玉米耕作栽培Maize Physiology · Biochemistry · Cultivation

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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

Abstract （138） 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

Abstract （258） 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

Abstract （240） 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

Abstract （219） 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 (N_min) 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 N_min 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

Abstract （136） 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

Abstract （215） 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

Abstract （158） 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

Abstract （160） 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

Abstract （292） 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

Abstract （187） 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

Abstract （152） 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

Abstract （118） 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

Abstract （113） 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 (P_n), 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 P_n 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

Abstract （139） 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 (W_max) 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

Abstract （152） 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 (P_n) and accelerated leaf senescence. The correlation results indicated that reduced P_n 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

Abstract （180） 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

Abstract （126） 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

Abstract （127） 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

Abstract （112） 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

Abstract （176） 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

Abstract （134） 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

Abstract （109） 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

Abstract （118） 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

Abstract （220） 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

Abstract （142） 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

Abstract （89） 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

Abstract （252） 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

Abstract （222） 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 (T_M (daily mean maximum temperature), T_M–m (T_m, 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

Abstract （632） 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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Nitrogen management improves lodging resistance and production in maize (Zea mays L.) at a high plant density

Irshad AHMAD, Maksat BATYRBEK, Khushnuma IKRAM, Shakeel AHMAD, Muhammad KAMRAN, Misbah, Raham Sher KHAN, HOU Fu-jiang, HAN Qing-fang

2023, 22 (2): 417-433. DOI: 10.1016/j.jia.2022.08.074

Abstract （311） PDF in ScienceDirect

Lodging in maize leads to yield losses worldwide. In this study, we determined the effects of traditional and optimized nitrogen management strategies on culm morphological characteristics, culm mechanical strength, lignin content, root growth, lodging percentage and production in maize at a high plant density. We compared a traditional nitrogen (N) application rate of 300 kg ha^–1 (R) and an optimized N application rate of 225 kg ha^–1 (O) under four N application modes: 50% of N applied at sowing and 50% at the 10th-leaf stage (N1); 100% of N applied at sowing (N2); 40% of N applied at sowing, 40% at the 10th-leaf stage and 20% at tasseling stage (N3); and 30% of N applied at sowing, 30% at the 10th-leaf stage, 20% at the tasseling stage, and 20% at the silking stage (N4). The optimized N rate (225 kg ha^–1) significantly reduced internode lengths, plant height, ear height, center of gravity height and lodging percentage. The optimized N rate significantly increased internode diameters, filling degrees, culm mechanical strength, root growth and lignin content. The application of N in four split doses (N4) significantly improved culm morphological characteristics, culm mechanical strength, lignin content, and root growth, while it reduced internode lengths, plant height, ear height, center of gravity height and lodging percentage. Internode diameters, filling degrees, culm mechanical strength, lignin content, number and diameter of brace roots, root volume, root dry weight, bleeding safe and grain yield were significantly negatively correlated with plant height, ear height, center of gravity height, internode lengths and lodging percentage. In conclusion, treatment ON4 significantly reduced the lodging percentage by improving the culm morphological characteristics, culm mechanical strength, lignin content, and root growth, so it improved the production of the maize crop at a high plant density.

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Novel models for simulating maize growth based on thermal time and photothermal units: Applications under various mulching practices

LIAO Zhen-qi, ZHENG Jing, FAN Jun-liang, PEI Sheng-zhao, DAI Yu-long, ZHANG Fu-cang, LI Zhi-jun

2023, 22 (5): 1381-1395. DOI: 10.1016/j.jia.2022.08.018

Abstract （186） PDF in ScienceDirect

Maize (Zea mays L.) is one of the three major food crops and an important source of carbohydrates for maintaining food security around the world. Plant height (H), stem diameter (SD), leaf area index (LAI) and dry matter (DM) are important growth parameters that influence maize production. However, the combined effect of temperature and light on maize growth is rarely considered in crop growth models. Ten maize growth models based on the modified logistic growth equation (Mlog) and the Mitscherlich growth equation (Mit) were proposed to simulate the H, SD, LAI and DM of maize under different mulching practices based on experimental data from 2015–2018. Either the accumulative growing degree-days (AGDD), helio thermal units (HTU), photothermal units (PTU) or photoperiod thermal units (PPTU, first proposed here) was used as a single driving factor in the models; or AGDD was combined with either accumulative actual solar hours (ASS), accumulative photoperiod response (APR, first proposed here) or accumulative maximum possible sunshine hours (ADL) as the dual driving factors in the models. The model performances were evaluated using seven statistical indicators and a global performance index. The results showed that the three mulching practices significantly increased the maize growth rates and the maximum values of the growth curves compared with non-mulching. Among the four single factor-driven models, the overall performance of the Mlog_PTU Model was the best, followed by the Mlog_AGDD Model. The Mlog_PPTU Model was better than the Mlog_AGDD Model in simulating SD and LAI. Among the 10 models, the overall performance of the Mlog_AGDD–APR Model was the best, followed by the Mlog_AGDD–ASS Model. Specifically, the Mlog_AGDD–APR Model performed the best in simulating H and LAI, while the Mlog_AGDD–ADL and Mlog_AGDD–ASS models performed the best in simulating SD and DM, respectively. In conclusion, the modified logistic growth equations with AGDD and either APR, ASS or ADL as the dual driving factors outperformed the commonly used modified logistic growth model with AGDD as a single driving factor in simulating maize growth.

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Plastic-film-side seeding, as an alternative to traditional film mulching, improves yield stability and income in maize production in semi-arid regions

ZHANG Bing-chao, HU Han, GUO Zheng-yu, GONG Shuai, SHEN Si, LIAO Shu-hua, WANG Xin, ZHOU Shun-li, ZHANG Zhong-dong

2023, 22 (4): 1021-1034. DOI: 10.1016/j.jia.2022.08.017

Abstract （356） PDF in ScienceDirect

Planting under plastic-film mulches is widely used in spring maize production in arid-cold regions for water conservation and warming the soil. To ameliorate the associated issues such as plastic-film residues and additional labor during the “seedling release” in spring maize production, we have developed a plastic-film-side seeding (PSS) technology with the supporting machinery. In the semi-arid regions of Northwest China, a 7-year trial demonstrated that PSS increased plant number per hectare by 6 547 and maize yield by 1 686 kg ha^–1 compared with the traditional method of seeding under plastic-film mulch (PM). Two-year experiments were conducted in two semi-arid regions to further understand the effects of PSS on three important aspects of production: (i) the moisture and temperature of soil, (ii) maize development, yield output, and water use efficiency (WUE), and (iii) the revenue and plastic-film residuals in comparison with that of flat planting (CK) and PM. Continuous monitoring of the soil status demonstrated that, compared with CK, the PSS treatment significantly increased the temperature and moisture of the 0–20 cm soil in the seeding row at the early stage of maize development, and it also promoted grain yield (at 884–1 089 kg ha^–1) and WUE, achieving a similar effect as the PM treatment. Economically, the labor inputs of PSS were equal to CK, whereas the PM cost an additional 960 CNY ha^–1 in labor for releasing the seedlings from below the film. Overall, the PSS system increased profits by 5.83% (547 CNY ha^–1 yr^–1) and 8.16% (748 CNY ha^–1 yr^–1) compared with CK and PM, respectively. Environmentally, PSS achieved a residual film recovery rate of nearly 100% and eliminated 96 to 130 kg ha^–1 of residual plastic-film in PM in 3–5 years of maize production. Collectively, these results show that PSS is an eco-friendly technique for improving yield stability and incomes for the sustainable production of maize in semi-arid regions.

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Better tillage selection before ridge–furrow film mulching can facilitate root proliferation, increase nitrogen accumulation, translocation, grain yield of maize in a semiarid area

ZHANG Miao-miao, DANG Peng-fei, LI Yü-ze, QIN Xiao-liang, Kadambot-H. M. SIDDIQUE

2023, 22 (6): 1658-1670. DOI: 10.1016/j.jia.2022.08.037

Abstract （254） PDF in ScienceDirect

Plastic film mulch systems are used widely in arid areas, and the associated tillage measures affect soil properties, root and crop growth, and nutrient uptake. However, much debate surrounds the most suitable tillage method for plastic film mulch systems. We conducted a two-year field experiment to explore the impact of three tillage treatments - rotary tillage before ridge–furrow plastic film mulch (MR), no-tillage before ridge–furrow plastic film mulch (MZ), and plow tillage before ridge–furrow plastic film mulch (MP) - on soil total nitrogen, available nitrogen, root stratification structure, nitrogen transfer and utilization, and maize yield. The results showed that MP had better soil quality than either MR or MZ over 2019 and 2020, with higher nitrate-nitrogen and total nitrogen in the 0–40 cm soil layer. MP improved the soil physicochemical properties more than the other treatments, producing significantly higher root numbers and root biomass for the aerial and underground nodal roots than MR and MZ. At harvest, MP had the highest root biomass density, root length density, and root surface area density in the different soil layers (0–20, 20–40, and 0–40 cm). Significant correlations occurred between root biomass and aboveground nitrogen accumulation during maize growth. During grain filling, MP had the greatest nitrogen transfer amount, significantly increasing root and aboveground nitrogen transfer by 19.63–45.82% and 11.15–24.56%, respectively, relative to the other treatments. MP significantly produced 1.36–26.73% higher grain yields and a higher grain crude protein content at harvest than MR and MZ. MP also had higher values for the nitrogen harvest index, nitrogen uptake efficiency, and partial factor productivity of nitrogen fertilizer than MR and MZ. In conclusion, plow tillage combined with a ridge–furrow plastic film mulch system facilitated maize root development and improved nitrogen utilization, thereby increasing maize yield more than the other treatments.

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Response of dryland crops to climate change and drought-resistant and water-suitable planting technology: A case of spring maize

FAN Ting-lu, LI Shang-zhong, ZHAO Gang, WANG Shu-ying, ZHANG Jian-jun, WANG Lei, DANG Yi, CHENG Wan-li

2023, 22 (7): 2067-2079. DOI: 10.1016/j.jia.2022.08.044

Abstract （226） PDF in ScienceDirect

Climate change has a significant impact on agriculture. However, the impact investigation is currently limited to the analysis of meteorological data, and there is a dearth of long-term monitoring of crop phenology and soil moisture associated with climate change. In this study, temperature and precipitation (1957–2020) were recorded, crop growth (1981–2019) data were collected, and field experiments were conducted at central and eastern Gansu and southern Ningxia, China. The mean temperature increased by 0.36°C, and precipitation decreased by 11.17 mm per decade. The average evapotranspiration (ET) of winter wheat in 39 years from 1981 to 2019 was 362.1 mm, demonstrating a 22.1-mm decrease every 10 years. However, the ET of spring maize was 405.5 mm over 35 years (1985–2019), which did not show a downward trend. Every 10 years, growth periods were shortened by 5.19 and 6.47 d, sowing dates were delayed by 3.56 and 1.68 d, and maturity dates advanced by 1.76 and 5.51 d, respectively, for wheat and maize. A film fully-mulched ridge–furrow (FMRF) system with a rain-harvesting efficiency of 65.7‒92.7% promotes deep rainwater infiltration into the soil. This leads to double the soil moisture in-furrow, increasing the water satisfaction rate by 110‒160%. A 15-year grain yield of maize increased by 19.87% with the FMRF compared with that of half-mulched flat planting. Grain yield and water use efficiency of maize increased by 20.6 and 17.4% when the density grew from 4.5×10⁴ to 6.75×10⁴ plants ha^–1 and improved by 12.0 and 12.7% when the density increased from 6.75×10⁴ to 9.0×10⁴ plants ha^–1, respectively. Moreover, responses of maize yield to density and the corresponding density of the maximum yield varied highly in different rainfall areas. The density parameter suitable for water planting was 174 maize plants ha^–1 with 10 mm rainfall. Therefore, management strategies should focus on adjusting crop planting structure, FMRF water harvesting system, and water-suitable planting to mitigate the adverse effects of climate change and enhance sustainable production of maize in the drylands.

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Review on the fully mulched ridge–furrow system for sustainable maize production on the semi-arid Loess Plateau

WANG Jin-bin, XIE Jun-hong, LI Ling-ling, ADINGO Samuel

2023, 22 (5): 1277-1290. DOI: 10.1016/j.jia.2022.09.023

Abstract （348） PDF in ScienceDirect

The fully mulched ridge–furrow (FMRF) system has been widely used on the semi-arid Loess Plateau of China due to its high maize (Zea mays L.) productivity and rainfall use efficiency. However, high outputs under this system led to a depletion of soil moisture and soil nutrients, which reduces its sustainability in the long run. Therefore, it is necessary to optimize the system for the sustainable development of agriculture. The development, yield-increasing mechanisms, negative impacts, optimization, and their relations in the FMRF system are reviewed in this paper. We suggest using grain and forage maize varieties instead of regular maize; mulching plastic film in autumn or leaving the mulch after maize harvesting until the next spring, and then removing the old film and mulching new film; combining reduced/no-tillage with straw return; utilizing crop rotation or intercropping with winter canola (Brassica campestris L.), millet (Setaria italica), or oilseed flax (Linum usitatissimum L.); reducing nitrogen fertilizer and partially replacing chemical fertilizer with organic fertilizer; using biodegradable or weather-resistant film; and implementing mechanized production. These integrations help to establish an environmentally friendly, high quality, and sustainable agricultural system, promote high-quality development of dryland farming, and create new opportunities for agricultural development in the semi-arid Loess Plateau.

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Detection of maize tassels for UAV remote sensing image with an improved YOLOX Model

SONG Chao-yu, ZHANG Fan, LI Jian-sheng, XIE Jin-yi, YANG Chen, ZHOU Hang, ZHANG Jun-xiong

2023, 22 (6): 1671-1683. DOI: 10.1016/j.jia.2022.09.021

Abstract （361） PDF in ScienceDirect

Maize tassel detection is essential for future agronomic management in maize planting and breeding, with application in yield estimation, growth monitoring, intelligent picking, and disease detection. However, detecting maize tassels in the field poses prominent challenges as they are often obscured by widespread occlusions and differ in size and morphological color at different growth stages. This study proposes the SEYOLOX-tiny Model that more accurately and robustly detects maize tassels in the field. Firstly, the data acquisition method ensures the balance between the image quality and image acquisition efficiency and obtains maize tassel images from different periods to enrich the dataset by unmanned aerial vehicle (UAV). Moreover, the robust detection network extends YOLOX by embedding an attention mechanism to realize the extraction of critical features and suppressing the noise caused by adverse factors (e.g., occlusions and overlaps), which could be more suitable and robust for operation in complex natural environments. Experimental results verify the research hypothesis and show a mean average precision (mAP_@0.5) of 95.0%. The mAP_@0.5, mAP_@0.5–0.95, mAP_{@0.5–0.95 (area=small)}, and mAP_{@0.5–0.95 (area=medium)} average values increased by 1.5, 1.8, 5.3, and 1.7%, respectively, compared to the original model. The proposed method can effectively meet the precision and robustness requirements of the vision system in maize tassel detection.

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Irrigation mitigates the heat impacts on photosynthesis during grain filling in maize

WANG Xing-long, ZHU Yu-peng, YAN Ye, HOU Jia-min, WANG Hai-jiang, LUO Ning, WEI Dan, MENG Qing-feng, WANG Pu

2023, 22 (8): 2370-2383. DOI: 10.1016/j.jia.2023.02.012

Abstract （246） PDF in ScienceDirect

Elevating soil water content (SWC) through irrigation was one of the simple mitigation measures to improve crop resilience to heat stress. The response of leaf function, such as photosynthetic capacity based on chlorophyll fluorescence during the mitigation, has received limited attention, especially in field conditions. A two-year field experiment with three treatments (control treatment (CK), high-temperature treatment (H), and high-temperature together with elevating SWC treatment (HW)) was carried out during grain filling with two maize hybrids at a typical station in North China Plain. Averagely, the net photosynthetic rate (P_n) was improved by 20%, and the canopy temperature decreased by 1–3°C in HW compared with in H in both years. Furthermore, the higher SWC in HW significantly improved the actual photosynthetic rate (Phi2), linear electron flow (LEF), variable fluorescence (F_v), and the maximal potential quantum efficiency (F_v/F_m) for both hybrids. Meanwhile, different responses in chlorophyll fluorescence between hybrids were also observed. The higher SWC in HW significantly improved thylakoid proton conductivity (gH⁺) and the maximal fluorescence (F_m) for the hybrid ZD958. For the hybrid XY335, the proton conductivity of chloroplast ATP synthase (vH⁺) and the minimal fluorescence (F_o) was increased by the SWC. The structural equation model (SEM) further showed that SWC had significantly positive relationships with P_n, LEF, and F_v/F_m. The elevating SWC alleviated heat stress with the delayed leaf senescence to prolong the effective period of photosynthesis and enhanced leaf photosynthetic capacity by improving Phi2, LEF, F_v, and F_v/F_m. This research demonstrates that elevating SWC through enhancing leaf photosynthesis during grain filling would be an important mitigation strategy for adapting to the warming climate in maize production.

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Integrating microRNAs and mRNAs reveals the hormones synthesis and signal transduction of maize under different N rates

YUE Kai, LI Ling-ling, XIE Jun-hong, Zechariah EFFAH, Sumera ANWAR, WANG Lin-lin, MENG Hao-feng, LI Lin-zhi

2023, 22 (9): 2673-2686. DOI: 10.1016/j.jia.2023.02.016

Abstract （191） PDF in ScienceDirect

The effect of nitrogen (N) fertilizer on the development of maize kernels has yet to be fully explored. MicroRNA-mRNA analyses could help advance our understanding of how kernels respond to N. This study analyzed the morphological, physiological, and transcriptomic changes in maize kernels under different N rates (0, 100, 200, and 300 kg ha^–1). The result showed that increasing N application significantly increased maize grains’ fresh and dry weight until N reached 200 kg ha^–1. Higher levels of indole-3-acetic acid, cytokinin, gibberellin, and a lower level of ethylene were associated with increased N applications. We obtained 31 differentially expressed genes (DEGs) in hormone synthesis and transduction, and 9 DEGs were regulated by 14 differentially expressed microRNAs (DEMIs) in 26 pairs. The candidate DEGs and DEMIs provide valuable insight for manipulating grain filling under different N rates.

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Combining nitrogen effects and metabolomics to reveal the response mechanisms to nitrogen stress and the potential for nitrogen reduction in maize

LU Yan-li, SONG Gui-pei, WANG Yu-hong, WANG Luo-bin, XU Meng-ze, ZHOU Li-ping, WANG Lei

2023, 22 (9): 2660-2672. DOI: 10.1016/j.jia.2023.03.002

Abstract （216） PDF in ScienceDirect

The physiological and metabolic differences in maize under different nitrogen (N) levels are the basis of reasonable N management, which is vital in improving fertilizer utilization and reducing environmental pollution. In this paper, on the premise of defining the N fertilizer efficiency and yield under different long-term N fertilization treatments, the corresponding differential metabolites and their metabolic pathways were analyzed by untargeted metabolomics in maize. N stress, including deficiency and excess, affects the balance of carbon (C) metabolism and N metabolism by regulating C metabolites (sugar alcohols and tricarboxylic acid (TCA) cycle intermediates) and N metabolites (various amino acids and their derivatives). L-alanine, L-phenylalanine, L-histidine, and L-glutamine decreased under N deficiency, and L-valine, proline, and L-histidine increased under N excess. In addition to sugar alcohols and the above amino acids in C and N metabolism, differential secondary metabolites, flavonoids (e.g., kaempferol, luteolin, rutin, and diosmetin), and hormones (e.g., indoleacetic acid, trans-zeatin, and jasmonic acid) were initially considered as indicators for N stress diagnosis under this experimental conditions. This study also indicated that the leaf metabolic levels of N2 (120 kg ha^–1 N) and N3 (180 kg ha^–1 N) were similar, consistent with the differences in their physiological indexes and yields over 12 years. This study verified the feasibility of reducing N fertilization from 180 kg ha^–1 (locally recommended) to 120 kg ha^–1 at the metabolic level, which provided a mechanistic basis for reducing N fertilization without reducing yield, further improving the N utilization rate and protecting the ecological environment.

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Combined application of organic fertilizer and chemical fertilizer alleviates the kernel position effect in summer maize by promoting post-silking nitrogen uptake and dry matter accumulation

Lichao Zhai, Lihua Zhang, Yongzeng Cui, Lifang Zhai, Mengjing Zheng, Yanrong Yao, Jingting Zhang, Wanbin Hou, Liyong Wu, Xiuling Jia

2024, 23 (4): 1179-1194. DOI: 10.1016/j.jia.2023.05.003

Abstract （178） PDF in ScienceDirect

Adjusting agronomic measures to alleviate the kernel position effect in maize is important for ensuring high yields. In order to clarify whether the combined application of organic fertilizer and chemical fertilizer (CAOFCF) can alleviate the kernel position effect of summer maize, field experiments were conducted during the 2019 and 2020 growing seasons, and five treatments were assessed: CF, 100% chemical fertilizer; OFCF1, 15% organic fertilizer+85% chemical fertilizer; OFCF2, 30% organic fertilizer+70% chemical fertilizer; OFCF3, 45% organic fertilizer+55% chemical fertilizer; and OFCF4, 60% organic fertilizer+40% chemical fertilizer. Compared with the CF treatment, the OFCF1 and OFCF2 treatments significantly alleviated the kernel position effect by increasing the weight ratio of inferior kernels to superior kernels and reducing the weight gap between the superior and inferior kernels. These effects were largely due to the improved filling and starch accumulation of inferior kernels. However, there were no obvious differences in the kernel position effect among plants treated with CF, OFCF3, or OFCF4 in most cases. Leaf area indexes, post-silking photosynthetic rates, and net assimilation rates were higher in plants treated with OFCF1 or OFCF2 than in those treated with CF, reflecting an enhanced photosynthetic capacity and improved post-silking dry matter accumulation (DMA) in the plants treated with OFCF1 or OFCF2. Compared with the CF treatment, the OFCF1 and OFCF2 treatments increased post-silking N uptake by 66.3 and 75.5%, respectively, which was the major factor driving post-silking photosynthetic capacity and DMA. Moreover, the increases in root DMA and zeatin riboside content observed following the OFCF1 and OFCF2 treatments resulted in reduced root senescence, which is associated with an increased post-silking N uptake. Analyses showed that post-silking N uptake, DMA, and grain yield in summer maize were negatively correlated with the kernel position effect. In conclusion, the combined application of 15–30% organic fertilizer and 70–85% chemical fertilizer alleviated the kernel position effect in summer maize by improving post-silking N uptake and DMA. These results provide new insights into how CAOFCF can be used to improve maize productivity.

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Grain yield and N uptake of maize in response to increased plant density under reduced water and nitrogen supply conditions

Jingui Wei, Qiang Chai, Wen Yin, Hong Fan, Yao Guo, Falong Hu, Zhilong Fan, Qiming Wang

2024, 23 (1): 122-140. DOI: 10.1016/j.jia.2023.05.006

Abstract （215） PDF in ScienceDirect

The development of modern agriculture requires the reduction of water and chemical N fertilizer inputs. Increasing the planting density can maintain higher yields, but also consumes more of these restrictive resources. However, whether an increased maize density can compensate for the negative effects of reduced water and N supply on grain yield and N uptake in the arid irrigated areas remains unknown. This study is part of a long-term positioning trial that started in 2016. A split-split plot field experiment of maize was implemented in the arid irrigated area of northwestern China in 2020 to 2021. The treatments included two irrigation levels: local conventional irrigation reduced by 20% (W1, 3,240 m³ ha^–1) and local conventional irrigation (W2, 4,050 m³ ha^–1); two N application rates: local conventional N reduced by 25% (N1, 270 kg ha^–1) and local conventional N (360 kg ha^–1); and three planting densities: local conventional density (D1, 75,000 plants ha^–1), density increased by 30% (D2, 97,500 plants ha^–1), and density increased by 60% (D3, 120,000 plants ha^–1). Our results showed that the grain yield and aboveground N accumulation of maize were lower under the reduced water and N inputs, but increasing the maize density by 30% can compensate for the reductions of grain yield and aboveground N accumulation caused by the reduced water and N supply. When water was reduced while the N application rate remained unchanged, increasing the planting density by 30% enhanced grain yield by 13.9% and aboveground N accumulation by 15.3%. Under reduced water and N inputs, increasing the maize density by 30% enhanced N uptake efficiency and N partial factor productivity, and it also compensated for the N harvest index and N metabolic related enzyme activities. Compared with W2N2D1, the N uptake efficiency and N partial factor productivity increased by 28.6 and 17.6% under W1N1D2. W1N2D2 had 8.4% higher N uptake efficiency and 13.9% higher N partial factor productivity than W2N2D1. W1N2D2 improved urease activity and nitrate reductase activity by 5.4% at the R2 (blister) stage and 19.6% at the V6 (6th leaf) stage, and increased net income and the benefit:cost ratio by 22.1 and 16.7%, respectively. W1N1D2 and W1N2D2 reduced the nitrate nitrogen and ammoniacal nitrogen contents at the R6 stage in the 40–100 cm soil layer, compared with W2N2D1. In summary, increasing the planting density by 30% can compensate for the loss of grain yield and aboveground N accumulation under reduced water and N inputs. Meanwhile, increasing the maize density by 30% improved grain yield and aboveground N accumulation when water was reduced by 20% while the N application rate remained constant in arid irrigation areas.

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Can soil organic carbon sequestration and the carbon management index be improved by changing the film mulching methods in the semiarid region?

Jialin Yang, Liangqi Ren, Nanhai Zhang, Enke Liu, Shikun Sun, Xiaolong Ren, Zhikuan Jia, Ting Wei, Peng Zhang

2024, 23 (5): 1541-1556. DOI: 10.1016/j.jia.2023.05.011

Abstract （143） PDF in ScienceDirect

Plastic film mulching has been widely used to increase maize yield in the semiarid area of China. However, whether long-term plastic film mulching is conducive to agricultural sustainability in this region remains controversial. A field experiment was initiated in 2013 with five different film mulching methods: (i) control method, flat planting without mulching (CK), (ii) flat planting with half film mulching (P), (iii) film mulching on ridges and planting in narrow furrows (S), (iv) full film mulching on double ridges (D), and (v) film mulching on ridges and planting in wide furrows (R). The effects on soil organic carbon (SOC) content, storage, and fractions, and on the carbon management index (CMI) were evaluated after nine consecutive years of plastic film mulching. The results showed that long-term plastic film mulching generally maintained the initial SOC level. Compared with no mulching, plastic film mulching increased the average crop yield, biomass yield, and root biomass by 48.38, 35.06, and 37.32%, respectively, which led to the improvement of SOC sequestration. Specifically, plastic film mulching significantly improved CMI, and increased the SOC content by 13.59%, SOC storage by 7.47% and easily oxidizable organic carbon (EOC) by 13.78% on average, but it reduced the other labile fractions. SOC sequestration and CMI were improved by refining the plastic film mulching methods. The S treatment had the best effect among the four mulching methods, so it can be used as a reasonable film mulching method for sustainable agricultural development in the semiarid area.

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The environment, especially the minimum temperature, affects summer maize grain yield by regulating ear differentiation and grain development

Jing Chen, Baizhao Ren, Bin Zhao, Peng Liu, Jiwang Zhang

2024, 23 (7): 2227-2241. DOI: 10.1016/j.jia.2023.06.034

Abstract （123） PDF in ScienceDirect

Ear differentiation, grain development and their interaction with factors in the growing environment, such as temperature, solar radiation and precipitation, greatly influence grain number and grain weight, and ultimately affect summer maize production. In this study, field experiments involving different sowing dates were conducted over three years to evaluate the effects of temperature factors, average solar radiation and total precipitation on the growth process, ear differentiation, fertilization characteristics, grain filling and yield of summer maize varieties with different growth durations. Four hybrids were evaluated in Huang-Huai-Hai Plain (HHHP), China from 2018 to 2020 with five different sowing dates. The results showed that the grain yield formation of summer maize was strongly impacted by the environment from the silking (R1) to milking (R3) stage. Average minimum temperature (AT_min) was the key environmental factor that determined yield. Reductions in the length of the growing season (r=–0.556, P<0.01) and the total floret number on ear (R²=0.200, P<0.001) were found when AT_min was elevated from the emerging (VE) to R1 stage. Both grain-filling rate (R²=0.520, P<0.001) and the floret abortion rate on ear (R²=0.437, P<0.001) showed quadratic relationships with AT_min from the R1 to physiological maturity (R6) stage, while the number of days after the R1 stage (r=–0.756, P<0.01) was negatively correlated with AT_min. An increase in AT_min was beneficial for the promotion of yield when it did not exceeded a certain level (above 23°C during the R1–R3 stage and 20–21°C during the R1-R6 stage). Enhanced solar radiation and precipitation during R1–R6 increased the grain-filling rate (R²=0.562, P<0.001 and R²=0.229, P<0.05, respectively). Compared with short-season hybrids, full-season hybrids showed much greater suitability for a critical environment. The coordinated regulation of AT_min, ear differentiation and grain development at the pre- and post-silking stages improved maize yield by increasing total floret number and grain-filling rate, and by reducing the floret abortion rate on ear.

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Timing effect of high temperature exposure on the plasticity of internode and plant architecture in maize

Binbin Li, Xianmin Chen, Tao Deng, Xue Zhao, Fang Li, Bingchao Zhang, Xin Wang, Si Shen, Shunli Zhou

2024, 23 (2): 551-565. DOI: 10.1016/j.jia.2023.07.003

Abstract （149） PDF in ScienceDirect

The occurrence of high temperature (HT) in crop production is becoming more frequent and unpredictable with global warming, severely threatening food security. The state of an organ’s growth and development is largely determined by the temperature conditions it is exposed to over time. Maize is the main cereal crop, and its stem growth and plant architecture are closely related to lodging resistance, and especially sensitive to temperature. However, systematic research on the timing effect of HT on the sequentially developing internode and stem is currently lacking. To identify the timing effect of HT on the morphology and plasticity of the stem in maize, two hybrids (Zhengdan 958 (ZD958), Xianyu 335 (XY335)) characterized by distinct morphological traits in the stem were exposed to a 7-day HT treatment from the V6 to V17 stages (Vn presents the vegetative stage with n leaves fully expanded) in 2019–2020. The results demonstrated that exposure to HT during V6–V12 accelerated the rapid elongation of stems. For instance, HT occurring at V7 and V12 specifically promoted the lengths and weights of the 3rd–5th and 9th–11th internodes, respectively. Meanwhile, HT slowed the growth of internodes adjacent to the promoted internodes. Interestingly, compared with control, the plant height was significantly increased soon after HT treatment, but the promotion effect became narrower at the subsequent flowering stage, demonstrating a self-adjusting mechanism in the maize plant in response to HT. Importantly, HT altered the plant architectures, including a rising of the ear position and increase in the ear position coefficient. XY335 exhibited greater sensitivity in stem development than ZD958 under HT treatment. These findings improve our systematic understanding of the plasticity of internode and plant architecture in response to the timing of HT exposure.

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Impacts of high temperature, relative air humidity, and vapor pressure deficit on the seed set of contrasting maize genotypes during flowering

Xin Dong, Baole Li, Zhenzhen Yan, Ling Guan, Shoubing Huang , Shujun Li, Zhiyun Qi, Ling Tang, Honglin Tian, Zhongjun Fu, Hua Yang

2024, 23 (9): 2955-2969. DOI: 10.1016/j.jia.2023.09.007

Abstract （141） PDF in ScienceDirect

Heat stress is a major constraint to current and future maize production at the global scale. Male and female reproductive organs both play major roles in increasing seed set under heat stress at flowering, but their relative contributions to seed set are unclear. In this study, a 2-year field experiment including three sowing dates in each year and 20 inbred lines was conducted. Seed set, kernel number per ear, and grain yield were all reduced by more than 80% in the third sowing dates compared to the first sowing dates. Pollen viability, silk emergence ratio, and anthesis–silking interval were the key determinants of seed set under heat stress; and their correlation coefficients were 0.89^***, 0.65^***, and –0.72^***, respectively. Vapor pressure deficit (VPD) and relative air humidity (RH) both had significant correlations with pollen viability and the silk emergence ratio. High RH can alleviate the impacts of heat on maize seed set by maintaining high pollen viability and a high silk emergence ratio. Under a warming climate from 2020 to 2050, VPD will decrease due to the increased RH. Based on their pollen viability and silk emergence ratios, the 20 genotypes fell into four different groups. The group with high pollen viability and a high silk emergence ratio performed better under heat stress, and their performance can be further improved by combining the improved flowering pattern traits.

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Soybean maize strip intercropping: A solution for maintaining food security in China

Jiang Liu, Wenyu Yang

2024, 23 (7): 2503-2506. DOI: 10.1016/j.jia.2024.02.001

Abstract （135） PDF in ScienceDirect

The practice of intercropping leguminous and gramineous crops is used for promoting sustainable agriculture, optimizing resource utilization, enhancing biodiversity, and reducing reliance on petroleum products. However, promoting conventional intercropping strategies in modern agriculture can prove challenging. The innovative technology of soybean maize strip intercropping (SMSI) has been proposed as a solution. This system has produced remarkable results in improving domestic soybean and maize production for both food security and sustainable agriculture. In this article, we provide an overview of SMSI and explain how it differs from traditional intercropping. We also discuss the core principles that foster higher yields and the prospects for its future development.

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