Excessive planting density and heavy rainfall weather threatens global agriculture, particularly affecting maize. Biochar is an environmentally friendly soil amendment that has a yield-increasing effect. However, the regulatory mechanism of biochar frequency on crop internode development and photosystem II photosynthetic efficiency remains unknown. A total of nine treatments were followed in this experiment. Three applications of biochar were as follows: no biochar application (B0); biochar application at 4.2 t ha−1 year−1 (B1); and biochar application at 8.4 t ha−1 2 year−1 (B2), alongside three nitrogen (N) fertilizer rates (0, N0; 180 kg ha−1, N1 and 225 kg ha−1, N2). The results showed that the internode thickness of the 2nd to 5th nodes under N2B2 treatment increased by 17.7%, 16.0%, 19.7%, and 21.7%, respectively, compared to N0B0. Annual biochar application had a higher stem diameter coefficient for the 1st to 3rd nodes than no biochar (B0) and treatments applied every two years (B2). Annual biochar application had the highest dry weight of internodes and plant height compared with B0 and B2. The relative chlorophyll content of leaves was significantly increased by biochar combined with N fertilizer or by N fertilizer alone. Biochar combined with N fertilizer significantly reduced NPQt and ΦNPQ, which were reduced by 59% and 50%, respectively, under N2B1 treatment compared with N0B0. The N2B1 treatment increased ΦII by 30% compared to N0B0. Stem diameter coefficient was significantly negatively correlated with NPQt and ΦNPQ and significantly positively correlated with ΦII and Fv/Fm. Compared to B1, B2 increased the maize yield. Annual biochar application combined with N fertilizer reduced stem collapse and enhanced post-flowering photosynthesis. Overall, considering the yield traits, 8.4 t ha−1 biochar application combined with 180 kg ha−1 N fertilizer treatment was the best. This study will provide reference data for cultivation regulation to enhance maize’s resistance to collapse and maintain photosynthetic capacity.

Further understanding is needed regarding how biochar, over the long term, influences N2O release and the associated communities of nitrifiers and denitrifiers in paddy soils. This field study examined the responses of these microbial communities to biochar applied for different durations (2016 or 2023) and at different doses (15 or 45 t & centerdot;ha(-1)), alongside a control (CK) without biochar addition. Relative to the control (CK), all biochar amendments led to a comprehensive enhancement of soil physicochemical properties. However, their impacts on N2O fluxes diverged: cumulative emissions rose by 18.44% under the high-rate (45 t & centerdot;ha(-1)), first-year application (NB45) in 2023, but were suppressed across all other biochar treatments. Microbial community composition diverged markedly between treatment chambers, with the abundances of Nitrospira and Chloroflexota showing distinct patterns. In 2016, the two bacterial species exhibited significantly high abundance proportions, with maximum shares of 23.55% (2016, 45 t & centerdot;ha(-1)) and 12.16% (2016, 45 t & centerdot;ha(-1)), the most abundant in nitrification and denitrification, respectively, which influenced the certainty of changes in the microbial community structure. Biochar enhances nitrogen metabolism in nitrifying microorganisms but inhibits denitrification processes, with the biochar applied in 2023 having a remarkable effect. Overall, biochar application effectively enhances soil physicochemical properties, mitigates N2O emissions over the long term, and modulates the community structure and functional traits of nitrifying and denitrifying microorganisms. These combined effects contribute to promoting environmental security for sustainable development within agricultural production systems while reducing the carbon footprint.

To investigate the effects of slightly acidic electrolyzed water (SAEW) treatment on rice seed germination, rice seeds were soaked with SAEW at different available chlorine concentrations (ACC) of 10, 20, 30, 40, 50, and 60 mg/L. A standard seed germination test was conducted to summarize the influence of SAEW with varying ACC on rice seed germination. Meanwhile, low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) technologies were employed to reveal the underlying mechanisms by studying the internal moisture changes, water migration patterns, and water distribution characteristics. The results demonstrated a hormetic effect of SAEW on rice seed germination, characterized by significant promotion at lower ACCs (10-40 mg/L) and inhibition at higher ACCs (50-60 mg/L). The most pronounced promotive effect was observed at an ACC of 30 mg/L. Low ACC SAEW accelerated the water storage rate within the rice seeds, facilitated the conversion and accumulation of free water, thereby providing favorable moisture conditions for seed germination and subsequently promoting rice growth. In contrast, high ACC SAEW damaged the rice cell walls under osmotic stress, leading to a reduced water absorption rate and consequently inhibiting rice growth. This study, starting from the pre-treatment of rice seeds, investigated the entire process, providing theoretical support and data reference for rice production and processing.

This study aimed to clarify how straw incorporation timing reshapes nitrogen (N)- cycling functional processes and regulates N retention and loss in paddy fields under different N fertilization regimes. It also evaluated the effects of these processes on rice yield and N uptake and utilization efficiency in cold-region rice systems, thereby addressing the shortage of field-based evidence from seasonally cold rice-growing regions. A two-year field experiment was conducted with three straw treatments, including no straw incorporation (CK), spring straw incorporation (ST), and autumn wet-harrow straw incorporation (SW). These treatments were combined with conventional N fertilization (N2) and a 20

Nitrogen (N) management is critical for ensuring food security and mitigating greenhouse gas (GHG) emissions. In rice paddies, the effectiveness of N management in maximizing yields and minimizing N losses is highly dependent on local environmental conditions and thus varies widely across regions. However, the influence of optimized, site-specific N management on methane (CH4) emissions remains poorly quantified and is not reflected in current IPCC Tier 1 methodologies. Here, we synthesize data from multiregional field experiments and conduct a meta-analysis to show that locally optimized N management practices-such as delayed fertilizer application, reduced N input, and deep placement-reduce CH4 emissions from rice paddies by 16%-21%. The experiments further show that these practices suppress CH4 emissions by lowering soil N availability and organic matter decomposition, thereby limiting substrates for methanogenesis. Combining survey data from 155 counties with machine learning models, we estimate that implementing optimized N strategies across China's rice-growing regions could reduce CH4 emissions by 16% while simultaneously increasing rice yields by 7%. These findings underscore the dual benefits of locally optimized N management for agricultural productivity and climate change mitigation, and provide a foundation for improving CH4 emission estimates under diverse management regimes.

Panicle development is a critical determinant of the grain yield in rice (Oryza sativa). In this study, we identified a bor1 mutant (boron transporter 1), which exhibits severe defects in panicle development. Bulked segregant analysis sequencing, genetic complementation, and gene knockout experiments demonstrated that OsBOR1 corresponds to LOC_Os12g37840. OsBOR1 encodes a boron efflux transporter that localizes to the plasma membrane and is highly expressed in roots and panicles. Disruption of the OsBOR1 function resulted in altered boron distribution among stems, leaves, and panicles, indicating a loss of boron homeostasis. Transcriptome analysis of the bor1 mutant revealed a significant enrichment of differentially expressed genes associated with primary metabolism, secondary metabolic processes, and oxidative stress responses. Consistently, elevated reactive oxygen species levels were observed in the mutant. Together, these results demonstrate that OsBOR1 is required for maintaining normal panicle development in rice, likely through the regulation of boron homeostasis and reactive oxygen species balance.

Cold stress severely impairs crop growth, development and yield. Exploring the regulatory genes underlying cold tolerance in crops and elucidating their molecular mechanisms is critical for cold tolerance breeding. In this study, quantitative real-time PCR (qRT-PCR) revealed that the expression of EXO70J7, which encodes an exocyst complex subunit localized to vesicles and the plasma membrane (PM), was induced by cold stress. EXO70J7 loss-of-function mutants generated using CRISPR-Cas9 exhibited reduced cold tolerance. Transcriptomic analysis revealed altered expression of cold-response pathway genes in EXO70J7 loss-of-function mutants under cold stress. Conversely, transgenic plants overexpressing EXO70J7 displayed enhanced cold tolerance. Transmission electron microscopy revealed that loss of EXO70J7 function exacerbated, whereas overexpression alleviated, cold-induced plasma membrane damage compared with wild-type plants (WT). Subcellular localization analysis of EXO70J7-GFP in root tip cells revealed cold-induced accumulation at the PM, which was inhibited by vesicle trafficking inhibitor, brefeldin A (BFA), treatment and restored upon BFA washout. Based on these results, we propose that EXO70J7 influences PM integrity by mediating PM-associated vesicle trafficking under cold stress, thereby contributing to cold tolerance in rice. In addition, haplotype and population genetic analyses revealed pronounced genetic divergence at EXO70J7 between indica and japonica subspecies, consistent with signatures of divergent selection driven by thermal adaptation, highlighting its great potential as a target for cold-tolerance rice breeding.

Addressing the issues of slow decomposition and low nutrient release efficiency associated with traditional straw returning, this study innovatively applied ultrasound-assisted centrifugal separation technology to prepare submicron/nano-straw particles and systematically conducted a multi-scale investigation from microscopic to macroscopic levels. The core finding reveals that when the particle size reaches the 1 μm threshold, ultrasonic cavitation vigorously disrupts the straw structure, leading to efficient lignin removal (77.45 %) and a significant reduction in cellulose crystallinity, thereby fundamentally enhancing the degradation rate. Concurrently, the cavitation effect optimizes elemental ratios (e.g., C, N, and K elemental proportions increasing by 1.05 to 8.50 times) and exposes active functional groups such as C-N and N-H bonds, effectively overcoming the bottleneck in nutrient release. Furthermore, cavitation increases the abundance of hydrophilic groups on the straw surface, enhancing its water-holding capacity by 13.84-18.52 %. Soil columns experiment and pot trials confirmed that the nano-straw prepared by this technology substantially reduces nutrient loss, significantly increases soil available potassium content, ultimately synergistically increasing rice yield by 25.27 %. In summary, by simultaneously optimizing the straw's degradability, fast-acting nutrient release capacity, and water retention, ultrasonic technology solves the core challenges of traditional straw returning and provides a novel strategy for developing new fast-acting straw fertilizers.

Whether the effects of nitrogen on starch granules differ according to the taste type of Japonica rice remains unknown. Here, two Japonica rice varieties, Akita-Komachi and Beijing No. 3, with different taste types were selected to explore the effect of nitrogen on their quality and starch characteristics. The results showed that Akita-Komachi exhibited a weak response to nitrogen, with minimal changes in eating quality, starch surface characteristics, and particle size; Beijing No. 3 exhibited a strong response to nitrogen. With the increase in nitrogen, the cooking and taste quality, viscosity, amylopectin fa and fb1 chain content, and peak viscosity of Beijing No. 3 significantly decreased, whereas the crystalline and amylose content significantly increased. A 5 % increase in the number of 6-10 μm particles resulted in a small change in starch particle number in Akita-Komachi small. This study provides a new strategy for rice starch determination and improves the rate of rice starch detection.

Biochar influences CH4 emissions, methane-associated microbial communities, and rice yields. However, the effects of biochar application over different durations remain unclear. This study investigated the impact of biochar application on CH4 emissions, methane-associated microbial communities, and rice yield across different years. Five treatments were assessed based on the year of biochar application (NB: applied in April 2023; FB: applied in April 2016) along with three biochar application rates (CK: 0 t.ha-1; NB15, FB15: 15 t.ha-1; NB45, FB45: 45 t.ha-1). Biochar application improved the physical and chemical properties of the soil, with NB45 exhibiting the most pronounced effect. Compared with CK, CH4 emissions increased under NB conditions but decreased under FB conditions. Additionally, emissions were higher at lower biochar application rates than at higher rates across all years. These trends were associated with shifts in the abundance of methanogenic and methane-oxidising bacteria in the soil. Biochar reduced the pmoA/ mcrA ratio in paddy soil, with FB45 showing the greatest reduction. The composition of methanogenic and methane-oxidising bacterial species differed significantly between NB and FB soils, with Chloroflexota exhibiting the highest relative abundance in both bacterial groups. Biochar application enhanced CH4 metabolism in methanogenic and methane-oxidising bacteria, with the strongest effect observed under the NB treatment. Moreover, biochar application significantly improved rice yield, increasing by 9.27 %, 12.58 %, 13.50 %, and 14.68 % under the NB15, NB45, FB15, and FB45 treatments, respectively. Overall, biochar effectively reduced CH4 emissions, modulated the structure and function of methane-associated microbial communities, and enhanced rice yield.

Selenium (Se) is a trace element that is beneficial in enhancing the quality of rice production. However, research on the effects of Se on rice quality under varying nitrogen (N) levels is limited and requires further investigation. This experiment utilized a randomized block design, incorporating an N fertilizer reduction and efficient application mode, with two N levels, CN (225 kg·hm−2) and LN (180 kg·hm−2), and three Se levels, HSe (0.12 kg·hm−2), LSe (0.06 kg·hm−2), and 0Se (0.00 kg·hm−2). The results indicated that the effects of Se on rice processing quality differ under different N levels. Selenium adversely affected the processing quality under the CN level, whereas it demonstrated some improvement at the LN level. Furthermore, Se application increased the Se content in rice by 46.48–141.82% and enhanced the taste value by 14.88–22.73%. It significantly improved the nutritional and cooking qualities of rice and positively influenced its appearance. Although N levels induced variations, their overall impact remained beneficial. Considering various indicators, applying 0.06 kg·hm−2 of Na2SeO3 under the LN level yielded optimal results. This study provides valuable insights into the effects of Se on rice quality under different N levels. It provides a more scientific basis for the application of selenium fertilizer in rice.

Global warming is a serious threat to human survival and development, ranking among the most formidable challenges humanity faces. Mitigating greenhouse gas (GHG) emissions, the main driver of climate warming, has become an urgent priority. As a unique soil amendment, biochar has substantial potential for reducing GHG emissions. Here, we summarizes and analyzes the differences in the role of biochar in carbon sequestration and GHG emission reduction mechanisms in paddy soils between northern and southern China, and reviews how biochar affects CH4 and N2O emissions, improves soil physical and chemical properties, and enhances rice growth in both regions. In southern China, initial crop residues and higher field temperatures create an optimal environment for methanogens; meanwhile, biochar promotes favorable conditions for methanotrophic bacteria. In contrast, the northern climate with repeated freeze-thaw cycles affects microbial the changes through the changes in soil temperature and structure, which in turn affects GHG emission mechanisms, as well as substrate availability. Northern soils have higher concentrations of substrates necessary for microbial reactions that facilitate nitrification processes related to N2O emissions. Therefore, the effect of biochar applied in the south to reduce CH4 emissions is more prominent, while the effect on mitigating N2O emissions is more prominent in the north. The rice cultivation system combined with freeze-thaw cycles significantly contributes to the observed differences between the two regions. This review provides theoretical guidance and a decision-making basis for the use of biochar to reduce GHG emissions in paddy soils, thereby advancing toward the China's agricultural carbon peak goal.

The aim of this study was to quantify the impact of biochar one-off application on split application of nitrogen fertilizers. We used the 15N tracer technique to explore the effects of biochar on greenhouse gas (GHG) emissions and NUE during three growth stages (tillering, panicle initiation, and ripening). Total nine treatments incorporated three biochar levels (0, C0; 15, C1; 45 t ha−1, C2) with three N levels (0, N0; 168, N1; conventional N fertilization at 210 kg N ha−1, N2). The high N2O emission rate during the tillering stage was significantly affected by biochar application and its interaction with N fertilization in both years, with 2016 yielding higher emissions (15.8%–65.2% of the total). Optimizing biochar application with a focus on the tillering and panicle initiation stages can helped mitigate global warming potential (GWP) in the initial application. Rice yields were highest in N2C0 and N2C2 treatments across years, which were 13.0% and 8.5% higher than yield in N1C0, respectively. The base fertilizers in 2 years reduced the 15N loss rate (NLR) in N1C2 treatment by 49.5% and 38.6% compared with N1C0, respectively. In the first year, the N recovery efficiency (NRE) in N1C2 treatment decreased by 55.2%, 44.0%, and 21.4% for base, tiller, and panicle fertilizers, respectively, compared to and N2C1 decreased the NRE of the base fertilizers by 27.9% in the following year. No significant differences in the NRE of tiller and panicle fertilizers were observed between N1C1 and N2C1 treatments in the following year. This study underscores the potential of biochar as a an environmentally friendly soil amendment for N loss reduction in rice systems. Biochar one-off application plays a role in mitigating GHG emissions, particularly during different fertilization periods which contributes to more sustainable agricultural practices.

To reveal the regulatory effects of nitrogen and phosphorus interactions on grain-filling- and starch-synthesis-related enzymes, and grain weight of superior grains (SGs) and inferior grains (IGs) and taste quality, the japonica rice cultivar Shennong 265 was grown under field conditions with three nitrogen levels (210, 178.5, and 147 kg N ha−1; N3, N2, and N1) and two phosphorus levels (105 and 73.5 kg P ha−1; P2 and P1). At the N3 level, the yield of P1 was significantly lower (by 19.26%) compared to P2; at the N2 and N1 levels, P1 yielded higher than P2, peaking at N2P1. Spikelets per panicle showed P2 exceeding P1 at the same nitrogen level, with the highest for both SGs and IGs observed at N2P2, followed by N2P1. Reductions in nitrogen and phosphorus decreased the grain-filling rate but prolonged the duration for grain-filling. N2P1 maintained grain weight by extending the grain-filling duration across the early, middle, and late stages of IGs, and the middle and late stages of SGs. Increased nitrogen enhanced the activities of soluble starch synthase (SSS) and starch branching enzyme (SBE), whereas increased phosphorus inhibited these activities in SGs but enhanced them in IGs. Reduced nitrogen and phosphorus fertilizer diminished ADP glucose pyrophosphorylase (AGPP) and granule-bound starch synthase (GBSS) activities in SGs and IGs, inhibiting amylose accumulation while enhancing taste value. Compared with N3P2, the taste value of N2P1 increased significantly by 6.93%, attributed to a higher amylopectin/amylose ratio. N2P1 (178.5 kg N ha−1 and 73.5 kg P ha−1) optimized enzyme activity, starch composition, and grain filling, balancing both yield and taste, and thus demonstrated an effective fertilization strategy for stable rice production.

The grain number per panicle is a key agronomic trait of ideal plant architecture in rice (Oryza sativa L.). Here, we characterized and cloned OsNPF4, a member of the NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER (NPF) family that substantially alters rice yield. Overexpression of OsNPF4 significantly increased grain number per panicle but decreased panicle number. OsNPF4 was activated by IDEAL PLANT ARCHITECTURE1 (IPA1) via the SQUAMOSA promoter binding protein-like (SPL) binding sites in its promoter. Additionally, OsNPF4 interacted with DENSE AND ERECT PANICLE1 (DEP1), whose transcription is also induced by IPA1. Our findings indicate that OsNPF4 contributes to establishing ideal plant architecture in rice, and manipulating its expression could help produce elite super rice varieties.

Leaves represent an important organ in plant photosynthesis, and moderately rolled leaves would be beneficial in establishing an ideal plant architecture and thereby increasing rice yields. In this study, a stable inherited rolled leaf mutant was obtained via ethyl methanesulfonate (EMS) mutagenesis from japonica variety WYJ27, which was named rll2 (rolling leaf 2). rll2 showed a leaf-rolling phenotype at the seedling stage, which increased with growth. Compared with the wild type, the leaves at all levels of rll2 were significantly shorter and narrower, and the leaf-rolling index gradually decreased from the highest leaf to the third-highest leaf. Semi-thin sections showed that the bulliform cells of rll2 were significantly larger than those of the wild type, and the number of cells was significantly higher than that of the wild type. Genetic analysis showed that rll2 is controlled by a pair of recessive nuclear genes. Map-based cloning revealed that RLL2 encodes a conserved and plant-specific calpain-like cysteine proteinase. RLL2 was mainly expressed in young roots, shoots, spikelets, and panicles. Transcriptome sequencing showed that a total of 104 genes were differentially expressed in the wild type and rll2. Moreover, several transcription factor genes were significantly altered in the rll2 mutant. Taken together, our findings indicate that RLL2 plays an important role in leaf rolling by regulating bulliform cells, which may be useful in breeding rice with an ideal plant architecture.

The tiller angle, which is an important agronomic trait, determines plant architecture and greatly influences the grain yield of rice. In this study, a population of chromosome segment substitution lines derived from a cross between a japonica variety with a compact plant architecture—Koshihikari—and an indica variety with a spread-out plant architecture—Nona Bokra—was used to investigate the genetic basis of the tiller angle. Five quantitative trait loci (qTA1, qTA5, qTA9-1, qTA9-2, and qTA11) for the tiller angle were detected on chromosomes 1, 5, 9, 9, and 11 in two different environments. The phenotypic variation in these QTLs ranged from 3.78% to 8.22%. Two pairs of digenic epistatic QTLs were detected in Lingshui. The epistatic interaction explained 15.19% and 13.60% of the phenotypic variance, respectively. Among the five QTLs, qTA9-2 was detected in both environments. An F2 mapping population containing the qTA9-2 QTL was established. The location of qTA9-2 was narrowed down to a 187 kb region between InDel markers M9 and M10 on chromosome 9. Thirty open reading frames (ORFs), including TAC1, a gene known to regulate the tiller angle, were identified in this region. The gene sequencing results suggested that a base substitution from G to A at position 1557 in the 3′-untranslated region led to a difference in the expression of qTA9-2 in Koshihikari and Nona Bokra. These findings provide a potential gene resource for the improvement of rice plant architecture.

Nitrogen is a crucial element that impacts rice yields, and effective tillering is a significant agronomic characteristic that can influence rice yields. The way that reduced nitrogen affects effective tillering is a complex quantitative trait that is controlled by multiple genes, and its genetic basis requires further exploration. In this study, 469 germplasm varieties were used for a genome-wide association analysis aiming to detect quantitative trait loci (QTL) associated with effective tillering at low (60 kg/hm2) and high (180 kg/hm2) nitrogen levels. QTLs detected over multiple years or under different treatments were scrutinized in this study, and candidate genes were identified through haplotype analysis and spatio-temporal expression patterns. A total of seven genes (NAL1, OsCKX9, Os01g0690800, Os02g0550300, Os02g0550700, Os04g0615700, and Os04g06163000) were pinpointed in these QTL regions, and were considered the most likely candidate genes. These results provide favorable information for the use of auxiliary marker selection in controlling effective tillering in rice for improved yields.

Northeast China is an important commercial grain base for China, but also the largest japonica rice production area. However, N, and K fertilizer application and unreasonable application times are prominent contradictions that restrict the development of japonica rice. This study aimed to investigate how to rationally apply N and K fertilizers to affect grain filling and ultimately increase the quality of the rice. In this field study, two N application levels and three K application ratios were set in 2020 and 2021 using Shennong 265 (SN265) and Meifengdao 61 (MF61). We found that the final seed growth and filling rate of SN265 were higher than those of MF61, and their filling characteristics were slow in the early stage and fast in the later stage, with large fluctuations. Appropriate reductions and increases of N and K fertilizer applications, respectively, in the early stage could improve grain filling. Compared with SN265, MF61 had a 3.2% increase in head rice rate, lower amylose and protein content, a decrease of chalkiness degree and chalkiness percentage by 23.96 and 34.00%, respectively, and more reasonable protein components. With the N application increase, the processing quality improved, the amylose and protein content and chalkiness increased, the protein components increased except for the milled rice glutelin, and the rice taste value decreased. At low N levels, increasing the proportion of K application was consistent with the effect of increasing N. The taste value of SN265 decreased linearly with the increase in the ratio of N application to pre-application of K, the highest taste value was obtained when the N fertilizer was applied at a rate of 180 kg ha−1, and the ratio of before and after K fertilizer application was about 1:2. The taste value of MF61 decreased linearly with the N application increase and showed a trend of increasing and then decreasing with the K application increase in the early stage. The taste peak gradually shifted back with the N application increase, and the highest taste value was obtained when N fertilizer was applied at 180 kg ha−1; the ratio of before and after K fertilizer application was about 3:2. By constructing the grain-filling quality evaluation system, the characteristic parameters of superior and inferior grains at the early and late stages of grain filling, respectively, greatly affected the rice taste value. Additionally, the percentage of the rice grain weight at the maximum grain-filling rate to the final rice grain weight (I) of superior grains, glutelin content, and value of the RVA profile characteristics were all critical reference indicators for rice taste quality.