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Improving crop yield and resource utilization efficiency is essential for agricultural productivity. In the Huang-Huai-Hai maize region of China, optimizing planting density, nitrogen (N) application, and fertilization methods are key strategies for enhancing maize yield and N use efficiency. However, traditional approaches have often hindered these improvements. To address this issue, we conducted a study in Baoding, Hebei, from 2022 to 2023, focusing on planting density, the N application rate, and the fertilization method on grain yield, N use efficiency, water use efficiency (WUE), and economic benefits. The trial involved two planting densities: 6.0 × 104 plants ha−1 (D1, typical local density) and 9.0 × 104 plants ha−1 (D2). Five N application rates were tested: 0 (N0), 120 kg ha−1 (N1), 180 kg ha−1 (N2), 240 kg ha−1 (N3), and 300 kg ha−1 (N4). The control treatment (D1N4) utilized the local planting density and traditional fertilization methods. Our findings revealed a positive correlation between the maize yield and N application rate, with the maximum yields (13.78–13.88 t ha−1), high WUE (24.42–29.85 kg m−3), agronomic efficiency of N (AEN) (18.11–19.00 kg kg−1), and economic benefits (2.44 × 104–2.47 × 104 CNY ha−1) observed with D2N3 and surface drip fertilization. This was significantly higher than the yield and resource efficiency of traditional fertilization methods and saved fertilizer and production costs. Therefore, adopting surface drip fertilization, adjusting planting density, and optimizing N application rates proved effective in enhancing maize yield and resource utilization efficiency in the Huang-Huai-Hai maize region. [ABSTRACT FROM AUTHOR]

We investigated the effects of variety, planting density, and irrigation amount on grain yield, water-use efficiency (WUE), and evapotranspiration (ETc). The trial was conducted in Tong Liao, Inner Mongolia, from 2021 to 2022, with compact variety Dika159 (DK159) and conventional variety Zhengdan958 (ZD958) as the test materials. The planting density was set to 6.0 × 104 plants/ha (D1, local farmer planting density) and 9.0 × 104 plants/ha (D2), with five irrigation levels: 450 mm (W450, irrigation amount used by local farmers, CK); 360 mm (W360); 270 mm (W270); 180 mm (W180); and 90 mm (W90). The results indicate that the yield and WUE of variety DK159 increased by 7.48% and 5.00%, compared to ZD958, respectively. Increasing planting density enhanced yield by 13.32–15.57% in maize yield and 9.55–11.47% in WUE. Maize yield exhibited a trend of increasing linearly with the irrigation amount before reaching a plateau, reaching a maximum (16.62–17.39 t/ha) and high WUE (2.45–2.49 kg/m3) with DK159-D2-W270. The highest water consumption intensity occurred during the silking stage to the milk stage for different densities and varieties. The results indicate that selecting compact varieties, increasing planting density, and optimizing irrigation amount through integrated drip irrigation and water fertilizer can effectively improve maize yield and WUE. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) is an important food crop in the world. Reasonably increasing planting density is an important way to increase maize yield. Test weight (TW) determines the classification and affects market price. In order to clarify the influence and mechanism of planting density on TW, in this study, a 2‐year field experiment was carried out in Tongliao, Inner Mongolia Autonomous Region in 2019 and 2020. Four widely planted maize hybrids and six planting densities (6.0, 7.5, 9.0, 10.5, 12.0, and 13.5 × 104 plants ha−1) were tested, using drip irrigation water and fertilizer integration. The output parameters measured were grain yield, TW, thousand‐kernel weight (TKW), kernel volume, kernel density (KD), kernels per unit volume (KPV), and kernel packing efficiency. The result showed that yields ranged from 12.04 to 16.58 ton ha−1and TW ranged from 751 to 807 kg m−3, which exceeded the requirements for classification as first‐grade maize (720 kg m−3). Both yield and TW have a quadratic curve relationship with planting density, but the planting density corresponding to the two indicators is different when they reach the maximum value. With the increase in planting density, the TKW decreased and KPV increased, which made the relationship between TW(y) and planting density (x) and expressed as y = ax2 + bx + c. Planting density had a significant influence on TW and the relationship between TW and planting density was consistent under growth years and maize varieties. Considering the economic benefits, the planting density corresponding to the maximum yield is strongly recommended for future maize production. Core Ideas: Both yield and test weight of maize have a quadratic curve relationship with planting density.Decreased thousand‐kernel weight (TKW) and increased kernels per unit volume (KPV) cause test weight (TW) to vary with increasing planting density.Growing maize at the planting density corresponding to the highest yield can achieve the greatest benefits. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) grain quality is an important economic trait directly determining the market price and application value of maize. In this study, maize grain starch, protein, oil, fiber concentrations, and bulk density were investigated based on a multi‐site experiment across China to determine the regional distribution trend of grain quality and its influencing factors. It showed that the mean starch, protein, oil, fiber concentrations, and bulk density in China were 73.4%, 9.5%, 4.2%, 3.6%, and 77.2 kg hL−1, respectively. Overall, each nutritional composition concentration did not show the same spatial distribution as grain yield that was in the order of Northwest (NW) > North (NM) > Huanghuaihai (HM) > Southwest (SW) maize region. The starch and protein concentrations were highest in SW and HM, respectively. The oil concentration was lowest in NW. The interregional difference in bulk density was not significant. As for cultivars, the starch and oil concentrations of ZD958 were higher than that of XY335 in each region, but the protein, fiber concentrations, and bulk density appeared to be the opposite trend. Correlation analysis indicated that the fiber concentration and bulk density were positively correlated with grain yield. The protein, oil, and fiber concentrations were negatively correlated with starch concentration. Among the considered climatic factors, the protein, fiber concentrations, and bulk density were mainly positively affected by temperature factors in China. The results provide a reference for the division of maize advantageous quality regions and the construction of high‐yield and quality technology model in typical ecological regions. Core Ideas: The key nutritional and commodity quality of maize were investigated across China.The region of NW and NM had better nutritional quality yield potential than that of HM and SW.The temperature factors mainly affected maize grain quality across China. [ABSTRACT FROM AUTHOR]

BACKGROUND: Global warming has led to methods of planting late‐maturing maize varieties in northeast China that have hindered the development of physiological maturity (PM) at harvest and the use of mechanical grain harvesting (MGH). Under these conditions it is difficult to balance the drying characteristics of maize varieties and to make full use of accumulated temperature resources in such a way as to reduce grain moisture content (GMC) at harvest. RESULTS: The effective accumulated temperature (AcT) and the drying rates of different varieties vary. In northeast China, with a GMC of 25%, the growth periods of a fast‐drying variety (FDV) and a slow‐drying variety (SDV) were 114–192 days and 110–188 days respectively. After PM, the FDV needed 47 days and the SDV needed 51 days to reduce the GMC to be ready for MGH. Harvested with a GMC of 20%, the growth period for the FDV was 97–175 days and for the SDV it was 90–171 days. After PM, the FDV required 64 days and the SDV needed 70 days to reduce the GMC to be ready for MGH. CONCLUSION: Matching cultivars with AcT can help farmers to choose suitable varieties. Promoting MGH may boost maize production, thus ensuring China's food security. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

In maize (Zea mays L.), rational root structure promotes high grain yield under dense sowing conditions. This study was conducted at Qitai Farm in Xinjiang, China, in 2019 and 2021. A traditional wide and narrow row planting method was adopted, with wide rows of 0.7 m and narrow rows of 0.4 m. The cultivars DH618 and SC704, which have grain yield potentials of 22.5 and 15 Mg ha−1, respectively, were selected for study of the root structure and distribution characteristics under high-yield and high-density planting conditions. The highest yield (20.24 Mg ha−1) was achieved by DH618 under a planting density of 12 × 104 plants ha−1. The root structure of DH618 was well developed at that planting density, and the root dry weight (RDW) was 17.49 g plant−1 and 14.65 g plant−1 at the silking and maturity stages, respectively; these values were 7.56% and 11.86% higher, respectively, than those of SC704. At the silking stage, the proportions of RDW at soil depths of 0–10, 10–20, 20–40, and 40–60 cm were 66.29%, 11.83%, 16.51%, and 5.38%, respectively, for DH618; over the 20–60 cm soil layer, this was an average of 4.04% higher than the RDW of SC704. At maturity, the proportions of RDW at soil depths of 0–10, 10–20, 20–40, and 40–60 cm were 61.40%, 11.19%, 17.19%, and 10.21%, respectively, for DH618, which was an average of 9.59% higher than that of SC704 over the 20–60 cm soil layer. At maturity, DH618 roots were mainly distributed in the narrow rows, accounting for 72.03% of the root structure; this was 9.53% higher than the roots of SC704. At silking and maturity, the root weight densities of DH618 were 471.98 g m−3 and 382.98 g m−3, respectively (5.18% and 5.97% higher, respectively, than the root weight densities of SC704). The root lengths of DH618 were 239.72 m plant−1 and 199.04 m plant−1 at the silking and maturity stages, respectively; these were 16.45% and 25.39% higher, respectively, than the root lengths of SC704. The root length densities were 0.58 cm cm−3 and 0.46 cm cm−3 at the silking and maturity stages, respectively, and these were 16.86% and 17.08% higher, respectively, than the root length densities of SC704. This study indicated that the maize hybrid DH618 had a more developed root structure with increased root distribution in the deep soil and narrow rows under high-density planting compared to cultivar SC704, contributing to high grain yield under dense planting. [ABSTRACT FROM AUTHOR]

Solar dimming due to global climate change is becoming increasingly more common in some agricultural areas. Such low-light stress inhibits maize ear number, kernel number per unit area (KN), and kernel weight (KW) as vital yield components. However, which yield component factors are most important for yield formation under low-light stress remains unknown. In this study at Qitai Farm in Xinjiang, China, in 2019 and 2020, we planted three maize (Zea mays L.) cultivars (Denghai 618 (DH618), Xianyu 335 (XY335), and Zhengdan 958 (ZD958)) at two densities (7.5 × 104 (D1) and 12 × 104 (D2) plants ha−1). We used four shading treatments (85% (S1), 70% (S2), and 50% (S3) natural light and no shading (CK)) from the three-leaf stage until maturity to create different light conditions. KN was the key factor that directly affected yield under low-light stress. For every 100 MJ m−2 decrease in photosynthetically active radiation (PAR), the KN decreased by 803.2 kernels per m2. When the PAR was >674.3 MJ m−2 , KW tended to stabilize at 36.2 g/hundred kernels and the growth rate was 5.82 g/100 MJ m−2 per hundred kernels. DH618 and XY335 KNs were more sensitive to lowered solar radiation than ZD958. When density increased, DH618 required fewer light resources than the other cultivars to produce an equivalent amount of photosynthates for kernels. Therefore, in the face of climate change, particularly solar dimming, there is an urgent need to breed maize cultivars, such as DH618, with low-light stress tolerance and high grain yield. [ABSTRACT FROM AUTHOR]

Planting maize (Zea mays L.) reasonably densely and adding amounts of appropriate nitrogen fertilizer are essential measures to improve the efficiency of maize yield and nitrogen use. In this study, two planting densities of 7.5 × 104 plants ha−1 and 12.0 × 104 plants ha−1 were established with the maize varieties DengHai 618 (DH618) and XianYu 335 (XY335). Simultaneously, 18 levels of nitrogen application were established, including a lack of nitrogen (N0) and increments of 45 kg ha−1 nitrogen up to 765 (N765) kg ha−1. The variables studied included the effects of the rate of nitrogen application on the characteristics of dry matter accumulation and the yield under drip irrigation, and they were integrated into water–fertilizer integration. The results indicated that the yield, harvest index, and dry matter accumulation of maize displayed a trend of increasing and then tending to be flat as the amount of nitrogen applied increased. The use of linear plus platform equation fitting indicated that the change in yield with nitrogen administered had the lowest turning point at N = 279 and N = 319, respectively. The next parameter that was measured was the harvest index. When highly dense maize was grown before silking, the rate of nitrogen applied was more obviously impacted by the accumulation of dry matter. The harvest index contributed 22.9–27.2% of the yield, and the total dry matter accumulation before and after silking contributed more than 70% of the production. Increasing the amount of nitrogen fertilizer is beneficial to prolonging the dry matter accumulation time and increasing the dry matter accumulation rate. The accumulation amount of dry matter was positively correlated with accumulation time and rate, and the correlation between dry matter and accumulation rate was greater. In conclusion, applying the right amount of nitrogen can dramatically increase the harvest index, accumulation of materials, and yield, with dry matter accumulation having the greatest influence on yield. The creation of dry matter is influenced by the time and rate of its accumulation, with its rate serving as the primary controlling factor. [ABSTRACT FROM AUTHOR]

Nitrogen (N) utilization for crop production under N deficiency conditions is subject to a trade-off between maintaining specific leaf N content (SLN) important for radiation-use efficiency versus maintaining leaf area (LA) development, important for light capture. This paper aims to explore how maize deals with this trade-off through responses in SLN, LA and their underlying traits during the vegetative and reproductive growth stages. In a 10-year N fertilization trial in Jilin province, Northeast China, three N fertilizer levels have been maintained: N deficiency (N0), low N supply (N1) and high N supply (N2). We analysed data from years 8 and 10 of this experiment for two common hybrids. Under N deficiency, maize plants maintained LA and decreased SLN during vegetative stages, while both LA and SLN decreased comparably during reproductive stages. Canopy SLA (specific leaf area, cm2 g–1) decreased sharply during vegetative stages and slightly during reproductive stages, mainly because senesced leaves in the lower canopy had a higher SLA. In the vegetative stage, maize maintained LA at low N by maintaining leaf biomass (albeit hence having N content/mass) and slightly increasing SLA. These responses to N deficiency were stronger in maize hybrid XY335 than in ZD958. We conclude that the main strategy of maize to cope with low N is to maintain LA, mainly by increasing SLA throughout the plant but only during the vegetative growth phase. [ABSTRACT FROM AUTHOR]

While plastic film mulching and proper high-density planting are important methods that can improve maize yield, years of accumulated residual film have created soil pollution and degraded soil, and thus has impeded sustainable agriculture development. Here, we compared the stalk and root lodging resistances of three maize cultivars grown at two planting densities both with (FM) and without (NM) plastic film mulch. Our aim was to provide a theoretical basis that may help assure a future of successful no-film planting with increased planting density. The results showed that, compared with FM, the average dry weight per unit length and bending strength of basal internode decreased for all cultivars at both planting densities in the NM treatment. At 9.0 × 104 plants ha−1, the stalk breaking force (SFC) of Xinyu77, KWS9384, and KWS2030 in the NM treatment decreased by 4%, 21%, and 22%, respectively. At 12.0 × 104 plants ha−1, SFC of Xinyu77 and KWS2030 increased by 14% and 1%, respectively, while KWS9384 decreased by 10%. Additionally, the root diameter, length, volume, width, depth, and the vertical root-pulling force of maize decreased. Although the lodging resistance of maize grown without film mulch was lower than that of maize grown with it, those adverse effects can be mitigated by selecting suitable cultivars and by using proper high-density planting and appropriate cultivation measures. [ABSTRACT FROM AUTHOR]

High grain yield and water use efficiency (WUE) are the key goals when producing maize (Zea mays L.) under irrigation in arid areas. Increasing the planting density and optimizing irrigation are important agronomic practices for increasing the maize grain yield and WUE. A two-year field experiment was conducted to investigate the effects of planting density and irrigation on the maize grain yield, WUE, and economic return of spring maize under a mulch drip irrigation system in Xinjiang, Northwest China. The experiment included four irrigation levels and five planting densities. The results showed that the reduction of irrigation decreased the yield and evapotranspiration (ETc) but improved the WUE. Increasing the planting density increased the ETc, but there was a quadratic curve relationship between yield and WUE and planting density. Treatment with 600 mm of water and 12 plants m−2 obtained the highest grain yield (21.0–21.2 t ha−1) and economic return (3036.0 USD ha−1) and a relatively high WUE (2.64–2.70 kg kg−1). Therefore, a reasonable increase in planting density and an appropriate reduction of irrigation combined with drip irrigation under a mulch system can simultaneously achieve high yields and economic return and high WUE in maize production. [ABSTRACT FROM AUTHOR]

A quantitative understanding of the factors driving changes in grain filling is essential for effective prioritization of increasing maize yield. Grain filling is a significant stage in maize yield formation. Solar radiation is the energy source for grain filling, which is the ultimate driving factor for final grain weight and grain filling capacity that determine maize yield. Here, we first confirmed the quantitative relationships between grain filling parameters and photosynthetically active radiation (PAR) by conducting field experiments using different shading and plant density conditions and cultivars in 2019 and 2020 in Xinjiang, China. The results showed that with every 100 MJ m−2 increase in PAR, the average grain filling rate (G ave), maximum grain-filling rate (G max), and the kernel weight at the time of maximum grain-filling rate (W max) increased by 0.073 mg kernel−1 day−1, 0.23 mg kernel−1 day−1, and 0.24 mg kernel−1, and the time of maximum grain-filling rate (T max) delayed by 0.91 day. Relative changes in PAR were significantly and positively correlated with relative changes in yield and G ave. With every 1% change in PAR, yield and G ave changed by 1.16 and 0.17%, respectively. From the perspective of grain filling capacity, DH618 was a more shade-resistant cultivar than XY335 and ZD958. It is urgent to breed maize cultivars with low light tolerance and high grain yield in the face of climate change, particularly the decrease in solar radiation. [ABSTRACT FROM AUTHOR]

The rational application of nitrogen fertilizer and close planting are two important ways to obtain high yields and efficient growth from maize (Zea mays L.). This study utilized the maize varieties DengHai 618 and XianYu 335 as test materials from 2019 to 2020 and the maize variety XianYu 335 as the test material in 2021. The planting densities were 7.5 × 104 plants ha−1 and 12.0 × 104 plants ha−1, respectively. Application rates of nitrogen within the range of 0–765 kg ha−1 per 45 kg ha−1 were considered the nitrogen application gradient. The results showed that as the nitrogen application rate increased, the yield of the maize increased at first and then tended to remain flat. Under conditions of 7.5 × 104 plants ha−1 density, the best yield was 17.6–20.2 t ha−1, and the required nitrogen application rate was 219–337 kg ha−1. Under conditions of 12.0 × 104 plants ha−1 density, the best yield was 18.7–21.9 t ha−1, and the required nitrogen application rate was 243–378 kg ha−1. With the increase in the nitrogen application rate, the dry matter weight showed a linear/platform relationship in each growth period. The best nitrogen application rate was obtained for dry matter accumulation in various stages by fitting the nitrogen application rate and dry matter accumulation in different stages. It is concluded that when the planting density was 7.5 × 104 plants ha−1, the recommended nitrogen application rate was 340 kg ha−1, and the distribution ratio of the nitrogen application rates before and after silking were 61.2% and 38.8%, respectively. When the planting density was 12.0 × 104 plants ha−1, the recommended nitrogen application rate was 380 kg ha−1, and the distribution rates before and after flowering were 65.8% and 34.2%, respectively. In summary, increasing planting density can improve maize yield, and the amount of nitrogen applied should be increased before flowering. [ABSTRACT FROM AUTHOR]

Accurate estimation of the canopy chlorophyll content (CCC) plays a key role in quantitative remote sensing. Maize (Zea mays L.) is a high-stalk crop with a large leaf area and deep canopy. It has a non-uniform vertical distribution of the leaf chlorophyll content (LCC), which limits remote sensing of CCC. Therefore, it is crucial to understand the vertical heterogeneity of LCC and leaf reflectance spectra to improve the accuracy of CCC monitoring. In this study, CCC, LCC, and leaf spectral reflectance were measured during two consecutive field growing seasons under five nitrogen treatments. The vertical LCC profile showed an asymmetric 'bell-shaped' curve structure and was affected by nitrogen application. The leaf reflectance also varied greatly between spatio–temporal conditions, which could indicate the influence of vertical heterogeneity. In the early growth stage, the spectral differences between leaf positions were mainly concentrated in the red-edge (RE) and near-infrared (NIR) regions, whereas differences were concentrated in the visible region during the mid-late filling stage. LCC had a strong linear correlation with vegetation indices (VIs), such as the modified red-edge ratio (mRER, R2 = 0.87), but the VI–chlorophyll models showed significant inversion errors throughout the growth season, especially at the early vegetative growth stage and the late filling stage (rRMSE values ranged from 36% to 87.4%). The vertical distribution of LCC had a strong correlation with the total chlorophyll in canopy, and sensitive leaf positions were identified with a multiple stepwise regression (MSR) model. The LCC of leaf positions L6 in the vegetative stage (R2-adj = 0.9) and L11 + L14 in the reproductive stage (R2-adj = 0.93) could be used to evaluate the canopy chlorophyll status (L12 represents the ear leaf). With a strong relationship between leaf spectral reflectance and LCC, CCC can be estimated directly by leaf spectral reflectance (mRER, rRMSE = 8.97%). Therefore, the spatio–temporal variations of LCC and leaf spectral reflectance were analyzed, and a higher accuracy CCC estimation approach that can avoid the effects of the leaf area was proposed. [ABSTRACT FROM AUTHOR]

Improved canopy structure was instrumental in setting maize yield records, and yet it has rarely been examined in China. At Qitai Farm in Xinjiang, we conducted a 4‐year field experiment using China's six highest‐yielding maize hybrids sorted into three yield level groups that were grown at similar growth durations and at optimum densities. The average yield of high‐yield level (HL, 22.3 Mg ha−1) was 7.2% and 24.6% higher than that of medium‐yield level (ML) and low‐yield level (LL), respectively. For each yield level, we measured morphological traits that influence canopy structure and yield. They included plant height, ear height, ear ratio, internode length, leaf numbers, leaf angle, LOV, leaf area, and spatial density of leaf area. Among the preceding morphological traits of the three yield levels, HL's best optimized the canopy structure, as shown by improved light distribution (19.0% light transmission at the ear) and increased light interception per unit leaf area per day (LIPA, 51.7 MJ m−2 day−1) in the canopy. In comparison, light transmission was 12.2% and 15.9% at the ear and the total LIPAs were 37.2 and 29.0 MJ m−2 day−1 at silking for ML and LL, respectively. HL had significantly longer leaf area duration and a higher photosynthetic rate, especially at the grain filling stage, and its total accumulated biomass at maturity was significantly better (by 13.9%) than LL's. HL's harvest index (0.54) was significantly higher than that of ML (0.52) and LL (0.48). HL's radiation and heat use efficiencies were 2.61% and 1.37 g °C−1 day−1 m−2, both significantly greater than those of ML and LL. Therefore, optimum maize plant types can significantly improve canopy structure and increase resource use efficiency and grain yield. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the effect of row spacing and plant density on maize (Zea mays L.) yield and radiation use efficiency (RUE). This experiment that was conducted in 2018 and 2019 contained two plant densities (90,000 and 120,000 plant ha−1) and four row spacings (60–50, 70–40, 80–30, and 90–20 cm). In this experiment the distance between four rows in the 60–50 treatment was 50, 60, and 50 cm, whereas the distance between four maize rows in the 90–20 treatment was 20, 90, and 20 cm. For a given planting rate, the leaf area index (LAI) for the 70–40 treatment was higher than the 60–50, 80–30, or 90–20 treatments. The averaged post‐silking RUE was 11.1% higher in the high (HD) than low density (LD) seeding. Planting maize in a 70–40 arrangement had higher post‐silking RUE than planting in the 80–30 and 90–20 cm arrangements. These grain numbers per ear decreased and grain numbers per square increased with increased planting densities under the same planting patterns. Compared to LD, the average annual grain yield of DH618, KWS9384 and KWS2030 in HD increased by 5.21, 4.84, and 3.68%, respectively. Compared to 90–20 treatment, the average annual grain yield under 60–50, 70–40, and 80–30 treatments increased by 7.20, 6.39, and 5.20% in LD, and 5.15, 6.39, and 1.72% in HD, respectively. Therefore, we concluded that 60–50, 70–40, and 80–30 treatments in LD, 60–50 and 70–40 treatments in HD will increase grain yields in the tested environment. Core Ideas: Optimizing the row spacing improve the light distribution.Increasing planting density can increase radiation use efficiency and yield.Increasing planting density and decreasing row spacing are suitable for increase yield. [ABSTRACT FROM AUTHOR]

Understanding the impact of changes in the crop canopy on yield is important in order to meet future food demands. We designed a field experiment to investigate the relationships between crop‐related factors and yield gaps in maize to enhance crop yields from 2010 to 2018 in Qitai, China. Maize grain yields (n = 247) were divided into four yield ranges: <15 Mg ha−1 (n = 30), 15–18 Mg ha−1 (n = 79), 18–21 Mg ha−1 (n = 114), and >21 Mg ha−1 (n = 24). The characteristics of the maize canopy structure as well as the light interception, photosynthetic potential, and radiation utilization efficiency in these four yield ranges were analyzed. The canopy structure of treated fields with yields >21 Mg ha−1 had a higher leaf area index (7.2), lower ear ratio (0.39), longer internodes above the ear (20.1 cm), larger leaf orientation value (LOV) above the ear (48.6), smaller leaf angle above the ear (18°), and smaller LOV below the ear (36.0) when compared to the other treatments. These findings suggested that the yield gap is dependent on canopy structure, and the evolutionary trend also accounted for significant increases in post‐LAD (p < 0.01), changes in crop growth rate (CGR; p < 0.01), net assimilation rate (NAR; p < 0.05), and radiation utilization efficiency. The radiation utilization efficiencies in the 15–18, 18–21, and >21 Mg ha−1 treatments (1.23, 1.28, and 1.38 g MJ−1, respectively) were higher than for the <15 Mg ha−1 treatment (1.10 g MJ−1). Furthermore, there are opportunities to narrow the yield gaps by optimizing the canopy structure to make full use of the solar radiation resources. Our results will help breeders choose an ideal canopy structure to improve yield. In addition, our results may serve as a general guide for other maize growing regions. [ABSTRACT FROM AUTHOR]

Solar radiation is the energy source for crop growth, as well as for the processes of accumulation, distribution, and transfer of photosynthetic products that determine maize yield. Therefore, learning the effects of different solar radiation amounts on maize growth is especially important. The present study focused on the quantitative relationships between solar radiation amounts and dry matter accumulations and transfers in maize. Over two continuous years (2017 and 2018) of field experiments, maize hybrids XY335 and ZD958 were grown at densities of 4.5 × 104 (D1), 7.5 × 104 (D2), 9 × 104 (D3), 10.5 × 104 (D4), and 12 × 104 (D5) plants/ha at Qitai Farm (89°34′E, 44°12′N), Xinjiang, China. Shading levels were 15% (S1), 30% (S2), and 50% (S3) of natural light and no shading (CK). The results showed that the yields of the commonly planted cultivars XY335 and ZD958 at S1, S2, and S3 (increasing shade treatments) were 7.3, 21.2, and 57.6% and 11.7, 31.0, and 61.8% lower than the control yields, respectively. Also, vegetative organ dry matter translocation (DMT) and its contribution to grain increased as shading levels increased under different densities. The dry matter assimilation amount after silking (AADMAS) increased as solar radiation and planting density increased. When solar radiation was <580.9 and 663.6 MJ/m2, for XY335 and ZD958, respectively, the increase in the AADMAS was primarily related to solar radiation amounts; and when solar radiation was higher than those amounts for those hybrids, an increase in the AADMAS was primarily related to planting density. Photosynthate accumulation is a key determinant of maize yield, and the contributions of the vegetative organs to the grain did not compensate for the reduced yield caused by insufficient light. Between the two cultivars, XY335 showed a better resistance to weak light than ZD958 did. To help guarantee a high maize yield under weak light conditions, it is imperative to select cultivars that have great stay-green and photosynthetic efficiency characteristics. [ABSTRACT FROM AUTHOR]

Solar radiation is an important environmental factor affecting maize (Zea mays L.) root and shoot growth and grain yield. This study was conducted in Qitai and Yinchuan, China, in 2018 and 2019. The maize cultivars of XY335, ZD958, and DH618 and planting densities of 7.5 × 104 (D1) and 12 × 104 plants ha−1 (D2) were adopted under shading levels of 15 (S1), 30 (S2), and 50% (S3) with natural light as the control (CK). The results showed that averaging all shading and density treatments over the 2 yr, shading reduced the grain yields of XY335, ZD958, and DH618 by an average of 40.4, 39.2, and 35.6%, respectively, compared with the CK. The effect of solar radiation on the root dry weight was greater than that on the shoot dry weight, which resulted in a decrease in root/shoot ratio with increasing shading level. The quantitative analysis results showed that for every 1‐MJ m−2 decrease in solar radiation, the root dry weight, shoot dry weight, and root/shoot ratio decreased by 0.1938 g m−2, 1.3517 g m−2, and 0.0103 × 10−2, respectively. According to this quantitative relationship, it was helpful to select cultivars and planting density with suitable root characteristics under different solar radiation conditions in different regions. From the aspects of shoot and grain yield, DH618 was more shade resistant, and its root system rapidly adjusted to compensate for shoot growth and yield formation when solar radiation decreased. Such cultivars should be given attention in future production and breeding. [ABSTRACT FROM AUTHOR]

Increasing plant density usually increases the intra‐specific competition of maize plants. This study was conducted to determine whether maize (Zea mays L.) hybrid density tolerance is related to intra‐specific competition. Field experiments were conducted using a split‐plot design, the main plots contained four maize hybrids, and subplots were 12 plant densities varied from 1.5 to 18 × 104 plants ha−1. This study focused on dry matter accumulation, grain yield (GY), competition intensity (CI), and absolute severity of competition (ASC) based on the above treatments. Among all tested hybrids, GY exhibited a curvilinear response to plant density, which was well characterized by the Steinhart–Hart equation. Maize hybrids differed in optimum GY in descending order as follows: Zhongdan909 (ZD909) > Xianyu335 (XY335) = Yedan13 (YD13) > Zhongdan2 (ZD2). The CI and ASC of tested maize hybrids indicated that intra‐specific competition increased with increasing plant density. In most cases, the CI and ASC of older maize hybrids were higher than those of modern maize hybrids when plant density exceeded 9.0 × 104 plants ha−1. The results showed that the slope of the linear regression of ASC and plant density (i.e., the k‐value) could be used to compare the intra‐specific CI of maize hybrids, and there were significant negative correlations of k‐value with optimum plant density and GY. Intra‐specific competition is negatively correlated with the density tolerance of maize hybrids. This relationship may provide new insights for determining future maize breeding targets. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) kernel moisture content at physiological maturity significantly differs among hybrids and is affected by the environment. Nonetheless, 35% was previously reported and is widely accepted as the moisture content at physiological maturity. To verify whether the 35% moisture content could be applied to various hybrids and regions, a multi‐area, multi‐year trial was conducted from 2015 to 2018 in six locations in different maize‐planting regions of China. Time‐series kernel moisture contents and kernel dry weights were investigated for 156 hybrids in total to ascertain the growth pattern of the percentage maximum kernel dry weight as a function of kernel moisture content. The growth patterns were fitted with a tri‐linear model with a plateau, and at the point at which the percentage maximum kernel dry weight first reached its maximum (physiological maturity), the kernel moisture contents were 32% for summer maize, 34% for spring maize, and 38% for Daqing (a special spring maize region). We found that regional variation existed in kernel moisture content at physiological maturity. The regional average moisture content at physiological maturity could thus be used as an indicator to determine physiological maturity for most hybrids in the region. In addition, varietal differences in moisture content could be accounted for when using the regional average value. [ABSTRACT FROM AUTHOR]

The reason for different maize (Zea mays L.) hybrids exhibiting differences in stalk lodging risk between the 12‐leaf (V12) and flowering stages is unclear. This study tracked internode development included morphology, carbohydrate accumulation, and mechanical strength of basal internodes in four widely‐planted maize hybrids in China for two consecutive growing seasons. And then used logistic model to estimate the time of initiation and termination of rapid thickening, lengthening, accumulation of dry weight per unit length (DWUL), cellulose, lignin, and increase in rind penetration strength (RPS) of internodes. Planting density was 7.5 × 104 plants ha−1. The results shows that basal internodes development in maize begins with a period of rapid thickening and lengthening, followed by DWUL accumulation, and finally an increase in RPS. The period of DWUL accumulation was the longest of these developmental periods and occurred throughout internode development. For hybrid with a low risk of stalk lodging, RPS development began in later part of the rapid elongation period. In contrast, rapid RPS development in hybrid with a high risk of stalk lodging began after the rapid elongation period. Rapid DWUL accumulation and RPS development can reduce the adverse effects caused by rapid elongation of basal internodes. The shorter the interval between rapid elongation, DWUL accumulation, and RPS development of the basal internodes, the greater a plant's resistance to stalk lodging. Therefore, lodging risk can be reduced through selection and breeding strategies that achieve synergistic development of morphology, dry matter accumulation, and mechanical strength in maize stalks. [ABSTRACT FROM AUTHOR]

Understanding the contribution of aboveground dry matter (DM) production and harvest index (HI) to maize grain yield is essential to further improve grain yield to ensure future food growing requirements. In this study, we collected 548 sets of data of DM, HI, and grain yield from a multisite (40 sites) and multiyear (2009–2016) experiment conducted in major maize‐growing regions across China and 615 sets of data from 40 published papers distributed from 1988 to 2018 to assess the performance of DM, HI, and their contributions to grain yield. It was found that the average contribution rate of DM was 73.71%, which was much higher than those of HI (26.28%) across China. For the five different modern hybrids, the contribution rates of DM to grain yield (ranged from 71.36% to 89.10%) were also significantly higher than those of HI (ranged from 10.79% to 28.64%) on a large spatial scale. The significant differences in grain yields between cultivars were mainly due to the differences in HI. Among the four maize‐growing regions, the contribution rates of DM in both NW (57.34%) and NM (64.46%) were higher than those of HI (42.66% and 35.54%, respectively). In contrast, the contribution rates of HI in HM (52.67%) and SW (50.92%) were slightly higher than those of DM (47.33% and 49.08%, respectively). The interregional differences in grain yield were mainly attributed to the differences in DM between regions. Additionally, combining the data of this study and data collected from previous studies, we found that the increase in maize grain yield under lower yield levels (<15 Mg/ha) was mainly attributed to the increase in both DM and HI, while that under higher yield levels (>15 Mg/ha) was mainly dependent on the increase in DM. [ABSTRACT FROM AUTHOR]

High grain yield and N use efficiency are key goals of crop production. Increasing planting density and supplying adequate N application are important agronomic practices to increase maize grain yield. However, little is known about the interaction between the planting density and N application rate of high‐yield maize under mulch drip irrigation. The objectives of this study were to determine the impacts of planting density and N application rate on the grain yield, economic return, nitrogen partial factor productivity (PFPN), and nitrogen agronomic efficiency (AEN) of super high‐yield maize under mulch drip irrigation in Northwest China. To achieve this, field experiments were conducted in 2017 and 2018 in Qitai farm, Xinjiang. The experiments included four N application levels−no nitrogen (N0), and 270 (N1), 360 (N2), and 450 kg N ha−1 (N3)−and five planting densities−7.5 (D1), 9.0 (D2), 10.5 (D3), 12.0 (D4), and 13.5 plants m−2 (D5). It was found that the N2D4 treatment obtained the highest grain yield (21.5−21.6 t ha−1) and economic return (US$3,399.7−$3,440.3 ha−1) and the relative higher PFPN (59.7−60.1 kg kg−1) and AEN (23.7−25.1 kg kg−1). The PFPN and AEN declined with increasing N application and varied according to a quadratic relationship with increasing planting density. Therefore, a reasonable increase of planting density and an appropriate reduction of N application combined with integrated irrigation−fertilization technology under mulch drip irrigation cannot only obtain high maize yield and economic return but can also improve the N utilization efficiency. [ABSTRACT FROM AUTHOR]

The effects of uniformity in border rows and population structure on the yield of hybrid maize (Zea mays L.) grown at high planting density was studied in field experiments at Qitai Farm (89°34′E, 44°12′N), Xinjiang, China, during 2013 and 2014. The experiments incorporated a planting density of 12.0 plants m–2 and three maize cultivars (M753, LY66, LD565). Border effects and uniformity in the border rows were studied at the silking and maturity stages. Yields of M753, LY66 and LD565 were 16.46, 15.02 and 11.45 Mg ha–1, respectively. Analysis of yield components in border rows indicated that the number of kernels per ear, 1000-kernel weight and yield per plant of M753 stopped decreasing after the second row in the border, whereas those of LY66 and LD565 stopped decreasing after the third row in the border, demonstrating a stronger border effect. The cultivars intercepted >95% of the light, but light transmission was lower for M753 than for LY66 and LD565, which resulted in the highest light interception in the upper canopy layers of M753. Analysis of uniformity in the border rows showed that the uniformity values for plant height, ear height, stem diameter, number of kernels per ear, 1000-kernel weight and yield per plant were higher for M753 than for LY66 and LD565. For the three cultivars, uniformity values could be ranked in the order plant height > ear height > stem diameter. The results suggest that cultivars with weaker border effects and greater uniformity in border rows can produce higher yields when grown at a high planting density. The magnitude of margin effect reflects the density-tolerance of maize cultivars. Uniformity plays an important role in higher maize yield achievement especially under high planting density. The weakest marginal effects and greatest uniformity in border rows were closely related to higher grain yield. [ABSTRACT FROM AUTHOR]

Meeting maize (Zea mays L.) production targets of high grain yields and nitrogen use efficiency (NUE) requires the development of stress‐tolerant cultivars and corresponding cultivation practices that maximize efficiency. Therefore, our objectives were to (i) determine the impacts of N application rate, planting density, and maize cultivar (which have improved with each successive release date) on the N partial productivity factor (PFPN) and N agronomic efficiency (AEN), and to (ii) characterize the responses of maize cultivars indexes to different cultivation conditions. We found that maize PFPN and AEN values were affected by N application, planting density, and cultivar. The PFPN and AEN declined with increasing N but increased with increasing planting density or genetic improvement (i.e. later year of release). The responses of PFPN and AEN to planting density and N application, taken either as single factors or as interacting factors, were greater for recently released cultivars than for older cultivars. The PFPN and AEN values were not automatically associated with maize yields, indicating that the genetic improvements that led to increases in PFPN and AEN were due to unconscious selection. Thus, improvements in NUE resulted from improvements in cultivars' tolerance to planting density stresses and from cultivation practices that employed higher planting densities from the 1950s to 2010. [ABSTRACT FROM AUTHOR]

Nitrogen is an essential element for maize (Zea mays L.). Farmers in developed countries most often apply more N fertilizer than necessary, which reduces N use efficiency (NUE). Improving radiation and N distribution, and thus the NUE of modern maize production systems with high plant density, is of great significance. In this study, field experiments were conducted in 2014 and 2015 in Xinjiang, China, using hybrid maize cultivar DH618 with high density. In addition, a synthesis analysis was conducted using data from 95 publications to observe N characteristics under different yield levels and compare the experimental results with existing studies. The relationship between radiation and N distribution in the canopy of high‐yield maize was also assessed. Nitrogen uptake was significantly correlated with grain yield. However, N uptake per unit grain yield and grain N concentration at maturity decreased as grain yield increased. The positive correlations between radiation and leaf and stalk N concentrations at silking showed that N concentration at silking increased as the height of the canopy layer increased because of increased radiation in the canopy. These results indicate that maize hybrids with erect upper leaves and high post‐silking N uptake can coordinate and optimize the distribution of radiation and N in different canopy layers and thus improve NUE and yield under high‐density production. [ABSTRACT FROM AUTHOR]

The competitiveness of crop cultivars has been observed to decrease along with breeding progress. Changes in the competitiveness of maize ( Zea mays L.) as a consequence of breeding over past decades have not been reported. The main objectives of this study were to (1) test Donald’s concept of communal ideotype in maize, and (2) determine the specific changes in competitiveness of maize hybrids due to breeding. Field experiments were conducted in the 2013 and 2014 growing seasons, using a de Wit replacement series design. Three maize hybrids, ZD2 (1972), YD13 (1992) and ZD909 (2011), which differed in release dates, were used in this study. Each hybrid was grown in multiple row replacement series (0:6, 1:5, 2:4, 3:3, 4:2, 5:1, and 6:0), with a total plant density of 67,500 seeds/ha. Inter-cultivar competition reduced dry matter accumulation (DMA) and grain yield per plant of the cultivars in the replacement series. In each replacement series, plant DMA, grain yield and harvest index (HI) of hybrids decreased with increasing proportion of the older hybrid. Population grain yield exhibited the same trend. Based on competitive outcome and aggressivity (AG), maize hybrids differed in their competitiveness. Breeding reduced the competitiveness of maize hybrids, which ranked ZD2 > YD13 > ZD909, but the varying characteristics of plant traits were not at all consistent with competitiveness. The competitiveness of maize hybrids decreased during the past few decades, supporting Donald’s communal ideotype, which states that modern high yielding hybrids should not perform well in competition with other genotypes. Shorter plants with erectophile leaves and lower root:shoot ratios could contribute to weak competitiveness. Based on an analysis of aggressivity (AG), the AG of ZD2 relative to YD13 (AG ZD2 → YD13 ) was 0.121, the AG of YD13 relative to ZD909 (AG YD13 → ZD909 ) was 0.091, the AG of ZD2 relative to ZD909 (AG ZD2 → ZD909 ) was 0.153, and AG ZD2 → YD13 + AG YD13 → ZD909 ≠ AG ZD2 → ZD909 , indicating that the changes in competitiveness were not consistent with the breeding process. Our results show that the competitiveness of maize bybrids was reduced by breeding, but that variation in architectural plant traits among genotypes was not completely consistent with the changes in their competitiveness. [ABSTRACT FROM AUTHOR]

This paper revisits the debate on the role of agriculture in promoting economic growth in a selection of nine developing countries. We investigated the causal linkages between agriculture and gross domestic product growth with the aid of directed acyclic graphs, a recently developed algorithm of inductive causation. The results suggest that while agriculture could be an engine of economic growth, the impact varies across countries. In some cases, we found strong evidence in support of the agriculture-led growth hypothesis. In contrast, the results for some other countries indicate that having a vibrant aggregate economy is a prerequisite for agricultural development. [ABSTRACT FROM AUTHOR]

Abstract: Environmental conditions greatly affect the growth of maize. To examine differences in phenological responses of maize (Zea mays L.) to climatic factors under different environmental conditions as induced by latitude, experiments were conducted from 2007 to 2010 at 34 sites in seven Chinese provinces located in the north spring maize region of China between latitudes 35°11′ and 48°08′N in the cultivation of hybrid zhengdan958 (ZD958). Latitude is an important geographical factor which significantly affects temperature, sunshine hours, and the duration of crop growth. The findings of this study indicate that for every 1° increase in the latitude, northward, the growth durations of sowing to emergence and emergence to silking were significantly increased by 0.7 d and 1.25 d, respectively as a consequence of lowering temperatures (mean, maximum, and minimum temperatures). Reproductive growth duration (silking to maturity), which was significantly correlated with the precipitation, decreased by 0.8 d with each 1° increase in latitude northward. At higher latitudes, the number of growing degree days (GDD) of maize vegetative growth duration (emergence to silking) was significantly higher, and the GDD of the reproductive growth duration were significantly lower. The average photoperiod during the photoperiod-sensitive phase of maize development across all the experimental sites was 14.9h with a range of 13.7–15.6h. Total leaf numbers increased from 18.7 to 23.7 with an average of 21.0 across all experimental sites. Significant and positive linear relationships were found to occur between both latitude and photoperiods and latitude and total leaf number. In the north China spring maize region, the mean growth duration of ZD958 was 143.73 d, which constituted 82.8% of the frost free period, the percentage increasing with higher latitude. These findings strongly indicate that in order to ensure high and stable production of maize in the north spring maize region of China, with its limited heat resources, especially in the high-latitude regions, there is a need to cultivate short-growth-duration cultivars. [Copyright &y& Elsevier]

The root system connects the plant with the soil, which is a key factor in determining the utilization of soil resources and plant growth potential. Solar radiation can change maize shoot and root growth and affect grain formation. In this study, the effects of different solar radiation conditions on root morphology of three maize cultivars XY335, ZD958 and DH618 and their quantitative relationships were studied by conducting shading experiments. This study was conducted in maize high yield region of Qitai and Yinchuan, China, in 2018 and 2019. The planting densities were 7.5 × 104 (D1) and 12 × 104 (D2) plants ha−1. The shading levels were natural light (CK), shading 15% (S1), 30% (S2) and 50% (S3). The results showed that maize responded to the decreased solar radiation through the increase in ratio of shoot dry weight (SWR) to whole plant dry weight and the decrease in ratio of root dry weight (RWR) to whole plant dry weight. As the solar radiation decreased, the root length density (RLD), root surface area (RSA), average root diameter (ARD) and root length ratio (RLR) decreased, while the specific root length (SRL) increased. With 100 MJ m−2 decrease in solar radiation, the RWR, RLD, RSA and RLR each decreased by 1.47%, 0.5 mm cm−3,0.4 m m−2 and 0. 19 m g−1, respectively. Among the cultivars, the changes of DH618 were the fastest followed by XY335 and ZD958 but DH618 maintained the largest root system under any solar radiation condition. After the decrease of solar radiation, RWR, RLD and RLR were significantly positively correlated with the yield. This indicated that large root systems were conducive to the rapid response to decreased solar radiation and important for achieving stable and high yield. Maize cultivars with these type of root systems should be recommended to better adapt low solar radiation induced by regional variation or climate change. [ABSTRACT FROM AUTHOR]

Stalk lodging in Huang-Huai-Hai summer maize is a serious problem that reduces maize yields and precludes the use of mechanical grain harvesting equipment. In order to determine the effect of nitrogen management on the lodging resistance of maize stalk, three nitrogen application rates of 150, 250, and 350 kg ha−1 (denoted as N150, N250, and N350), and different nitrogen application periods (sowing, 6-leaf, 12-leaf, silking) were set. Plant morphology, stalk mechanical strength, total carbohydrate, nitrogen content, and yield were measured in the different treatments. The results showed that as the nitrogen application rate increased and nitrogen application was postponed, the stalk breaking force, plant height, ear height, center of gravity height, stalk basal internode diameter, rind penetration strength, content of carbohydrate, and total N of maize stalk also increased. The stalk lodging resistance was improved by the increased nitrogen application rate and postponed nitrogen application by increasing the stalk material accumulation and mechanical strength. The nitrogen application rates had no significant effect on grain yield. Under N250 and N350, the treatments with no base fertilizer significantly decreased the kernel number per ear, reflected in some in grain yield. In summary, under the conditions of integrated water and fertilizer drip irrigation and fractional nitrogen fertilizer applications, increased nitrogen fertilizer input can stimulate the growth of high-quality maize populations, significantly improve stalk lodging resistance in the early growth stage, delay stalk senescence, improve stalk strength and influence stalk composition in later growth stages. Based on the summer maize grain yield and stalk lodging resistance, under N250 treatment, a base fertilizer combined with topdressing at the 12-leaf and silking stages was beneficial to the growth of summer maize. [ABSTRACT FROM AUTHOR]