Background and objectives Increased upper-plant load in high-yielding rice populations may exacerbate lodging risk. However, the relationships linking root morphology and basal internode traits to theoretical grain yield and lodging risk remain unclear in cold-region japonica rice under integrated management. This study compared theoretical grain yield and lodging index among six integrated management treatments and identified the root and basal-internode trait relationships associated with relatively high yield and low lodging risk. Methods A field experiment was conducted from 2023 to 2025 using the japonica rice cultivar Jijing 88. Six integrated management treatments (S0M1, S0M2, S0M3, SM1, SM2, and SM3) were evaluated. Root morphological traits across soil layers, plant architecture, upper-plant load-related traits, and structural, compositional, and mechanical traits of the second basal internode were measured; theoretical grain yield and lodging index were calculated. Partial least squares structural equation modeling (PLS-SEM) was used to construct a trait-pathway model. Results The six integrated management treatments produced distinct theoretical grain yield–lodging index combinations. SM3 achieved the highest theoretical grain yield by increasing panicle number. Its three-year mean panicle number and theoretical grain yield were 6.9% and 3.0% greater, respectively, than those of SM2, whereas its lodging index was 5.1% higher. Although SM2 had a slightly lower theoretical grain yield than SM3, the breaking moment and bending stress of its second basal internode were 6.6% and 4.1% greater, respectively. SM2 also had the highest root length density, root surface area density, and root volume density in both the 0–10 and 10–20 cm soil layers and generally more favorable structural and compositional traits of the second basal internode. PLS-SEM associated root morphology with theoretical grain yield through yield components and with lodging index through second basal internode structural traits and breaking force. Conclusions and significance Relatively high theoretical grain yield and low lodging risk occurred together in treatments with favorable root morphology and stronger structural, compositional, and mechanical traits of the second basal internode despite a relatively high upper-plant load. SM2 combined a relatively high theoretical grain yield with the lowest lodging index. SM3 had the highest theoretical grain yield, but its second basal internode provided less mechanical support than that of SM2. Under the tested conditions, SM2 was therefore the more suitable treatment when both theoretical grain yield and lodging resistance were considered, whereas basal culm strengthening remains the main improvement target for SM3.

Soil degradation poses a significant threat to agricultural sustainability and food security, with straw incorporation emerging as an effective measure for sustainable agricultural development. However, the synergistic effects of adjusting straw carbon-to-nitrogen (C/N) ratios on soil quality and rice root systems remain unclear. To address this knowledge gap, we conducted a four-year field experiment employing a single-factor randomized block design. Conventional cultivation (CK) was used as the control, and five treatments were established under straw incorporation conditions: no nitrogen application (SN0) and four C/N ratios of 35:1 (SN1), 31:1 (SN2), 27:1 (SN3), and 23:1 (SN4). The study aimed to investigate the impact of regulating straw C/N ratios on soil quality, root growth, and yield, while elucidating their interrelationships. Results demonstrate that straw incorporation significantly enhances the soil quality index, with improvements ranging from 58.51 % to 173.79 %. Low C/N treatments mitigate the inhibitory effects of straw incorporation on root growth during the tillering stage and promote mid-to-late stage root development through soil quality optimization, leading to a significant 10.74 % yield increase in SN3. Linear regression analysis reveals a significant positive correlation between the soil quality index and the sustainability yield index. Partial least squares path modeling indicates that soil biological properties are the primary drivers, directly influencing the soil quality index and indirectly affecting rice yield. Various indicators exhibit unimodal responses with decreasing C/N ratios, reaching a threshold at SN3. In conclusion, SN3 achieves a synergistic enhancement of the soil quality index and root growth, consequently improving rice yield and stability. These findings provide valuable guidance for enhancing soil quality and developing sustainable agriculture.

To address the development dilemma of ''high yield, high resource consumption'' in the cold-region rice cropping areas of Northeast China and to respond to the national ''dual carbon'' strategy, this study aimed to systematically evaluate the sustainability of different rice cultivation models by integrating water, carbon, energy, and economic footprints. The goal was to identify an optimized path that balances food security, environmental friendliness, and economic feasibility. A field experiment was conducted from 2019 to 2020 in Changchun, Jilin Province, comparing four cultivation models: traditional transplanted flooded rice (TFR), wet direct-seeded flooded rice (WDSF), dry direct-seeded flooded rice (DDSF), and dry direct-seeded rice with alternate wetting and drying (DDSA). A comprehensive evaluation framework was established, incorporating water footprint (WF), carbon footprint (CF), energy footprint (EF), and net ecosystem economic benefit (NEEB). A bivariate sensitivity analysis was introduced to explore the impact of carbon and rice price fluctuations on economic decision-making. The DDSA model exhibited the optimal environmental performance, with its total water and carbon footprints reducing by 42.4% and 29.6%, respectively, compared to TFR. This was primarily attributed to a 95% reduction in methane (CH4) emissions and significant blue water savings. However, it suffered from a significant yield loss and increased nitrous oxide (N2O) emissions, revealing a trade-off between CH4and N2O emissions. Although the DDSF model showed considerable emission reduction potential, its severe yield loss led to the poorest NEEB, highlighting a sharp conflict between environmental improvement and economic viability. The WDSF model maintained a relatively high yield while achieving the highest NEEB (a 5.9% increase over TFR), demonstrating the best overall benefits. Sensitivity analysis indicated that the NEEB of the WDSF model remained the highest across carbon prices (0–300 CNY t-1CO2-eq) and rice price fluctuations (±20%), exhibiting high robustness. Under scenarios of normal rice prices with a carbon price exceeding 250 CNY t-1CO2-eq, or a 20% drop in rice prices, the economic competitiveness of the DDSA model would surpass that of TFR. Under the conditions of this study, based on the four-dimensional assessment, the WDSF model achieves synergistic optimization of environmental and economic benefits while ensuring a relatively high yield, making it the most feasible and balanced model for promoting the sustainable transformation of cold-region rice cultivation at present. Future efforts should focus on enhancing the yield of dry direct-seeded rice through technological breakthroughs and leveraging policy levers such as carbon pricing to activate the economic value of its environmental benefits, ultimately promoting the transition of cold-region rice production towards a sustainable, ''eco-value-added'' paradigm.

ObjectiveTo investigate the comprehensive effects of nitrogen application level on rice yield and quality, and identify the key factors influencing the synergistic improvement of rice yield and quality. MethodUsing japonica rice cultivars ‘Jiyu Japonica’ and ‘Wuyou Rice No. 4’ as test materials from 2021 to 2022, three nitrogen application levels were set at 0, 150, and 300 kg/hm2. The effects of nitrogen application levels on rice yield, yield components, and quality indicators were analyzed. ResultNitrogen application increased grain protein content and yield, but reduced amylose content, taste value and gel consistency. Appropriate nitrogen application enhanced the activities of ADP glucose pyrophosphorylase (AGP), starch synthase, starch branching enzyme, and sucrose synthase during the grain filling stage, increased total starch content in grains, raised setback viscosity and pasting temperature, as well as decreased peak viscosity, final viscosity and breakdown viscosity. Compared with non-nitrogen treatment, the 150 kg/hm2 nitrogen application level treatment obviously increased the activities of AGP, starch branching enzyme, starch synthase and sucrose synthase, raised total starch content by an average of 18.21%, and increased yield by 32.50%. A comprehensive grain yield and quality index (GYQI) was derived through principal component analysis, with the treatments ranked as 150 kg/hm2 > 300 kg/hm2 > 0 kg/hm2 in terms of GYQI. Further random forest analysis indicated that grains per panicle, starch synthase activity, and peak viscosity contributed the most to GYQI, followed by yield and glutelin content. Although the 150 kg/hm2 treatment reduced taste value, it significantly increased grains per panicle, starch synthase activity, and glutelin content, which had higher contribution weights. The positive effects of these three factors far outweighed the negative impact of taste value reduction, ultimately resulting in the highest GYQI under the 150 kg/hm2 condition. ConclusionGrains per panicle, starch synthase activity, and peak viscosity are the dominant factors influencing GYQI. A nitrogen application rate of 150 kg/hm2 achieves the maximum grains per panicle, the strongest starch synthase activity, and a relatively high peak viscosity, and is identified as the optimal level for the synergistic improvement of rice yield and quality. In practical production, key indicators such as grains per panicle, starch synthase activity, and peak viscosity shall be prioritized for optimization to achieve coordinated enhancement of both yield and quality.

Objective The lodging problem restricts the development of the rice industry. This study screened japonica rice varieties with strong lodging resistance and key indicators for lodging resistance identification in japonica rice, and japonica rice varieties with different lodging resistances were further selected to compare the differences in their physicochemical properties, which could provide high-quality parental resources for the breeding of lodging-resistant japonica rice varieties, and offer theoretical basis for optimizing breeding strategies and analyzing the cultivation regulation mechanism of lodging resistance. Method This study took 50 japonica rice germplasm resources as experimental materials, and determined 14 lodging resistance traits. Through comprehensive genetic diversity index analysis and comprehensive evaluation, the 50 japonica rice germplasm resources were rated and classified, and the grey correlation analysis was used to screen the key indicators for identifying lodging resistance. On this basis, japonica rice varieties with different lodging resistances were further selected: Jiudao 325 (lodging-resistant type), Jiyujing (relatively lodging-resistant type), and Wuyoudao 4 (lodging-sensitive type) as experimental materials. Subsequently, the stem characteristics, material metabolism, and gene expression characteristics were systematically analyzed to deeply explore the physiological mechanism of lodging resistance in japonica rice. Result The coefficient of variation for lodging resistance traits among the 50 japonica rice varieties ranged from 5.38% to 21.08%, with genetic diversity indices between 1.76 and 2.06. Principal component analysis (PCA) extracted four principal components, and the comprehensive evaluation D-values calculated using the membership function method ranged from 0.12 to 0.72. Cluster analysis classified the 50 germplasms into three groups: Group 1 (30%) as lodging-resistant, Group 2 (32%) as moderately lodging-resistant, and Group 3 (38%) as lodging-sensitive. Grey relational analysis indicated that the length and wall thickness of the second basal internode (N2) exhibited the highest correlation with the D-value. The correlation degree between spike weight, the third basal internode (N3) length, N2 length and N2 intercellular wall thickness and japonica rice yield was the highest. Compared with lodging-sensitive varieties, lodging-resistant and moderately lodging-resistant varieties showed significant reductions in N2 internode length by 37.02% and 9.09%, respectively, accompanied by increases in large vascular bundle area by 20.55% and 6.81%, respectively, and cortical thickness by 15.04% and 12.86%, respectively. Upregulated expression of cellulose synthase and lignin synthase genes led to increased cellulose content by 37.30% and 9.19%, respectively, and lignin content by 49.32% and 17.71%, respectively, with Guaiacyl lignin (G-type) and Syringyl lignin (S-type) lignin monomers accounting for 92.36%-93.90% of total lignin. Conclusion This study screened elite germplasm resources with excellent lodging resistance traits, such as Jiudao 325, Qinglin 168, and Hajingdao 1. The internode length and internode wall thickness of N2 could be used as key indicators for evaluating and identifying high-yield lodging resistance. Compared with lodging-sensitive japonica rice varieties, lodging-resistant and moderately lodging-resistant varieties upregulated the expression levels of genes related to cellulose and lignin synthase by promoting the biosynthesis of cellulose, lignin monomers, and lignin. Meanwhile, they accumulated higher contents of starch and soluble sugars by optimizing the physical and anatomical structural characteristics of stems, thereby enhancing the lodging resistance of japonica rice.

IntroductionAbscisic acid (ABA) is a key regulator of seed dormancy and stress responses, but its effects on seed germination depend on concentration, developmental stage, and environmental conditions. This study investigated whether exogenous ABA seed priming could alleviate low-temperature-induced inhibition of germination and improve early seedling establishment in direct-seeded rice.MethodsRice seeds were primed with different ABA concentrations and then exposed to low-temperature stress during germination and early seedling growth. Germination performance, reserve mobilization, respiratory metabolism, antioxidant responses, endogenous ABA and GA contents, selected SOD-related gene expression, and seedling growth traits were analyzed.ResultsABA seed priming showed concentration-dependent effects, with 40 μmol L-1 ABA exhibiting the most favorable overall performance under low-temperature conditions. Compared with the low-temperature control, low-to-moderate ABA priming improved germination performance, enhanced α-amylase activity, increased soluble sugar accumulation, and increased respiratory rate. ABA priming also enhanced antioxidant enzyme activities and reduced H2O2 and malondialdehyde accumulation. Expression analysis of selected SOD-related genes showed gene-specific responses rather than uniform transcriptional activation. In addition, ABA seed priming was associated with lower endogenous ABA accumulation, higher GA content, and a reduced ABA/GA ratio under low-temperature stress. The beneficial effects observed during germination were partly maintained at the three-leaf stage, particularly in root growth, chlorophyll accumulation, and antioxidant capacity.DiscussionThese results suggest that appropriate ABA seed priming can improve germination and early seedling establishment under low-temperature stress in direct-seeded rice, mainly through physiological adjustments involving reserve mobilization, oxidative damage mitigation, antioxidant responses, and endogenous hormonal status. Further studies involving GA metabolism genes, ABA signaling components, and additional mechanistic validation are needed.

The high basal fertilizer model is mismatched with the requirements of direct-seeded rice during the germination stage in cold regions, which exacerbates the combined stress of low temperature and urea hydrolysis products, thereby limiting grain yield and nitrogen use efficiency. Using the low-temperature-tolerant cultivar "Jijing 305" as the experimental material, this study conducted an indoor controlled-temperature culture experiment (16 degrees C/20 degrees C & times; urea levels of 0 (N0), 29.6 (N1), 59.2 (N2) mg kg-1) and a field nitrogen management experiment (with a total nitrogen application of 150 kg ha-1, four modes were set: basal:tillering:panicle fertilizer = 0:0:0 (N0:0:0), 2:4:4 (N2:4:4), 4:3:3 (N4:3:3), and 6:2:2 (N6:2:2)) to explore the rules of seed germination, seedling establishment, and yield formation in direct-seeded rice. The results showed that at 16 degrees C, the N1 treatment optimized the GA/ABA balance, promoted alpha-amylase activity and soluble sugar accumulation, and enhanced the activities of hexokinase (HK), phosphofructokinase (PFK), and pyruvate kinase (PK), thereby significantly increasing the seed vigour index. At 20 degrees C, the germination response exhibited a pattern characterized by the synergistic involvement of energy metabolism and hormonal regulation; however, the N2 treatment, despite a higher nitrogen supply, did not further improve the hormonal balance or vigour index. In the field experiment, compared with the N4:3:3 and N6:2:2 treatments, the N2:4:4 treatment increased the seedling emergence rate by 6.72% and 17.46%, respectively, optimized the root architecture (increased root length, surface area, and dry weight, with decreased root diameter), and significantly increased the dry matter accumulation rate and total amount during the late growth stage. Ultimately, it synergistically increased the panicles, seed-setting rate, and 1000-grain weight, resulting in yield increases of 5.15% and 8.37% compared with N4:3:3 and N6:2:2, respectively. In conclusion, under the conditions of this study, the regulatory effect of moderate urea on germination physiology exhibits significant temperature dependence, whereas reducing basal nitrogen and postponing topdressing optimizes root establishment and source-sink relationships, providing a theoretical basis for stress-resistant and stable-yield cultivation of direct-seeded rice in cold regions.

Rice yield could be increased by apply higher level of nitrogen fertilizer, but excessive use of nitrogen fertilizer will cause plant lodging. This study aimed to investigate the effect of nitrogen application rate on lodging resistance of rice stems. Four japonica rice varieties with different lodging resistance were used, and six nitrogen fertilizer levels were set up to analyze the morphological structure, mechanical properties, and chemical components of rice stems under such treatments. The dynamic changes of lodging resistance of rice stems under different nitrogen fertilizer application rates were exanimated. The study provide valuable insights for improving lodging resistance and subsequently increasing rice yield. The results indicated that WYD4 exhibited the highest yield under the N1 treatment, whereas JYJ, JJ 525, and JND 667 achieved the highest yield under the N2 treatment. The lodging index of rice varieties fluctuated at the filling stage, peaking 30 days after heading. Moreover, the lodging index increased progressively with higher nitrogen fertilizer application rates, reaching its maximum under the N5 treatment, which corresponded to an increased lodging risk. Specifically, the lodging index under the N5 treatment increased by 0.63–1.21 times compared to the optimal nitrogen fertilizer level. Concurrently, the fracture bending point (s) and lodging resistance of the rice stem exhibited a gradual decline. Additionally, plant height, internode length, and barycenter height significantly increased with rising nitrogen application rates and were positively correlated with the lodging index. Conversely, the wall thickness of the second basal node decreased and showed a negative correlation with the lodging index. Furthermore, the contents of lignin, cellulose, soluble sugar, and starch in the second internode diminished with increasing nitrogen rates, and were positively correlated with the breaking moment.

The yield of direct-seeded rice (DSR) was constrained by inadequate grain filling. Recent studies have indicated that paclobutrazol application plays a significant role in enhancing crop agronomic traits and increasing yield. This study aimed to examine the effects of paclobutrazol seed soaking (PSS) on non-structural carbohydrate accumulation and grain enrichment in DSR, potentially providing a theoretical foundation for achieving high-yield DSR cultivation. The experiment utilized two rice varieties, Jiyujing (JYJ) and Jijing305 (JJ305), with seeds soaked in paclobutrazol concentrations of 0 mg L-1 and 100 mg L-1 . PSS demonstrated increased chlorophyll content, net photosynthetic rate, and leaf area, as well as an extended photosynthetic function period during the filling stage. It also elevated soluble sugar and starch contents in the flag leaf (during the filling stage) and stem sheath (after heading), decreased starch content in the top panicle while increasing it in the middle and lower panicle during the filling stage, and enhanced spikelet per unit area and seed setting rate, thereby improving DSR yield. In conclusion, PSS enhanced the photosynthetic capacity of DSR during the filling stage, coordinated the filling process of superior and inferior grains, maintained source-sink balance, and facilitated stable and orderly filling, ultimately resulting in improved yield.

Context or problem: Lodging is an important limiting factor for increasing yield and quality in direct-seeded rice (DSR) production. Optimizing crop plant types and the light environment within the canopy are crucial for improving lodging-related traits, and increasing yield. It is imperative to thoroughly investigate the correlation between basal internodes strength of DSR and canopy structure needs to be studied in depth. Objective or research question: The objectives of this study were to explore the mechanism of lodging resistance in DSR as affected by plant types and the light environment within the canopy, especially its related leaf traits changes and response to foliar application of paclobutrazol. Methods: In this study, a field experiment was conducted in Changchun, Jilin Province, China, by using two japonica rice varieties Jiyujing (JYJ) and Jijing305 (JJ305), with four different foliar application of paclobutrazol rates (0 mg L- 1, P0; 200 mg L- 1; P1; 300 mg L- 1; P2; 400 mg L- 1, P3) in 2021 and 2022. Results: Foliar application of paclobutrazol increased the grain yield of DSR by enhancing the chlorophyll content (SPAD) of the upper three leaves and net photosynthetic rate of the top leaves. Compared to the P0 treatment, the yield under the P1 treatment increased by 10.62 %-14.11 %. Principal component analysis revealed that lodging resistance of DSR was closely related to the photosynthetic performance of leaves and canopy light transmittance. Foliar application of paclobutrazol reduced the leaf angle of the upper three leaves of DSR, resulting in a more compact plant structure and improving light transmittance at the lower canopy levels, ultimately optimizing stem structure and internode quality. The increase of the SPAD value of the upper three leaves and net photosynthetic rate of the top leaves under paclobutrazol treatments also led to increased cellulose and lignin accumulation, enhancing the breaking strength of the basal internode and reducing lodging rate. Compared to the P0 treatment, the lodging rate of DSR decreased by 10.4 %-16.10 %. Conclusions and Implications: Foliar application of paclobutrazol improved the canopy light transmittance and leaf photosynthetic capacity by regulating leaf morphology and stem structure, reducing the lodging risk and ensuring the formation of DSR yield. Our results will assist breeders in breeding lodging-resistant and agronomists in improving field management practices for low lodging rate and high yield, and it will be illuminating for the resistance-lodging cultivation of DSR.

IntroductionDirect-seeded rice is characterized by simplicity, efficiency, and environmental friendliness, with its planting area progressively expanding. However, inappropriate seeding rates can result in issues such as lodging and reduced productive tillers, thereby constraining yield potential. Consequently, this study investigated the response mechanisms of tillering, the heterogeneity between main stems and tillers, and the susceptibility to lodging under varying seeding rates in direct-seeded rice. The aim was to identify an appropriate seeding rate that maximizes yield while mitigating lodging risks, thus providing a theoretical foundation for high-yield cultivation practices.MethodsUsing Jiyujing as the experimental material, a single-factor experimental design was employed, with seeding rates set at 45 kg ha-1 (S45), 75 kg ha-1 (S75), 105 kg ha-1 (S105), and 135 kg ha-1 (S135). ResultsResults indicated that the low seeding rate S45 enhanced tillering capacity and productive tillers but was constrained by an insufficient number of effective panicles, limiting overall yield. Conversely, the high seeding rate S135 increased the number of effective panicles but intensified intra-population competition, which hindered individual development, decreased spikelets per panicle, seed setting rate, thousand-grain weight, and lodging resistance, ultimately restricting yield. The intermediate seeding rate S105 achieved the highest yield by balancing population dynamics with individual growth and optimizing the synergy between effective panicle numbers and per-plant productivity. Furthermore, the high seeding rate S135 reduced the diameter, wall thickness, fullness, and physical-chemical component content of basal second internodes, elevating lodging risks. S135 also diminished the average diameter, volume, and surface area of the root system, exacerbating root lodging and yield losses.DiscussionTherefore, the seeding rate S105 represents the optimal choice for simultaneously enhancing high yield and lodging resistance in direct-seeded rice, offering a theoretical basis for rational plant density management in direct-seeded rice cultivation.

The plastic film mulching technique can mitigate the yield-limiting effects of low-temperature chilling injury on rice yield in Northeast China, while rational fertilization practices contribute to improved soil quality. However, research remains scarce regarding the combined effects of plastic film mulching with different fertilizer types on rice dry matter accumulation and translocation, and the underlying mechanisms governing their roles in rice yield formation remain unclear. This study used "Jinongda 738" and "Jijing 525" as experimental materials and set up four different cultivation modes: 1) Bare land with organic fertilizer application (NMF0); 2) Plastic-mulched land with organic fertilizer application (MF0); 3) Bare land with chemical fertilizer application (NMF1); 4) Plastic-mulched land with chemical fertilizer application (MF1). The study aimed to explore the effects of plastic film mulching and different types of fertilizers on the growth of rice and the transportation of photosynthetic substances. Compared with bare land, film mulching improved the agronomic traits of rice. Under mulching conditions, chemical fertilizers increased the relative chlorophyll content (SPAD) and net photosynthetic rate (Pn) of leaves from the tillering stage to the heading stage, which was beneficial for the accumulation and transportation of dry matter. Under the same mulching conditions, the application of organic fertilizer slowed down the decline of photosynthesis from the grain filling stage to the maturity stage. Compared with the bare land treatment, under the combined application of chemical fertilizers and organic fertilizers, the film mulching treatment increased the yield by 2.98% to 3.30% and 1.39% to 7.40% respectively.Compared with the application of organic fertilizers, under bare land and film mulching conditions, the application of chemical fertilizers increased the yield by 23.19-26.44% and 21.62-25.13% respectively.Under the conditions of this experiment, MF1 had the best yield-increasing effect, with an increase of 2.98% to 30.62% compared to other treatments. It was a superior treatment method. This research aims to provide a theoretical basis for achieving green and efficient rice production.

Saline-sodic stress not only impacts the absorption of nutrient ions, such as Zn2+, in rice but also induces physiological water shortages and ion toxicity in rice plants, significantly hindering their growth. To investigate this phenomenon, the present study utilized two rice varieties, ‘Changbai 9’ and ‘Tonghe 899’, as test subjects to simulate conditions of saline-sodic soil stress. Four-week-old rice seeds under four treatments: control (CT), 2 μmol L-1 zinc treatment alone (Z), 50 mmol L−1 saline-sodic treatment (S), and 50 mmol L−1 saline-sodic treatment with 2 μmol L-1 zinc (Z+S). The study aimed to examine the effect of zinc on water transport in rice plants under conditions of saline-sodic stress. Research indicates that the application of zinc positively influences the growth of rice under saline-sodic stress.The application of zinc not only reduces the Na+/K+ ratio and malondialdehyde (MDA) content, but also increases the levels of Zn2+, Cu2+, and other ions. Additionally, it enhances the expression of aquaporins in the plasma membrane of rice roots, which in turn increases the hydraulic conductance of the roots and ultimately improves the water absorption capacity of the root system under stress conditions. Additionally, zinc application promotes auxin (IAA) synthesis, facilitating root growth and expanding the root absorption area, which in turn enhances the water absorption rate and helps maintain higher leaf water content. Moreover, zinc application regulates stomatal conductance through an increase in potassium ion concentration and abscisic acid (ABA) content, thereby elevating the transpiration rate of rice leaves and promoting water absorption and transportation within the rice plants. Therefore, the addition of zinc under saline-sodic stress not only alleviates the effects of such stress but also enhances water absorption and transportation in rice plants. This results in a higher water content within the plants, positively influencing their growth and development under saline-sodic conditions.

Saline-sodic stress can limit the absorption of available zinc in rice, subsequently impacting the normal photosynthesis and carbohydrate metabolism of rice plants. To investigate the impact of exogenous zinc application on photosynthesis and carbohydrate metabolism in rice grown in saline-sodic soil, this study simulated saline-sodic stress conditions using two rice varieties, 'Changbai 9' and 'Tonghe 899', as experimental materials. Rice seedlings at 4 weeks of age underwent various treatments including control (CT), 2 μmol·L−1 zinc treatment alone (Z), 50 mmol·L−1 saline-sodic treatment (S), and 50 mmol·L−1 saline-sodic treatment with 2 μmol·L−1 zinc (Z + S). We utilized JIP-test to analyze the variations in excitation fluorescence and MR820 signal in rice leaves resulting from zinc supplementation under saline-sodic stress, and examined the impact of zinc supplementation on carbohydrate metabolism in both rice leaves and roots under saline-sodic stress. Research shows that zinc increased the chloroplast pigment content, specific energy flow, quantum yield, and performance of active PSII reaction centers (PIABS), as well as the oxidation (VOX) and reduction rate (Vred) of PSI in rice leaves under saline-sodic stress. Additionally, it decreased the relative variable fluorescence (WK and VJ) and quantum energy dissipation yield (φDO) of the rice. Meanwhile, zinc application can reduce the content of soluble sugars and starch in rice leaves and increasing the starch content in the roots. Therefore, the addition of zinc promotes electron and energy transfer in the rice photosystem under saline-sodic stress. It enhances rice carbohydrate metabolism, improving the rice plants’ ability to withstand saline-sodic stress and ultimately promoting rice growth and development.

Soil salinization is a severe environmental problem that restricts crop productivity. Straw amendment could increase the fertility of saline–sodic soils by improving soil physical properties and carbon sequestration; however, the chemical mechanism of saline soil improvement via straw reclamation is not clear. This study aimed to investigate the effects of straw return with nitrogen fertilizer on soil leaching characteristics, rice organ ion concentrations, and yield. Therefore, a soil column leaching experiment was conducted in 2021 in Baicheng, Jilin Province, using two straw application rate treatments (0 and 8 t hm−2) and three nitrogen application rate treatments (0, 180, and 360 kg hm−2). The results revealed the following: 1. The combination of straw return and nitrogen fertilizer significantly increased the soil leachate volume, leachate pH, Na+ concentration, and Na+/K+ ratio, thereby reducing Na+ stress on rice; 2. The application of nitrogen fertilizer during straw return effectively minimized soil nitrogen loss by lowering the ammonium and nitrate nitrogen concentrations in the soil leachate; 3. This combination also reduced plant Na+ concentrations while increasing plant K+ concentrations, thus improving the Na+/K+ ratio in the plants; 4. Straw return with nitrogen fertilizer significantly enhanced rice yield, which increased with higher nitrogen application rates. In summary, the integration of straw return with nitrogen fertilizer not only regulates rice salinity tolerance but also boosts rice yield, presenting a novel approach for improving saline–sodic soils.

Abstract Saline-sodic stress restricts the absorption of zinc by rice, consequently impacting the photosynthesis process of rice plants. In this experiment, Landrace 9 was selected as the test material and the potting method was employed to investigate the influence of ZnO nanoparticles (ZnO NPs) on zinc absorption and chlorophyll fluorescence in rice grown in saline-sodic land. The research findings demonstrate that the application of ZnO NPs proves to be more advantageous for the growth of rice in saline-sodic soil. Notably, the application of ZnO NPs significantly decreases the levels of Na+ and MDA in rice leaves in saline-sodic soil, while increasing the levels of K+ and Zn2+. Additionally, ZnO NPs enhances the content of chloroplast pigments, specific energy flux, quantum yield, and the performance of active PSII reaction center (PI ABS) in rice leaves under saline-sodic stress. Furthermore, the relative variable fluorescence (W K and V J) and quantum energy dissipation rate (φ Do) of rice are also reduced. Therefore, the addition of ZnO NPs enhances the transfer of electrons and energy within the rice photosystem when subjected to saline-sodic stress. This promotes photosynthesis in rice plants growing in saline-sodic land, increasing their resistance to saline-sodic stress and ultimately facilitating their growth and development.

Straw return is an effective management practice for improving physical and chemical properties of saline–sodic soil in Northeast China. Straw decomposition and nutrient release are deeply influenced by soil and climatic factors. In Northeast China, straw decomposes slowly due to the long winter with low temperatures. Therefore, the season of straw return may be a key issue affecting rice. However, the impact of returning straw in different seasons on rice is disregarded and not commonly researched. We conducted a 2-year field experiment, including two residue management treatments: spring straw return treatment (SR) and autumn straw return treatment (AR), each containing five different N rates (0, 90, 180, 270, and 360 kg ha−1) as sub-treatments. The results reveal that, compared with the spring straw returning treatment, the autumn straw returning treatment significantly improved root morphology and root vigor and increased the number of spikes per unit area, which directly increased rice yield by 4.76% (2020) and 6.62% (2021). In addition, rice yield showed an increasing and then decreasing trend with the increase in N fertilizer application, and it was at its maximum when the N application rate was 270 kg ha−1. Compared to the spring straw return treatment, the autumn straw return treatment was able to reduce 31.46% (2020) and 38.48% (2021) of N fertilizer application without decreasing rice yield. Our findings demonstrate that straw return combined with nitrogen fertilization may be a promising management practice for improving rice root systems and yield in saline–sodic soils, and under the conditions of the autumn straw returning treatment, the best nitrogen fertilizer application rate was 270 kg ha−1.

Soil salinization poses a significant challenge to agriculture. The practice of returning straw to the field has garnered increasing attention as a sustainable method to improve salinized land. This study aimed to investigate the impact of nitrogen application rates on rice straw decomposition, rice straw nutrient release, and rice yield in saline sodic rice field conditions. The field experiment was designed with five nitrogen (N) fertilizer rates with 0 (N0), 90 (N1), 180 (N2), 270 (N3), and 360 kg N ha−1 (N4) under the condition of full return (8 t ha−1) of straw from sodic-saline paddy fields, nylon mesh bag filling method was used to study the decomposition process of rice straw. The field experiment was conducted in a completely randomized design with three replications. The results showed that the application of N fertilizer promoted the decomposition of rice straw and the release of C, N and P from the straw, but had no effect on the release of K from the straw. Compared with N0, the cumulative decomposition rates of rice straw in N1, N2, N3 and N4 treatments were significantly increased by 10.05

Shaping the canopy architecture and delaying leaf senescence in maize are pivotal strategies for extending the crop’s photosynthetic period and improving yield. The application of plant growth regulators (PGRs) is a critical cultivation measure, with the timing of application being of paramount importance. To explore the effects of PGR application time on maize canopy structure, leaf senescence characteristics and yield, a comparative two-year field study was undertaken during the 2019–2020 growing seasons at the Gongzhuling Experimental Station of the Jilin Academy of Agricultural Sciences, utilizing a PGR containing ethephon as the active ingredient. The experiment was structured with two plant densities of 60,000 and 90,000 plants ha−1, and three distinct PGR application protocols: T10 (application of PGR at the 10th leaf stage), T15 (application at the 15th leaf stage), and CK (control group sprayed with water). The result indicated that the yield increased by 5.62% following T15 treatment compared to the CK under high density (90,000 plants ha−1). Furthermore, the kernel per ear and the 1000-kernel weight increased by 3.93% and 5.62% respectively, while the abortion rate decreased. Correlation analysis showed that yield and yield components were correlated with plant morphology, physiology, and aging characteristics under 90,000 plants ha−1. Pollen density was also positively correlated with the top leaf area and the top leaf angle (p < 0.01). Furthermore, relative green leaf area at maturity (RGLAM) showed positive correlations with chlorophyll b, superoxide dismutase activity (SOD), peroxidase activity (POD), catalase activity (CAT), and soluble protein content (p < 0.01), while displaying a negative correlation with malondialdehyde content (MDA) (p < 0.01). Spraying plant growth regulators at the 15-leaf stage under high density can effectively enhance the top canopy structure of the maize and reduce the upper leaf area and angle, increase pollen density, and boost the number of grains. Furthermore, it delayed the senescence of leaves, prolonged the functional period of the leaves, increased kernel weight, optimized light resource utilization, and ultimately enhanced the maize yield.