip tape irrigation

Lowland rice flooding, while consuming considerable water, has adverse environmental effects, including releasing methane into the atmosphere, aggravating climate change. Several drawbacks can be attributed to water-saving alternatives, such as aerobic rice, whereas rice drip irrigation techniques have been evaluated primarily under aerobic conditions. This study investigated drip tape irrigation technique with different lateral spacings for transplanted rice in puddled paddy soil at the Rice Research Institute of Iran in Rasht over two years (2020 and 2021), compared to intermittent irrigation. In twelve isolated concrete basins, three treatments with lateral spacings of 40 (T40), 60 (T60), and 80 cm (T80), were compared with a fixed five-day period intermittent irrigation (INT). In 2020 and 2021, the INT treatment produced the highest grain yield (3814 and 4758 kg ha−1, respectively) and among drip tape treatments, T40 demonstrated the highest grain yield (3613 and 4020 kg ha−1, respectively), comparable with INT’s yield but with the highest sterile spikelets ratio. In contrast, T80 resulted in the lowest grain weight (2892 and 3653 kg ha−1, respectively) and yield characteristics values, while producing the highest weeds population. Drip tape irrigation significantly reduced water application by 27% and 36% in 2020 and 2021, respectively and T40 achieved the highest water productivity, at 0.68 kg m−3. The economic water productivity estimation of drip tape irrigation can range from 0.11 to 0.51 US$ m−3 in various scenarios, while that of intermittent irrigation remains at 0.25 US$ m−3.

Plant Physiological Performances, Plant Growth, Grain Yield and Methane Emission of Rice (Oryza Sativa L.) in Response to Water Management as Adaptation Strategy for Climate Change

Continuously flooded rice systems are a major contributor to the greenhouse gases (GHG) emissions in the agriculture sector in Malaysia. Intermittent irrigation has been recommended to replace conventional rice water management to save water and reduce GHG emissions without compromising rice yields. This study was conducted in two growing seasons at Malaysia’s largest rice granary area to determine the effectiveness of different water management practices on conserving water, mitigating GHG and maintaining rice grain yields. Three water management treatments were continuous flooding (CF), saturated and wet conditions from transplanting to heading and flooding until maturity (S-F) and continuous saturated and wet conditions (CS). The results showed that S-F and CS reduced water inputs between 15.0-16.8% and 32.0-34.0% as compared to CF, respectively. Water-saving treatments mostly did not significantly affect the plant's physiological performance, plant growth parameters, growth rate, grain yield and yield parameters. The results indicated that soil saturated and wet conditions provided adequate soil moisture content for the plant’s requirement similar to flooding conditions. Maintaining soil at saturated and wet conditions during the vegetative stage reduced 24.18-39.76% of methane emissions. However, maintaining soil at saturated and wet conditions throughout the growing season reduced 34.52-55.08% of methane emissions. In conclusion, intermittent irrigation could be an effective adaptation technique for simultaneously saving water and mitigating GHG while maintaining high rice grain yields in rice cultivation systems.

Intermittent irrigation as a solution for reduced emissions and increased yields in ratoon rice systems

Intermittent irrigation as a solution for reduced emissions and increased yields in ratoon rice systems

Balancing Non‐CO2 GHG Emissions and Soil Carbon Change in U.S. Rice Paddies: A Retrospective Meta‐Analysis and Agricultural Modeling Study

AbstractU.S. rice paddies, critical for food security, are increasingly contributing to non‐CO2 greenhouse gas (GHG) emissions like methane (CH4) and nitrous oxide (N2O). Yet, the full assessment of GHG balance, considering trade‐offs between soil organic carbon (SOC) change and non‐CO2 GHG emissions, is lacking. Integrating an improved agroecosystem model with a meta‐analysis of multiple field studies, we found that U.S. rice paddies were the rapidly growing net GHG emission sources, increased 138% from 3.7 ± 1.2 Tg CO2eq yr−1 in the 1960s to 8.9 ± 2.7 Tg CO2eq yr−1 in the 2010s. CH4, as the primary contributor, accounted for 10.1 ± 2.3 Tg CO2eq yr−1 in the 2010s, alongside a notable rise in N2O emissions by 0.21 ± 0.03 Tg CO2eq yr−1. SOC change could offset 14.0% (1.45 ± 0.46 Tg CO2eq yr−1) of the climate‐warming effects of soil non‐CO2 GHG emissions in the 2010s. This escalation in net GHG emissions is linked to intensified land use, increased atmospheric CO2, higher synthetic nitrogen fertilizer and manure application, and climate change. However, no/reduced tillage and non‐continuous irrigation could reduce net soil GHG emissions by approximately 10% and non‐CO2 GHG emissions by about 39%, respectively. Despite the rise in net GHG emissions, the cost of achieving higher rice yields has decreased over time, with an average of 0.84 ± 0.18 kg CO2eq ha−1 emitted per kilogram of rice produced in the 2010s. The study suggests the potential for significant GHG emission reductions to achieve climate‐friendly rice production in the U.S. through optimizing the ratio of synthetic N to manure fertilizer, reducing tillage, and implementing intermittent irrigation.

Phenology, gas exchange, biomass accumulation, and irrigated rice yield under alternative irrigation managements

AbstractIn Brazil, rice production is predominantly concentrated in the South region, employing a continuous flood irrigation system throughout the crop cycle. However, this irrigation management strategy in the tropical region contributes to low water‐use efficiency owing to adverse climatic conditions. Furthermore, with climate change projections indicating reduced water availability, the study aims to investigate the impact of alternative irrigation management strategies on the phenological development, gas exchange, biomass accumulation, and productivity of tropical irrigated rice. Three alternative irrigation management approaches—intermittent flood irrigation with aeration (IFA), intermittent flood irrigation throughout the growth cycle (IFC), and intermittent flooding up to the flowering stage (IFF)—were compared with the traditional continuous flood irrigation throughout the growth cycle. Phenological data, gas exchange, growth, and productivity dynamics were subject to analysis, providing overarching insights into management practices. Notably, irrigation management exhibited no influence on the vegetative phase of the crop. The implementation of intermittent flood irrigation facilitated a reduction in water supply without compromising the physiological performance of tropical irrigated rice. Strategies promoting judicious water utilization, such as IFA and IFC, can be readily integrated into the cultivation of tropical irrigated rice without detriment to grain yield or harvest index.

Arthroscopically assisted closed reduction for displaced lateral humeral condyle fractures over 4 mm in children

IntroductionLateral humeral condyle fractures (LHCFs) are the most common intra-articular fracture occurring at the elbow in children. Conventional treatment for displaced pediatric LHCFs is open reduction and percutaneous pinning, and few studies have regarded the efficacy of arthroscopic-assisted techniques. We aimed to evaluate the efficacy of anatomic reduction via elbow arthroscopy for pediatric humeral lateral condyle fractures with displacements >4 mm. MethodsA total of 32 children with LHCFs featuring displacements >4 mm were enrolled in this retrospective study. Arthroscopically assisted reduction was performed as the primary treatment approach. For simple displaced fractures, arthroscopically assisted reduction was directly employed with intermittent intra-articular irrigation. For fractures with distal fragment rotation, the rotated fragments were firstly realigned into a simple displaced position under fluoroscopy before proceeding with arthroscopy. The success rate of arthroscopically assisted reduction and clinical outcomes at the latest follow-up were assessed, and complications related to the procedure were monitored. ResultsTwenty-nine of 32 (90.62 %) enrolled cases were successfully treated with arthroscopically assisted reduction. Failure cases were attributed to soft tissue swelling, which hindered the manipulation of the fracture fragments for reduction or fixation. We subsequently adapted the surgical procedure, resulting in a significant increase in the success of arthroscopically assisted reduction, rising from 71.43 % to 96 %. Among the 29 successfully treated cases, excellent functional outcomes were observed in 18 cases, and 11 cases showed good outcomes. Regarding the carrying angle outcomes, 28 patients achieved excellent results, with one patient having a good outcome. The most frequent radiographic finding after surgery was lateral spur formation without further negative effects. Only one case of superficial infection occurred, promptly healing with topical management. No significant complications such as neurovascular injury or compartment syndrome were observed. ConclusionArthroscopically assisted anatomic reduction provides a promising alternative to open reduction for LHCFs with displacements exceeding 4 mm, offering direct visualization of the articular surface and minimizing soft tissue dissection.

Effects of Climate Change on Rice Yield in Northern Areas of Iran: Humidity as a Large Variability of Climate

Climate has a significant effect on social and economic activities, and currently is a major problem, especially in agricultural yields. This study used two types of climatic and agricultural data. To simulate the climate for the next 30 years (2021-2050) from daily temperature and precipitation data for the base period 1986-2015, Reanalysis Atmospheric Data (NCEP) as observational predictors data and CanESM2 Atmospheric General Circulation Model data with two scenarios RCP 2.6 and RCP 8.5 were used as large-scale predictors. The data is related to the Rasht Rice Research Center field experiments. The results abstained from simulations showed that in future climate conditions, the average temperature would be 0.7 to 0.9°C, and precipitation would be 20 to 70 mm in the study area based on both emission scenarios compared to the base period (1986-2015) increases. The effect of climate change on the rice yield on the planting date of June 5, especially in the eastern parts of the region, is unfavourable in the future. At the regional level, in all planting dates, the length of the rice growth period in the future period (2021-2050) will decrease by 2 to 4 days compared to the base period. The planting date treatment of 5 May with a density level of 50 plants per square meter, a nitrogen fertiliser level of 195 kg per hectare with an intermittent irrigation regime (8-day cycle) is the most suitable adaptation strategy to reduce the negative effects of climate change and increase rice yield in the entire surface of the coastal area in the Caspian Sea.

Effects of straw addition on biological nitrogen fixation under continuous and intermittent flooding irrigation in a rice cropping system

Both straw addition and water management affect biological nitrogen fixation (BNF), but it is still unclear how straw addition impacts BNF under continuous or intermittent flooding irrigation in a rice cropping system. A 15N2-labelling chamber system placed in a rice field was used to evaluate BNF under straw addition with continuous or intermittent flooding irrigation for 90 days. The nitrogenase reductase (nifH) gene and reverse transcription gene (cDNA) in the soil were amplified using Real-time polymerase chain reaction (qPCR), and nifH gene high-throughput sequencing was applied. The BNF in the straw addition treatment (14.0 g straw added to 1.40 kg soil) under continuous flooding (14.3 kg ha-1) was 116% higher than that under intermittent flooding (6.62 kg ha-1). Straw addition and continuous flooding showed significant synergistic effects on BNF and the gene copy numbers of nifH DNA and nifH cDNA. The increase in BNF was mainly due to the increase in the abundance of heterotrophic diazotrophs such as Desulfovibrio, Azonexus, and Azotobacter. These results indicate that straw addition under continuous flooding stimulates BNF relative to intermittent flooding, which may ultimately lead to a rapid enhancement of soil fertility.