Drought poses a significant threat to global rice production, and a comparative study between rice and wheat serves as an essential approach to unravel the mechanisms relating to drought tolerance. This study examined the differential responses of gas exchange, leaf hydraulic conductance, and leaf morpho-anatomical traits in Shanyou 63 (Oryza sativa) and Yannong 19 (Triticum aestivum). Our findings revealed that rice photosynthesis was more sensitive to drought than wheat, primarily due to greater reductions in stomatal conductance (gs) and mesophyll conductance (gm). The larger reduction of gs in rice was related to a more substantial decrease in leaf hydraulic conductance, which was driven by more severe downsizing of leaf xylem conduits and the thickened mestome cell walls. The more severe depression of gm in rice under drought was associated with the decreased chloroplast surface area exposed to intercellular airspaces and cell wall porosity (φ/τ) as well as the thickened mesophyll cell walls (Tcw-mes). The thicker Tcw-mes and the decreased φ/τ may be related to the biosynthesis and deposition of cellulose and hemicellulose. This study provides evidence that the regulation of cell wall components and the retention of leaf morphological and anatomical structures play a critical role in maintaining a high photosynthetic capacity under drought stress.

Maize (Zea mays L.) grain yield potential in China exhibited substantial improvement from the 1980s to 2010s. However, the genetic gains in lodging tolerance during population structure optimization (selection of cultivars and planting densities) of maize remain poorly characterized. This study evaluated genetic gains through era-specific optimal population densities for representative hybrids in China, enabling accurate capture of genetic improvement in practical maize production systems. Seven era-representative hybrid cultivars were employed to plant at four planting densities (75000, 105000, 120000, and 135000 plants ha-1) during the 2021-2022 maize growing seasons, with the density corresponding to peak grain yield designated as the optimal population density (OPD) for each hybrid, to evaluate genetic gains in lodging tolerance under different densities and OPD, respectively. Annual genetic gain analysis revealed an average yield increase of 190.25 kg ha-1 year-1 (1.13% per year of release [YOR]) under the OPD, contrasting with significant reductions in lodging tolerance parameters: stalk-breaking force (SBF) (-0.64 N year-1;-1.87% YOR-1). Mechanical strength metrics demonstrated progressive declines with crush strength (-1.17% YOR-1), and bending strength (-1.65% YOR-1) under the OPD. Basal internode structural integrity parameters including dry matter (-1.41% YOR-1), dry matter per unit length (-1.44% YOR-1), and diameter (-0.61% YOR-1) exhibited negative trends under the OPD. However, by analyzing stalk lodging tolerance under different planting densities it was found that cultivars exhibited significant increases in stalk lodging tolerance under the density of 135,000 plants ha-1 from the 1980s to 2010s. The genetic gain of SBF averaged 0.27 N year-1 (2.70% YOR-1). This improvement was primarily attributed to significant reductions in ear height (-0.73% YOR-1) and center of gravity height (-0.41% YOR-1). In contrast, neither SBF nor vertical root-pulling resistance (VRPR) showed significant genetic gains across cultivars under other density conditions. These findings demonstrate that modern breeding priorities have successfully enhanced yield potential under optimal (higher) population densities while inadvertently compromising structural stability traits. With high-density maize cultivation becoming a prerequisite for yield maximization, the decline in stalk lodging tolerance has emerged as a critical risk factor during progress toward higher yields, despite modern cultivars exhibiting relatively lower ear height and center of gravity height. Our results demonstrate that the average diameter and dry matter per unit length of basal internodes are critical factors for enhancing stalk lodging tolerance in maize plants. This investigation provides novel insights into the genetic trade-offs of modern maize breeding and proposes strategic approaches for developing hybrids optimized for intensive cropping systems.

Confronted with the dual imperatives of ensuring food security and reducing environmental pollution in China's intensive agricultural systems, this study proposes and validates an innovative crop management paradigm: a High-Density Production System enabled by Precision Stage-Specific Regulation (HD-PSR). Based on a three-year field experiment spanning a wide nitrogen (N) application gradient (0-765 kg N ha-1), we assessed the effects of N rate on grain yield, nitrogen partial factor productivity (PFPN), plant N dynamics (uptake, distribution, and remobilization), soil residual N, and nitrous oxide (N2O) emissions. The results show that the system achieved a clear yield plateau of 14.7-16.5 t ha-1 at 243.8-306.4 kg N ha-1 , while sustaining efficient internal N uptake and remobilization, providing a strong physiological basis for high yield. Simultaneously, the system markedly reduced the direct N2O emission factor to a consistently low range of 0.3 %-0.9 %, well below the IPCC default. Notably, both cumulative N2O emissions and the emission factor exhibited a strictly linear relationship with N application rate, in contrast to the exponential increases widely reported under conventional fertilization. This linearity is attributed to split application, which prevents the accumulation of soil mineral N that typically triggers microbial N2O emission pulses. A comprehensive benefit index identified approximately 289 kg N ha-1 as the synergistic optimum for high yield and low emissions. Collectively, these findings demonstrate that HDPSR-through deep integration of high-density planting with whole-season, physiology-oriented precision regulation-can simultaneously enhance grain yield and nitrogen-use sustainability, offering a practical systemic pathway for the sustainable intensification of cereal production.

Farm size significantly affects the yield, nutrient use efficiency, and environmental effects of wheat–maize systems. A case study of a wheat–maize rotation system in the North China Plain (Henan Province) was conducted to enhance large-scale farm size. The study area included numerous differently sized wheat–maize crop systems in different ecological zones, representing 596 farming households. The average yield, resource use efficiency, and environmental indicators of the wheat–maize systems were analyzed. Combining our parameter-based analysis with field irrigation experiments, we conclude that in the wheat–maize rotation areas of the North China Plain, a farm size of 10.0–16.7 ha optimizes yield, resource use efficiency, and economic and environmental benefits. Moreover, improving irrigation efficiency, such as switching from flood to drip irrigation, significantly enhances the system yield (15.5%–17.5%) and output-to-input ratio (33.5%–44.4%). This study offers recommendations for optimizing farm size and achieving multi-objective sustainability in wheat–maize double-cropping areas.

Farmers in China often use nitrogen (N) fertilizers to ensure adequate crop growth. However, inappropriate applications have increased the risk of environmental pollution, lowered maize yields, and reduced profits for farmers. Proper N fertilizer management is crucial for improving yield and nitrogen use efficiency (NUE). This study conducted a three-year experiment involving nine N treatments (0, 45, 90, 135, 180, 225, 270, 315, and 360 kg ha-1) on a field under nitrogen fertilizer precision management (NFPM) in Northeast China. The results were compared with studies published within the past decade that analyzed yield and dry matter (DM) content under two management practices in Northeast China: conventional nitrogen fertilization management (CNFM) and water-saving fertilization management (WSFM). The findings reveal that maize yield increases with rising N application rates up to 270 kg ha-1, after which yield decreases. The kernel number (KN) and kernel weight (KW) of maize grown under NFPM were 13.7 and 14.7% higher than those grown under WSFM, respectively. Furthermore, they surpassed crops grown under CNFM by 38.4 and 21.2%, respectively. The maximum total yield of the NFPM treatment was 41.8 and 78.8% higher than under WSFM and CNFM, respectively. In addition, compared with CNFM and WSFM, NFPM significantly increased NUE across the various N-level treatments. Optimizing nitrogen management can help farmers to achieve higher yields and promote sustainable agricultural development.

Context: Given the current context of climate change, declining solar radiation is becoming a critical limiting factor for high yield maize. However, a quantitative understanding of the structural pathways between crop morphology, canopy structure, radiation use efficiency (RUE) and yield remains lacking. Methods: In this study, the changes in canopy morphological structure in response to reduced solar radiation were systematically analyzed based on a two-year study (2021 and 2022) involving three maize cultivars (Xianyu335, Denghai618, and Zhengdan958), two planting densities (75 000 plants/ha and 120 000 plants/ha), and four shading treatments (85% (S1), 70% (S2), 50% (S3) natural light and no shading (CK)). Results: The results indicated that the above-ear canopy was most sensitive to solar radiation variations, exhibiting significant changes in above-ear leaf area index (LAI), leaf angle, leaf orientation value (LOV), spatial density of leaf area (SDLA), and internode length. However, the below-ear canopy showed no such sensitivity. Structural equation modeling revealed that increased plant height significantly reduced RUE, whereas enhanced above-ear spatial distribution characteristics of leaves (SDCL) positively correlated with yield. Cubic regression analysis of yield and photosynthetically active radiation (PAR) identified an optimal PAR intensity range of 951-1126 MJ/m2 across maize cultivars and planting densities, where the ideal plant type tended to be consistent across cultivars. Conclusions: These findings suggested that canopy structural adjustment was one key mechanism for sustaining yield under reduced radiation, providing quantitative guidance for selecting maize plant type and for designing management strategies in low radiation regions.

Canopy nitrogen density (CND) is a critical indicator of plant growth, with applications in nutrient diagnosis, disease monitoring, and carbon cycling. However, optical remote sensing of nitrogen is constrained by VI saturation, particularly in dense canopies. Here, we propose a novel strategy to mitigate saturation by resolving two key issues: (1) the sensing depth of canopy spectra and (2) the quantification of vertical nitrogen heterogeneity. Saturation characteristics of VIs were first analyzed using inflection and saturation points. We found that CND at the inflection point enhanced the linear correlation with canopy spectra. The 3rd-7th leaf layers contributed most to canopy reflectance, accounting for 67.24%-72.15% of canopy spectra and 62.39% of total CND. Beyond the 7th-8th leaf layers, saturation became prominent. To capture vertical heterogeneity, we employed a bell-shaped model, with the coefficient omega linking the inflection point CND to canopy CND across structural variations. Integrating inflection points with vertical heterogeneity characteristics improved the robustness of VI-CND relationships, reducing RMSE by 10.8%-33.9%. This approach offers an intuitive framework to mitigate VI saturation, enabling more accurate CND estimation under diverse field conditions.

Under the premise of 0 increase in nitrogen input and environmental friendliness, optimizing planting density to improve canopy nitrogen distribution is conducive to balancing the contradiction between resource consumption and yield increase, and promoting a cleaner production model of high yield and high efficiency in maize. We studied the effects of nitrogen application on grain yield, grain nitrogen concentration, grain protein concentration, nitrogen utilization efficiency, and vegetative organ nitrogen uptake, distribution, remobilization, economic returns and environmental benefit of two high-yielding maize hybrids under different planting densities (7.5 x104 plant ha- 1 and 12.0 x 104 plant ha- 1) and nitrogen applications (0, 180, 360, and 540 kg N ha- 1) during 2019-2020. The results showed that the maize yield, grain nitrogen concentration and grain protein concentration reached the maximum of 22.7 t ha- 1, 1.9 %, 12.7 % corresponding to planting density of 12.0 x 104 plant ha- 1 and nitrogen application of 360 kg ha- 1. The economic returns were also maximized which was 5.4 x 103 USD ha- 1. Nitrogen utilization efficiency decreased with increasing nitrogen application, while increased with increasing planting density. The nitrogen accumulation and remobilization of plants had a positive response to nitrogen application and planting density. Higher yields were obtained due to higher vegetative organs of pre-silking nitrogen accumulation and stalk nitrogen remobilization and high nitrogen accumulation in the middle leaf. Under this high-yielding condition, both reactive nitrogen losses and greenhouse gas emissions of the optimal combination were 6.1 % lower than the low-yielding combination. Therefore, under high planting density, selecting suitable hybrids, defining the appropriate nitrogen application and optimizing nitrogen distribution in maize canopy can achieve high-yield and efficient production of maize while reduce environmental risks. This study highlights the importance of optimizing canopy nitrogen distribution in maize, and likewise provides new insights into mitigating the negative environmental effects of agricultural production.

Urban–rural integration (URI) plays a crucial role in advancing rural revitalization and the modernization of agriculture. Nevertheless, numerous nations encounter persistent obstacles, including inefficient resource mobility across urban–rural divides and uneven industrial distribution, while striving to foster such integration. Agricultural new quality productive forces (ANPFs) offer an innovation-led production framework fueled by advances in agricultural technology, allowing urban–rural integration (URI) through improved resource mobility between cities and rural regions. Utilizing panel data from 30 Chinese provinces (2013–2022), this study employs a two-way fixed effects model, mediation analysis model, threshold regression model, and the spatial Durbin model to investigate the transmission mechanism and spatial spillover effect of agricultural new quality productive forces (ANPFs) on urban–rural integration (URI). The findings show the following: (1) Agricultural new quality productive forces (ANPFs) significantly influence urban–rural integration (URI). (2) The influence is significantly stronger in western China than in the eastern and central regions. (3) Industrial restructuring and upgrading (IND) function as a mediating influence in this connection. (4) The role of informatization (INF) has a dual-threshold effect. (5) Geographically, while these forces promote local integration, they may impede progress in nearby regions. This study provides new empirical insights into the factors that influence urban–rural integration (URI) and proposes policy solutions to promote sustainable regional development.

Maize is a critical grain crop in China, having the largest planting area and highest total yield of all grain crops. In the four-primary maize-producing regions of China (Northeast, North China Plain, Northwest and Southwest), persistent regional production challenges and yield-limiting factors have impeded the realization of efficient maize production. This paper reviews sustainable, yield-enhancing and efficiency-improving practices for maize production in China. By addressing the regional constraints in major maize-producing areas and incorporating strategies, such as high-yield population construction, the establishment of appropriate tillage layers and soil fertility enhancement through precise matching technologies, this study integrates regionalized integrated fertilizer application and a government-enterprise-university-research-application collaborative model, focusing on the Science and Technology Backyards. The goal is to facilitate sustainable, efficient, scaled and modernized development across diverse maize-growing regions in China. This approach is expected to provide a foundation for sustainable and efficient maize production in China.

High environmental costs can be incurred in wheat-based agricultural systems (WBASs), from wheat grain production to straw management. Carbohydrate accumulation and partitioning determine the grain and straw yields, and the related food security and environmental cost in the whole system. We systemically investigated the wheat carbohydrate partitioning pattern to develop the new regional grain/straw yield models for China. Based on the newly developed models and a life cycle assessment, we assessed the carbon (C) mitigation potential for different grain yield increases scenarios. When the grain yield increased by > 9 t ha-1, more carbohydrates were allocated to aboveground straw. Grain carbohydrate partitions could be significantly diminished by cultivar types, inappropriate N supply, modest early sowing, and manure addition, particularly in central China where total biomass and harvest index (HI) are highest. Combined with national farmers survey campaign, the estimated straw yield was overestimated by 30.2 %, 29.3 %, and 23.5 % by official figures and other meta-analyses value using a fixed HI regardless of grain yield levels in North China Plain (NCP), Yangtze River Plain (YR), and southwest (SW) regions, respectively. The estimated C emissions from straw management (recycling and open-field burning) were 1.3-13.2 times lower than for grain production in the northeast (NE), northwest (NW), NCP, and SW regions, but were 26.7 % greater in the YR. A scenario analysis suggested that the estimated C mitigation potential was in the range of 5.4-57.6 % through the region-specific integrated straw resources and chemical fertilizer management, while the grain yield simultaneously increased by more than 30 %. The environmental cost of the WBASs should be significantly reduced based on the region-specific optimal combination of inorganic resource inputs, straw management, and balanced carbohydrate partitioning, which would simultaneously further enhance the grain yield potential. This conceptual framework could serve as a reference for simultaneously ensuring food and environmental security apart from China and wheat agricultural systems.

Corn smut, caused by Ustilago maydis, significantly threatens maize production. This study evaluated 199 maize inbred lines at the seedling stage under greenhouse conditions for resistance to U. maydis, identifying 39 highly resistant lines. A genome-wide association study (GWAS) using the mrMLM model detected 19 significant single-nucleotide polymorphism (SNP) loci. Based on a linkage disequilibrium (LD) decay distance of 260 kb, 226 candidate genes were identified. Utilizing the significant loci chr1_244281660 and chr5_220156746, two kompetitive allele-specific PCR (KASP) markers were successfully developed. A PCR-based sequence-specific oligonucleotide probe hybridization technique applied to the 199 experimental lines and 60 validation lines confirmed polymorphism for both markers, with selection efficiencies of 48.12% and 43.33%, respectively. The tested materials were derived from foundational inbred lines of domestic and foreign origin. Analysis of 39 highly resistant lines showed that the advantageous alleles carrying thymine/cytosine (T/C) predominated at frequencies of 94.87% and 53.84%, respectively. The genotype TTCC conferred high resistance, while CCTT was highly susceptible. The resistance exhibited high heritability and significant gene-by-environment interaction. This work systematically dissects the genetic basis of common smut resistance in maize, identifies favorable alleles, and provides a novel KASP marker-based strategy for developing disease-resistant germplasm.

Due to continuous increases in the global population and the limited availability of arable land resources,issues related to food security have attracted increasing attention.Maize is the most productive and most widely planted food crop in China and has the highest yield potential among different crops.Increasing the yield of maize per unit area has become one of the key goals in agriculture in China.This study summarized the key limiting factors,such as solar radiation,temperature,water,soil resources and extreme weather events that currently limit the yield and resource use efficiency of maize production,as well as the main problems existing in the process of maize production,such as unsuitable cultivar selection,low planting density and inappropriate fertilizer application.Then the maize population was optimized on the basis of quantitative design principles.By this approach,crop planting density was matched with solar radiation levels,the population structure was matched with appropriate cultivars,and the plow layer-root system-canopy functions were matched with grain yield to ensure increases in grain yield and resource use efficiency in maize production.These factors can significantly improve maize production and related economic benefits,reduce production costs and environmental burdens,and provide a scientific basis and technical support for realizing sustainable agricultural development in China.

The growing demand for food, fuel, and other agricultural products is reached to be met by increasing production on the land currently under cultivation. To tackle this challenge, we conducted 468 plots containing 263 maize hybrids during 2010-2021. Plots were divided into three yield bands: < 17.7, 17.7-21.0, and > 21.0 Mg/ha. The average yield was 19.2 Mg/ha, with a range of 9.8-24.9 Mg/ha. Dry matter (DM) accumulation and harvest index (HI) are key factors that determine the final grain yield. From < 17.7 Mg/ha to > 21.0 Mg/ha, mean yield increased by 40.8 %, dry matter (DM) accumulation, post-silking DM and HI increased by 13.2 %, 14.7 % and 10.4 %, respectively. Yield increased from the lowest to the highest yield band, the proportion of dry grains weight to post-silking DM and grain leaf ratio increased, while the remobilization efficiency of pre-silking DM decreased. The contribution of pre-silking DM to yield decreased as yield increased, whereas the contributions of post-silking DM to yield increased. When the yield was > 21.0 Mg/ha, the proportion of pre- and post-silking DM was about 4:6. HI increased with the increase of yield. When the yield was >= 18.08 Mg/ha, the HI was stable at 0.53. In conclusion, under high plant density conditions, increased yield requires higher post-silking DM and HI. Our results are crucial to identify methods of enhancing yield at the population level and meet the food demands of the growing human population.

The implementation of green technologies has facilitated the sustainable development of China's agriculture. However, the impact of green technologies in China's major crops production, their mechanisms of action and their future potential have not been systematically investigated. This study used national statistics data to summarize the impact of technological innovation on production and efficiency of major grain crops in China, and to identify which technologies have made the most important contributions.National statistics data showed changes in grain production(58% increase),total planting area(8.6% increase) and structure, nutrient input(0.83 Mt decrease) and reactive nitrogen losses, and optimized planting and fertilizer structure in 2022 compared to 2000. Of these, the proposal of integrated soilcrop system management significantly decreased reactive nitrogen losses and greenhouse gas emissions by 30% and 11%, respectively. Root zone nutrient regulation techniques, such as in-season nitrogen management, increased yields by 8% and decreased nitrogen rate by 25%. Rhizosphere nutrient regulation technology increased yield by 20.2% and decreased nitrogen rate by 20%–30%. According to predictions, integrated soil-crop system management will demonstrate significant advantages in both unit area yield and total yield by the year 2050. The adoption of integrated soil-crop system management is expected to increase the total production of rice, wheat and maize by 45.8,115 and 360 Mt, respectively. Currently, China's agriculture is confronted by significant challenges, including rising food demand, excessive inorganic nutrient inputs, and low utilization rates of organic resources. Three key recommendations arise from this study: the implementation of precise management for organic manure; the promotion of enhanced-efficiency fertilizers; and the adoption of new technologies including integrated soil-crop system management combined with rhizosphere nutrient regulation and intelligent nutrient management. These measures will drive the development of green, high-yield and efficient agriculture.

This study aimed to explore the possible changes in the contents of grain nutritional components and test weight when increasing maize yield by increasing planting density, and how to address the impacts of these changes on maize supply and demand. A two-year field experiment was conducted in Tongliao, Inner Mongolia Autonomous Region from 2020 to 2021. Using drip irrigation with integrated water and fertilizer technology, the experiment involved two maize hybrids, Dika 159 (DK159) and Xianyu 335 (XY335), at six planting densities (6.0, 7.5, 9.0, 11.5, 12.0, 13.5 x 104 plants per hectare). Research indicators included grain yield, test weight, the contents and yields of protein, starch, oil, and fiber, as well as the test weight of these four nutrients. Results showed that a reasonable increase in planting density could boost yield by 0.26-2.93 t ha-1. Although there were significant differences in test weight among treatments, all were first-grade test weight maize. Increasing planting density significantly increased starch and oil contents, and while it reduced protein content, the yields of the four nutrients increased significantly with higher grain yield and peaked at the highest grain yield. The protein test weight decreased significantly with increased density, while the starch test weight first increased and then decreased. Compared with traditional test weight-based pricing, the new maize pricing model developed in this study can better balance growers' production benefits and processing enterprises' quality requirements, providing a feasible approach to optimize maize production and enhance overall benefits.

The unreasonable application of nitrogen fertilizer poses a threat to agricultural productivity and the environment protection in Northeast China.Therefore,accurately assessing crop nitrogen requirements and optimizing fertilization are crucial for sustainable agricultural production.A three-year field experiment was conducted to evaluate the effects of planting density on the critical nitrogen concentration dilution curve （CNDC） for spring maize under drip irrigation and fertilization integration,incorporating two planting densities:D1 (60,000 plants ha -1 ) and D2 (90,000 plants ha -1 ) and six nitrogen levels:no nitrogen （N0）,90 （N90）,180 （N180）,270 （N270）,360 （N360）,and 450 （N450） kg ha -1 .A Bayesian hierarchical model was used to develop CNDC models based on dry matter （DM） and leaf area index （LAI）.The results revealed that the critical nitrogen concentration exhibited a power function relationship with both DM and LAI,while planting density had no significant impact on the CNDC parameters.Based on these findings,we propose unified CNDC equations for maize under drip irrigation and fertilization integration:Nc=4.505DM -0.384 （based on DM） and Nc=3.793LAI -0.327 （based on LAI）.Additionally,the nitrogen nutrition index （NNI）,derived from the CNDC,increased with higher nitrogen application rates.The nitrogen nutrition index （NNI） approached 1 with a nitrogen application rate of 180 kg ha -1 under the D1planting density,while it reached 1 at 270 kg ha -1 under the D2 planting density.The relationship between NNI and relative yield （RY） followed a‘‘linear+plateau”model,with maximum RY observed when the NNI approached 1.Thus,under the condition of drip irrigation and fertilization integration in Northeast China’s spring maize production,the optimal nitrogen application rates for achieving the highest yields were 180 kg ha -1 at a planting density of 60,000 plants ha -1 ,and 270 kg ha -1 at a density of 90,000 plants ha -1 .The CNDC and NNI models developed in this study are valuable tools for diagnosing nitrogen nutrition and guiding precise fertilization practices in maize production under integrated drip irrigation and fertilization systems in Northeast China.

Photosynthesis is a major trait of interest for the development of high-yield crop plants. However, little is known about the effects of high-density planting on photosynthetic responses at the whole-canopy level. Using the high-yielding maize (Zea mays L.) cultivars "LY66," "MC670," and "JK968," we conducted a 2-yr field experiment to assess ear development in addition to leaf characteristics and photosynthetic parameters in each canopy layer at 4 planting densities. Increased planting density promoted high grain yield and population-scale biomass accumulation despite reduced per-plant productivity. MC670 had the strongest adaptability to high-density planting conditions. A physiological analysis showed that increased planting density primarily led to decreases in the single-leaf area above the ear for LY66 and MC670 and below the ear for JK968. Furthermore, high planting density decreased chlorophyll content and the photosynthetic rate due to decreased canopy transmission, leading to severe decreases in single-plant biomass accumulation in the lower canopy. Moreover, increased planting density improved presilking biomass transfer, especially in the lower canopy. The yield showed significant positive relationships with photosynthesis and biomass in the lower canopy, demonstrating the important contributions of these leaves to grain yield under dense planting conditions. Increased planting density led to retarded ear development as a consequence of reduced glucose and fructose contents in the ears, indicating reductions in sugar transport that were associated with limited sink organ development, reduced kernel number, and yield loss. Overall, these findings highlighted the photosynthetic capacities of the lower canopy as promising targets for improving maize yield under dense planting conditions.

The grain moisture content of maize inbred lines at maturity is one of the most important indicators for mechanical harvesting of kernels. In this study, 116 maize inbred lines from a wide range of sources were used as research materials and 30 traits of grain moisture content were analyzed using multivariate statistical analysis. The results showed that all 30 traits had some correlations. Principal component analysis downscaled the 30 traits into 10 principal component factors, reflecting 77.674% of the information in the original traits. Cluster analysis categorized the 116 inbred lines into 5 major groups containing 26, 29, 31, 16 and 14 inbred lines. Based on the D value of the overall evaluation, discriminant analysis reclassified the maize inbred lines by principal component scores and 98 maize inbred lines were correctly discriminated with a probability of 84.48%, which can be regarded as a relatively reliable clustering result. The stepwise regression method was further used to screen seven traits: GMC2, GDR1, HMC3, NH, GDR2, CD and EL and to establish a comprehensive evaluation model for the grain moisture content of maize inbred lines. Among 116 maize inbred lines, 14, represented by H21 and MS71, had the lowest grain moisture content at maturity.