Maize (Zea mays L.) is an important food and silage crop with high production potential and economic benefits (Erenstein et al. 2022).  Understanding the maize yield potential can provide reliable theoretical and practical support for achieving breakthroughs in grain yield (Meng et al. 2013).  It was one of the effective ways to explore the grain yield potential based on the model on a national scale.

In China, maize was widely cultivated. The four major maize regions span from 21° to 53°N in latitude and 73° to 135°E in longitude and cover the most complex climatic conditions suitable for maize growing in the world (Xu et al. 2017).  The regional climate heterogeneity tends to induce ecological adaptability responses of maize, which can also lead to variations in the interregional adaptability of crop models (Abbas et al. 2023).  In addition, in the context of global climate change, crop production has been severely affected by extreme weather events, especially maize and wheat (Schmitt et al. 2022).  Clarifying the regional adaptability of the crop growth models is an important basis for analyzing the response of maize to climate change.

Nowadays, crop growth models have been increasingly developed and applied, which play a crucial role in regional simulation, future climate scenario simulation, optimization of cultivation measures, and assessment of meteorological disaster impacts.  Currently, the main crop models applied in China include AquaCrop, APSIM, and WOFOST models, most of them were mainly focused on wheat and rice and the application status varied with regions (Jin et al. 2016; Kheir et al. 2021).  The Hybrid-Maize model is a maize-specific process model developed on the studies of high-yielding maize in the United States, which has been tested and widely used in the United States and South Asia (Yang et al. 2004; Timsina et al. 2010).  It can simulate the maize grain yield potential in specific years and regions by inputting the required relevant parameters including meteorological data, the tested cultivars, and field management information (Yang et al. 2004).  Most importantly, it provides a basis for clearing the maize grain yield improvement space and technical approach to reduce the yield gap.  Currently, under the background of dense panting conditions to increase maize grain yield, the application of this model in China has gradually attracted attention.  However, previous studies on the Hybrid-Maize model were mainly limited to specific regions or sites and applied under low planting conditions (Liu et al. 2012; Meng et al. 2013; Hou et al. 2014).  There were few reports assessing its adaptability at large spatial scales and under dense planting conditions. The climatic conditions were diverse in different maize growing regions across China.  Therefore, it is crucial to evaluate the adaptability of models under dense planting conditions in different regions.  In this study, we evaluated the performance of the Hybrid-Maize model in the major maize growing regions of China based on field data at 22 experimental sites under high planting density (7.5×10⁴ plants ha^-1) during the period of 2011-2015.  The maize growing information and climatic conditions of the experimental sites were listed in the Appendix A.  The findings can provide a reference for the application of the Hybrid-Maize model under dense planting conditions in different regions of China.

The results of this study showed that the normalized root mean square error (NRMSE) were all below 30.0% and the index of agreement (D) were approached to 1, which indicated that the simulated yield was within an acceptable range (Fig. 1-A).  Particularly, the model showed the best adaptability in the NW (Northwestern maize growing region, NRMSE=9.8%).  A similar performance in the prediction of grain yield (NRMSE=7.1%) was observed in the United States under high density (Abimbola et al. 2022).  It was mainly that the Hybrid-Maize model was developed based on high-yielding fields in the United States, where the planting densities commonly exceed 7.5×10⁴ plants ha^-1 (Yang et al. 2004).  It was also shown that the average maize grain yield in the NW was significantly higher than that in the SW (Southwestern maize growing region), HHH (Huang-Huai-Hai maize growing region), and NM (Northern Spring maize growing region).  The average measured grain yield in the NW (18.2 Mg ha^-1) was higher than that in the SW (9.4 Mg ha^-1), HHH (11.0 Mg ha^-1), and NM (13.2 Mg ha^-1).

Aboveground biomass and harvest index (HI) are the bases for maize grain yield formation.  It was indicated that the model had better simulation effects in aboveground biomass with a lower NRMSE value in the NW (17.2%) than that of SW (24.8%), HHH (22.9%), and NM (26.2%) (Fig, 1-B).  The simulation accuracy of this model for aboveground biomass in the NM (NRMSE=26.2%) was similar to a previous study conducted in the Northeast region under sufficient irrigation conditions (NRMSE=24.4%) (Liu et al. 2012).  However, the performance of the model was slightly different in these growing stages with a similar trend in simulated accuracy (i.e., the jointing stage>silking stage>maturity stage) for these four regions.  As for the harvest index, it was shown that the Hybrid-Maize model perform well in the NM and HHH under dense planting conditions (Table 1).  The simulated HI for all regions with the trend of HHH>NM>NW>SW that differed from the spatial distribution (NW>SW>NM>HHH) in the previous study (Liu et al. 2020), which may be related to the overestimation of the HI in the HHH and NM and underestimation in the NW and SW by this model.  Therefore, further optimization in the HI is required for this model when applied across different regions.

The dynamic changes in leaf area index (LAI) are shown in Fig. 1-C.  There were significant differences in the performance of the Hybrid-Maize model between regions under dense planting conditions.  The performance of the model in simulating LAI was better in the HHH (NRMSE=28.8%) and NM (NRMSE=22.0%) than that in the NW (NRMSE=33.4%) and SW (NRMSE=44.2%).  Additionally, it was observed that the Hybrid-Maize model showed a good fitting degree in the jointing and mature stage period in most of these regions.  Overall, this simulated values were higher than the measured with an average overestimation of 37.0% for the whole growth season.  Specifically, the simulated values in the SW were on average 43.6% higher than the measured.  In the NM, the simulated values were on average 12.5% lower than the measured after silking.

In summary, the Hybrid-Maize model showed good adaptability in the simulation of grain yield and dynamic changes of aboveground biomass in the four major maize growing regions of China under moderate planting density conditions, especially in the NW and SW.  However, there was a significant underestimation of HI in the NW and SW.  Conversely, there was an overestimation of LAI in these regions.  Further evaluation of the model can be calibrated by adjusting the LAI and HI to refine the prediction of grain yield potential.  Overall, the Hybrid-Maize model can provide relatively acceptable simulation references in the HHH and NM for all parameters under dense planting conditions. 

Promoting the strip intercropping model of soybean and corn is one of the effective ways to improve soybean production capacity. The practice of strip intercropping of soybean and corn was based on in the Huaibei, Anhui Province, and its efficient cultivation techniques were summarized from the aspects of variety selection, planting model selection, seed treatment, and etc. In terms of variety selection, selecting soybean varieties with limited podding habits, shade tolerance, dense planting tolerance, high temperature tolerance, lodging resistance, disease resistance, and drought resistance; corn varieties with compact plant type, moderate height, high temperature tolerance, dense planting tolerance, ear rot tolerance, disease resistance, and suitable for machine harvesting. Selecting the planting model of 4 rows of corn and 6 rows of soybeans. Seed treatment including seed selection, sun drying, pesticide mixing or coating. Selecting 4 rows of corn seeders and 6 rows of soybean seeders for simultaneous fertilization and sowing. After sowing and before sprouting, timely sealing and weeding should be carried out. For plots with poor sealing and weeding effects, corn and soybean specific herbicides should be used for targeted isolation and weeding during the 1-2 compound leaf stage of soybeans and 4-5 leaf stage of corn. To meet the water and fertilizer supply needs during the corn bell mouth stage, soybean flowering and pod setting stage, and grain filling stage, the integrated technology of micro spray irrigation and fertilization is adopted for irrigation, topdressing, and foliar fertilization. Spraying control agents on 6-9 leaves of corn and early flowering stage of soybeans to control plant growth. Adhering to the principle of prevention first and combining prevention and control, and timely apply appropriate drugs to prevent and control diseases and pests such as soybean virus disease, aphid, corn stem rot disease, and Spodoptera frugiperda, etc. Choosing soybean varieties that are resistant to high temperature and heat damage, apply fertilizers reasonably, and water them in a timely manner to prevent soybean ‘disease greening’. Selecting varieties of corn that are resistant to high temperature and heat damage, water them in a timely manner, and use artificial pollination to prevent and control the impact of high temperature and heat damage on the tasseling and silk emergence stages of corn. Based on the maturity of soybeans and corn in the field, choose the method of harvesting first after maturity or harvesting with different machines simultaneously. This article provides references for further promotion and application of the soybean corn strip intercropping model in relevant regions.

The aim is to study the effects of different planting densities and planting ratios on biomass accumulation, nitrogen absorption, yield and economic benefits, and soil nutrient status of maize and soybean. Based on a field experiment, six treatments, including maize monoculture (M), soybean monoculture (S), maize/soybean 2:4 mode (I₁) [60000 maize plants/hm²+135000 soybean plants/hm² (D₁), 67500 maize plants/hm²+135000 soybean plants/hm² (D₂)], and maize/soybean 4:6 mode (I₂) [60000 maize plants/hm²+135000 soybean plants/hm² (D₁), 67500 maize plants/hm²+135000 soybean plants/hm² (D₂)], were designed. The results showed that maize/soybean planting pattern significantly decreased crop yield and biomass, compared to M and S, maize yield was decreased by 18.91%-25.45%, biomass was decreased by 12.62%-30.69%, soybean yield was decreased by 50.43%-56.79%, and biomass was decreased by 36.84%-46.61%. The biomass and yield of maize in I₁ were lower than that of I₂, while soybean showed the opposite trend. Under the same planting ratio, the maize yield of D₁ was significantly higher than that of D₂, while the soybean yield was not significantly different. Due to the difference of yield and input cost, the economic benefits of different planting patterns are different. Among them, the economic benefits of I₁D₁ were increased the most compared with M and S, which were 38.61% and 22.25%, respectively. In addition, different maize/soybean planting patterns could improve the soil chemical properties, especially the contents of soil alkali-hydrolyzed nitrogen and organic matter in maize soil. Compared with M, I₁D₁ significantly increased the contents of alkali-hydrolyzed nitrogen and organic matter by 14.17% and 16.61%, respectively. Overall, the maize/soybean 2:4 planting pattern combined with 60000 maize plants/hm²+135000 soybean plants/hm² is the optimal treatment in terms of improving crop yield and economic benefits of the system and improving soil nutrient status, etc. The research results have certain theoretical value for the application and promotion of maize/soybean combined planting pattern in Shandong Province.

【Objective】Husk is an important trait that affects the mechanical harvesting of maize grain, and identification of the genetic loci and candidate genes can provide theoretical basis for genetic improvement of maize husk traits. 【Method】To identify significantly associated single nucleotide polymorphisms (SNPs) and predict candidate genes for three husk traits, 251 maize inbred lines were used as plant materials and evaluated for husk number (HN), length (HL), and coverage (HC) in two environments. The genome-wide association study (GWAS) was conducted by multi-locus random-SNP-effect mixed linear model (mrMLM) with 32 853 SNPs across entire genome. 【Result】The three husk traits exhibited abundant variation among 251 maize inbred lines with 10.65%-40.60% of phenotypic variation coefficients. The variances of genotype, environment, and the genotype×environment interactions were significant at P<0.01 for each trait, and the broad-sense heritability for each trait was more than 80%. A total 92 SNPs significantly associated with three husk traits were identified in two environmental and best linear unbiased predictors (BLUP) across two environments values by GWAS. Among these SNPs, 35 SNPs were significantly associated with HN, and the phenotypic variance explained by single SNP ranged from 1.48% to 10.53%. 33 SNPs were significantly associated with HL, and the phenotypic variance explained by single SNP ranged from 1.61% to 21.69%. 24 SNPs were significantly associated with HC, and the phenotypic variance explained by single SNP ranged from 2.17% to 20.86%. However, none of SNP could be significantly associated with two husk traits. Five of 92 SNPs were stable, as they were repeatedly detected in two environments and BLUP, also they were novel loci for first reported in this study. Based on the five stable SNPs and qRT-PCR analysis for husk tissue of 17 maize inbred lines, three candidate genes (Zm00001d003850, Zm00001d033706 and Zm00001d025612) related to maize husk were screeded out, which encoded BOI-related E3 ubiquitin-protein ligase, GeBP transcription factor, and protein of unknown function, respectively. 【Conclusion】A total of 92 SNPs significantly associated with three husk traits were identified, including five stable SNPs. Three candidate genes were predicted that might be involved in maize husk growth and development.

【Objective】This study explored the effects of different mulching methods on the production of photosynthetic substances and water use of maize under the intercropping mode of maize and soybean, aiming to determine the suitable mulching method for maize and soybean plantation in dryland agriculture in northern Shaanxi, so as to provide a basis for high-yield and efficient production of maize and soybean and ecological environment protection. 【Method】This study was conducted in irrigated land and nonirrigated land in 2022, using 'Zhonghuang 30' soybean and 'Xianyu 335' maize as materials. The two-factor complete randomized design was carried out, and the control group combined single crop (maize “M”, soybean “S”) and film mulching (bare land, interbrane “J”), and the test group combined intercropping crop (maize “M”, soybean “S”) and film mulching (bare land, interbrane “J” and whole film “Q”), with a total of 13 treatment groups. The characteristics changes of growth, photosynthesis, and water use efficiency of intercropped maize under different mulching methods were studied. 【Result】 (1) From jointing to silking stage, the growth space of intercropped maize was limited, resulting in a disadvantage in aboveground biomass of intercropped maize compared with monoculture. The biomass during the jointing stage of S/MQ, SQ/MJ, and SQ/MQ was 5.1%, 6.3%, and 1.7% higher than that of monoculture M, respectively; under intercropping, SJ/MJ maize plants had the fastest growth rate and a sharp increase in growth. SQ/MQ S/M, S/MJ, SQ/MJ, and SJ/M in dry land had a better promoting effect on the photosynthetic products of maize during the silking stage, and the aboveground biomass was 0.6%-105.9% higher than that of monoculture M. (2) To some extent, intercropping and mulching treatments improved the photosynthetic characteristics of maize, and the net photosynthetic rate (Pn) content of paddy maize. There was a certain degree of positive relationship between stomatal conductance (Gs), cellular CO₂ concentration (Ci) and transpiration rate (Tr). The photosynthetic parameters of SQ/MJ and SJ/MQ were relatively high, while SJ/M and SQ/MQ were lower than non film coated S/M; there was a weak negative correlation between Pn and Ci in dryland maize, and the effect of maize mulching was not significant among different treatments. The Gs of intercropping treatment was 5.7% -38.1% lower than that of monoculture M, and Tr was also reduced by 5.6% -25.6%. Only the Pn of SJ/M and SQ/M, as well as the Ci of SQ/MJ and S/M, were higher than monoculture M. (3) The intercropping film mulching had a significant impact on water use efficiency (WUE). The WUE of the intercropping treatment was 41.1% -74.0% higher than that of monoculture M, among which SJ/M, S/M and S/MJ were relatively high; among all treatments in arid land, SQ/MJ had the highest WUE (19.04 kg∙mm^-1∙hm^-2), followed by SJ/MJ (17.07 kg∙mm^-1∙hm^-2), and the WUE of SJ/M and SQ/M was significantly lower than that of monoculture M by 26.7% and 20.6%, respectively. (4) Compared with monoculture M, intercropping S/MJ between irrigated land and dry land SJ/M and SJ/MJ maize increased yields by 76.8%, 73.0%, and 72.3%, respectively, while soybean yield reduction was relatively less among all intercropping treatments, demonstrating higher economic benefits; dry land intercropping SJ/MJ and SJ/MQ maize increased production by 17.1% and 23.5%, respectively, while economic benefits decreased by 17.5% and 22.8%, respectively. 【Conclusion】Compared with single cropping M, SJ/MJ model improved the photosynthetic performance, biomass, and yield of maize in irrigated land, and improved system economic benefit and promoted water use efficiency. In dry land, through the complementary effect and resource allocation in the intercropping system, it maintained maize yield and improved water use efficiency, but the increase of total input in agricultural materials reduced the economic feasibility. Therefore, in the dryland agriculture of Northern Shaanxi, the intercropping planting pattern of maize with degradable film and soybeans with degradable film was recommended for both irrigated land and moderately irrigated dry farm, aiming to enhance water use efficiency, increase production and profitability, and promote sustainable ecological agriculture development.

This study is dedicated to the development of iron- and zinc-rich high folate maize (Fe ≥ 40 mg/kg, Zn ≥ 40 mg/kg, folate ≥ 150 μg/100 g), to improve the utilization rate of folate, and to prolong the shelf-life of freshly-eaten iron- and zinc-rich high folate maize. Five groups of iron- and zinc-treated groups with different concentrations and one group of clear water control group were set up, and the foliar spraying of iron and zinc mixed micronutrient fertilizer was carried out by unmanned aerial vehicles to obtain iron- and zinc-rich high folate maize. Different processing techniques were adopted to treat the obtained high folate maize to analyze the changes of folate content in the iron- and zinc-rich high folate maize under different processing and storage conditions, and to screen out the optimal processing and storage methods. Foliar spraying of iron and zinc mixed micronutrient fertilizer on high folate maize during the growth period significantly increased the iron and zinc content in the kernels, achieving the effect of iron and zinc nutrient fortification. The rate of folate loss during processing of vacuum-packed fresh maize was 11.97%, and the rate of folate loss during processing of vacuum-packed instant maize was 23.36%. Combined with the loss rate of folic acid in different processes and the changes of folic acid content under different storage conditions, the best effect of vacuum-packed instant maize was achieved by storing it at 4℃ for 60 d.

In order to study the influence of maize-peanut intercropping on crop and soil characteristics, this paper sets up the root separation test of corn and peanut potted plants to study the influence of maize and peanut intercropping on crop agronomic traits, physiological activities, soil microorganisms, soil enzyme activity and soil rapid nutrients. The results showed that maize-peanut intercropping affected the morphological and physiological indexes of crops. Plant height and relative chlorophyll content of peanut were increased by 71.4% and 11.3%, but root length, root weight and leaf weight were not significantly affected. Plant height, leaf fresh weight and root length of maize were increased by 43.9%, 122% and 45.6%, respectively. But there was no significant effect on the relative content of chlorophyll. Maize-peanut intercropping improved plant stress resistance, increased SOD and POD activities of peanut leaves by 66.7% and 129%, and decreased MDA content of peanut roots by 19.8%, respectively. The activities of SOD in leaves and roots of maize were increased by 39.9% and 17.0%, respectively, while MDA content in roots decreased by 61%. Maize-peanut intercropping changed soil available nutrient content, decreased peanut soil available N by 79.5%, but increased soil available P by 11.5%, and had no effect on soil available K content. It had no effect on maize soil available N and K, but decreased soil available P by 9.4%. Maize-peanut intercropping affected soil biological characteristics and increased soil enzyme activities, especially the alkaline phosphates activity. The soil alkaline phosphates activity in peanut and maize fields increased by 122% and 330%, respectively. The Maize-peanut intercropping could improve soil microenvironment and physiological activities of leaves and roots in seedling stage.

Based on the practical production and cultivation, the reasons for the formation of poorly sturdy corn cob and multiple ears were summarized and analyzed by referring to relevant literature, corresponding countermeasures were proposed, and the research direction was prospected. The main reasons for the formation of poorly sturdy corn cob and multiple ears included genetic factors of the variety, external environmental factors (high temperature and drought, cloudy and rainy), and cultivation management factors (sowing date, density, pest control, disease and insect pests, and pesticide application). By selecting stress resistant varieties, and carrying out field management such as reasonable fertilization, timely weeding, soil loosening, and timely watering, the stress resistance of corn can be improved, and poor ear development caused by improper management can be avoided. The next step of research will utilize modern technologies such as gene editing to analyze the mechanism of poorly sturdy corn cob and multiple ears formation; explore new agronomic measures such as foliar fertilization to improve maize yield and quality. This paper provides references for improving corn yield and promoting the healthy development of related industries.

The aim was to explore the regulation mechanism of different coupling ratio of irrigation and nitrogen fertilizer application on photosynthesis, transpiration rate, chlorophyll value, dry matter accumulation characteristic and yield of maize. In this research, using the corn variety of ‘Yuyu 22’ as research material, a split plot design field experiment was carried out in dryland areas of Gansu Province in 2022. Three irrigation application amount treatments of 3150 m³/hm² (W₁), 3825 m³/hm² (W₂) and 4500 m³/hm² (W₃) were set as the main plot, and three nitrogen application amount treatments of 0 (N₀), 272 kg/hm² (N₁) and 320 kg/hm² (N₂) were set as the split plot. Photosynthetic rate, transpiration rate, chlorophyll value, dry matter accumulation characteristic and yield at the growth period of maize were determined. The results showed that under a reduction of 15% in irrigation amount during growth, compared with the W₂N₀ and W₂N₂ treatments, the photosynthetic rate, transpiration rate and chlorophyll value under the W₂N₁ treatment were increased by 30.91%, 13.53% and 39.78%, 26.46% and 32.33%, 9.21%, respectively. The maximum growth rate of dry matter in W₂N₁ treatment was 7.5 and 3.7 days later than that in W₂N₀ and W₂N₂ treatments, respectively. The Vmax of W₂N₁ treatment was 11.25% and 4.24% higher than that of W₂N₀ and W₂N₂ treatment, respectively. Compared with W₂N₀ and W₂N₂ treatments, the biological yield and grain yield of maize with the W₂N₁ treatment were increased by 29.97%, 5.15% and 48.61%, 10.78%, respectively. The conclusion showed that the treatment with application coupling of irrigation and nitrogen (i.e. reduction of 15% irrigation amount during growth with 3825 m³/hm² and reduction of 15% N application amount with 272 kg/hm² at growth stage) could be considered as the best cultivation pattern management, which could provide technical guidance for further exploring for water-saving and fertilizer-saving and high yield and efficient cultivation of agriculture in the dryland areas.

The fall armyworm (Spodoptera frugiperda) is an invasive species and a destructive pest of maize, which significantly impacts native species and communities via complex mechanisms like competition for resources. However, the interaction between S. frugiperda and local pests remains unclear. In this study, we determined that Oriental armyworm (Mythimna separata) females with different mating status displayed different approach-avoidance behaviors towards maize which was damaged by S. frugiperda larvae. The virgin M. separata females were repelled, while the mated females were attracted by the S. frugiperda-damaged maize. To further understand the olfactory mechanism of this phenomenon, seven volatiles induced by S. frugiperda in maize were characterized by gas chromatography and mass spectrometry (GC-MS), including trans-2-hexenal, linalool, trans-β-farnesene, cis-3-hexenyl acetate, β-caryophyllene, trans-α-bergamotene, and isopentyl acetate. Additionally, electrophysiological and behavioral assays of the seven compounds were performed using both virgin and mated females of M. separata. We determined that virgin and mated females displayed different responses to the HIPV compounds. Trans-β-farnesene was the core compound for repelling virgin females, and trans-2-hexenal was the key attractant for oviposition in mated female M. separata individuals. These findings help our comprehension of the relationships between maize pests and offer new possibilities for controlling them by olfactory-based strategies. 

【Objective】The objective of this study is to optimize the classification and discriminant method of maize heterotic groups, and provide guidance and reference for maize breeding practices.【Method】Solid-phase chips were used to genotype 60 waxy maize inbred lines, and high-quality SNP markers with different density were obtained through quality control. Population structure analysis and genetic distance clustering were used to classify the 60 waxy maize inbred lines into different groups, and the differences between different classification methods were compared. On this basis, random forest and support vector machine methods were used to sample and discriminate the results of different classification methods. Five-fold cross-validation was used for sampling, and the prediction accuracy of maize group classification based on different classification methods was compared.【Result】Using different quality control standards, 11 431 and 4 022 molecular markers were obtained, respectively. Based on these two molecular marker densities, 60 materials were divided into 5 and 4 clusters, respectively. When using 11 431 SNP markers, the population structure analysis and genetic distance clustering results showed that the intra-cluster sample consistency was 63.33%. When using 4 022 SNP markers for clustering, the intra-cluster sample consistency was 90.00%. The prediction accuracy results for discriminating maize inbred line clusters showed that the average prediction accuracy (91.43%) of Random Forest and Support Vector Machine using 4 022 markers were higher than that of 11 431 markers (86.25%). Among them, the highest prediction accuracy was achieved by Random Forest using 4 022 markers, with a prediction accuracy of 94.17%.【Conclusion】Clustering analysis ultimately divided 60 waxy maize inbred lines into 4 clusters. Sampling and cross-validation results using Random Forest and Support Vector Machine for cluster classification showed that Random Forest achieved higher prediction accuracy than Support Vector Machine.

【Objective】Based on the long-term experiment in the North China Plain (NCP), the differences in soil nutrient and aggregate nutrient distribution between diversified crops and wheat-maize rotation systems were investigated. Additionally, it provided a comprehensive evaluation of soil quality indices (SQI), offering a scientific basis for enhancing soil quality and productivity in the NCP. 【Method】Four diversified crop rotation systems were evaluated, including spring sweet potato-winter wheat-summer maize (Psw-WM), spring peanut-winter wheat-summer maize (Pns-WM), spring sorghum-winter wheat-summer maize (Ps-WM), with winter wheat-summer maize (WM-WM) serving as the control. The soil samples from the 0-40 cm depth were collected during the second rotation in 2022, at the flowering and harvesting stages of winter wheat. The soil enzymes activities, aggregate stability, organic matter, and concentrations of nitrogen, phosphorus, and potassium in soil and aggregates of different sizes (>2.00 mm, 0.50-2.00 mm, 0.25-0.50 mm, and <0.25 mm) were assessed. The SQI for each crop rotation system was then comprehensively evaluated. 【Result】Compared with WM-WM, the three other crop rotations increased soil inorganic nitrogen content. Psw-WM significantly enhanced organic matter in the 0-20 cm layer, total nitrogen in soil aggregates (>2.00 mm, 0-10 cm), and organic matter in soil aggregates (>2.00 mm and 0.50-2.00 mm, 0-10 cm), which also increased cellulase, catalase, and alkaline protease activities. Pns-WM improved organic matter in the 20-40 cm layer and available potassium in soil aggregates (0.25-0.50 mm and >2.00 mm, 10-20 cm), as well as organic matter in soil aggregates (0-10 cm, >2.00 mm and 10-20 cm, >0.50 mm), which also increased sucrase, urease, and alkaline protease activities. Psw-WM improved the stability of 0-10 cm soil aggregates, while Pns-WM improved the stability of 0-30 cm soil aggregates. Both Pns-WM and Psw-WM significantly improved the SQI, with Pns-WM showing a higher improvement than Psw-WM. The path analysis revealed that the average weight diameter (MWD) of aggregates was a direct and significant affecting SQI. It also had a significant indirect positive effect on SQI by influencing inorganic nitrogen. Additionally, the increased organic matter led to a higher proportion of large aggregates, which significantly affected SQI indirectly. 【Conclusion】Legume (peanut) and root crop (sweet potato) rotations with wheat-maize rotations could significantly improve soil quality and enhance the soil nutrient supply capacity in the NCP.

To establish a solid theoretical foundation for the efficient management of insect pests in corn crops, practical plant protection strategies that reduce the amount of pesticides should be explored. A study was conducted to investigate the occurrence of Spodoptera frugiperda on maize in the mountainous area of Mengga Town, Mangshi City, Dehong Prefecture, Yunnan Province. Two types of pesticides, 5% emamectin benzoate and 15% indoxacarb, were tested on Spodoptera frugiperda in corn fields using plant protection drones and knapsack electric sprayers. Spodoptera frugiperda larvae can cause damage in the whole growth period of maize, and the infestation rate, damage index, number of insects per 100 plants, and the proportion of different insect ages in different growth stages of maize are significant different, and Spodoptera frugiperda is the most harmful in the big bell stage of maize. Two different methods of applying 5% emamectin benzoate and 15% indoxacarb had a significant impact on the incidence of Spodoptera frugiperda in maize fields. The damage rate and index of maize also showed a significant decrease between 3 to 14 days after application. There was no significant difference in the relative control efficacy of the same pesticide against Spodoptera frugiperda under two different methods. Still, the use of plant protection drones pesticide application had the advantages of labor-saving, time-saving, and pesticide-saving. Spodoptera frugiperda control had a positive effect on increasing the production of maize in the yield, and the experimental treatments results showed a significant increase in yield of the test variety 'Yunrui 62', with 25.28% to 28.93% production increase compared to the control treatment. In total, it is recommended to use UAVs equipped with anti-spray technology to protect plants during large-scale Spodoptera frugiperda control. Additionally, it's important to conduct thorough investigations and implement field management practices to prevent corn insect infestations, which are crucial for achieving high and stable crop yields. It's important to focus on integrating, demonstrating, and promoting the use of this technology in the future.

To analyze the utilization rate of nitrogen, phosphorus and potassium fertilizer in corn planting in Yanyuan, promote scientific fertilization to increase efficiency, and promote the protection and quality improvement of cultivated land, we set up treatments of no fertilizer, no nitrogen, no phosphorus, no potassium and NPK full fertilizer to carry out the utilization rate analysis of NPK fertilizer for corn. The results indicated that stem diameter, ear height, number of grains per ear and 1000-grain weight of NPK fertilizer treatment were higher than those of other treatments, except that plant height was lower than that of no potassium; the grain yield and stem and leaf yield were also the highest, which were 12.07 t/hm² and 13.55 t/hm², respectively. The order from high to low was full fertilizer zone (T₅) > potassium-free zone (T₄) > phosphorus free zone (T₃) > nitrogen free zone (T₂) > fertilizer free zone (T₁). The yield to investment ratio of NPK fertilizer area was the lowest (4.73), but the economic benefit was the highest. The utilization rates of N, P and K in the experimental field were from high to low as K > N > P, and the utilization rates were 56.61%, 43.14% and 9.55%, respectively. Therefore, the composite fertilizer containing nitrogen, phosphorus and potassium should be selected for corn production in Yanyuan, and the content of potassium and nitrogen should be higher than that of phosphorus. At the same time, we should increase the application of organic fertilizer and plant green fertilizer to improve the ecological environment and improve the quality of crops.

In order to analyze the agronomic traits, yield and yield composition of machine-harvested maize under different density treatments, machine-harvested maize ‘Ludan 608’ was used as the material. Five planting densities of 60000 plants /hm² (D₁), 69000 plants /hm² (D₂), 75000 plants /hm² (D₃), 82500 plants /hm² (D₄) and 90000 plants /hm² (D₅) were set to analyze their agronomic traits and yield. The results showed that plant height, ear height, lodging rate and bare plant rate increased with the increase of planting density, while double ear rate decreased. The highest maize yield was 11231.31 kg/hm² with the planting density of 82500 plants /hm². The LAI increased with the increase in planting density. The accumulation of dry matter in maize at both individual and population levels showed an ‘S-shaped’ growth curve of ‘slow-fast-slow’. The dry matter amount of single plant decreased with the increase in planting density. In the range of D₁-D₄, dry matter amount of population increased with the increase of planting density. And it began to decrease when planting density was more than D₄.

The study aims to explore the effects of nitrogen fertilizer and organic fertilizer combination on photosynthesis, dry matter accumulation, nitrogen use efficiency and yield of maize during the growth period. In this research, the cultivar ‘Woyu No.3’ was applied as research material. A split plot field experiment was conducted from 2022 to 2023 in Hexi Oasis Irrigation Area of Gansu Province. Four nitrogen fertilizer applications, i.e. without N application (N₀, CK), traditional N fertilizer application (N₁), 15% N fertilizer reduction (N₂) and 30% N fertilizer reduction (N₃), were set as the main plot, and three organic fertilizer applications, namely 3.5×10³ (O₁), 3.0×10³ (O₂) and 2.5×10³ (O₃) kg/hm², were used as the split plot. Photosynthetic, chlorophyll relative content, dry matter accumulation, nitrogen use efficiency and yield were determined. The result showed that, under the level of same nitrogen application in growth stages of maize, compared with the N₂O₁ and N₂O₃ treatments, the photosynthetic rate and transpiration rate and stomatal conductance under the N₂O₂ treatments were increased by 17.91%, 10.59% and 19.13%, 18.46% and 20.13%, 26.62%. Compared with the N₂O₁ and N₂O₃ treatments, the chlorophyll value and V_max and biological yield under the N₂O₂ treatments were increased by 18.73%, 9.77% and 13.79%, 17.84% and 7.14%, 6.78%. Compared with the N₂O₁ and N₂O₃ treatments, the grain yields and nitrogen use efficiency under the N₂O₂ treatments were increased by 18.77%, 20.14% and 15.68%, 8.02%. In summary, in the Hexi Oasis Irrigation Area with resource shortage, the reduction of N fertilizer by 15 % (306 kg/hm², N₂) combined with organic fertilizer (3000.00 kg/hm², O₂) could replace part of N fertilizer, which had high nutrient supply potential and the best effect on maize yield stability.

In order to study the changes of germination index and physiological index of maize under PEG simulated drought stress, 20% PEG-6000 was set up for drought treatment. The germination rate, germination potential, germination index, radicle length, chlorophyll value (SPAD), superoxide dismutase (SOD) activity and malondialdehyde (MDA) content of maize at germination stage were measured, and the drought resistance of different varieties was evaluated by membership function method. The results showed that compared with CK, the germination rate, germination potential, germination index and radicle length of each maize variety decreased under drought stress, the chlorophyll value and SOD activity decreased, and the MDA content increased. The average value of the membership function of ‘Xinnong 008’ was greater than 0.7, which was a strong drought-resistant variety. The average value of membership function of ‘Zhongyu No.9’, ‘Zhongyu No.1’ and ‘Woyu No.3’ was less than 0.4, which belonged to weak drought-resistant varieties.

In order to study the separation characteristics of plant traits in maize, ten maize inbred lines from different sources were selected for cross-mating, and two 8-parent hybrid F₁ segregated populations A and B were obtained. The phenotype of five plant traits of the segregated populations was identified, and the correlation analysis and path analysis between plant traits were carried out. The results showed that the variation coefficient of plant height in two segregating populations was large, and the coefficient of variation was 10.34% and 10.54%. Correlation analysis showed that the plant height showed extremely significant positive correlation with ear height, tassel length and average length of internode above ear, and tassel length showed extremely significant positive correlation with average length of internode above ear in two segregated populations. But the correlation between other plant traits of the two populations was not completely consistent. The path analysis showed that the ear height, tassel length and average length of internode above ear had significant positive direct effect on plant height. The tassel length had a large positive indirect effect on plant height through the average length of internode above ear. This study analyzed the relationship between plant traits, which could provide reference for genetic improvement of plant traits in maize.

The causes of common diseases and pests in corn planting process were summarized and analyzed, and corresponding control measures according to the types of common diseases and pests were put forward. In the process of corn production, soil nutrient deficiency and light insufficiency, excessive water and other factors will lead to the occurrence of diseases and insect pests. The common diseases in corn production included Puccinia sorghi, Bipolaris maydis, Exserohilum turcicum, Sphacelotheca reiliana; common pests included Spodoptera frugiperda, Ostrinis furnacalis and Rhopalosiphum maidis. Based on the occurrence characteristics of diseases and pests, the rule and the way of transmission were put forward, such as cleaning up diseased plants and weeds, selecting disease-resistant varieties and applying chemical agents, biological bacteria and other pest control measures. The research results provides references for the control of diseases and pests in large-scale corn production.

The current situation of summer corn production in the Northern Anhui Province were summarized and analyzed based on practical experience, and proposes corresponding strategies to improve yield. The production of summer corn in the research area was affected by catastrophic weather conditions such as high temperatures, droughts, and floods, there were still issues that need to be further improved, including the construction of agricultural water conservancy facilities, agricultural technology training, variety selection and sowing quality, as well as field management. Based on the current production situation, it was proposed to increase the construction of agricultural water conservancy infrastructure and enhance the disaster resistance of farmland; strengthen publicity and training efforts to improve agricultural production efficiency; improving the quality of sowing (scientific selection, seed treatment, reasonable planting and mechanical sowing), ensuring uniform and strong emergence of seedlings, and strengthening field management (seedling stage management, trumpet stage management, mid to late stage management, and suitable early sowing and late harvesting), effectively enhancing disaster resistance and other effective strategies to increase summer corn yield. Provide references for the high and stable yield of summer corn in the research area.

In order to explore a new intercropping model that suitable for the flatland and shallow hill in Chongqing and similar ecological areas, increase the yield and economic benefits of crops, and provide reference for research on crop intercropping models, an intercropping experiment with fresh maize, sweet potato, and soybean was conducted. In this experiment, three different row ratios of maize-sweet potato-soybean intercropping models were used, with one fresh waxy maize variety, three fresh sweet potato varieties, and one fresh soybean variety as materials. The results showed that there were no significant differences in the yield components of fresh waxy maize in different row ratio intercropping models, but there was a significant difference in the average fresh ear weight per plant and yield. There were no significant differences in the number of branches, effective pod number per plant, and fresh pod yield of fresh soybean in different row ratio intercropping models. In the intercropping system, sweet potatoes in different row ratio intercropping were affected by the shading of maize, resulting in varying degrees of reduction in storage root yield. The different row ratio intercropping models had inconsistent effects on the number of storage root per plant and commodity rate of different sweet potato varieties. Increasing the intercropping planting density of fresh sweet potato and waxy maize properly is beneficial for achieving high yields. Using the row ratio model of 2:2:3, and intercropping fresh waxy maize and fresh soybean with sweet potato variety ‘Pushu32’ can achieve the highest total economic benefits.

In this paper, the risk assessment system for high temperature and drought combined stress of summer maize in Henan Province was constructed, and the weight distribution of drought comprehensive risk and high temperature comprehensive risk was calculated by using analytic hierarchy process (AHP). The paper also comprehensively evaluated the risk distribution from four aspects: the risk of disaster causing factors, the exposure of carriers, the vulnerability of disaster pregnant environment, and the ability of disaster prevention and reduction. The results show that the areas with high comprehensive risk of drought are mainly concentrated in the north of Henan Province, and the areas with high comprehensive risk of high temperature are mainly concentrated in the south of Henan Province. The comprehensive assessment system for drought and high temperature combined stress disasters of summer maize in Henan Province was constructed, and the weights of drought risk and high temperature risk were 0.4938 and 0.5062 respectively. The risk distribution of combined high temperature and drought stress was not closely related to latitude, but was also influenced by various factors such as natural conditions. Most parts of the province are in low-risk areas, and the high-risk areas are mainly concentrated in western Henan and a small part of the southwest. The evaluation results provide theoretical support for disaster prevention and reduction and ensuring the production of corn in Henan Province.

Concerning the issue of soil quality decline caused by excessive use of chemical fertilizers, and to provide scientific fertilization reference for corn cultivation and soil improvement in this region, this study explored the effects of reducing chemical fertilizers with applying mineral biochar on soil properties and corn yields in the Yellow River floodplain area. In order to study their effects on corn yield and soil properties, different chemical fertilizer reduction combined with mineral biochar treatments were set in this study, including conventional fertilization (F1, applying diammonium phosphate 300 kg/hm²), reducing 12.5% fertilizer with 75 kg/hm² mineral biochar (F2), reducing 25% fertilizer with 150 kg/hm² mineral biochar (F3), reducing 37.5% fertilizer with 300 kg/hm² mineral biochar (F4), and reducing 50% fertilizer with 600 kg/hm² mineral biochar (F5). The results indicated that the application of mineral biochar in the 0-20 cm soil layer enhanced nitrogen uptake by crops, effectively stabilized soil potassium levels, and increased soil phosphorus content. Compared to F1, the combined application of fertilizer and mineral biochar could significantly improve the corn yields by 1.48%-12.61%. Especially, when the application rates were 262.5 kg/hm² of diammonium phosphate and 75.0 kg/hm² of mineral biochar, corn yields and economic benefits reached their maximum. These findings demonstrated that replacing chemical fertilizer with mineral biochar could improve soil properties and ensure corn yields.

The effects of green manure on soil microorganisms and physicochemical properties, corn yield, and quality were summarized and analyzed, based on relevant literature and work practice. By rolling or intercropping green manure crops, the organic matter and microbial content in the soil can be increased, its physical and chemical properties can be improved, and its water and fertilizer retention capacity can be enhanced; The application of green manure can promote the growth of corn, increase its grain yield, and also have a certain promoting effect on its quality traits such as amino acids and proteins. Different types of green manure have different effects on soil physical and chemical properties and corn growth. Suitable green manure crops should be selected based on soil fertility conditions, production goals, etc. to improve the yield and quality of corn.

The aim was to evaluate lodging resistance of germplasm in maize, and then breed maize hybrids with strong lodging resistance. In this study, four maize hybrids which were currently promoted in production were used as materials. Through measuring the lodging resistance related traits, mid-parent heterosis and over-parent heterosis of related traits were calculated. The results showed that there were significant or extremely significant differences in crushing strength, pushing strength and stem strength among different varieties, 'Shuoyu 172' had higher crushing strength and stem strength, and 'Shuoyu 173' had higher pushing strength. Compared with different lodging resistant related traits, mid-parent heterosis and over-parent heterosis of 5^th internode length, stem diameter, plant height, ear height, and tassel branch number of 3^rd, 4^th and 5^th internode were relatively higher, indicating that the heterosis of these traits was relatively strong. Compared with the different materials, the parents of 'Shuoyu 172', 'Zheng 58' and 'H7235', and the parents of 'Shuoyu 173', 'Z33-1' and 'H7875S', had strong heterosis in crushing strength, stalk strength, tassel branch number, tassel main axis length and angle of ear. The stem diameter plant height, ear height, ear leaf length and width of 3^rd, 4^th and 5^th internode between the parents of 'Baojing 186', 'Z33-1' and 'H7875A', and the parents of 'Zhengdan 958', 'Zheng 58' and 'Chang 7-2' had strong heterosis. Principal component analysis were used to evaluated lodging resistance of different varieties, the results showed that the lodging resistance of 'Shuoyu 172' was the strongest (Y: 1.401), followed by 'Shuoyu 173'. This study indicated that both of 'Shuoyu 172' and 'Shuoyu 173' had strong lodging resistance.

In order to study the impact of gale disasters on corn crops in high latitudes, based on the theory of natural disaster risk and combined with ArcGIS spatial analysis technology, this paper analyzed the risk factors of gale disasters in Heilongjiang Province, the environmental sensitivity of disaster, the exposure of disaster bearing bodies and the ability of disaster prevention and reduction, and carried out a comprehensive risk assessment. The research shows that the high incidence areas of corn gale disasters are concentrated in the southeast of Songnen Plain and the west of Sanjiang Plain. These areas have flat terrain, no large-scale vegetation coverage, high wind risk coefficient, large corn planting area and medium disaster prevention and mitigation ability. It is suggested that maize lodging damage could be prevented and controlled by giving priority to the selection of lodging-resistant varieties, sowing in warm and suitable climate, regularly reinforcing maize plants during planting, and taking measures such as mulching protection. The results provide a theoretical basis for the relevant departments to adjust the agricultural structure and formulate disaster prevention and mitigation countermeasures and measures.

To investigate the efficiency of Sedum alfredii in extracting heavy metals from farmland under intercropping systems, this study employed the technique of intercropping the Cd-hyperaccumulator Sedum alfredii with sweet corn to conduct experiments in moderately cadmium-contaminated farmland in South China. The results indicated that under the intercropping system, the yield of sweet corn increased, and the Cd content in the kernels significantly decreased by 8.3% compared to monoculture. Additionally, under the intercropping system, the biomass of Sedum alfredii increased by 16.5%, with Cd accumulation in the roots and shoots increasing by 8.8% and 3.6%, respectively. The enrichment coefficients improved by 15.7 and 6.6 units, respectively. After intercropping sweet corn with Sedum alfredii, the Cd content in the top soil significantly decreased. The experiment demonstrated that the phytoremediation model of intercropping Sedum alfredii with sweet corn not only allowed for the simultaneous remediation and production of polluted farmland but also enhanced the extraction efficiency of the hyperaccumulator plant. This approach presented a practical and green remediation technology for moderately heavy metal-contaminated farmland.

The aim was to explore the effects of different new urea on yield and nitrogen uptake and utilization of winter wheat-summer maize rotation system in the North China Plain, with a view to providing a theoretical basis for the application of new urea in practical production. Using common urea as a control, six new types of urea were applied for 5 consecutive years to measure the yield of wheat-maize rotation, analyze the effect of new urea on the composition of the yield, and at the same time, determine the nitrogen uptake of plants and seeds, and account for the nitrogen fertilizer agronomic efficiency, bioproductivity, and production benefits of the new types of urea. The results showed that compared to the ordinary urea, continuous application of the new urea all significantly increased the yield of wheat-maize rotation system (P<0.05), with the range of yield increase from 7.08% to 11.77%, of which 9.02% was increased by the loss-control urea in the wheat season, and 15.52% was increased by the zinc-containing urea in the maize season; there was no significant difference in nitrogen absorption and utilization of the new urea during the wheat season, while the average nitrogen fertilizer agronomic efficiency of loss-control urea fertilization and zinc containing urea in the corn season reached 9.49 kg/kg and 10.63 kg/kg, respectively. From the perspective of production efficiency, the net benefit of using loss-control urea in batches and zinc (manganese) containing urea was the highest. Under the conditions of this experiment, it was recommended to apply loss-control urea or zinc (manganese) containing urea in the winter wheat-summer corn rotation system in the North China.

【Objective】The physiological mechanism of starch accumulation and yield formation of spring maize in black soil under suitable nitrogen application was studied, in order to provide the theoretical basis for high yield and high efficiency cultivation technology of spring maize.【Method】Field experiments were conducted in the spring maize growing seasons of 2022 and 2023 in Gongzhuling City, Jilin Province, Jilin Academy of Agricultural Sciences. Five nitrogen application treatments were set up: no nitrogen (N0), 90 kg·hm^-2 (N90), 135 kg·hm^-2 (N135),180 kg·hm^-2 (N180), and 225 kg·hm^-2 (N225). The synthesis capacity of sucrose in the ear leaf and the activity of key enzymes in sucrose metabolism were measured to investigate the sucrose synthesis capacity of the ear leaf and grain starch synthesis capacity under different nitrogen application rates. The accumulation characteristics of total starch and its components in maize grain were fitted by Logistic equation to clarify the impact of nitrogen application rate on the dynamic of starch accumulation in maize grain and grain yield formation.【Result】(1) With the escalation of nitrogen application rates, the yield of spring maize exhibited an initial increase followed by a subsequent decrease. The average yields under N0, N90, N135, N180, and N225 treatments over two years were 8 992.90, 11 199.47, 12 126.78, 14 049.42, and 13 213.21 kg·hm^-2, respectively. Notably, the N180 treatment resulted in the highest yield. (2) The sucrose content, sucrose synthetase (SS) and sucrose phosphate synthetase (SPS) activities in ear leaves at 0, 12, 24, 36 and 48 days after flowering under N180 treatment were significantly higher than those under N0, N90 and N135 treatment, and there was no significant difference between N225 and N180 treatment. At 24, 36 and 48 days after flowering, the activity of soluble amylase (SSS) in grains treated under N180 was the highest, and the average SSS activity of grains under N0, N90, N135 and N225 was increased by 62.43%, 31.33%, 14.85% and 7.80%, respectively. (3) Logistic equation analysis showed that the accumulation rate and active accumulation period of total starch, branch chain and amylose in grains of each treatment first increased and then decreased with the increase of nitrogen application amount, and N180 treatment was the best. Compared with N0, N90, N135 and N225 treatments, the two-year average total starch accumulation rate and total starch accumulation active period under N180 treatment were 43.35%, 23.16%, 13.22%, 5.92% and 7.30%, 3.84%, 4.11%, 3.83%, respectively. When the average grain starch accumulation rate reached the maximum in two years, the grain starch accumulation amount was 12.90 g, and the total starch accumulation amount at each treatment maturity stage was 6 725.60, 8 510.17, 9 150.62, 10 387.35 and 9 604.04 kg·hm^-2, respectively. (4) Correlation analysis results showed that spring maize yield was significantly positively correlated with sucrose content, sucrose synthase activity, sucrose phosphate synthase activity, soluble starch synthase activity in grains, total starch accumulation, amylopectin accumulation and amylose accumulation in grains at ear position at filling stage. Sucrose content, sucrose synthetase activity, sucrose phosphate synthetase activity and soluble starch synthetase activity in grain were also significantly positively correlated with starch and its component accumulation in grain.【Conclusion】Under the treatment of 180 kg·hm^-2 nitrogen application, the spring maize during grain filling exhibited the highest activities of key sucrose metabolism enzymes in the ear sheath leaves, as well as the highest activity of starch synthesis enzymes in the soluble grains. Additionally, it showed the maximum rate of starch accumulation and longest period of active starch accumulation. Furthermore, this treatment resulted in the highest grain yield and starch accumulation, making it the optimal treatment under the experimental conditions.

【Objective】The purpose of this study was to determine the effects of nitrogen application amount on the yield composition, economic benefit of summer sowing intercropping crops and the yield of winter wheat. 【Method】From 2022 to 2023, the representative farmlands were selected in Yucheng City, Shandong Province, which was the main extension area of maize-soybean strip intercropping. Maize monoculture (Nitrogen application rate: 225 kg·hm^-2), soybean monoculture (Nitrogen application rate: 45 kg·hm^-2), maize-soybean intercropping with full nitrogen application (Nitrogen application rate: 270 kg·hm^-2), maize-soybean intercropping with reduced nitrogen application (Nitrogen application rate: 135 kg·hm^-2) were set up in summer sowing season, and the subsequent crops were planted with wheat without fertilizer treatment. The effects of different summer sowing treatments on photosynthetic characteristics, agronomic traits, economic benefits and yield of subsequent wheat were analyzed. 【Result】Both planting pattern and nitrogen application amount had significant effects on crop growth and development. Compared with maize monoculture, the chlorophyll content, P_n, G_s, C_i and T_r of maize leaves were significantly decreased by intercropping reduced nitrogen application (135 kg·hm^-2). However, the P_n, G_s and T_r of leaves of intercropping full nitrogen maize (270 kg·hm^-2) were significantly increased by 8.8%, 10% and 11.6%, respectively. Intercropping system resulted in decreased chlorophyll content of soybean, inhibited leaf P_n, G_s, and T_r. In terms of agronomic characteristics, stem length increased, pod number per plant decreased, and yield decreased by 65.1%-68.4%. There was no significant difference in the agronomic characteristics and yield of maize under the intercropping system with full nitrogen application, and the economic benefit was the highest under this system, reaching 22 607 yuan/hm², while the agronomic characteristics such as ear length, grain number per ear and hundred-grain weight of maize under reduced nitrogen application significantly decreased, and the yield decreased by 14.8%. However, in general, the land equivalent ratio of both maize and soybean treatments was also greater than 1. Economic benefit and nitrogen uptake were increased by 4.8%-11.5% and 19.7%-38% compared with monocrop. When winter wheat was not fertilized, the grain yield and crop nitrogen uptake of aftercrop winter wheat with full nitrogen application in summer sowing were higher than that under other treatments, and there was no significant difference between the yield of winter wheat with reduced nitrogen application between summer sowing seasons and that of winter wheat with summer sowing maize. 【Conclusion】Therefore, from the comprehensive analysis of agronomic characteristics, yield and economic benefits as well as the effects on aftercrop, the effect of total nitrogen application in intercropping was better than that of reduced nitrogen application in intercropping. However, considering the yield, economic and environmental benefits, the amount of nitrogen application in intercropping should be further optimized.

In order to provide theoretical basis, identification method and selection index for the identification and screening of low nitrogen tolerant maize varieties, the research reports on the influence of low nitrogen stress on maize growth and development, the material basis of low nitrogen tolerance and the selection of low nitrogen tolerant varieties in maize at home and abroad in the past 20 years were summarized. It was found that low nitrogen stress seriously affected the growth and development of maize roots and plants, and grain yield. However, different genotypes of maize showed great differences in morphological characteristics, physiological and biochemical characteristics, nitrogen utilization efficiency, and grain yield. Under low nitrogen stress, the low nitrogen tolerant genotype showed that the root system grew well, root-shoot ratio was larger, the root system vigor was stronger. Meanwhile, the changes in plant height and stem thickness were not obvious, while the ear leaf area was larger. It was higher for the content of soluble protein, soluble sugar, and amino acids in its root secretions as well as the contents of chlorophyll and nitrogen in ear leaf. Nitrate reductase and glutamine synthetase activity were stronger in the cells, and the ear was larger, grains per ear were much and 100-grain weight was higher, these genotypes could obtain the high grain yield. It was considered that under low nitrogen stress, the biomass of roots and plants was high, the root-shoot ratio and ear leaf area were large, the content of soluble protein and soluble sugar in root exudates, the content of chlorophyll and nitrogen in ear leaves were high, the activity of nitrate reductase and glutamine synthetase in cells was strong, the number of grains per ear was large, and the weight of 100 grains and the weight of grains per ear were high. The above information could be used as important indicators for selecting low nitrogen tolerant maize genotypes.

【Objective】Genetic improvement for efficient utilization of maize nutrients represents a crucial method to ensure national food security. Exploring quantitative trait locus (QTL) and related candidate genes of nitrogen use efficiency can provide a theoretical basis for improving the efficiency of nitrogen fertilizer in maize and cultivating high-yield and high-efficiency maize varieties. 【Method】In this study, QTL mapping analysis in one recombinant inbred line (RIL) population constructed by KA105 and KB024 was performed for grain yield under two different nitrogen treatments, including the derived traits partial factor productivity from applied nitrogen (PFPN), low nitrogen tolerance coefficient (LNTC) and nitrogen agronomic efficiency (NAE). Concurrently, integrating the seedling transcriptome data of the parent KA105 under nitrogen treatment, differentially expressed genes were identified, and candidate genes associated with maize nitrogen use efficiency were mined through co-expression analysis. Subsequently, the selected candidate genes were validated using qRT-PCR. 【Result】Through mapping analysis, a total of 36 QTLs distributed across different chromosomes were detected, explaining 1.63% to 17.26% of the phenotypic variation. Among these, eight major QTLs with a phenotypic variation explanation rate exceeding 10% were identified, along with seven genetically stable QTLs commonly identified across different traits or environments. Notably, qNNGYP1 located on chromosome 1 has been repeatedly detected in previous studies, with a phenotypic explanation rate of up to 11.73%. Additionally, other QTLs (qNNGYP1, qPFPN1) co-located in this interval across different environments, suggesting it as a focal region for further investigation. Combining transcriptome data of seedlings under low nitrogen stress, 39 differentially expressed genes within these QTL intervals were identified, and 6 key genes were identified through co-expression network prediction. The result of qRT-PCR indicated that the expression trends of the candidate genes under both nitrogen treatments were consistent with the transcriptome data. Specifically, GRMZM2G366873 was involved in the regulation of auxin homeostasis and may participate in maize responses to low nitrogen stress, drought stress, and boron stress through auxin signal transduction, also regulating ear length. GRMZM2G414192 was involved in the response of the photosynthetic system to low nitrogen stress and was regulated by brassinosteroids. GRMZM2G414043 was associated with maize grain length and biomass, while GRMZM2G040642 may be involved in the long-distance signal transduction of nitrogen. 【Conclusion】In summary, a total of 36 QTLs were identified, distributed across chromosomes 1, 4, 5, 7, 8, and 9, including eight major QTLs (PVE>10%). The candidate genes GRMZM2G366873, GRMZM2G414192, GRMZM2G414043, and GRMZM2G040642 were identified as potential genes for maize nitrogen efficiency.

【Objective】This study aimed to explore the underlying reasons for the reduction of maize photosynthesis under the high temperature and drought combined stress, so as to provide theoretical basis for alleviating the combined stress of high temperature and drought. 【Method】Maize cultivar “Denghai 605” was selected as the experimental material for this experiment. Two temperature levels were set, namely normal temperature control (30 ℃/22 ℃ for day (8:00-18:00)/ night (18:00- 8:00 the next day)) and high temperature treatment (38 ℃/28 ℃ for day/night). The two water conditions were normal water supply control (soil water content was 70%-80% of field capacity) and drought treatment (soil water content was set to 50%-60% of field capacity). There were four treatments in the experiment, including control (CK), high temperature stress (H), drought stress (D), high temperature and drought combined stress (HD), and the treatment began at VT stage (VT). The changes in leaf gas exchange parameters, photosystem Ⅱ (PSII) performance, key photosynthetic enzyme activity, plant biomass, and grain yield under different stress treatments were analyzed. 【Result】High temperature, drought and combined stress all led to the increase of chlorophyll fluorescence parameters, the ratio of a variable fluorescence F_K to F₀-F_J amplitude (W_K) and variable fluorescence F_J to F₀-F_J amplitude (V_J), and damaged the donor side and acceptor side of PSII. Compared with the control, PSII maximum quantum yield for primary photochemistry (φ_P0), the probability of captured excitons transferring electrons to other electron acceptors in the electron transfer chain beyond Q_A (Ψ₀), quantum yield for electron transport (φ_E0), quantum yield of energy dissipation (φ_D0), quantum yield for reduction of the end electron acceptors at the PSI acceptor side (φ_R0), and performance index based on absorption of light energy (PI_ABS) were significantly decreased, and the absorption and transfer of light energy were inhibited; absorbed photon flux per active PSII (ABS/RC), trapped energy flux per active PSII (TR₀/RC) and dissipated energy flux per active PSII (DI₀/RC) increased significantly, but the electron flux from Q_A^‒ to the PQ pool per active PSII (ET₀/RC) decreased significantly, which affected the energy distribution of reaction centers, reduced the number of PSII active reaction centers, and inhibited the performance of PSII. Combined stress could aggravate the inhibition of PSII performance by damaging the donor side, the acceptor side and the active reaction center. At the same time, the activities of ribose 1, 5-diphosphate carboxylase (Rubisco) and phosphoenolpyruvate carboxylase (PEPCase) decreased, which inhibited photosynthetic carbon assimilation. High temperature, drought, and combined stress reduced the net photosynthetic rate by reducing the performance of PSII and the activity of key photosynthetic enzymes. Compared with the control, the net photosynthetic rate of VT+5 d was reduced by 14.6%, 31.4%, and 39.9%, respectively. The decrease in photosynthetic rate inhibited the accumulation of biomass and its transport to grains. Under high temperature, drought, and combined stress, the grain yield decreased by 80.3%, 27.1%, and 84.0% than that under control, respectively. 【Conclusion】In summary, the combined stress of high temperature and drought mainly reduced net photosynthetic rate, hindered biomass, and reduced grain yield by inhibiting leaf PSII performance. The impact of combined stress on PSII performance and grain yield was greater than that of single stress under high temperature and drought.

【Objective】Reasonably increasing planting density combined with appropriate nitrogen (N) application rate is an important technical approach for increasing maize yield and resource use efficiency. Understanding the interactive effects of planting density and N rate on maize growth, evapotranspiration (ET) and water use efficiency (WUE) during the growing season, could provide a basis for improving its use efficiency when increasing planting density and controlling N input in maize production. 【Method】Field experiments were conducted during 2022 to 2023 in Jilin Province. Two maize cultivars, Liangyu 99 (LY99) and Demeiya 3 (DMY3), were used in this study. Three planting densities of 50 000, 70 000 and 90 000 plants/hm² and four N application rates of 0, 100, 200 and 300 kg N·hm^-2 were designed to investigate the effects of planting density and N application rate on grain yield and water productivity of different maize cultivars, as well as the dry matter (DM), soil water content, ET and WUE at various growth stages. 【Result】Planting density significantly affected DM and grain yield of maize, but the response trends varied between cultivars. Grain yields of LY99 with 70 000 plants/hm² was 11.1% and 18.3% higher than that with 50 000 and 90 000 plants/hm², respectively. The average yield of DMY3 planted with 70 000 plants/hm² and 90 000 plants/hm² was 10.5% and 9.3% higher than that of 50 000 plants/hm², respectively. Nitrogen fertilization significantly increased DM and grain yield of maize, and also showed significant interactive effects with cultivar or planting density. Compared with N0, grain yields of LY99 were increased by 38.0% to 60.7% under N1, and the yield increases for DMY3 were 24.4% to 38.2%. Notably, the yield responses to N rates were more pronounced for LY99 compared with DMY3. For both cultivars, the yield differences between low N rate and high N rate enlarged with increasing planting density, with LY99 showing a more distinct performance. The water consumption and utilization of maize plants were also significantly affected by planting density, N rate and their interaction. During the growing season, the total ET of DMY3 continually increased with increasing density, while that of LY99 showed the highest values with 70 000 plants/hm² among different densities. In each density condition, the ET of both cultivars increased with increasing N application rates. The WUE of maize plants showed complex responses to planting density and N rate at different growth stages, due to the varied annual precipitation and distribution patterns. The average increase of water productivity of LY99 under planting 50 000 and 70 000 plants/hm² was 8.6% and 10.4% compared with 90 000 plants/hm² respectively_. DMY3 had the highest water productivity when planting 70 000 plants/hm², which increased by 5.8% and 5.3% compared with 50 000 and 90 000 plants/hm², respectively. The water productivity showed different responses to N rate among the three densities. In general, the difference of nitrogen application under low density was small, but it increased significantly under medium and high density. Compared wtih DMY3, LY99 showed higher increases for water productivity when N fertilizer was applied under medium and high density conditions. The correlation analysis showed that interactive effects of planting density and N rate significantly affected maize yield and water productivity by influencing the water utilization at various growth stages. 【Conclusion】Planting density and N rate had significant interactive effects on maize yield and water utilization in the rain-fed region of Northeast China. The two maize cultivars used in this study could obtain high grain yield and water productivity under a moderately higher density of 70 000 plants/hm² combined with 200 kg N·hm^-2 rate.

The simple, practical and easy to popularize straw composting and fermentation technology was explored. The corn straw was used as the test material to test the temperature, putrefier and moisture affecting the fermentation of corn straw. Four treatments were set up, included treatment 1 film retting fermentation, treatment 2 film retting fermentation + putrefactive agent, treatment 3 film retting fermentation + putrefactive agent + water, treatment 4 direct retting fermentation，and each treatment was repeated three times. The temperature, height, weight and fermentation degree of straw pile were measured every one month, and the color changes were observed and recorded. The optimum fermentation conditions of corn straw were obtained by comprehensive evaluation. The results showed that the temperature, weight and fermentation degree of straw pile were in the order of treatment 3> treatment 2> treatment 1> treatment 4 from high to low. The height of the straw pile from low to high was treatment 3< treatment 2< treatment 1< treatment 4. The color depth of straw pile was in the order of treatment 3> treatment 2> treatment 1> treatment 4. It was concluded that the treatment 3 was the best for straw fermentation, using film, straw maturing agent and maintaining humidity at the same time, could make corn straw mature to the maximum extent and could obtain benefits certain economic in actual production.