This study systematically quantified the contribution rates and spatial heterogeneity of protein, starch, and fat—the three major nutritional components—to maize kernel test weight formation, and elucidated how genetic background, ecological region, and cultivation density interactively modulate both nutritional quality and test weight. The findings aim to establish a science-based foundation for region-specific optimization of maize quality and to advance an integrated “high-yield-high-qualityhigh-efficiency” production paradigm.

A nationwide field survey was conducted across four major maize-producing regions in China, encompassing 718 representative kernel samples from 77 leading cultivars grown under 24 distinct planting density gradients (37500-127500 plants/hm²). All samples were naturally air-dried to standardized moisture content (14% w.b.) prior to uniform physicochemical analysis. Protein, starch, and fat contents were determined using calibrated near-infrared reflectance spectroscopy (NIRS), and test weight was measured with a certified grain test weight instrument (ISO 7971-3 compliant). To dissect the complex determinants of test weight, we implemented a hierarchical analytical framework integrating: (ⅰ) multiple linear regression to estimate independent linear effects; (ⅱ) random forest modeling to capture nonlinear interactions and relative feature importance; and (ⅲ) structural equation modeling (SEM) to infer directional causal pathways among traits. Three-way ANOVA was further employed to assess the main and interactive effects of cultivar, ecological region, and cultivation density on test weight and each nutritional component.

Protein (β=8.406, P<0.001) and starch (β=6.413, P<0.001) emerged as statistically robust and biologically dominant drivers of test weight, accounting for 28% and 45% of the total explained variance in the random forest model, respectively—both exhibiting high path coefficient stability in SEM (standardized coefficients ≥0.72, P<0.001). In contrast, fat showed negligible explanatory power (2%), and its effect failed to reach statistical significance (P=0.09). Three-way ANOVA confirmed highly significant (P<0.001) main effects and two- and three-way interactions among cultivar, ecological region, and density for test weight, protein, and starch—indicating strong contextual dependency. Spatially, protein contributed most strongly in the Northeast spring maize region (43.9% of model variance), whereas starch dominated in the Huang-Huai-Hai summer maize region (52.9%). Critically, the synergistic contribution of protein and starch jointly explained 81.0% and 85.0% of the total model variance in these two regions, respectively. Structural equation modeling revealed a direct positive effect of protein on test weight, but an indirect negative effect stemming from the compensatory relationship between protein and starch accumulation, which underscores the physiological trade-off in kernel sink-filling.

Maize test weight formation was a biologically synergistic process driven by protein and starch, with fat playing no substantial role. Significant interactions existed among cultivar, ecological region, and density, with the same cultivar exhibiting distinct regulatory pathways under different ecological and cultivation conditions. Consequently, the Northeast region should prioritize high-protein cultivar selection and precise nitrogen management, while the Huang-Huai-Hai region should enhance carbon assimilation efficiency and regulate key starch-synthesis enzymes. All production areas should achieve a precise "cultivar-region-practice" matching strategy to synergistically improve maize yield and quality.

Reasonable increase of planting density and row spacing configuration is an important way to achieve high yield and high efficiency of maize. In order to provide the technical basis for high yield and high efficiency cultivation of drip irrigation maize in sandy land, the effects of dense planting and row spacing configuration on maize yield and water and fertilizer utilization efficiency in sandy land were studied under drip irrigation condition in Xiliaohe Plain.

Field experiments were carried out in Naiman Banner of Inner Mongolia in 2023 and 2024, and 'Zhengdan 958' was used as the test maize variety. Two planting densities: 60 000 plants/hm² (D1) and 90 000 plants/hm² (D2) and seven row spacing treatments: 60 cm+60 cm (L₆₀₊₆₀, CK), 40 cm+ 80 cm (L₄₀₊₈₀), 30 cm+90 cm (L₃₀₊₉₀), 30 cm+80 cm (L₃₀₊₈₀), 40 cm+70 cm (L₄₀₊₇₀), 30 cm+70 cm (L₃₀₊₇₀) and 20 cm+70 cm (L₂₀₊₇₀) were set. The effects of planting density and row spacing on maize yield, dry matter production, photosynthetic performance and water and nitrogen use efficiency under drip irrigation in sandy land were systematically analyzed.

Planting density and row spacing significantly affected the grain yield and water and nitrogen use efficiency of drip-irrigated maize in sandy land. In the two-year experiment, L₃₀₊₇₀ and L₃₀₊₈₀ obtained higher yield under D2 density, which were 15.6 and 15.5 t·hm^-2, respectively. The water use efficiency (WUE) reached 2.57 and 2.55 kg·m^-3, respectively, and the partial factor productivity of nitrogen fertilizer (PFP_N) reached 57.8 and 57.2 kg·kg^-1, respectively. Among them, the yield difference between L₃₀₊₈₀ and L₃₀₊₉₀ in 2023 did not reach a significant level, and the yield was 18.2% and 17.0% higher than that of L₆₀₊₆₀, respectively. The dry matter accumulation at silking stage (DMAS), dry matter accumulation at maturity stage (DMAM), dry matter accumulation after anthesis (DMAAS) and harvest index (HI) increased by 49.5%, 75.0%, 97.6%, 18.3% and 45.1%, 73.3%, 96.8%, 19.3% compared with L₆₀₊₆₀, respectively. The total photosynthetic potential increased by 33.6% and 30.1% compared with L₆₀₊₆₀ during the growth period. The light transmittance (Tr) of the bottom layer and ear layer decreased by 51.7%, 27.5% and 37.9%, 20.9% compared with L₆₀₊₆₀, respectively. The photosynthetic rate (Pn) of ear leaf at silking stage (R1) and maturity stage (R6) increased by 61.0%, 60.3% and 61.5%, 59.4%, respectively. WUE and PFPN increased by 19.7%, 17.8% and 21.1%, 16.8% compared with L₆₀₊₆₀, respectively. In 2024, there was no significant difference in yield between L₃₀₊₇₀ and L₃₀₊₈₀, which was 14.3% and 13.8% higher than that of L₆₀₊₆₀, respectively; DMAS, DMAM, DMAAS and HI increased by 56.6%, 87.0%, 118.4%, 28.9% and 52.1%, 81.0%, 114.6%, 29.0%, respectively; the total photosynthetic potential increased significantly by 65.9% and 63.0% during the growth period, respectively; the Tr of the bottom layer and the ear layer decreased by 53.8%, 24.9% and 52.1%, 22.8%; the Pn of ear leaf of R1 and R6 increased by 18.7%, 86.6% and 65.6%, 86.2%, respectively. WUE and PFP_N increased by 18.7%, 13.6% and 18.9%, 14.1%, respectively. Correlation analysis showed that maize yield was significantly positively correlated with 1000-grain weight, grain number per spike, number of harvested spikes, HI, WUE and PFP_N. DMAS and DMAAS were significantly positively correlated with grain number per spike, 1000-grain weight, LAD before anthesis, LAD after anthesis and Pn, and negatively correlated with Tr.

Under the condition of drip irrigation and fertilizer integration in the sandy land of Xiliaohe Plain, the interaction between planting density and row spacing mainly affected the grain yield and water and nitrogen use efficiency of maize by affecting the light transmittance of maize population, leaf photosynthetic capacity, dry matter accumulation and LAD. Therefore, the high yield and water and nitrogen production efficiency could be obtained by reasonably increasing the density of high-yield varieties to 90 000 plants/hm² and wide-narrow row spacing of 30 cm+70/80 cm.

Under the background of mechanical grain harvesting, the purpose of this study was to determine the accumulated temperature requirements of maize in different planting regions after physiological maturity by dehydration to the suitable harvest date, so as to provide the theoretical guidance for selecting suitable grain harvesting varieties, and rationally arrange agricultural operations and improve mechanical utilization efficiency in each planting region.

From 2014 to 2018, 141 maize varieties with different maturity periods selected to observe the dynamic changes of grain moisture content at typical test points in the northwest maize region (NW), the north maize region (NM) and Huang-huai-hai maize region (HM). Combining with meteorological date, the accumulated temperature requirements of maize field stalk dehydration to 25% and 20% grain moisture content after the physiological maturity were analyzed in different production regions.

The grain moisture content was different at physiological maturity in different production regions. The average grain moisture content was 28.5%, 29.9% and 29.6% in HM, NW and NM, respectively. Correlation analysis showed that there was no significant correlation between the growth period of different varieties and the grain moisture content at physiological maturity. The accumulated temperature of grain moisture content from physiological maturity to 25%, 20% and grain moisture content at physiological maturity were used as indexes. By using the two-way average method, the tested varieties were divided into 4 types, including low accumulated temperature demand and high moisture content (I), high accumulated temperature demand and high moisture content (II), low accumulated temperature demand and low moisture content (III), and high accumulated temperature and low moisture content (IV). For the northwest China, north China and northeast China, III and IV could be selected, but IV varieties needed to reserve enough accumulated temperature to dehydrate in the field. While the summer maize with growing twice a year in the Huanghuaihai region, III varieties could better coordinate the production and allocation of wheat and maize, and make full use of the excess temperature that could be used for grain dehydration.

Because of different dehydrating conditions such as temperature, the days when grain moisture content from physiological maturity to 25%, 20% showed that the northwest maize region was longer than the north maize region and Huang-huai-hai maize region. Grain moisture content and harvest quality can be effectively reduced by selecting the accumulated temperature varieties suitable for different regions and scientifically setting the harvest date.

In this study, the date when the kernel moisture content of different types of maize variety dehydrates to a suitable level for mechanical grain harvesting was predicted for different sowing dates in the Ningxia Hui Autonomous Region of China, in order to provide a basis for the variety selection at the regional scale, the determination of a suitable harvest period, and the development of the mechanical harvesting of maize varieties with a low moisture content.

Using the average kernel moisture content at physiological maturity (30.1%) and the average accumulated temperature (3 274.3 °C·d) required for sowing to physiological maturity ≥0 ℃·d as indicators, 38 common maize varieties were classified into four types by the two-way average method: type I varieties were characterized by late maturity and slow dehydration; Type II were characterized by early maturity and slow dehydration; type III varieties were characterized by early maturity and fast dehydration; type IV varieties were characterized by late maturity and fast dehydration. According to the production practice in Ningxia, the varieties with medium kernel moisture content and accumulated temperature requirement at physiological maturity stage were selected as the representative variety of each type. Then, the Logistic Power nonlinear growth model was used to predict the dehydration of the 38 maize varieties base on 10 years of recent meteorological data (2008-2017). Based on these data, the kernel moisture characteristics of each type of variety were predicted for various regions of Ningxia with different heat resources for three different sowing dates (initial sowing, peak sowing, and initial sowing).

The results showed that, initial sowing could obtain an accumulated temperature of 162.2-229.8 °C·d in crop growth more than that of final sowing. The accumulated temperatures required for kernel dehydration to a moisture content of 25% from sowing for Type I, Type II, Type III, and Type IV cultivars were 3 615.2, 3 290.6, 3 138.0, and 3 426.6 °C·d, respectively. In northern and central Ningxia, all types of varieties could meet the requirement that the kernel moisture content be reduced to 25%, while in the southern regions, Type III varieties could meet the requirement that the kernel moisture content be reduced to 25% for sowing at the initial and peak sowing times. The predicted accumulated temperatures from sowing to dehydration required for kernel dehydration to a moisture content of 16% for Type I, Type II, Type III, and Type IV cultivars were 4 320.6, 3 816.4, 3 632.9, and 4 023.6 °C·d, respectively. For the Type III varieties, in northern Ningxia on the initial sowing date and final sowing date, the kernel moisture content of both could be reduced to 16%; in the central region on the initial sowing date and peak sowing date, the accumulated temperature required for dehydration to 16% could be satisfied.

The heat resources of Ningxia could be used rationally through the selection of maize varieties with appropriate dehydration characteristics and early planting, thereby help to achieve high-quality mechanical maize kernel harvesting in this region. In northern and central Ningxia, it was recommended to select early-maturing, fast-dehydrating (Type III) varieties in order to achieve the mechanical harvesting of maize with a low kernel moisture content and thus convert regional heat resources into economic benefits.

Mechanical grain harvesting is the development direction of maize harvesting technique, however, under a crop rotation system of winter wheat and summer maize, which is hardly to be achieved in China, resulting from insufficient heat resource in limited growing season for maize. So far, the northern Huang-Huai-Hai area is the area where the mechanical grain harvesting for maize is most difficult to be applied and spread all over the world. Thus, a study on the feasibility of corn’s mechanical grain harvesting is considerably significant to the whole-process mechanization, quality, proceeds and industrial competitiveness of corn production in Huang-Huai-Hai area.

In northern Huang-Huai-Hai area, the dynamic observation for the accumulated temperature requirements for grain dehydration of 5 maize cultivars with different physiological maturity, including Zhengdan958, Xianyu335, Dika517, Jingnongke728 and Fengken139, were designed in Xiangxiang, Henan province from 2016 to 2017 and then in Beijing, in 2018 respectively. Then, based on the meteorological data from 2007 to 2018, after reserving 500 ℃·d for winter wheat growth, the northern Huang-Huai-Hai area was divided into 7 accumulated temperature zones according to a temperature gradient of 100 ℃, so as to spatially illustrate the heat resource distribution during maize growth season in this area. Hence, the different cultivars’ accumulated temperature requirements for grain dehydration were mapped under the heat resource distribution in this area.

Under the conventional sowing condition of summer maize, each cultivar’s coverage that mechanical grain harvesting could be achieved after physiological maturity, with the advance of maturity, which were gradually extended northwardly, commonly 5-10 d later than the current sowing time for winter wheat in northern Huang-Huai-Hai area. However, the heat resource of accumulated temperature zonesⅠ-Ⅲ (1 900-2 800 ℃·d) were still hardly able to meet the requirements of Jingnongke728 and Fengken139 for a relative earlier physiological maturity than other 3 tested cultivars, not to metion reaching a grain moisture content of 25%. When the double cropping per year (winter wheat-summer maize) was reformed into the triple cropping per 2 years (summer maize-spring maize-winter wheat), the grain moisture content of all the tested cultivars, no matter planted in spring or summer, could reach 25% even less, achieving mechanical grain harvesting. Besides, for early-matured cultivars, by drying in filed and delaying harvesting, their moisture content might reach below 20% before winter wheat’s sowing, thus not only elevating harvesting quality, but also cutting drying costs.

In Northern Huang-Huai-Hai area, the problem, hindering maize production that insufficient heat resource in limited growing season issues in the difficult achievement of mechanical grain harvesting, could be effectively solved by reforming the current cropping system. Meanwhile, it also might provide a new horizon with theoretical foundation for the application of maize mechanical grain harvesting, further improving the quality and efficiency of maize production in Northern Huang-Huai-Hai area.