Meteorological factors are one of the important factors that determine maize kernel weight and grain nutritional quality. Analyzing the influence of meteorological factors before and after anthesis on maize kernel weight and nutritional quality components is of great significance for improving corn yield and quality. Therefore, five different maize hybrids and conducted continuous experiments from 2018 to 2021 were selected in this study, to explore the response of maize kernel weight and grain nutritional quality to meteorological factors in different growth periods, and to quantify the linear relationship between grain nutritional quality parameters, grain weight, and meteorological factors. The main results were as follows: the 100-grain weight reached the maximum value of 39.53 g in 2018; the contents of crude protein, total starch, and crude fat in grains reached the maximum in 2018, 2020, and 2018, respectively, which were 9.61%, 69.2%, and 5.1%. Meteorological factors significantly affected the maize grain weight (p < 0.05). Before anthesis, total sunshine duration, average temperature, relative humidity, and the accumulated temperature had strong effects on grain weight. After anthesis, average daily temperature, total rainfall, temperature difference, accumulated temperature, average daily highest temperature, and total sunshine hours had strong effects on grain weight. There was also a significant correlation between grain weight and grain nutritional quality components (p < 0.05). The multivariate polynomial equation analysis revealed that further potential for maize grain weight could be exploited by adjusting the content of each quality component of the kernels under the current test conditions. Meteorological elements can indirectly affect the 100-grain weight through their relationship with the nutritional quality of the grains, with accumulated temperature before anthesis, average temperature after anthesis, and accumulated temperature after anthesis having the greatest indirect effect on the 100-grain weight. Therefore, the effects of pre-anthesis accumulation temperature, post-anthesis average temperature, and post-anthesis accumulation temperature on the nutritional quality of the grains can be harmonized by the application of hybrids of different lengths of vegetation and by adjusting the sowing time in agricultural production. Ultimately, maize grain weight can be increased on the basis of optimizing the content of various quality components in the grains.

This study examined the planting density tolerance, grain yield improvement potential, and mechanisms of high-yielding spring maize varieties under increasing planting density and subsoiling. We planted two high-yielding spring maize varieties with a high or low tolerance to high planting densities (LM33 and XD20, respectively) at five different densities (D1: 60,000 plants ha⁻¹, D2: 75,000 plants ha⁻¹, D3: 90,000 plants ha⁻¹, D4: 105,000 plants ha⁻¹, and D5: 120,000 plants ha⁻¹) using two tillage methods (35-cm subsoiling and 15-cm traditional rotary tillage). The response characteristics used to compare the performance of the two maize varieties under different planting densities and tillage methods included root characteristics, canopy physiology, yield, and yield components. The results show that: (1) Under rotary tillage, with the increase of planting density from 75,000 plants ha⁻¹ to 90,000 plants ha⁻¹, yields of high-yielding spring maize varieties improved. However, when the planting densities were beyond 90,000 plants ha⁻¹, the yields stopped increase, or even decrease. Subsoiling increased the planting density by 15,000 plants ha⁻¹, enhanced the highest yield by 1080 kg ha⁻¹–1940 kg ha⁻¹, and raised the yield gain by 11.17–30.72%. (2) Under rotary tillage, the functional indexes of the roots and canopy of high-yielding spring maize decreased as planting density increased, and the largest reductions of root dry weight, leaf area index (LAI) of post-anthesis, light transmission percentage (LTP) of ear leaves, bottom leaves LTP, and dry matter accumulation all occurred between D2 and D4. The largest decline of high tolerance variety emerged between D3 and D5, and the extent was smaller than the low tolerance variety. (3) Compared with rotary tillage, subsoiling reduced the extent declines in root dry weight, root length, and root surface area; delayed the attenuation of LAI and the relative chlorophyll content (SPAD) determined in leaves; and improved the LTP of ear layers and bottom layer during the late growth stage. The post-anthesis populations dry matter accumulation of XD20 and LM33 increased by 7.07% and 13.18%, respectively. In addition, subsoiling significantly increased the number of kernels/spike and 1000-grain weight as the planting density increased. Meanwhile, the planting densities at which dry root weight, population LAI, ear leaf LTP, bottom leaf LTP, and dry matter accumulation arose the largest reductions was raised to 15,000 plants ha⁻¹. The effects of subsoiling in the high density-tolerant variety were more pronounced than the low density-tolerant variety.

To clarify the effect of tillage methods on saline–alkali land improvement and maize growth in cropland salinized to different degrees, we set up two treatments (shallow rotation (15 cm depth; CK) and deep straw return (35 cm depth; DPR)) in land characterized by three different salinization degrees and analyzed the effects of the two treatments on soil nutrient content, salinity index, chlorophyll fluorescence, growth status, and yield at three salinization levels. The results show that (1) compared with CK, alkaline N, total N, Olsen P, exchangeable K, and organic matter in saline soils were all significantly improved, and total salt and pH values were reduced by 34.01–50.79% and 2.56–7.54%, respectively, under deep straw return conditions, representing the largest values in moderately saline–alkali land. (2) Compared with CK, chlorophyll fluorescence was significantly improved, and maximum photochemical efficiency (Fv/Fm), photochemical quenching (qP), and effective quantum yield of PSII (ΦPSII) were significantly increased by 8.09–15.41%, 9.13–17.93%, and 38.79–70.83% following deep straw return treatment; these increases were the largest ones observed in moderately saline–alkali land. (3) Deep straw return promoted the growth of maize and significantly increased the yield of maize. Plant height, leaf area index, and yield increased the most in moderately saline–alkali land and increased by 6.84–21.79%, 0.59–2.28 units, and 12.78–28.07%, respectively. The yield increased by 33.89 %, which was mainly due to the increase in 1000-grain weight. The results provide a theoretical basis for taking straw return measures to improve soil and increase maize yield in saline–alkali land.

Dehydration of maize grains in the field can reduce costs associated with drying after harvest. A delayed harvest approach after physiological maturity, in which plants stand in the field to allow the stems to dry, has been widely adopted in maize production. However, it remains unclear how harvesting at different time points during the dehydration stage may affect grain yield and quality. In the present study, experiments were conducted in the Ningxia Irrigation Area of northwest China from 2019 to 2022, we continuously observed and used a linear-plateau model to analyze the changes in grain weight and quality traits (such as bulk density and levels of starch, protein, oil, fiber, and free fatty acids) during the field dehydration period of maize hybrids with differing maturity times. Harvesting at a grain moisture content of >31.0% was shown to affect grain weight, whereas harvesting at a moisture content of <25.9% did not affect grain weight or yield. The stable period for grain weight occurred during the physiological maturity stage for an early-maturing hybrid and 5–12 days before physiological maturity for the mid–late-maturing hybrids. When the field grain moisture content was <37%, harvesting did not affect the grain bulk density. Grain bulk density tended to stabilize one to two weeks earlier than grain weight and two to three weeks before the physiological maturity period. The protein, oil, fiber, and free fatty acid contents in maize kernels at 30 days after silking were not affected by the harvesting period, and the starch contents were unaffected in maize kernels harvested at any time later than 50 days after silking. Overall, maize grain should be harvested during field dehydration and delayed harvesting after physiological maturity with relatively low moisture content to get a better yield with superior quality.; delayed harvesting is therefore an important technical approach to improve the efficient production of high-quality maize.

To achieve high maize (Zea mays L.) yields and quality grain, it is necessary to develop stress-resistant cultivars and related cultivation practices, aiming to maximize efficiency. Thus, our objectives were (i) to investigate the impact of tillage practices and maize hybrids (which have improved over time) on yield and its components, and (ii) to characterize the response pattern of maize hybrid grain nutrient quality components to subsoiling. To achieve this, we conducted field trials with five maize hybrids from different eras under two tillage practices: rotary tillage and subsoiling. We compared grain yield, nutritional quality, and other indicators across different tillage conditions from the 1970s to the 2010s. The main results of this study are as follows: under rotary tillage conditions, the 2010s hybrid (DH618) significantly increased yields (9.37–55.89%) compared to hybrids from the 1970s–2000s. After subsoiling, the physiologically mature grains of all hybrids exhibited minimal changes in crude protein and fat content, while there was a significant reduction in the total soluble sugar content of the grains. After subsoiling, there was a substantial 8.14 to 12.79 percent increase in total starch accumulation in the grain for all hybrids during the period of 47–75 days post-anthesis. Furthermore, during the period of 47–75 days after anthesis, the consumption of grain crude protein significantly contributed to the accumulation of total starch in the grains. Ultimately, subsoiling significantly increased the yield of each hybrid and enhanced the total grain starch content at physiological maturity of all hybrids, with the 2010s hybrid (DH618) performing exceptionally well.

High grain water content at harvest stage is the main limiting factor for realizing mechanized maize grain harvest in China. Under the background of yield gain by density increase, it is necessary to clarify the effect of planting density increase on maize grain dehydration characteristics, which would provide theoretical support for realizing mechanized grain harvest under high planting density conditions. Therefore, this study selects five main hybrids, ZD2, DY13, YD13, XY335, and DH618, released in different eras that were widely promoted in Inner Mongolia from the 1970s to 2010s. The experiment was conducted in the Chilechuan Modern Agriculture Expo Park, Tumed Right Banner, Baotou city, Inner Mongolia, in 2018 and 2019. Under the three densities of 45,000 plants ha⁻¹ (low density), 75,000 plants ha⁻¹ (medium density) and 105,000 plants ha⁻¹ (high density), the indexes of grain dehydration, leaf stay-green, bract and cob dehydration of the different maize hybrids were measured and analyzed. The results show that MCpm (moisture content at physiological maturity) of hybrids in the 1970s and 1990s was significantly reduced by 1.57 and 1.14 percentage points, respectively, and MCh (moisture content at harvest time) in the harvest period of hybrids in the 1970s was significantly reduced by 0.99 percentage points, from a low to medium density. The GDRbm (rate of grain dehydration before maturation) and the GDRam (rate of grain dehydration after maturation) showed an increasing trend from a low to medium density. From a medium to high density, the MCpm from the 1980s to 2000s could be significantly reduced by 1.78, 1.53 and 1.88 percentage points; the MCh from the 1980s could be significantly reduced by 1.77 percentage points; and the GDRbm from the 1970s was significantly increased by 0.101%/d, but the improvement of GDRam was not significant. With the planting density increase, the decreased ratios of relative GLAD (green leaf area duration) and leaf SPAD (soil and plant analyzer development) per plant of old maize hybrids were more than that of modern maize hybrids, which promoted the decrease in grain water content and the rate increase in grain dehydration for old maize hybrids. There was a direct positive correlation between the bract and grain dehydration rates, but the cob dehydration rate had no significant effect on the grain dehydration rate. With the increase in planting density, the relative GLAD and leaf SPAD values of plants decreased, and the stay-green of plants worsened, and a significant increase in the dehydration rate of bracts in old and modern eras was an important reason for the decrease in grain moisture content and increase in dehydration rate.