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Frontiers in Agronomy ·

Volume 8 - 2026 | https://doi.org/10.3389/fagro.2026.1859893

Impact of YHJ spraying on the mechanical and physiological properties of corn stalks under varied density conditions

  • Yongping Li1*corresponding author
  • Chang Zhang1
  1. College of Agronomy, Shanxi Agricultural University, Taiyuan, China
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Abstract

This study aims to investigate the effects of spraying YHJ on the mechanical and physicochemical properties of corn stalks under varying planting densities, elucidate its regulatory mechanisms, determine the optimal combination of YHJ application and planting density, and provide a theoretical foundation and appropriate chemical control measures for dense, high-yielding corn cultivation in experimental and neighboring areas. A two-factor randomized block design was employed, with planting density as the primary factor, consisting of four treatments: 60,000 plants/hm² (M1), 67,500 plants/hm² (M2), 75,000 plants/hm² (M3), and 82,500 plants/hm² (M4). The secondary factor included two levels: spraying with YHJ and a control treatment using an equal amount of water (CK). Agronomic traits, mechanical properties, enzyme activity, and yield were measured at different growth stages. (1) YHJ treatment significantly reduced the plant height, ear height, and center of gravity height of maize compared to the CK treatment at the same density level. Under M3 density conditions, maize treated with YHJ exhibited the shortest basal internode length and the largest stalk diameter. (2) The mechanical properties of maize stalks were significantly enhanced by YHJ treatment. Specifically, under M3 density conditions, the average rind penetrometer resistance(RPR), stalk crushing strength(SCS), and stem breaking strength(SBS) of maize basal internodes 3, 4, and 5 reached their maximum values of 56.84 N/mm², 456.67 N/mm², and 453.06 N/mm², respectively. (3) At the M3 density level, spraying YHJ increased PAL, TAL, and CAT enzyme activities by 48.00%, 88.89%, and 67.79% over the control, while POD enzyme activity decreased by 17.16%. (4) Under M3 density conditions, spraying YHJ resulted in the highest yield of 13,084.02 kg/hm², representing a 0.63% increase compared to the control. Spraying YHJ under M3 density (75,000 plants/hm²) is the optimal combination, effectively improving agronomic traits, mechanical properties, and enzyme activities of maize stalks, ultimately achieving higher yields.

Keywords

1 Introduction

As one of the most important food crops both in China and globally, maize plays a pivotal role in ensuring food security (Yinjun et al., 2019). According to the Food and Agriculture Organization of the United Nations (FAO), the global population is projected to reach 8.5 to 10 billion by 2050, necessitating a 50% to 110% increase in global crop production from 2006 levels to meet rising food demands (Tester and Langridge, 2010; Dubois, 2011; Leaman, 2011; Tilman et al., 2011). However, maize faces significant challenges due to shrinking arable land, worsening rural labor shortages and aging populations, global climate change, and water scarcity. As the cereal with the largest gap between domestic demand and supply, maize has become increasingly critical for maintaining national food security and fulfilling market needs.

Reasonable dense planting is one of the key cultivation techniques to achieve high maize yields. Extensive research has demonstrated that planting density significantly influences corn yield (Chen et al., 2023; Zhang et al., 2022; Cao et al., 2021; Liu et al., 2021; Li et al., 2021). Within the optimal density range, as planting density increases, the number of leaves per unit area rises, enhancing photosynthesis and leading to a corresponding increase in yield (Tollenaar and Lee, 2002). However, when density surpasses the critical threshold, competition for light, water, and nutrients intensifies among plants, resulting in abnormally tall, thin, and weak stalks with a lowered center of gravity, ultimately leading to lodging (Liu et al., 2010; Tokatlidis and Koutroubas, 2004). Corn lodging can be classified into three types: root lodging, stem lodging, and stem breakage, with stem lodging having the most severe impact on yield, potentially causing substantial economic losses or total crop failure. Moreover, stem lodging disrupts the vascular system within the stalk, impeding the normal transport of nutrients and water, which not only complicates harvesting but also diminishes kernel quality and commercial value.

The mechanical properties and morphological characteristics of maize stalks are intricately linked to their resistance to lodging. Research has demonstrated that key factors influencing corn’s lodging resistance include rind penetrometer resistance (RPR), stalk crushing strength (SCS), plant height, ear height, stalk diameter, basal internode length, and internode thickness (Pickett et al., 1969; Guang et al., 2010). Notably, there is a highly significant positive correlation between the third internode’s phenylalanine ammonia-lyase(PAL) activity and lignin content and the stalk’s resistance to lodging (Xu et al., 2019; Zhao et al., 2022). Presently, most studies on maize lodging resistance focus on agronomic and mechanical traits, while the mechanisms by which physiological and biochemical indicators, such as enzyme activities within the stalks, influence lodging resistance remain relatively underexplored.

Plant growth regulators, a class of compounds that modulate the balance and metabolism of endogenous hormones in plants, exhibit significant potential for enhancing crop resistance and yield (Dong et al., 2014; Jisha et al., 2013; Xue-Hui et al., 2006; Meng-Zhu et al., 2017; Wu et al., 2024). YHJ, specifically formulated for corn, is a plant growth regulator composed primarily of ethephon and aminohydrin. Research has demonstrated that YHJ application effectively reduces plant height and ear height, shortens internode length, increases internode dry weight, and lowers the plant’s center of gravity. Consequently, it significantly enhances lodging resistance and demonstrates a notable yield-increasing effect under dense planting conditions, making it an efficient chemical regulator (Wei et al., 2015).

This study employs the Qiangsheng 192 corn variety as the test material, conducting a two-year positioning trial to systematically investigate the effects of YHJ spraying on corn stalk growth indices, folding strength, and related physicochemical properties under varying planting densities. The research delves into the regulatory mechanisms of these effects, aiming to identify the optimal combination of YHJ application and planting density. This will provide a robust theoretical foundation and technological support for high-yield cultivation of corn in dense planting conditions in Shanxi Province and neighboring regions.

2 Materials and methods

2.1 Experimental materials

The maize variety Qiangsheng 192, provided by Shanxi Qiangsheng Seed Industry Co. Ltd., was selected for this experiment. This variety is classified as a medium-late maturity type suitable for spring sowing in Shanxi, with a fertility period of approximately 128 days, which is one day longer than the control variety, Xianyu 335. The plant exhibits a semi-compact growth habit, featuring 20–21 leaves, a plant height of 257 cm, and an ear position at 105 cm. The ear type is cone to cylinder-shaped, with a red rachis, an average ear length of 18.7 cm, and 16–18 kernel rows. The kernels are yellow and dent-type, with a weight of 39.8 g per 100 kernels and a seed set rate of 86.7%.

The chemical control agent used in the experiment was 30% diethyl aminoethyl hexanoate·ethephon AS(YHJ).

2.2 Overview of the test site

The multi-year field experiment was physically conducted at the established Dongyang Experimental Base, operated by Shanxi Agricultural University. This region experiences a warm temperate semi-humid continental monsoon climate. While the historical average annual baseline temperature is 9.7 °C with a reliable frost-free agricultural period of 158 days, the actual environmental conditions during the maize growing season (from late April to late September) exhibited significant temperature fluctuations. During the critical reproductive periods across the 2024–2025 seasons, the monthly average temperatures ranged from approximately 15.7 °C to 25.0 °C, with absolute maximum and minimum daily average temperatures recorded at roughly 28.8 °C and 9.6 °C, respectively. The primary rainy season aligns synchronously with the region’s hot season. Comprehensive weather tracking recorded 240.1 mm of concentrated precipitation (specifically during the 2024 growing season), which primarily occurred throughout July and August. Pre-trial soil analysis of the 0–20 cm tillage layer on April 28, 2024, revealed an organic matter content of 14.847 g/kg, total nitrogen content of 0.587 mg/kg, available phosphorus content of 28.79 mg/kg, available potassium content of 274.54 mg/kg, and a pH value of 8.26.

2.3 Design and management of field trials

The test variety for this trial was Qiangsheng 192, and the test agent was a 30% Amine ethephon (YHJ). As illustrated in Figure 1,The experiment employed a two-factor randomized block design, with planting density as the primary factor, comprising four levels: M1 (60,000 plants/hm²), M2 (67,500 plants/hm²), M3 (75,000 plants/hm²), and M4 (82,500 plants/hm²). and the sub-area for the YHJ(YHJ) spraying treatment and the clear water control (CK). Each plot measured 10 m in length and 4 m in width, covering an area of 40 m², with three replications. YHJ was applied to corn at the jointing stage, strictly following the product instructions or professional guidance to ensure uniform coverage on both leaf surfaces. All other field management practices, including fertilization and plowing, were consistent with standard field procedures. This experiment was conducted from 2024 to 2025. The data presented in the charts in the text are the average values of the two-year period.

Experimental design drawing.
Figure 1. Experimental design drawing.

2.4 Measurement items and methods

2.4.1 Measurement of plant agronomic traits indicators

Plant height, ear height, center of gravity height, internode length, and internode diameter were measured.

At the early stage of corn grain filling, plant height (cm), ear height (cm), and center of gravity height (cm, Figure 2) were measured using a tower ruler. The coefficient of ear position was then calculated. Additionally, a vernier caliper was used to measure the internode length (cm) and internode diameter (mm) at nodes 3, 4, and 5 above ground. Five consecutive plants in each plot were measured for these parameters.

Center of gravity height measurement.
Figure 2. Center of gravity height measurement.

2.4.2 Determination of stem mechanical indices

Rind penetrometer resistance(RPR), stalk crushing strength(SCS), and stem breaking strength(SBS).

RPR: During the early stage of corn grain filling, three representative corn plants were selected from different treatments. Using the YYD-1 stalk strength tester manufactured by Zhejiang Top Instrument Co., Ltd. Specifically, a test head with a cross-sectional area of 0.01 cm² was inserted into the middle sections of the 3rd, 4th, and 5th nodes at a constant slow speed perpendicular to the stalk axis until rupture occurred. The readings were recorded. This procedure was repeated three times for each node, and the average value was calculated.

SCS: During the early stage of corn grain filling, three representative corn plants were selected for each treatment. The roots were removed in the field, and the internodes of the stalks were separated. Using the YYD-1 stalk strength tester manufactured by Zhejiang Top Instrument Co., Ltd., the 3rd, 4th, and 5th internodes from the base of the stalk were placed horizontally in the tester’s groove. The stalks were pressed down quickly to induce bending, and the corresponding values were recorded. This procedure was repeated three times, and the average value was calculated.

SBS: During the early stage of corn grain filling, three representative corn plants were selected from each treatment group. The plants were excavated in the field, and their roots were removed. Subsequently, the basal stem nodes were separated. The 3rd, 4th, and 5th nodes of the basal stem were placed horizontally in the groove of the YYD-1 type stalk strength tester manufactured by Zhejiang Topu Instrument Co., Ltd. The stem was rapidly pressed until it fractured, and the corresponding force value was recorded. This procedure was repeated three times for each plant, and the average value was calculated.

2.4.3 Measurement of culm physiological traits

The activities of phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), peroxidase (POD), and catalase (CAT) in the culm were measured.

At V12, VT, R2, and R6, ten representative and uniformly growing plants were selected from each plot. A 4 cm segment from the middle of the third internode, was excised and stored at -80 °C for subsequent analysis.

2.4.4 Yield measurement in the field and indoor seed testing

At harvest, the middle two rows of each plot were selected for yield measurement. The total number of plants, the number of fallen plants, and the actual number of spikes harvested were recorded to calculate the lodging rate (lodging rate = number of fallen plants/total number of plants × 100%). Concurrently, thirty spikes were randomly sampled, naturally air-dried until moisture content was below 20%, for indoor seed testing. This included measuring the spike length (cm), awnless tip length (cm), and spike count, as well as determining the mass of one hundred grains (g) after threshing and air-drying, and to calculate the seed yield based on a moisture content of 14% in the grains, by integrating data from both the laboratory tests and field yield measurements.

2.5 Data processing

The experimental data were analyzed using DPS 7.05 software and subsequently plotted using Microsoft Excel 2007.

3 Results and discussion

3.1 Effect of planting density and YHJ on agronomic traits of maize stalks

As shown in Table 1, with the increase in planting density, both the CK treatment and YHJ treatment exhibited a trend where plant height and center of gravity height initially increased and then decreased, reaching their maximum values at the M3 density level. In contrast, spike height and the coefficient of ear position showed a consistently increasing trend.

Table 1. Effects of density and YHJ on agronomic traits of maize stalks.

Density (Plants/hm2)TreatmentPlant height (cm)Ear height (cm)Ear height coefficientCenter of gravity height (cm)
M1CK231.00 ± 2.83 b64.17 ± 0.71 f0.28 ± 0.00 b75.75 ± 0.12 b
YHJ211.67 ± 2.36 e61.17 ± 0.71 g0.29 ± 0.01 ab66.67 ± 0.47 e
M2CK235.50 ± 2.59 ab68.17 ± 0.24 d0.29 ± 0.02 ab80.50 ± 3.06 a
YHJ221.83 ± 2.59 c64.67 ± 0.00 f0.29 ± 0.02 ab71.00 ± 0.94 cd
M3CK239.00 ± 2.83 a70.50 ± 0.71 c0.29 ± 0.03 ab81.00 ± 1.89 a
YHJ226.00 ± 2.83 c66.17 ± 0.71 e0.29 ± 0.04 ab73.00 ± 2.36 bc
M4CK234.83 ± 1.65 ab77.50 ± 0.71 a0.33 ± 0.04 ab76.17 ± 0.71 b
YHJ217.00 ± 0.00 d74.33 ± 0.94 b0.34 ± 0.04 a69.00 ± 1.89 de

After the same column of data, different lowercase letters indicate that the difference between different treatments is significant at 0.05 level. The following table is the same.

The plant height, ear height, and center of gravity height of maize were significantly lower (P<0.05) under the YHJ treatment compared to the CK treatment at the same planting density. However, the effect of YHJ varied with different planting densities. As planting density increased, the plant height of maize decreased by 8.37%, 5.80%, 5.44%, and 7.59%; ear height decreased by 4.68%, 5.13%, 6.15%, and 4.09%; and the center of gravity height decreased by 11.99%, 11.80%, 9.88%, and 9.41%, respectively, relative to the corresponding densities in the CK treatment. These results indicate that applying YHJ can effectively reduce maize plant height, ear height, and center of gravity height.

3.2 Effects of density and YHJ on the length of corn stalk internodes

As illustrated in Figure 3, with increasing planting density, the lengths of the 3rd, 4th, and 5th internodes of maize under the CK treatment exhibited a gradual increase. Under identical density conditions, the internode lengths followed the order: 3rd internode < 4th internode < 5th internode.

Effect of density and YHJ on internode length of maize stalks.
Figure 3. Effect of density and YHJ on internode length of maize stalks.

The 3rd, 4th, and 5th internode lengths of maize under the YHJ treatment were significantly shorter than those under the CK treatment at the same density level. However, the effect of YHJ on internode length reduction varied across different density conditions. Specifically, the shortening effect was more pronounced under M3 and M4 densities compared to M1 and M2 densities. Additionally, the degree of internode length reduction under the YHJ treatment followed the order: 3rd internode < 4th internode < 5th internode. These findings indicate that applying YHJ can effectively reduce the length of basal internodes in maize stalks, with the shortest internode lengths observed under M3 density.

3.3 Effects of density and YHJ on stalk thickness of corn stalks

As illustrated in Figure 4, under the CK treatment, both the long-axis and short-axis diameters of maize stalks exhibited a gradual decrease as planting density increased. Additionally, these diameters shortened with an increase in the number of internodes.

Effect of density and YHJ on corn stalk diameter. Lowercase letters above the bars indicate statistically significant differences between different treatments at the P < 0.05 level based on Duncan’s multiple range test. Bars sharing the same letter are not significantly different at P \ge 0.05.
Figure 4. Effect of density and YHJ on corn stalk diameter. Lowercase letters above the bars indicate statistically significant differences between different treatments at the P < 0.05 level based on Duncan’s multiple range test. Bars sharing the same letter are not significantly different at P \ge 0.05.

Under the YHJ treatment, the long-axis and short-axis diameters of the 3rd, 4th, and 5th internodes were significantly larger compared to those under the CK treatment at the same density levels. Notably, the effect of YHJ on increasing the diameter of basal internodes was more pronounced under M3 and M4 density conditions than under M1 and M2 conditions. These findings suggest that applying YHJ can effectively enhance the stem thickness of basal internodes in corn stalks. Specifically, the long-axis and short-axis diameters of the 3rd, 4th, and 5th basal internodes treated with YHJ reached their maximum values under the M3 density condition.

3.4 Effect of density and YHJ on mechanical properties of corn stalks

3.4.1 RPR

As illustrated in Figure 5, RPR of corn stalks exhibited a gradual decline with increasing planting density under CK treatment. Moreover, RPR of corn stalks also progressively decreased as the number of internodes increased.

Effect of density and YHJ on RPR of maize stalk crust. Lowercase letters above the bars indicate statistically significant differences between different treatments at the P < 0.05 level based on Duncan’s multiple range test. Bars sharing the same letter are not significantly different at P \ge 0.05.
Figure 5. Effect of density and YHJ on RPR of maize stalk crust. Lowercase letters above the bars indicate statistically significant differences between different treatments at the P < 0.05 level based on Duncan’s multiple range test. Bars sharing the same letter are not significantly different at P \ge 0.05.

Under the YHJ treatment, RPR of the 3rd, 4th, and 5th internodes of maize was significantly higher than that under the CK treatment at the same density level. Notably, under M3 and M4 density conditions, the enhancement effect of YHJ on RPR of maize basal internodes was markedly greater compared to M1 and M2 density conditions. Under M3 and M4 density conditions, RPR of the basal internodes in the YHJ treatment showed a significant difference from that in the CK treatment. These findings suggest that applying YHJ can effectively increase RPR of maize basal internodes, with the maximum strength observed under the M3 density condition.

3.4.2 SCS

As illustrated in Figure 6, under CK treatment, SCS of corn stalks exhibited a gradual decline as planting density increased. Furthermore, SCS of corn stalk sclerotinia also showed a progressive reduction with an increase in the number of internodes.

Effects of density and YHJ on SCS of maize stalk crust. Lowercase letters above the bars indicate statistically significant differences between different treatments at the P < 0.05 level based on Duncan’s multiple range test. Bars sharing the same letter are not significantly different at P \ge 0.05.
Figure 6. Effects of density and YHJ on SCS of maize stalk crust. Lowercase letters above the bars indicate statistically significant differences between different treatments at the P < 0.05 level based on Duncan’s multiple range test. Bars sharing the same letter are not significantly different at P \ge 0.05.

Under the YHJ treatment, SCS in the 3rd, 4th, and 5th internodes of maize was significantly higher than that under the CK treatment at the same density level. Notably, under M3 and M4 density conditions, the enhancement effect of YHJ on SCS of basal internodes was significantly greater compared to M1 and M2 density conditions. Under M3 and M4 density conditions, there was a significant difference in SCS of the basal internodes between the YHJ treatment and the CK treatment. These results indicate that applying YHJ can effectively increase SCS of basal internodes in corn stalks, with the maximum strength observed under M3 density conditions.

3.4.3 SBS

As illustrated in Figure 7, under CK treatment, SBS of corn exhibited a gradual decline as planting density increased. Moreover, SBS of maize stalks also progressively diminished with an increase in the number of internodes.

Effect of density and YHJ on SBS of maize stalk crust. Lowercase letters above the bars indicate statistically significant differences between different treatments at the P < 0.05 level based on Duncan’s multiple range test. Bars sharing the same letter are not significantly different at P \ge 0.05.
Figure 7. Effect of density and YHJ on SBS of maize stalk crust. Lowercase letters above the bars indicate statistically significant differences between different treatments at the P < 0.05 level based on Duncan’s multiple range test. Bars sharing the same letter are not significantly different at P \ge 0.05.

Under the YHJ treatment, SBS of maize 3rd, 4th, and 5th internodes was significantly higher than that of the CK treatment at the same density level. Specifically, under M3 and M4 density conditions, the enhancement effect of YHJ on SBS of basal internodes was notably more pronounced compared to M1 and M2 density conditions. Under M3 and M4 density conditions, there was a significant difference in SBS of basal internodes between the YHJ treatment and the CK treatment. These findings suggest that applying YHJ can effectively enhance SBS of basal corn internodes, with the maximum improvement observed under M3 density conditions.

3.5 Effects of density and YHJ on phenylalanine ammonia-lyase activity in corn stalks

As illustrated in Figure 8, PAL activity in maize stalks exhibited an increasing and then decreasing trend during the growth and development process, peaking in the R2 stage. Within the same reproductive period, as planting density increased, PAL activity in maize stalks similarly showed an increasing and then decreasing pattern, reaching its peak at the M3 density level.

Effects of density and YHJ on activity in maize stalks. V12, VT, R2, and R6 represent the twelve-leaf stage, tasseling stage, grain filling stage, and maturity stage, respectively. This notation applies consistently throughout. Lowercase letters above the bars indicate statistically significant differences between different treatments at the P < 0.05 level based on Duncan’s multiple range test. Bars sharing the same letter are not significantly different at P \ge 0.05.
Figure 8. Effects of density and YHJ on activity in maize stalks. V12, VT, R2, and R6 represent the twelve-leaf stage, tasseling stage, grain filling stage, and maturity stage, respectively. This notation applies consistently throughout. Lowercase letters above the bars indicate statistically significant differences between different treatments at the P < 0.05 level based on Duncan’s multiple range test. Bars sharing the same letter are not significantly different at P \ge 0.05.

During the reproductive stages of V12, VT, R2, and R6, the PAL activity in maize stalks treated with YHJ was significantly higher than that of the control at various densities (P<0.05). This indicates that YHJ treatment effectively enhances PAL activity. Specifically, during the R2 stage, as planting density increased, PAL activity in the YHJ treatment rose by 73.91%, 37.70%, 48.00%, and 38.30% compared to the CK treatment. These results demonstrate that YHJ application can significantly boost PAL activity across all fertility periods, particularly reaching its peak during the R2 stage when applied at the M3 density level.

3.6 Effects of density and YHJ on tyrosine aminotransferase activity in corn stalks

As illustrated in Figure 8, TAL activity in maize stalks exhibited an increasing and then decreasing trend during its growth and development, peaking in the R2 period. Within the same reproductive stage, as planting density increased, TAL activity in maize stalks also followed an increasing and then decreasing pattern, reaching its peak at the M3 density level.

During the reproductive stages of V12, VT, R2, and R6, the TAL activity in corn stalks treated with YHJ was significantly higher than that of the control group at various planting densities (P<0.05). This indicates that YHJ treatment can substantially enhance TAL activity. Specifically, during the R2 stage, as planting density increased, the TAL activity in the YHJ treatment rose by 87.62%, 82.14%, 88.89%, and 53.85% compared to the CK treatment, respectively. These results demonstrate that the application of YHJ effectively boosts TAL activity in corn stalks. Notably, at the M3 density level, TAL activity was significantly elevated across all fertility periods, reaching its peak during the R2 stage.

3.7 Effects of density and YHJ on peroxidase activity in corn stalks

As illustrated in Figure 8, the POD activity within maize stalks exhibited a gradual increase during the growth and development phase, peaking at the R6 stage. Within the same reproductive period, as planting density increased, POD activity in maize stalks initially rose and then declined, reaching its maximum at the M3 density level.

During the reproductive stages of V12, VT, R2, and R6, the POD activities in corn stalks treated with YHJ were significantly lower than those in the control group at various planting densities (P<0.05), indicating that YHJ effectively inhibited POD activity. Specifically, as planting density increased, the POD activity in the R6 stage decreased by 9.69%, 11.04%, 17.16%, and 16.56% compared to the control treatment (CK). These results demonstrate that YHJ can significantly reduce POD activity in corn stalks, particularly when applied at the M3 density level, where inhibition was most pronounced during the ripening period (R6).

3.8 Effects of density and YHJ on catalase activity in corn stalks

As illustrated in Figure 8, CAT activity within corn stalks exhibited an initial increase followed by a decrease during the growth and development process, peaking during the VT period. Within the same reproductive phase, as planting density increased, CAT activity in maize stalks similarly showed an upward trend followed by a decline, with the highest activity observed at the M3 density level.

During the reproductive stages of V12, VT, R2, and R6, the CAT activities in corn stalks treated with YHJ were significantly higher than those in the control group at various planting densities (P<0.05). This indicates that YHJ treatment can significantly enhance CAT activity in corn stalks. Specifically, during the VT period, as planting density increased, CAT activity in the YHJ treatment rose by 46.72%, 64.01%, 67.79%, and 58.94% compared to the control treatment (CK). These results demonstrate that the application of YHJ effectively increases CAT activity in corn stalks. Notably, CAT activity was significantly elevated across all fertility periods when YHJ was applied at the M3 density level, reaching its peak during the VT period.

3.9 Effects of density and YHJ on corn yield and lodging rate

As illustrated in Table 2, as planting density increased, the bald tip length of maize initially decreased and then increased. In contrast, ear length, the number of grains per ear, and the weight of 100 grains exhibited a consistent downward trend. Yield traits followed a pattern of initial increase followed by a decrease, peaking at the M3 density level. Compared to other density levels, the differences in yield and other ear biological traits were statistically significant (P<0.05) under the M3 density level treatment.

Table 2. Effects of density and YHJ on maize yield and lodging rate.

DensityTreatmentBare top length (cm)Ear length(cm)Ear grain number100-grain weight(g)Yield (kg·hm-2)The lodging rate/%
M1CK1.40 ± 0.03 b19.5 ± 0.28 a660.72 ± 6.32 a46.33 ± 0.60 a10236.92 ± 20.78 g3.42
YHJ1.60 ± 0.07 a19.46 ± 0.24 a649.49 ± 4.73 ab44.35 ± 0.42 b9614.84 ± 24.39 h3.53
M2CK1.26 ± 0.03 c19.4 ± 0.32 a647.49 ± 9.32 abc43.38 ± 0.18 c12313.94 ± 21.80 c4.02
YHJ1.27 ± 0.05 c19.37 ± 0.01 ab640.56 ± 9.14 bcd43.33 ± 0.39 c11274.53 ± 12.23 d4.11
M3CK1.11 ± 0.08 d18.88 ± 0.16 c633.35 ± 9.48 d43.75 ± 0.78 bc13002.75 ± 22.51 b7.02
YHJ0.91 ± 0.06 e18.93 ± 0.29 bc635.92 ± 3.17 cd43.98 ± 0.46 bc13084.02 ± 17.88 a6.65
M4CK1.37 ± 0.02 b18.35 ± 0.03 d599.86 ± 3.25 e42.18 ± 0.53 d10381.19 ± 13.94 f19.36
YHJ1.33 ± 0.02 bc18.83 ± 0.24 c612.20 ± 4.82 e43.63 ± 0.25 bc10742.36 ± 15.35 e16.12

Different lowercase letters within the same column indicate statistically significant differences among treatments at the P < 0.05 level based on Duncan's multiple range test.

The yields at different densities were M3 > M2 > M4 > M1. At low density, the bald tip length of the YHJ treatment was significantly elongated, resulting in lower yields and poorer spike biology compared to the CK treatment at the same density, with an increased lodging rate. Conversely, at high density, the bald tip length of the YHJ treatment was significantly shortened, leading to higher yields and improved spike biology relative to the CK treatment at the same density, with a decreased failure rate. Under M3 density conditions, spraying YHJ increased yield by 0.63% and 100-grain quality by 0.51% compared to the CK treatment. These results indicate that applying YHJ under appropriate density conditions can effectively reduce the length of corn bald tips, enhance ear length, grain number, and 100-grain quality, thereby increasing yield. Additionally, the application of YHJ at M3 density significantly reduced maize lodging rate, further enhancing maize yield.

3.10 Correlation analysis between agronomic traits, physiological and biochemical indicators of corn stalks, and their mechanical strength

As illustrated in Figure 9, this study conducted a correlation analysis between the agronomic traits, physiological and biochemical indices of corn stalks and their mechanical strength. The results indicated that the internode lengths at nodes 3 and 5 were significantly negatively correlated (P<0.05) with both compressive and flexural strengths. Conversely, the long axis diameters at nodes 3 and 4, along with the short axis diameters at nodes 3 and 5, exhibited significant positive correlations (P<0.05) with SCS and SBS. These findings suggest that the geometric characteristics of corn stalks are closely associated with their mechanical strength and can serve as a critical indicator for evaluating the resistance of maize stalks to buckling.

Correlation analysis between agronomic traits, physiological and biochemical indices of maize stalks, and mechanical strength of stalks.
Figure 9. Correlation analysis between agronomic traits, physiological and biochemical indices of maize stalks, and mechanical strength of stalks.

In terms of physiological and biochemical indices, phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), and peroxidase (POD) activities were significantly and positively correlated (P<0.05) with SCS of section 5. Additionally, these enzyme activities exhibited positive correlations with RPR of section 4 and SCS of sections 3, 4, and 5. Notably, PAL and TAL activities were specifically correlated with RPR of section 3. CAT activity demonstrated a significant positive correlation (P<0.05) with the SCS of sections 3, 4, and 5, as well as SBS of section 4. Furthermore, CAT activity was positively correlated with RPR of sections 3 and 5 and SBS of section 5. These *findings provide strong evidence for the close relationship between the activities of PAL, TAL, POD, and CAT enzymes and the mechanical properties of maize stalks.

4 Discussion

4.1 Effects of planting density and YHJ on agronomic traits of maize stalks

Different planting densities significantly influenced the agronomic traits of corn stalks. According to Bian et al. (2015; 2023), as planting density increased, maize plant height and ear height also increased significantly, while stem thickness, RPR, and SBS decreased markedly. Furthermore, Zhang et al. (2023) observed that higher planting densities led to a significant decrease in plant height and ear height for the tested maize varieties, an increase in the length of the bald tip, a reduction in ear thickness, and a declining trend in ear traits such as ear length and the weight of 100 kernels. Yao et al. (2015) found that high-density cultivation resulted in inadequate light supply within the population, leading to a significant increase in plant height, ear height, and center of gravity height, thereby increasing the maize lodging rate. Zheng et al. (2021) demonstrated that spring maize plant height and ear height initially increased and then decreased with increasing density. These findings collectively indicate that agronomic traits such as plant height, ear height, center of gravity height, internode length, and stem thickness are highly sensitive to changes in planting density.

Wang Chunpeng’s (2023) study demonstrated that chemical regulation significantly enhances corn’s lodging resistance. This improvement is evidenced by a substantial reduction in summer corn plant height, basal internode length, and an increased basal internode thickness ratio. Additionally, the SBS and the RPR were significantly higher compared to the control group, resulting in a more than 50% decrease in field lodging rates, particularly under high-density conditions. Jin-Jun et al. (2015) found that different chemical regulators effectively reduce corn plant height and ear height, shorten basal internode length, and increase basal stem thickness, thereby enhancing the corn’s lodging resistance. Yang (2016) reported that applying YHJ reduces plant height and ear height while increasing single-plant dry matter accumulation. It also significantly increases the internode diameter at the third, fifth, and seventh nodes, shortens internode length, and enhances the dry matter weight and tensile strength of each node, thus significantly improving the corn’s lodging resistance.

The results of this experiment demonstrate that the application of YHJ significantly reduces corn plant height, ear height, and lowers the plant’s center of gravity. Additionally, it shortens the basal internode length while increasing the basal internode stem thickness. Under M3 density conditions, corn treated with YHJ exhibited the shortest basal internode length, with the diameters of the long and short axes of the 3rd, 4th, and 5th nodes reaching their maximum values, which aligns with previous research findings.

4.2 Effects of density and YHJ on the mechanical properties of corn stalks

Maize stalk strength is closely associated with planti ng density, serving as a critical indicator for evaluating maize’s resistance to failure. Jiang et al. (2022) demonstrated that maize RPS was significantly correlated with yield and influenced by planting density. Xu et al. (2023) observed that RPR, SCS, and SBS of corn stalks decreased as planting density increased. Wu et al. (2021) further indicated that planting density had a decisive impact on SCS, which also diminished with higher density. Collectively, these studies highlight that increasing planting density notably reduces the mechanical properties of corn stalks. However, in practical agricultural settings, density should not be indiscriminately increased solely to boost yield; instead, the crop’s adaptability to high-density conditions must be considered to mitigate lodging rates.

The results of this experiment demonstrated that spraying YHJ significantly enhances the mechanical properties of corn stalks. Under the M3 density condition, RPR, SCS, and SBS of the 3rd, 4th, and 5th basal nodes of maize treated with YHJ reached their peak values. This suggests that applying YHJ at an appropriate density can effectively mitigate the degradation of stalk mechanical properties associated with increased planting density, thereby reducing lodging rates and improving yield.

4.3 Effects of density and YHJ on corn stalk enzyme activity

Currently, there is a wealth of research on the physicochemical properties of maize stalks; however, fewer studies have explored the relationship between their lodging resistance and their internal chemical composition. In this study, it was observed that the activities of phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), and catalase (CAT) in maize stalks initially increased and then decreased with increasing planting density, reaching peak levels at M3 density. The application of YHJ significantly enhanced PAL, TAL, and CAT activities. Conversely, peroxidase (POD) activity followed a similar trend of initial increase followed by decrease with increasing density, but YHJ treatment notably suppressed POD activity.

Studies have demonstrated that POD functions synergistically with superoxide dismutase (SOD) and catalase (CAT) to form an enzymatic defense system in plants under adverse conditions, thereby enhancing plant stress tolerance by scavenging excess free radicals (Wei et al., 2020; Yun-Fen et al., 2019). Moreover, POD, TAL, and PAL are critical enzymes involved in lignin synthesis (Long et al., 2021; Chen et al., 2011). The findings of this experiment revealed that spraying YHJ at M3 density conditions could maximize the activities of PAL, TAL, and CAT while inhibiting POD activity. This modulation of enzyme activities improves maize stress tolerance, promotes lignin synthesis, and ultimately enhances maize’s lodging resistance under high-density conditions, leading to increased yield.

4.4 Effects of density and YHJ on corn yield and lodging rate

Dong et al. (2008) demonstrated that spraying corn with an appropriate concentration of YHJ at the 8-leaf stage could lead to increased yields. Jin-Tao et al. (2009) observed that for Zhongdan 808, when planting density reached or exceeded 75,000 plants/hm², the application of chemical control agents significantly reduced lodging rates and enhanced yield. Cheng-Hao et al. (2011) reported that for Danyu 39 planted at a density of 52,500 plants/hm², chemical control treatments markedly increased yield compared to the control group, particularly under adverse weather conditions. The findings of this experiment align closely with these previous studies: under low-density conditions, the yield from the YHJ treatment was marginally lower than the control; however, under high-density conditions, the YHJ treatment led to a significant increase in yield, with the highest yield observed under M3 density conditions.

This experiment examined the effects of spraying YHJ on corn yield and its components at varying planting densities. The results demonstrated that as density increased, both the number of grains per ear and the 100-grain mass gradually decreased, leading to a seed yield trend that initially increased and then declined, consistent with previous findings (Trachsel et al., 2016). This indicates that exceeding a certain planting density threshold adversely affects population seed yield. However, under M3 density conditions, spraying YHJ significantly reduced the length of corn bald tips, increased ear length, grain count per ear, and 100-kernel quality, thereby substantially enhancing corn yield.

5 Conclusion

Under M3 planting density, spraying YHJ significantly regulated the morphology, mechanical properties, physicochemical properties, and yield composition of maize. Specifically: (1) plant shape optimization, where YHJ treatment notably reduced plant height and ear height, lowered the center of gravity, shortened basal internode length, and increased stalk diameter; (2) mechanical characteristics, where RPR, SCS, and SBS of maize basal internodes 3, 4, and 5 were significantly enhanced; (3) physicochemical properties, where activities of phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), and catalase (CAT) were significantly increased, while peroxidase (POD) activity was significantly inhibited; (4) yield components, where maize bald tip length was significantly reduced, cob length, cob kernel number, and 100-kernel weight were significantly increased, leading to the highest final kernel yield.

Based on the study results, the synergistic effect of M3 density and YHJ treatments significantly enhanced corn’s lodging resistance and its yield potential. These findings provide a theoretical foundation for high-yield and lodging-resistant maize cultivation, recommending large-scale demonstration and promotion in similar ecological regions.

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Footnotes

Edited by: Stéphane Cordeau, UMR Agroécologie, France

Reviewed by: Miftakhul Bakhrir Rozaq Khamid, Universitas Singaperbangsa Karawang, Indonesia

Alejandro Hernández-López, Secretaría de Ciencia Tecnología e Innovación, Mexico

Statements

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Funding

The author(s) declared that financial support was received for this work and/or its publication. The research leading to these results received funding from Central Guidance for Local Science and Technology Development Fund Project (YDZJSX20231B008). All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript.

Data availability

The original contributions presented in the study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding author.

Author contributions

YL: Writing – original draft, Writing – review & editing. CZ: Writing – original draft.

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Citation

Li, Y. & Zhang, C. (2026). Impact of YHJ spraying on the mechanical and physiological properties of corn stalks under varied density conditions. Frontiers in Agronomy, Volume 8. https://doi.org/
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Copyright © 2026 Li and Zhang.

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*Correspondence: Yongping Li

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