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Wet direct‐seeded rice (WDSR) is considered as a practicable substitute to transplanted‐flooded rice (TFR) because it copes with labor and water shortages, and reduces greenhouse gas emissions. However, the differences between WDSR and TFR in leaf senescence after flowering and the associated mechanisms have rarely been identified. In this study, the growth dynamics, SPAD value of flag leaf, dry matter accumulation and translocation, and the contents of plant hormones (ABA, CTKs, and GA3) in WDSR and TFR rice flag leaves after flowering were compared during the rice‐growing seasons of 2013, 2014, and 2018. The results showed that leaf senescence after flowering in WDSR was faster in comparison with TFR. The amount of dry matter acquired after flowering (ΔW) in WDSR was significantly lower and might be related to the faster leaf senescence after flowering in WDSR compared with TFR. The CTK content in flag leaves after flowering was lower in WDSR than in TFR, and CTK content declined earlier than SPAD value, which implied that decrease in CTK content could be a possible reason for the early leaf senescence in WDSR. In conclusion, faster leaf senescence after flowering in WDSR was mainly attributed to the decline in leaf CTK content. 1. Faster leaf senescence after flowering in WDSR as compared with TFR. 2. The differences in leaf senescence rates between WDSR and TFR might be attributed to the changes in contents of endogenous hormones, which then altered the accumulation and translocation of carbohydrates within the plants. 3. Techniques for delaying the rapid leaf senescence after flowering in WDSR should be developed in future.

An experiment involving four soils and three irrigation-water As concentrations was conducted in undisturbed soil columns during 2004-2006, with Boro (winter dry-season, flood-irrigated rice, using As-contaminated water for irrigation), T. Aman (summer monsoon, rain-fed flooded rice), Boro, and T. Aman rice grown in sequence, to examine the fate of added As from irrigation water during flooded rice culture. The As content in the column leachate represented only 1.17-5.08% of the total applied As, indicating the substantial build-up of soil As. Most of the irrigation-applied As remained in the zone of maximum root activity at the top 0-15 cm of soil. Increased As concentrations in soil from the application of As-contaminated water resulted in substantially reduced rice-grain yields and increased As concentrations in rice grain and straw, indicating the potential hazards of continued irrigation with As-contaminated water to sustainable rice production and food security in South Asia.

The study aimed to design efficient and sustainable phosphorus (P) management modules for non-flooded rice [system of rice intensification (SRI)]-lentil systems on an alkaline Fluvisol . For this, seven variable P management treatments i.e., one P control (P [0–0] ) [subscript value represents kg P ha −1 to non-flooded rice followed by lentil], three sole fertilizer-P treatments with variable rates to component crops (P [22–22] , P [33–11] , P [11–33] ), three integrated treatments ([P 11–11  + phosphate solubilizing bacteria (B)], [P 16.5–5.5  + rice residue recycling (RR) + B], [P 5.5–16.5  + lentil residue recycling (LR) + B]) along with recommended sole fertilizer-P rate to flooded rice-lentil system (P [22–22]FR ) as conventional practice were evaluated for soil–plant P relations, crop yield, nutrient use efficiency and budgeting. The rice residue recycling integrated treatment (P [16.5–5.5]  + RR + B) increased P availability in both rice (5–6%) and lentil (9–10%) seasons, subsequently resulting in increased agronomic P use efficiency (175–183%) and system productivity (7%) over the recommended sole fertilizer-P treatment P [22–22] ( p  < 0.05). The system-based sole fertilizer-P treatments (P [22–22] , P [33–11] , P [11–33] ) did not differ in system productivity; however, a higher rate of fertilizer-P for rice (33 kg P ha −1 ) increased its yield. Both crop residue recycling integrated treatments resulted in a marginal negative P balance (− 2.5 to − 1.6 kg P ha −1 y −1 ), while the sole fertilizer-P treatments led to a higher positive P balance (> + 14 kg P ha −1 y −1 ). Hence, system-based rice residue recycling integrated P management could be an improved P management option for non-flooded rice-lentil systems on alkaline soils given that a positive P balance is maintained.

Rice, the predominant food crop in India, is being grown traditionally with improper plant nutrient management mostly under the flooded situation. Recent advancement in research on crop science focuses on water-saving rice technologies for maximization in crop and water productivity under the backdrop of a shrinking water resource base for ensuring environmental and agricultural sustainability. Under this situation, an experiment was conducted in two consecutive years in a split-plot design keeping rice cultivation methodologies, viz., aerobic culture, System of Rice Intensification (SRI), and conventional flooded culture in main plots and integrated plant nutrient management (INM) treatments in sub-plots. The experiment was aimed at understanding the effects of different rice production systems and INM on nutrient content, uptake, and use efficiency. The change in soil quality parameters was also studied to understand the impact of crop establishment methods (CEM) and INM options. Significant reduction (p ≤ 0.05) in nutrient uptake and use efficiency was observed under aerobic culture compared to SRI and flooded method, although aerobic culture showed the highest physiological nitrogen use efficiency. Post-harvest available Fe status was significantly lower in aerobic rice (mean 10.39 ppm) compared to other crop establishment technologies; however, Zn status was higher in aerobic rice over the flooded situation. Although available potassium was not affected due to rice cultivation methods, available nitrogen and phosphorus status were influenced remarkably. Soil microbial quality was improved in aerobic rice in comparison to flooded rice. SRI proved to be the most efficient rice establishment method for enhancement in nutrient uptake, use efficiency, and enrichment of soil chemical and microbiological quality. Irrespective of crop culture, integrated plant nutrition in rice improved the nutrient uptake, use efficiency, and soil quality parameters. The study revealed that, under the alluvial soils of the Indo-Gangetic Plains of Eastern India, SRI can be considered as a water-saving rice production method. The method can also improve nutrient uptake, efficiency, and soil quality parameters if proper INM is adopted.

Denitrification has long been considered a major mechanism of N loss when N fertilizer is applied to flooded rice paddies. However, the direct determination of denitrification in soils is almost impossible because of the high atmospheric background of dinitrogen (N₂). Dissolved N₂ in a small water sample can be rapidly and precisely measured through membrane inlet mass spectrometry (MIMS). This study is the first to directly measure N₂ flux through MIMS in flooded rice paddy plots that received different amounts of urea. Ammonia (NH₃) volatilization was measured simultaneously to verify whether NH₃ volatilization and denitrification are complementary loss mechanisms. The average cumulative N₂–N loss measured by MIMS 21 days after fertilization was 4.7 ± 1.7 % of the applied N, which was within the range of the reported values obtained by cumulative recovery of (N₂ + N₂O)–¹⁵N and ¹⁵N-balance technique. Underestimation or overestimation of denitrification can be prevented in MIMS given that N₂ can be measured directly without ¹⁵N-labeled fertilizer. A good positive correlation was found between the dissolved in situ N₂ concentrations of floodwater and the denitrification rates of intact soil cores. Urea incorporation reduced NH₃ volatilization unlike surface broadcasting. However, urea incorporation significantly increased cumulative N₂–N loss during the 21 days after fertilization. Correlation analysis showed that nitrate (NO₃ ⁻–N) concentration in floodwater could be the primary restricting factor for soil denitrification in the experimental field. Results suggest that MIMS is a promising technique for the measurement of denitrification in a flooded rice paddy.

Abstract High-temperature events are projected to increase in frequency under future climate scenarios, threatening rice yields globally. This study investigated the physiological and molecular responses of two Brazilian flooded rice varieties, IRGA 428 and BR-IRGA 409, during the anthesis stage under high-temperature stress, aiming to uncover mechanisms of heat tolerance. Plants were exposed to a daytime temperature of 38°C for 7 h across 3, 5, or 7 days. Prolonged heat stress led to a significant reduction in filled grain in both cultivars, although BR-IRGA 409 demonstrated greater heat tolerance, particularly under 3 days of stress, as it maintained higher spikelet fertility compared to IRGA 428. Comparative transcriptome analysis revealed that BR-IRGA 409 had more differentially expressed genes in response to heat stress, including a significant upregulation of canonical heat-responsive genes such as heat shock factors, heat shock proteins, and peptidyl-prolyl isomerase FK506-binding proteins (FKBPs). Furthermore, BR-IRGA 409 displayed enhanced modulation of the mitochondrial electron transport pathway, which is crucial for adenosine triphosphate (ATP) synthesis and cellular energy production. Interestingly, while photosynthetic performance varied between cultivars, only a few genes associated with photosynthesis were significantly altered in response to heat stress. Instead, BR-IRGA 409 displayed a higher basal expression of photosynthesis-related genes, suggesting that this pre-adaptation might mitigate heat stress impacts on photosynthesis. The ability to preserve functional photosynthetic activity is critical for sustaining the energy-intensive process required to cope with heat stress. This study highlights the difference between the varieties in their response to heat stress and identifies candidate molecular and physiological mechanisms that contribute to maintaining cellular energy homeostasis and heat tolerance in Brazilian rice, providing valuable insights for crop improvement strategies. In rice, high temperatures during flowering can reduce yields. However, genotype-specific variation can be leveraged to develop heat-tolerant varieties. Brazilian rice offers an untapped resource for genotypic diversity. This study examined how two Brazilian rice varieties respond to heat stress. BR-IRGA 409 showed greater tolerance than IRGA 428, maintaining higher grain fertility and activating more heat-responsive genes. The results suggest that maintaining energy production and a strong baseline of photosynthesis-related activity may help protect rice plants from heat damage, offering useful targets for breeding heat-tolerant varieties.

Original fish-farming developments occur in west-central and south-western Côte d’Ivoire and in the forest area of the Republic of Guinea. Oreochromis niloticus and Heterotis niloticus are the main species produced in dam ponds with little or no feeding. Flooded rice is often grown here. The products supply local markets. In this article, we seek to understand the innovation trajectories that have led to three practices characteristic of these systems: ‘large tilapia production with little feed in dam ponds’, ‘tilapia and Heterotis polyculture’ and ‘flooded rice cultivation in ponds’. We then assess the contribution of these innovations to ecological intensification. The practices that form the basis for current developments were developed in the 1990s on family farms. The suitability of technical choices at certain key moments depended entirely on the fish farmers who judged the tested techniques on their own terms. Our assessment shows that these farmers have contributed positively to ecological intensification. They suffer from recurrent cash flow problems and have thus natural resources and ecological functions in their fish farming system: stocking density to make the best use of the natural trophic resources, improved by polyculture and additional rice production that is more efficient than traditional lowland rice production. The promotion of reliance on existing know-how and anchoring in local culture strengthen the contribution to these systems’ ecological intensification. The analysis shows that this development of integrated commercial fish farming in family farms questions ecological intensification and innovation in aquaculture.

Climatic variations have created many challenges for farmers, but the most important one is the change in the dynamics of nutrient uptake by plants. Nutrients that were sufficient in soil are now found deficient, an issue that needs more focus in order to sustain crop productivity. Magnesium is very important plant nutrient that has a direct role in chlorophyll synthesis and interacts with other nutrients to manage physiological mechanisms. We designed field experiments focusing on the foliar application of magnesium at different growth and reproductive stages of a rice crop. Results reveal that the combination of rice cultivation system and magnesium application, i.e., flooded rice with Mg application at seedling + tillering + panicle initiation (F6T2), significantly improved crop growth and exhibited noticeable results in crop yield and grain quality. Moreover, the rice crop also recorded the highest benefit cost ratio (BCR) when kept flooded and fertilized with Mg at three stages; viz seedling, tillering, and panicle initiation; during both the years. Combined application of magnesium at growth and reproductive stages improved crop performance both in aerobic as well as in flooded rice, but the crop grown under flooded condition showed accelerated performance in both cropping seasons, which reflects its viability and economic feasibility.

Improved irrigation management is identified as a potential mitigation option for methane (CH4) emissions from rice (Oryza sativa). Furrow-irrigated rice (FR), an alternative method to grow rice, is increasingly adopted in the Mid-South U.S. However, FR may provide a potential risk to yield performance and higher emissions of nitrous oxide (N2O). This study quantified the grain yields, CH4 and N2O emissions from three different water management practices in rice: multiple-inlet rice irrigation (MIRI), FR, and FR with cereal rye (Secale cereale) and barley (Hordeum vulgare) as preceding winter cover crops (FRCC). CH4 and N2O fluxes were measured from May to September 2019 using a static chamber technique. Grain yield from FR (11.8 Mg ha−1) and MIRI (12.0 Mg ha−1) was similar, and significantly higher than FRCC (8.5 Mg ha−1). FR and FRCC drastically reduced CH4 emissions compared to MIRI. Total seasonal CH4 emissions decreased in the order of 44 > 11 > 3 kg CH4-C ha−1 from MIRI, FR, and FRCC, respectively. Cumulative seasonal N2O emissions were low from MIRI (0.1 kg N2O-N ha−1) but significantly higher from FR (4.4 kg N2O-N ha−1) and FRCC (3.0 kg N2O-N ha−1). However, there was no net difference in global warming potential among FR, FRCC and MIRI. These results suggest that the increased N2O flux from furrow-irrigated rice may not greatly detract from the potential benefits that furrow-irrigation offers rice producers.

After flooding in rice crops, the Fe 3+ ions from iron oxide minerals are reduced to Fe 2+ in the anaerobic conditions, making it soluble. The excess of Fe 2+ in soil solution can be toxic to plants, resulting in decreasing rice yield. Pyrolyzed materials from rice crop residues, such as rice husk, can be an environmentally friendly option to reduce iron availability in soil solution, provided they have appropriate chemical and physical characteristics regarding iron adsorption. In this study, rice husk biochar (RHB) and rice husk ashes (RHA1 and RHA2) were characterized regarding physical and chemical characteristics and the iron adsorption capacity. The different oxygenation conditions in obtaining the materials resulted in chemical and physical differences (e.g., biochar carbon content of 46% and ashes of 16% and 0.93%), but there were no significant differences related to iron adsorption capacity in aqueous solution. The iron adsorption capacity of the biochar was 5.53 mg Fe 2+ g −1 and of the ashes was 6.74 and 7.22 mg Fe 2+ g −1 for the two materials tested, which demonstrates potential of these materials to mitigate iron toxicity in flooded rice crops.