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    玉米耕作栽培合辑Maize Physiology · Biochemistry · Cultivation · Tillage

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    Systemic regulation of photosynthetic function in maize plants at graining stage under vertically heterogeneous light environment
    WU Han-yu, QIAO Mei-yu, ZHANG Wang-feng, WANG Ke-ru, LI Shao-kun, JIANG Chuang-dao
    2022, 21 (3): 666-676.   DOI: 10.1016/S2095-3119(20)63440-2
    Abstract111)      PDF in ScienceDirect      
    To cope with a highly heterogeneous light environment, photosynthesis in plants can be regulated systemically.  Currently, the majority of studies are carried out with various plants during the vegetative growth period.  As the reproductive sink improves photosynthesis, we wondered how photosynthesis is systemically regulated at the reproductive stage under a vertically heterogeneous light environment in the field.  Therefore, changes of light intensity within canopy, chlorophyll content, gas exchange, and chlorophyll a fluorescence transient were carefully investigated at the graining stage of maize under various planting densities.  In this study, a high planting density of maize drastically reduced the light intensities in the lower canopy, and increased the difference in vertical light distribution within the canopy.  With the increase of vertical heterogeneity, chlorophyll content, light-saturated photosynthetic rate and the quantum yield of electron transport in the ear leaf (EL) and the fourth leaf below the ear (FLBE) were decreased gradually, and the ranges of declines in these parameters were larger at FLBE than those at EL.  Leaves in the lower canopy were shaded artificially to further test these results.  Partial shading (PS) resulted in a vertically heterogeneous light environment and enhanced the differences in photosynthetic characteristics between EL and FLBE.  Removing the tassel and top leaves (RTL) not only improved the vertical light distribution within the canopy, but also reduced the differences in photosynthetic characteristics between the two leaves.  Taken together, these results demonstrated that maize plants could enhance the vertical heterogeneity of their photosynthetic function to adapt to their light environment; slight changes of the photosynthetic function in EL at the graining stage under a vertically heterogeneous light environment indicated that the systemic regulation of photosynthesis is weak at the graining stage.

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    Image-based root phenotyping for field-grown crops: An example under maize/soybean intercropping
    HUI Fang, XIE Zi-wen, LI Hai-gang, GUO Yan, LI Bao-guo, LIU Yun-ling, MA Yun-tao
    2022, 21 (6): 1606-1619.   DOI: 10.1016/S2095-3119(20)63571-7
    Abstract184)      PDF in ScienceDirect      
    Root architecture, which determines the water and nutrient uptake ability of crops, is highly plastic in response to soil environmental changes and different cultivation patterns.  Root phenotyping for field-grown crops, especially topological trait extraction, is rarely performed.  In this study, an image-based semi-automatic root phenotyping method for field-grown crops was developed.  The method consisted of image acquisition, image denoising and segmentation, trait extraction and data analysis.  Five global traits and 40 local traits were extracted with this method.  A good consistency in 1st-order lateral root branching was observed between the visually counted values and the values extracted using the developed method, with R2=0.97.  Using the method, we found that the interspecific advantages for maize mainly occurred within 5 cm from the root base in the nodal roots of the 5th–7th nodes, and that the obvious inhibition of soybean was mostly reflected within 20 cm from the root base.  Our study provides a novel approach with high-throughput and high-accuracy for field research on root morphology and branching features.  It could be applied to the 3D reconstruction of field-grown root system architecture to improve the inputs to data-driven models (e.g., OpenSimRoot) that simulate root growth, solute transport and water uptake.
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    Grain yield and grain moisture associations with leaf, stem and root characteristics in maize
    XU Chen-chen, ZHANG Ping, WANG Yuan-yuan, LUO Ning, TIAN Bei-jing, LIU Xi-wei, WANG Pu, HUANG Shou-bing
    2022, 21 (7): 1941-1951.   DOI: 10.1016/S2095-3119(20)63598-5
    Abstract161)      PDF in ScienceDirect      
    Improving grain yield (GY) and reducing grain moisture (GM) are urgent demands for directly harvesting kernels with combine harvesters in maize production.  GY and GM are both related to leaf, stem and root characteristics, but the relationships are not fully understood.  To better understand these relationships, we conducted a field trial involving 12 maize hybrids with two sowing dates in 2017 and 10 maize hybrids with one sowing date in 2019.  GY ranged from 6.5–14.6 t ha–1 in early-sown varieties and 9.3–12.7 t ha–1 in late-sown varieties in 2017, and 5.9–7.4 t ha–1 in 2019, respectively, with corresponding GM variations of 29.8–34.9%, 29.4–34.5% and 31.9–37.1% at harvest.  A large maximum leaf area contributed to a high yield, a fast leaf senescence rate accelerated grain dehydration in the late growth period, and a compact root structure resulted in both of high-yield and fast-grain dehydration.  A strong stem improved lodging resistance but maintained a high GM at harvest, and it is challenging to combine high GY and low GM in maize.  High GY co-existed with low GM in some varieties that should have a rapid grain filling, a relatively long grain-filling duration, and a rapid grain dehydration in the late growth period.  A high daily temperature in the late growth period also improved GY and reduced GM by influencing grain filling and dehydration, suggesting that adjusting the sowing date should be an alternative strategy to combine high GY and low GM in kernel harvesting. 
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    Strip deep rotary tillage combined with controlled-release urea improves the grain yield and nitrogen use efficiency of maize in the North China Plain
    HAN Yu-ling, GUO Dong, MA Wei, GE Jun-zhu, LI Xiang-ling, Ali Noor MEHMOOD, ZHAO Ming, ZHOU Bao-yuan
    2022, 21 (9): 2559-2576.   DOI: 10.1016/j.jia.2022.07.009
    Abstract162)      PDF in ScienceDirect      
    Inappropriate tillage practices and nitrogen (N) management have become seriously limitations for maize (Zea mays L.) yield and N use efficiency (NUE) in the North China Plain (NCP).  In the current study, we examined the effects of strip deep rotary tillage (ST) combined with controlled-release (CR) urea on maize yield and NUE, and determined the physiological factors involved in yield formation and N accumulation during a 2-year field experiment.  Compared with conventional rotary tillage (RT) and no-tillage (NT), ST increased the soil water content and soil mineral N content (Nmin) in the 20–40 cm soil layer due to reduction by 10.5 and 13.7% in the soil bulk density in the 0–40 cm soil layer, respectively.  Compared with the values obtained by common urea (CU) fertilization, CR increased the Nmin in the 0–40 cm soil layers by 12.4 and 10.3% at the silking and maturity stages, respectively.  As a result, root length and total N accumulation were enhanced under ST and CR urea, which promoted greater leaf area and dry matter (particularly at post-silking), eventually increasing the 1 000-kernel weight of maize.  Thus, ST increased the maize yield by 8.3 and 11.0% compared with RT and NT, respectively, whereas CR urea increased maize yield by 8.9% above the values obtained under CU.  Because of greater grain yield and N accumulation, ST combined with CR urea improved the NUE substantially.  These results show that ST coupled with CR urea is an effective practice to further increase maize yield and NUE by improving soil properties and N supply, so it should be considered for sustainable maize production in the NCP (and other similar areas worldwide).
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    Study of corn kernel breakage susceptibility as a function of its moisture content by using a laboratory grinding method 
    GUO Ya-nan, HOU Liang-yu, LI Lu-lu, GAO Shang, HOU Jun-feng, MING Bo, XIE Rui-zhi, XUE Jun, HOU Peng, WANG Ke-ru, LI Shao-kun
    2022, 21 (1): 70-77.   DOI: 10.1016/S2095-3119(20)63250-6
    Abstract107)      PDF in ScienceDirect      
    The rate of corn kernel breakage in the grain combine harvesters is a crucial factor affecting the quality of the grain shelled in the field.  The objective of the present study was to determine the susceptibility of corn kernels to breakage based on the kernel moisture content in order to determine the moisture content that corresponds to the lowest rate of breakage.  In addition, we evaluated the resistance to breakage of various corn cultivars.  A total of 17 different corn cultivars were planted at two different sowing dates at the Beibuchang Experiment Station, Beijing and the Xinxiang Experiment Station (Henan Province) of the Chinese Academy of Agricultural Sciences.  The corn kernel moisture content was systematically monitored and recorded over time, and the breakage rate was measured by using the grinding method.  The results for all grain samples from the two experimental stations revealed that the breakage rate y is quadratic in moisture content x, y=0.0796x2−3.3929x+78.779; R2=0.2646, n=512.  By fitting to the regression equation, a minimum corn kernel breakage rate of 42.62% was obtained, corresponding to a corn kernel moisture content of 21.31%.  Furthermore, in the 90% confidence interval, the corn kernel moisture ranging from 19.7 to 22.3% led to the lowest kernel breakage rate, which was consistent with the corn kernel moisture content allowing the lowest breakage rate of corn kernels shelled in the field with combine grain harvesters.  Using the lowest breakage rate as the critical point, the correlation between breakage rate and moisture content was significantly negative for low moisture content but positive for high moisture content.  The slope and correlation coefficient of the linear regression equation indicated that high moisture content led to greater sensitivity and correlation between grain breakage and moisture content.  At the Beibuchang Experiment Station, the corn cultivars resistant to breakage were Zhengdan 958 (ZD958) and Fengken 139 (FK139), and the corn cultivars non-resistant to breakage were Lianchuang 825 (LC825), Jidan 66 (JD66), Lidan 295 (LD295), and Jingnongke 728 (JNK728).  At the Xinxiang Experiment Station, the corn cultivars resistant to breakage were HT1, ZD958 and FK139, and the corn cultivars non-resistant to breakage were ZY8911, DK653 and JNK728.  Thus, the breakage classifications of the six corn cultivars were consistent between the two experimental stations.  In conclusion, the results suggested that the high stability of the grinding method allowed it to be used to determine the corn kernel breakage rates of different corn cultivars as a function of moisture content, thus facilitating the breeding and screening of breakage-resistant corn.

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    Dynamics of maize grain drying in the high latitude region of Northeast China
    CHU Zhen-dong, MING Bo LI Lu-lu, XUE Jun, ZHANG Wan-xu, HOU Liang-yu, XIE Rui-zhi, HOU Peng, WANG Ke-ru, LI Shao-kun
    2022, 21 (2): 365-374.   DOI: 10.1016/S2095-3119(20)63434-7
    Abstract169)      PDF in ScienceDirect      
    A high grain moisture content at harvest has been an important problem in the high latitude region of Northeast China, and it is closely related to the genotypes of varieties, local meteorological factors and planting management.  However, delayed harvest at a low temperature could not effectively reduce the grain moisture content.  In this study, we continuously observed the grain drying during the late stage of different maturing types of maize varieties in Daqing, Heilongjiang Province, China in 2016 and 2017.  A two-segment linear model was used to analyze the different stages of the drying processes: 1) Two-segment linear model fitting can divide the grain drying process of all varieties into two separate linear drying processes with different slopes.  2) During the rapid drying stage, the drying was faster at a higher temperature.  The rate of slow drying was influenced by air vapor pressure.  3) The moisture content and meteorological factors when the drying rate turns from one stage into the other were not consistent between varieties and years.  After entering the frost period, temperatures below 0°C will significantly reduce the rate of grain drying.  4) Due to the short growth period of early-maturing varieties, the drying time was prolonged, and the grain moisture content was lower than that of the mid-late maturing varieties.  Local meteorological conditions do not allow the drying of mid-late maturing varieties to achieve a lower moisture content.  When the temperature falls below 0°C, the drying rate of grain decreases markedly.  Therefore, one feasible way to solve the problem of high moisture content is to replace the early-maturing varieties and implement the corresponding cultivation techniques.
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    Factors influencing seed reserve utilization during seedling establishment in maize inbred lines
    LI Min, WEN Da-xing, SUN Qing-qing, WU Cheng-lai, LI Yan, ZHANG Chun-qing
    2022, 21 (3): 677-684.   DOI: 10.1016/S2095-3119(21)63608-0
    Abstract115)      PDF in ScienceDirect      
    Strong seedlings are essential for high yield.  To explore the foundation of strong seedlings, we investigated various factors influencing the conversion and distribution of seed storage reserves during seedling establishment in maize inbred lines.  Three maize inbred lines were used to explore the effects of seed size, seed vigor, illumination duration, temperature, water content, and salt concentration of the seedling medium on the utilization of seed storage reserves during seedling establishment.  The results showed that the conversion rate of small seeds was 3.69 to 17.71% higher than that of large seeds.  Moreover, prolonged illumination time was conducive to the formation of strong seedlings.  However, low temperature, drought stress and salt stress reduced the conversion rate of seed storage reserves and increased the root/shoot ratio.  These results could be used to guide field management during seedling emergence and develop improved germplasm with a high conversion rate of seed storage reserves.
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    Grain dehydration rate is related to post-silking thermal time and ear characters in different maize hybrids
    SHI Wen-jun, SHAO Hui, SHA Ye, SHI Rong, SHI Dong-feng, CHEN Ya-chao, BAN Xiang-ben, MI Guo-hua
    2022, 21 (4): 964-976.   DOI: 10.1016/S2095-3119(21)63641-9
    Abstract131)      PDF in ScienceDirect      
    Mechanized grain harvest of maize becomes increasingly important with growing land plot size in Northeast China.  Grain moisture is an important factor affecting the performance of mechanized grain harvest.  However, it remains unclear what influences grain dehydration rate.  In this study, maize grain dehydrating process was investigated in a two-year field experiment with five hybrids under two planting densities in 2017 and 2018.  It was found that damaged-grain ratio was the main factor affecting mechanized harvest quality, and this ratio was positively correlated with grain moisture content at harvest (R2=0.6372, P<0.01).  To fulfill the national standard of <5% damaged-grain ratio for mechanized grain harvest, the optimal maize grain moisture content was 22.3%.  From silking to physiological maturity, grain dehydrating process was mostly dependent on the thermal time (growing degree days, GDDs) (r=–0.9412, P<0.01).  The average grain moisture content at physiological maturity was 29.4%.  Thereafter, the linear relationship between GDDs and grain moisture still existed, but the correlation coefficient became smaller (r=–0.8267, P<0.01).  At this stage, grain dehydrating process was greatly affected by genotypes.  Grain dehydrated faster when a hybrid has a smaller husk area (r=0.6591, P<0.05), larger ear angle (r=–0.7582, P<0.05), longer ear peduncle (r=–0.9356, P<0.01) and finer ear (r=0.9369, P<0.01).  These parameters can be used for breeders and farmers to select hybrids suitable for mechanized grain harvest.  
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    Nitrogen application affects maize grain filling by regulating grain water relations
    WU Ya-wei, ZHAO Bo, LI Xiao-long, LIU Qin-lin, FENG Dong-ju, LAN Tian-qiong, KONG Fan-lei, LI Qiang, YUAN Ji-chao
    2022, 21 (4): 977-994.   DOI: 10.1016/S2095-3119(20)63589-4
    Abstract226)      PDF in ScienceDirect      
    Grain water relations play an important role in grain filling in maize.  The study aimed to gain a clear understanding of the changes in grain dry weight and water relations in maize grains by using hybrids with contrasting nitrogen efficiencies under differing nitrogen levels.  The objectives were: 1) to understand the changes in dry matter and percent moisture content (MC) during grain development in response to different nitrogen application rates and 2) to determine whether nitrogen application affects grain filling by regulating grain water relations.  Two maize hybrids, high N-efficient Zhenghong 311 (ZH311) and low N-efficient Xianyu 508 (XY508), were grown in the field under four levels of N fertilizer: 0, 150, 300, and 450 kg N ha–1 during three growing seasons.  Dry weight, percent MC and water content (WC) of basal–middle and apical grains were investigated.  The difference in the maximum WC and filling duration of basal–middle and apical grains in maize ears resulted in a significant difference in final grain weight.  Grain position markedly influenced grain drying down; specifically, the drying down rate of apical grains was faster than that of basal–middle grains.  Genotype and grain position both influenced the impact of nitrogen application rate on grain filling and drying down.  Nitrogen rate determined the maximum grain WC and percent MC loss rate in the middle and the late grain-filling stages, thus affecting final grain weight.  The use of high N-efficient hybrids, combined with the reduction of nitrogen application rate, can coordinate basal–middle and apical grain drying down to ensure yield.  This management strategy could lead to a win–win situation in which the maximum maize yield, efficient mechanical harvest and environmental safety are all achieved. 

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    Weakened carbon and nitrogen metabolisms under post-silking heat stress reduce the yield and dry matter accumulation in waxy maize
    YANG Huan, GU Xiao-tian, DING Meng-qiu, LU Wei-ping, LU Da-lei
    2020, 19 (1): 78-88.   DOI: 10.1016/S2095-3119(19)62622-5
    Abstract156)      PDF in ScienceDirect      
    Post-silking high temperature is one of the abiotic factors that affects waxy maize (Zea mays L. sinensis Kulesh) growth in southern China.  We conducted a pot trial in 2016–2017 to study the effects of post-silking daytime heat stress (35°C) on the activities of enzymes involved in leaf carbon and nitrogen metabolisms and leaf reactive oxygen species (ROS) and water contents.  This study could improve our understanding on dry matter accumulation and translocation and grain yield production.  Results indicated that decreased grain number and weight under heat stress led to yield loss, which decreased by 20.8 and 20.0% in 2016 and 2017, respectively.  High temperature reduced post-silking dry matter accumulation (16.1 and 29.5% in 2016 and 2017, respectively) and promoted translocation of pre-silking photoassimilates stored in vegetative organs, especially in leaf.  The lower leaf water content and chlorophyll SPAD value, and higher ROS (H2O2 and O2-·) content under heat stress conditions indicated accelerated senescent rate.  The weak activities of phosphoenolpyruvate carboxylase (PEPCase), Ribulose-1,5-bisphosphate carboxylase (RuBPCase), nitrate reductase (NR), and glutamine synthase (GS) indicated that leaf carbon and nitrogen metabolisms were suppressed when the plants suffered from a high temperature during grain filling.  Correlation analysis results indicated that the reduced grain yield was mainly caused by the decreased leaf water content, weakened NR activity, and increased H2O2 content.  The increased accumulation of grain weight and post-silking dry matter and the reduced translocation amount in leaf was mainly due to the increased chlorophyll SPAD value and NR activity.  Reduced PEPCase and RuBPCase activities did not affect dry matter accumulation and translocation and grain yield.  In conclusion, post-silking heat stress down-regulated the leaf NR and GS activities, increased the leaf water loss rate, increased ROS generation, and induced pre-silking carbohydrate translocation.  However, it reduced the post-silking direct photoassimilate deposition, ultimately, leading to grain yield loss.
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    Quantitative design of yield components to simulate yield formation for maize in China
    HOU Hai-peng, MA Wei, Mehmood Ali NOOR, TANG Li-yuan, LI Cong-feng, DING Zai-song, ZHAO Ming
    2020, 19 (3): 668-679.   DOI: 10.1016/S2095-3119(19)62661-4
    Abstract96)      PDF in ScienceDirect      
    Maize (Zea mays L.) stands prominently as one of the major cereal crops in China as well as in the rest of the world.  Therefore, predicting the growth and yield of maize for large areas through yield components under high-yielding environments will help in understanding the process of yield formation and yield potential under different environmental conditions.  This accurate early assessment of yield requires accuracy in the formation process of yield components as well.  In order to formulate the quantitative design for high yields of maize in China, yield performance parameters of quantitative design for high grain yields were evaluated in this study, by utilizing the yield performance equation with normalization of planting density.  Planting density was evaluated by parameters including the maximum leaf area index and the maximum leaf area per plant.  Results showed that the variation of the maximum leaf area per plant with varying plant density conformed to the Reciprocal Model, which proved to have excellent prediction with root mean square error (RMSE) value of 5.95%.  Yield model estimation depicted that the best optimal maximum leaf area per plant was 0.63 times the potential maximum leaf area per plant of hybrids.  Yield performance parameters for different yield levels were quantitatively designed based on the yield performance equation.  Through validation of the yield performance model by simulating high yields of spring maize in the Inner Mongolia Autonomous Region and Jilin Province, China, and summer maize in Shandong Province, the yield performance equation showed excellent prediction with the satisfactory mean RMSE value (7.72%) of all the parameters.  The present study provides theoretical support for the formulation of quantitative design for sustainable high yield of maize in China, through consideration of planting density normalization in the yield prediction process, providing there is no water and nutrient limitation.
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    Interacting leaf dynamics and environment to optimize maize sowing date in North China Plain
    TIAN Bei-jing, ZHU Jin-cheng, LIU Xi-wei, HUANG Shou-bing, WANG Pu
    2020, 19 (5): 1227-1240.   DOI: 10.1016/S2095-3119(19)62831-5
    Abstract87)      PDF in ScienceDirect      
    Leaf growth and its interaction with the growing environment critically affect leaf area, distribution, and function, and ultimately affects grain yield of maize (Zea mays L.).  To detect the effects of leaf area dynamics, growth periods, and the environment on maize grain yield, a three-year field experiment was conducted using two maize varieties, medium plant-size variety Zhengdan 958 (ZD958) and large plant-size variety Zhongnongda 4 (ZND4), and three to five sowing dates.  The sowing date significantly affected maize yield as a result of changes in leaf area, growth stage, and growing environment.  Prior to the 12th leaf stage, significant correlations between leaf area dynamics, environment, and yield were seldom detected.  The expansion of leaf area from 12th leaf stage to silking stage was significantly positively correlated with growing degree days (GDD), solar radiation, and grain yield, indicating the importance of leaf area dynamics during this period.  After silking, solar radiation played a more important role in inducing leaf senescence than GDD, particularly in the 2nd half of the grain filling stage.  Accelerated leaf senescence in late growth period can increase maize yield.  The environment affected leaf area dynamics and yield of the large plant-size variety (ZND4) more easily than the medium plant-size variety (ZD958) at the optimum plant density, reflecting the difference in varietal capacity to adapt to the growing environment.  This study indicates that optimizing the interaction among leaf area dynamics, growth periods, and environment is a sound strategy to increase maize yield.  Favorable interactions are useful to determine the optimal sowing date of a given variety.
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    Effects of urea mixed with nitrapyrin on leaf photosynthetic and senescence characteristics of summer maize (Zea mays L.) waterlogged in the field
    REN Bai-zhao, HU Juan, ZHANG Ji-wang, DONG Shu-ting, LIU Peng, ZHAO Bin
    2020, 19 (6): 1586-1595.   DOI: 10.1016/S2095-3119(19)62725-5
    Abstract84)      PDF in ScienceDirect      
    Waterlogging is one of the major abiotic stresses in agricultural crop production.  However, the application of 2-chloro-6-(trichloromethyl) pyridine (nitrapyrin) can effectually mitigate the losses of nitrogen efficiency and grain yield of summer maize induced by waterlogging.  In order to explore its role to alleviate waterlogging stress on leaf antioxidative system and photosynthetic characteristics of summer maize, a field experiment was executed to research effects of nitrapyrin application on leaf photosynthetic and senescent characteristics of waterlogged summer maize Denghai 605 (DH605) and Zhengdan 958 (ZD958).  Experimental treatments consisted of waterlogging treatment that was applying only urea (WL), waterlogging treatment that was applying urea mixing with nitrapyrin (WL-N), and no waterlogging treatment that was only applying urea (NWL).  Results showed that WL significantly decreased leaf area index (LAI), SPAD, photosynthetic rate (Pn), and protective enzyme activities, accelerated leaf aging, eventually led to a remarkable yield reduction by 38 and 42% for DH605 and ZD958, respectively, compared to NWL.  However, the application of nitrapyrin was useful for relieving waterlogging damages on leaf photosynthetic ability.  LAI, SPAD and Pn of WL-N for DH605 were 10, 19 and 12–24% higher, and for ZD958 were 12, 23 and 7–25% higher, compared to those of WL, respectively.  Moreover, application of nitrapyrin effectually relieved waterlogging losses on antioxidative enzyme activities.  Leaf superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities of WL-N were averagely increased by 24, 15 and 30%, respectively, while malondialdehyde (MDA) content was averagely decreased by 13%, compared to those of WL.  Visibly, nitrapyrin application could improve leaf photosynthetic characteristics and retard leaf aging induced by waterlogging, thereby leading to a yield increase of waterlogged maize.
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    Integrated agronomic practices management improved grain formation and regulated endogenous hormone balance in summer maize (Zea mays L.)
    YU Ning-ning, ZHANG Ji-wang, LIU Peng, ZHAO Bin, REN Bai-zhao
    2020, 19 (7): 1768-1776.   DOI: 10.1016/S2095-3119(19)62757-7
    Abstract112)      PDF in ScienceDirect      
    Compared with single agronomic practices management during grain formation, knowledge about integrated agronomic practices management on grain-filling characteristics and physiological function of endogenous hormones was limited.  In order to clarify this issue, two field experiments, integrated agronomic practices management (IAPM), T1 (local conventional cultivation practices), T2 (an optimized combination of cropping systems and fertilizer treatment), T3 (treatment based on high-yield studies), and T4 (further optimized combination of cropping systems and fertilizer treatment), and nitrogen rate testing (NAT) (four nitrogen rates, 0, 129.0, 184.5, and 300.0 kg N ha–1) were performed with summer maize hybrid Zhengdan 958 (ZD958). Results showed that with increased nitrogen rate, the endogenous hormone balance was promoted and the grain-filling characteristics were improved sufficiently to resulting in a significant increase in grain yield.  However, the grain-filling characteristics deteriorated and yield was reduced with excessive nitrogen fertilization.  However, IAPM could promote hormone balance and improve grain filling characteristic.  The indole-3-acetic acid (IAA), zeatin riboside (ZR), and gibberellin (GA3) contents under T2 and T4 treatments were higher and the abscisic acid (ABA) content was lower, and the ZR and GA3 contents under T3 were higher than those under T1.  Those resulted in the maximum grain-filling rate (Wmax) and the active grain-filling period (P) under T2, T3 and T4 were significantly increased than those under T1, and hence promoted kernel weight and grain yield.  So IAPM promoted hormone balance by improving tillage model, optimizing fertilizer rate and fertilization period, appropriately increasing planting density and delaying harvest, which promoted grain filling rate and lengthened active grain-filling period, finally increased grain yield.
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    Effects of post-silking water deficit on the leaf photosynthesis and senescence of waxy maize
    YE Yu-xiu, WEN Zhang-rong, YANG Huan, LU Wei-ping, LU Da-lei
    2020, 19 (9): 2216-2228.   DOI: 10.1016/S2095-3119(20)63158-6
    Abstract104)      PDF in ScienceDirect      
    Waxy maize is widely cultivated under rainfed conditions and frequently suffers water shortage during the late growth stage.  In this study, a pot trial was conducted to examine the effects of post-silking drought on leaf photosynthesis and senescence and its influence on grain yield.  Two waxy maize hybrids, Suyunuo 5 (SYN5) and Yunuo 7 (YN7), were grown under the control and drought (soil moisture content was 70–80% and 50–60%, respectively) conditions after silking in 2016 and 2017.  The decrease in yield was 11.1 and 15.4% for YN7 and SYN5, respectively, owing to the decreased grain weight and number.  Post-silking dry matter accumulation was reduced by 27.2% in YN7 and 26.3% in SYN5.  The contribution rate of pre-silking photoassimilates transferred to grain yield was increased by 15.6% in YN7 and 10.2% in SYN5, respectively.  Post-silking drought increased the malondialdehyde content, but decreased the contents of water, soluble protein, chlorophyll, and carotenoid in the leaves.  The weakened activities of enzymes involved in photosynthesis (ribulose-1,5-bisphosphate carboxylase and phosphoenolpyruvate carboxylase) and antioxidant system (catalase, superoxide dismutase and peroxidase) reduced the photosynthetic rate (Pn) and accelerated leaf senescence.  The correlation results indicated that reduced Pn and catalase activity and increased malondialdehyde content under drought conditions induced the decrease of post-silking photoassimilates deposition, ultimately resulted in the grain yield loss.
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    Key indicators affecting maize stalk lodging resistance of different growth periods under different sowing dates
    WANG Qun, XUE Jun, CHEN Jiang-lu, FAN Ying-hu, ZHANG Guo-qiang, XIE Rui-zhi, MING Bo, HOU Peng, WANG Ke-ru, LI Shao-kun
    2020, 19 (10): 2419-2428.   DOI: 10.1016/S2095-3119(20)63259-2
    Abstract138)      PDF in ScienceDirect      
    The accurate evaluation of maize stalk lodging resistance in different growth periods enables timely management of lodging risks and ensures stable and high maize yields.  Here, we established five different sowing dates to create different conditions for maize growth.  We evaluated the effects of the different growth conditions on lodging resistance by determining stalk morphology, moisture content, mechanical strength and dry matter, and the relationship between stalk breaking force and these indicators during the silking stage (R1), milk stage (R3), physiological maturity stage (R6), and 20 days after R6.  Plant height at R1 positively affected stalk breaking force.  At R3, the coefficient of ear height and the dry weight per unit length of basal internodes were key indicators of stalk lodging resistance.  At R6, the key indicators were the coefficient of the center of gravity height and plant fresh weight.  After R6, the key indicator was the coefficient of the center of gravity height.  The crushing strength of the fourth internode correlated significantly and positively with the stalk breaking force from R1 to R6, which indicates that crushing strength is a reliable indicator of stalk mechanical strength.  These results suggest that high stalk strength and low ear height benefit lodging resistance prior to R6.  During and after R6, the coefficient of the center of gravity height and the mechanical strength of basal internodes can be used to evaluate plant lodging resistance and the appropriate time for harvesting in fields with a high lodging risk.
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    Kernel crack characteristics for X-ray computed microtomography (μCT) and their relationship with the breakage rate of maize varieties
    DONG Peng-fei, XIE Rui-zhi, WANG Ke-ru, MING bo, HOU Peng, HOU Jun-feng, XUE Jun, LI Chao-hai, LI shao-kun
    2020, 19 (11): 2680-2689.   DOI: 10.1016/S2095-3119(20)63230-0
    Abstract92)      PDF in ScienceDirect      
    The most significant problem of maize grain mechanical harvesting quality in China at present is the high grain breakage rate (BR).  BR is often the key characteristic that is measured to select hybrids desirable for mechanical grain harvesting.  However, conventional BR evaluation and measurement methods have challenges and limitations.  Microstructural crack parameters evaluation of maize kernel is of great importance to BR.  In this connection, X-ray computed microtomography (μ-CT) has proven to be a quite useful method for the assessment of microstructure, as it provides important microstructural parameters, such as object volume, surface, surface/volume ratio, number of closed pores, and others.  X-ray computed microtomography is a non-destructive technique that enables the reuse of samples already measured and also yields bidimensional (2D) cross-sectional images of the sample as well as volume rendering.  In this paper, six different maize hybrid genotypes are used as materials, and the BR of the maize kernels of each variety is tested in the field mechanical grain harvesting, and the BR is used as an index for evaluating the breakage resistance of the variety.  The crack characteristic parameters of kernel were detected by X-ray micro-computed tomography, and the relationship between the BR and the kernel crack characteristics was analyzed by stepwise regression analysis.  Establishing a relationship between crack characteristic parameters and BR of maize is vital for judging breakage resistance.  The results of stepwise multiple linear regression (MLR) showed that the crack characteristics of the object surface, number of closed pores, surface of closed pores, and closed porosity percent were significantly correlated to the BR of field mechanical grain harvesting, with the standard partial regression coefficients of –0.998, –0.988, –0.999, and –0.998, respectively.  The R2 of this model was 0.999.  Results validation showed that the Stepwise MLR Model could well predict the BR of maize based on these four variables. 
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    Giving maize an excited start – Effects of dopamine on maize germination
    CHENG Hang-yuan, WANG Xing, FENG Tian-yu, PENG Chuan-xi, WANG Wei, YANG Mu-yu, ZHOU Yu-yi
    2020, 19 (11): 2690-2698.   DOI: 10.1016/S2095-3119(20)63252-X
    Abstract111)      PDF in ScienceDirect      
    Dopamine (DA) is a neurotransmitter which takes charge of brain activities about memory and self-stimulation behavior in animals.  Interestingly, our results suggest that DA could also give maize an “excited state”.  The results showed that 1  mmol L–1 DA promoted maize germination by 23.2% significantly, and accelerated the growth rate of roots and shoots by 21.4 and 24.7%, respectively.  As we all known, abscisic acid (ABA) is the key hormone involved in seed dormancy.  In our research, ABA levels in roots and shoots dramatically decreased by 16.45 and 57.57%, respectively.  To further investigate how DA reduces the ABA level in budding seed, we studied ABA synthesis and catabolism pathway.  Specific expression of key ABA-synthesis genes, such as ZmNCED1, ZmNCED3 and ZmZEP were down-regulated by DA.  Simultaneously, the expression levels of ABA8OX1a and ABA8OX1b which are major transcripts of ABA 8´-hydroxylase in ABA catabolism were up-regulated at least 1.5- and 4.6-fold, respectively.  Our results enriched the functions of animal hormones in plants.
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    Innovation of the double-maize cropping system based on cultivar growing degree days for adapting to changing weather conditions in the North China Plain
    WANG Dan, LI Guo-rui, ZHOU Bao-yuan, ZHAN Ming, CAO Cou-gui, MENG Qing-feng, XIA Fei, MA Wei, ZHAO Ming
    2020, 19 (12): 2997-3012.   DOI: 10.1016/S2095-3119(20)63213-0
    Abstract79)      PDF in ScienceDirect      
    Double-maize cropping system is an effective option for coping with climate change in the North China Plain.  However, the effects of changes in climate on the growth and yield of maize in the two seasons are poorly understood.  Forty-six cultivars of maize with different requirements for growing degree days (GDD), categorized as high (H), medium (M) or low (L), and three cultivar combinations for two seasons as LH (using JD27 and DMY1 from category L in the first season; and YD629 and XD22 from category H in the second season), MM (using JX1 and LC3 from category M in the first season; and ZD958 and JX1 from category M in the second season) and HL (using CD30 and QY9 from category H in the first season; and XK10 and DMY3 from category L in the second season) were tested to examine the eco-physiological determinants of maize yield from 2015 to 2017.  The correlations between the combinations of cultivars and grain yield were examined.  The combination LH produced the highest annual grain yield and total biomass, regardless of the year.  It was followed, in decreasing order, by MM and HL.  Higher grain yield and biomass in LH were mainly due to the greater grain yield and biomass in the second season, which were influenced mainly by the lengths of the pre- and post-silking periods and the rate of plant growth (PGR).  Temperature was the primary factor that influenced dry matter accumulation.  In the first season, low temperatures during pre-silking decreased both the duration and PGR in LH, whereas high temperatures during post-silking decreased the PGR in MM and HL, resulting in no significant differences in biomass being observed among the three combinations.  In the second season, high temperatures decreased both the PGR and pre- and post-silking duration in MM and HL, and consequently, the biomass of those two combinations were lower than that in LH.  Moreover, because of lower GDD and radiation in the first season and higher grain yield in the second season, production efficiency of temperature and radiation (Ra) was the highest in LH.  More importantly, differences in temperature and radiation in the two seasons significantly affected the rate and duration of growth in maize, and thereby affecting both dry matter and grain yield.  Our study indicated that the combination of LH is the best for optimizing the double-maize system under changing climatic conditions in the North China Plain.
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    N, P and K use efficiency and maize yield responses to fertilization modes and densities
    LI Guang-hao, CHENG Qian, LI Long, LU Da-lei, LU Wei-ping
    2021, 20 (1): 78-86.   DOI: 10.1016/S2095-3119(20)63214-2
    Abstract117)      PDF in ScienceDirect      
    Optimal planting density and proper fertilization method are important factors to improve maize yield and nutrient utilization.  A two-year (2016 and 2017) field experiment was conducted with three plant densities (6.0, 7.5 and 9.0 plants m−2) and three fertilization modes (no fertilizer, 0F; one-off application of slow-released fertilizer, SF; twice application of conventional fertilizer, CF).  Results indicated that the grain yields and N, P and K use efficiencies under SF with the optimal planting density (7.5 plants m−2) were the highest among all the treatments in 2016 and 2017.  Compared with CF, SF could increase post-silking dry matter accumulation and promote N, P and K uptake at pre- and post-silking stages; this treatment increased grain N, P and K concentrations and resulted in high N, P and K use efficiencies.  Nutrient (N, P and K) absorption efficiencies and partial productivity, and nutrient (N and P) recovery efficiency in SF treatment were significantly higher than those in CF treatments under the planting density of 7.5 plants m−2.  Under both SF and CF conditions, the grain yield, total N accumulation and nutrient use efficiencies initially increased, peaked at planting density of 7.5 plants m−2, and then decreased with increasing plant density.  Based on the yield and nutrient use efficiency in two years, plant density of 7.5 plants m−2 with SF can improve both the grain yield and N, P and K use efficiency of spring maize in Jiangsu Province, China.
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    Reduced square Bacillus thuringiensis insecticidal protein content of transgenic cotton under N deficit
    CHEN Yuan, LIU Zhen-yu, Leila I. M. TAMBEL, ZHANG Xiang, CHEN Yuan, CHEN De-hua
    2021, 20 (1): 100-108.   DOI: 10.1016/S2095-3119(20)63190-2
    Abstract97)      PDF in ScienceDirect      
    To clarify the effect of the N deficit on the amount of square Bt insecticidal protein, different N application rates (0, 75, 150, 225, and 300 kg ha–1) were imposed on the conventional cultivar Sikang 1 (SK-1) and hybrid cultivar Sikang 3 (SK-3) during 2015–2016 cotton growth seasons.  Under different N application rates, the square number per plant, square volume and square dry weight reduced when the N rates decreased from conventional rate (300 kg ha–1) to 0 kg ha–1.  And the square Bt protein content decreased accordingly.  The analysis of N metabolism showed that soluble protein content, GPT and GOT activities decreased, free amino acid, peptidase and protease activities increased under N deficit.  Correlation analysis indicated that the reduced Bt protein content under N deficit was related to altered N metabolism.  In conclusion, square development and the amount of square Bt toxin both decreased under N deficit, indicating that promoting the square development under appropriate N application rate would also promote the insect resistance during squaring stage.
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    Difference in corn kernel moisture content between pre- and post-harvest
    LI Lu-lu, MING Bo, XUE Jun, GAO Shang, WANG Ke-ru, XIE Rui-zhi, HOU Peng, LI Shao-kun
    2021, 20 (7): 1775-1782.   DOI: 10.1016/S2095-3119(20)63245-2
    Abstract85)      PDF in ScienceDirect      
    The harvest method of shelling corn (Zea mays L.) kernels in the field decreases labor costs associated with transporting, drying and threshing the crop.  However,  it was previously found that the kernel moisture content increased after field harvest, which decreased the value of corn kernels.  To identify the reasons underlying the increase, we conducted a multi-year and -area trial in the Huang-Huai-Hai Plain, China and performed a staged-harvest test at several phases of kernel dry-down.  The test investigated a range of parameters such as the kernel moisture content pre- and post-harvest, the kernel breakage rate, the amount of impurities, and the moisture content of various other plant tissues.  An analysis of 411 pairs of pre- and post-harvest samples found that kernel moisture content after harvest was 2.2% higher than that before harvest.  In the staged-harvest test, however, a significant increase was only observed when the kernel moisture content before harvest was higher than 23.9%.  The increase in post-harvest kernel moisture content was positively associated with the pre-harvest kernel moisture content, breakage rate and impurity rate.  Typically, at harvest time in this region, there is a significant fraction of immature crops with a high moisture content, resulting in kernels that are prone to breakage or impurities that ultimately lead to increases in water content after harvest.  Therefore, we suggest using hybrids that quickly wither late in the growing stage.  Additionally, farmers should delay harvest in order to minimize the pre-harvest kernel moisture content and thus reduce breakages and impurities, thereby improving the quality of kernels after harvest and the efficiency of corn kernel farming in China.
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    The effect of elevating temperature on the growth and development of reproductive organs and yield of summer maize
    SHAO Rui-xin, YU Kang-ke, LI Hong-wei, JIA Shuang-jie, YANG Qing-hua, ZHAO Xia, ZHAO Ya-li, LIU Tian-xu
    2021, 20 (7): 1783-1795.   DOI: 10.1016/S2095-3119(20)63304-4
    Abstract89)      PDF in ScienceDirect      
    Compared to other crops, maize production demands relatively high temperatures. However, temperatures exceeding 35°C lead to adverse effects on maize yield.  High temperatures (≥35°C) are consistently experienced by summer maize during its reproductive growth stage in the North China Plain, which is likely to cause irreversible crop damage.  This study investigated the effects of elevating temperature (ET) treatment on the yield component of summer maize, beginning at the 9th unfolding leaf stage and ending at the tasseling stage.  Results demonstrated that continuous ET led to a decrease in the elongation rate and activity of silks and an elongated interval between anthesis and silking stages, and eventually decreased grain number at ear tip and reduced yield.  Although continuous ET before tasseling damaged the anther structure, reduced pollen activity, delayed the start of the pollen shedding stage, and shortened the pollen shedding time, it was inferred, based on phenotypical and physiological traits, that continuous ET after the 9th unfolding leaf stage influenced ears and therefore may have more significant impacts.  Overall, when maize plants were exposed to ET treatment in the ear reproductive development stage, the growth of ears and tassels was blocked, which increased the occurrence of barren ear tips and led to large yield losses.
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    Lignin metabolism regulates lodging resistance of maize hybrids under varying planting density
    LI Bin, GAO Fei, REN Bai-zhao, DONG Shu-ting, LIU Peng, ZHAO Bin, ZHANG Ji-wang
    2021, 20 (8): 2077-2089.   DOI: 10.1016/S2095-3119(20)63346-9
    Abstract156)      PDF in ScienceDirect      
    Hybrids and planting density are the main factors affecting maize lodging resistance.  Here, we aimed to elucidate the mechanism of the regulation of maize lodging resistance by comparing two hybrids at various planting densities from the perspective of lignin metabolism.  Our results showed that compared to lodging-susceptible hybrid Xundan 20 (XD20), lodging-resistant hybrid Denghai 605 (DH605) showed a lower center of gravity and culm morphological characteristics that contributed to the higher lodging resistance of this hybrid.  Lignin content, activities of key lignin synthesis-related enzymes and G-, S- and H-type monomer contents were significantly higher in hybrid DH605 than in hybrid XD20.  Stalk mechanical strength, lignin accumulation and enzyme activity decreased significantly with increasing planting density in the two hybrids.  While G-type monomers first decreased with increasing planting density but then remained stable, S-type monomers showed a decreasing trend, and H-type monomers showed an increasing trend.  Correlation analysis showed that lodging rate was significantly correlated with plant traits and lignin metabolism.  Therefore, maize hybrids characterized by high lignin accumulation, high lignin synthesis-related activities, high S-type monomer content, low center of gravity, high stem puncture strength, high cortical thickness, and small vascular bundle area are more resistant to lodging.  High planting densities reduce stalk lignin accumulation, relevant enzyme activities and mechanical strength, thereby, ultimately increasing the lodging rate significantly.
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    Variation of carbon partitioning in newly expanded maize leaves and plant adaptive growth under extended darkness
    LIANG Xiao-gui, SHEN Si, GAO Zhen, ZHANG Li, ZHAO Xue, ZHOU Shun-li
    2021, 20 (9): 2360-2371.   DOI: 10.1016/S2095-3119(20)63351-2
    Abstract109)      PDF in ScienceDirect      
    Plants must maintain a balance between their carbon (C) supply and utilization during the day–night cycle for continuous growth since C starvation often causes irreversible damage to crop production.  It is not well known how C fixation and allocation in the leaves of crops such as maize adapt to sudden environmental changes.  Here, to quantify primary C fixation and partitioning in photosynthetic maize leaves under extended darkness and to relate these factors to plant growth, maize seedlings were subjected to extended darkness (ED) for three successive days at the 6th leaf fully expanded stage (V6).  ED reduced plant growth and leaf chlorophyll levels but not the rate of net CO2 exchange.  As a result of the reduction in photoassimilates, the accumulation of starch and total soluble carbohydrates (TSC) in mature leaves also decreased under ED.  However, the percentage of the daily C fixation reserved in mature leaves increased.  These transient C pools were largely composed of TSC and were mainly used for consumption by increased nocturnal respiration rather than for transport.  As the days went on, both the amount of C accumulated and the percentage of the daily fixed C that was reserved in leaves decreased, which could be largely accounted for by the attenuated starch synthesis in all treatments.  The activities of ADP-glucose pyrophosphorylase and soluble starch synthase decreased significantly over time.  Therefore, this study concluded that both starch and TSC are involved in the coordination of the C supply and plant growth under a sudden C shortage but that they may be involved in different ways.  While the ratio of reserved C to daily fixed C increased to maintain blade function under acute C starvation, both the amount and the proportion of C reserved in mature leaves decreased as plant growth continued in order to meet the growth demands of the plant.
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    Does nitrogen application rate affect the moisture content of corn grains?
    ZHANG Yuan-meng, XUE Jun, ZHAI Juan, ZHANG Guo-qiang, ZHANG Wan-xu, WANG Ke-ru, MING Bo, HOU Peng, XIE Rui-zhi, LIU Chao-wei, LI Shao-kun
    2021, 20 (10): 2627-2638.   DOI: 10.1016/S2095-3119(20)63401-3
    Abstract70)      PDF in ScienceDirect      
    Nitrogen fertilizer application is an important measure to obtain high and stable corn yield, and the moisture content of corn grains is an important factor affecting the quality of mechanical grain harvesting.  In this study, four different nitrogen fertilizer treatments from 0 to 450 kg ha–1 pure nitrogen were set for a planting density of 12.0×104 plants ha–1 in 2017 and 2018, and 18 different nitrogen fertilizer treatments from 0 to 765 kg ha–1 pure nitrogen were set for planting densities of 7.5×104 and 12.0×104 plants ha–1 in 2019, to investigate the effect of nitrogen application rate on the moisture content of corn grains.  Under each treatment, the growth of corn, leaf area index (LAI) of green leaves, grain moisture content, and grain dehydration rate were measured.  The results showed that, as nitrogen application increased from 0 to 765 kg ha–1, the silking stage was delayed by about 1 day, the maturity stage was delayed by about 1–2 days, and the number of physiologically mature green leaves and LAI increased.  At and after physiological maturity, the extreme difference in grain moisture content between different nitrogen application rates was 1.9–4.0%.  As the amount of nitrogen application increased, the corn grain dehydration rate after physiological maturity decreased, but it did not reach statistical significance between nitrogen application rate and grain dehydration rate.  No significant correlation was observed between LAI at physiological maturity and grain dehydration rate after physiological maturity.  In short, nitrogen application affected the grain moisture content of corn at and after physiological maturity, however, the difference in grain moisture content among different nitrogen application rates was small.  These results suggest that the effect of nitrogen application on the moisture content of corn grains should not be considered in agricultural production.
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    Drip irrigation incorporating water conservation measures: Effects on soil water–nitrogen utilization, root traits and grain production of spring maize in semi-arid areas
    WU Yang, BIAN Shao-feng, LIU Zhi-ming, WANG Li-chun, WANG Yong-jun, XU Wen-hua, ZHOU Yu
    2021, 20 (12): 3127-3142.   DOI: 10.1016/S2095-3119(20)63314-7
    Abstract198)      PDF in ScienceDirect      
    The Northeast Plain is the largest maize production area in China, and drip irrigation has recently been proposed to cope with the effects of frequent droughts and to improve water use efficiency (WUE).  In order to develop an efficient and environmentally friendly irrigation system, drip irrigation experiments were conducted in 2016–2018 incorporating different soil water conservation measures as follows: (1) drip irrigation under plastic film mulch (PI), (2) drip irrigation under biodegradable film mulch (BI), (3) drip irrigation incorporating straw returning (SI), and (4) drip irrigation with the tape buried at a shallow soil depth (OI); with furrow irrigation (FI) used as the control.  The results showed that PI and BI gave the highest maize yield, as well as the highest WUE and nitrogen use efficiency (NUE) because of the higher root length density (RLD) and better heat conditions during the vegetative stage.  But compared with BI, PI consumed more soil water in the 20–60 and 60–100 cm soil layers, and accelerated the progress of root and leaf senescence due to a larger root system in the top 0–20 cm soil layer and a higher soil temperature during the reproductive stage.  SI was effective in improving soil water and nitrate contents, and promoted RLD in deeper soil layers, thereby maintaining higher physiological activity during the reproductive stage.  FI resulted in higher nitrate levels in the deep 60–100 cm soil layer, which increased the risk of nitrogen losses by leaching compared with the drip irrigation treatments.  RLD in the 0–20 cm soil layer was highly positively correlated with yield, WUE and NUE (P<0.001), but it was negatively correlated with root nitrogen use efficiency (NRE) (P<0.05), and the correlation was weaker in deeper soil layers.  We concluded that BI had advantages in water–nitrogen utilization and yield stability response to drought stress, and thus is recommended for environmentally friendly and sustainable maize production in Northeast China.
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    Maize grain yield and water use efficiency in relation to climatic factors and plant population in northern China
    LIU Yue-e, HOU Peng, HUANG Gui-rong, ZHONG Xiu-li, LI Hao-ru, ZHAO Jiu-ran, LI Shao-kun, MEI Xu-rong
    2021, 20 (12): 3156-3169.   DOI: 10.1016/S2095-3119(20)63428-1
    Abstract165)      PDF in ScienceDirect      
    Water scarcity has become a limiting factor for increasing crop production.  Finding ways to improve water use efficiency (WUE) has become an urgent task for Chinese agriculture.  To understand the response of different maize populations to changes in precipitation and the effects of changes in maize populations on WUE, this study conducted maize population experiments using maize hybrids with different plant types (compact and semi compact) and different planting densities at 25 locations across China.  It was found that, as precipitation increased across different locations, maize grain yield first increased and then decreased, while WUE decreased significantly.  Analyzing the relationship between WUE and the main climatic factors, this study found that WUE was significantly and negatively correlated with precipitation (R (daily mean precipitation) and R (accumulated precipitation)) and was positively correlated with temperature (TM (daily mean maximum temperature), TM–m (Tm, daily mean minimum temperature) and GDD (growing degree days)) and solar radiation (Ra (daily mean solar radiation) and Ra (accumulated solar radiation)) over different growth periods.  Significant differences in maize grain yield, WUE and precipitation were found at different planting densities.  The population densities were ranked as follows according to maize grain yield and WUE based on the multi-site experiment data: 60 000 plants ha–1 (P2)>90 000 plants ha–1 (P3)>30 000 plants ha–1 (P1).  Further analysis showed that, as maize population increased, water consumption increased significantly while soil evaporation decreased significantly.  Significant differences were found between the WUE of ZD958 (compact type) and that of LD981 (semi-compact type), as well as among the WUE values at different planting densities.  In addition, choosing the optimum hybrid and planting density increased WUE by 21.70 and 14.92%, respectively, which showed that the hybrid played a more significant role than the planting density in improving WUE.  Therefore, choosing drought-resistant hybrids could be more effective than increasing the planting density to increase maize grain yield and WUE in northern China.  Comprehensive consideration of climatic impacts, drought-resistant hybrids (e.g., ZD958) and planting density (e.g., 60 000 plants ha–1) is an effective way to increase maize grain yield and WUE across different regions of China.
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    Yield penalty of maize (Zea mays L.) under heat stress in different growth stages: A review
    LI Teng, ZHANG Xue-peng, LIU Qing, LIU Jin, CHEN Yuan-quan, SUI Peng
    2022, 21 (9): 2465-2476.   DOI: 10.1016/j.jia.2022.07.013
    Abstract501)      PDF in ScienceDirect      
    Maize (Zea mays L.) can exhibit yield penalties as a result of unfavorable changes to growing conditions.  The main threat to current and future global maize production is heat stress.  Maize may suffer from heat stress in all of the growth stages, either continuously or separately.  In order to manage the impact of climate driven heat stress on the different growth stages of maize, there is an urgent need to understand the similarities and differences in how heat stress affects maize growth and yield in the different growth stages.  For the purposes of this review, the maize growth cycle was divided into seven growth stages, namely the germination and seedling stage, early ear expansion stage, late vegetative growth stage before flowering, flowering stage, lag phase, effective grain-filling stage, and late grain-filling stage.  The main focus of this review is on the yield penalty and the potential physiological changes caused by heat stress in these seven different stages.  The commonalities and differences in heat stress related impacts on various physiological processes in the different growth stages are also compared and discussed.  Finally, a framework is proposed to describe the main influences on yield components in different stages, which can serve as a useful guide for identifying management interventions to mitigate heat stress related declines in maize yield.
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