Introduction

Roots system of plants is a fundamental component of the rhizosphere and plays a key role in supplying water and nutrients to the soil1. In addition, aboveground biomass production is highly dependent on plant roots2. Root growth and its distribution in the soil determine the crop’s nutrient absorption and water extraction capabilities3,4. Improving the plant’s root system allows the plant to uptake the soil moisture contents, nutrients, and minerals5. It is expected that approximately 49% of yield increases are due to variations in crop management practices, and the remaining 51% is due to genetic improvement6. Plant growth regulators that can decrease lodging and increase kernel weight are the key to increase productivity7. Lodging reduces water transport, nutrients, and photosynthesis, resulting in reduced maize yield8. The lodging rate also negatively impacts kernel number and kernel weight per ear, reducing crop quality9. Maize lodging occurs mainly at the 3rd basal node at the seed filling stage, because carbohydrates in the stem are transported to the ear of maize10,11. Early senescence and lodging are directly linked to maize root growth12. Root system research is one of the vital factors to improve production and reduce lodging in dry-land farming systems13.

Adequate moisture content considerably increases root dry weight density per unit area14,15. Plant growth regulator (PGR) applications enhance root uptake of water and soil nutrients compared to traditional in-plant application methods16. Root pressure is an indication of root sap flow, and amounts of root sap exudation17. Root sap exudation depends on its intensity and root activity varies with soil water status, crop type, and growing season18. Root behavior is difficult to understand in field trials, and root sap exudation can be used to calculate root behavior and nutrient and water uptake19. Root lodging is affected by several factors, including root number, diameter, and growth direction20,21. Lignin content is the key component of stalks which have an important influence on stalk lodging rates22. The ethephon is an actual growth regulator that reduces the risk of lodging23. Ethephon can be used to reduce maize root height, improve mechanical strength, and increase root adhesion force24. The ethephon and cycocel effectively increase lodging resistance and endogenous hormone signaling25. DA-6 considerably reduced lodging rate, panicle, and plant height and increased stem penetration26. Therefore, solving the lodging problem in crops is the key to achieving stable high yield.

The application of PGR is an actual method to decrease lodging in maize and increase endogenous plant hormones27. Earlier research has shown that chemical conditioning plays an essential role in improving plant morphology, and stem bending strength, and thus reducing lodging rate18. The PGR can enhance the activity of lignin-related enzymes, increase lignin content, and improve lodging strength28. Ali et al.29 study that PGR promotes the development of corn plank roots and reduces root lodging. Yuhuangjin is the PGR which is a combination of DA-6 and ethephon, improving lodging resistance and yields30. Conventional tillage (CT) with crop residues offers the advantage of 5.8% higher yield, and 25.9% higher net profit21. In addition, minimum tillage and crop residues can improve the water available to plants31,32. Peng et al.33 showed that rotational tillage increases the WUE and yield of maize by improving plant uptake capacity. RT improved water infiltration and storage, increased soil moisture content, and improved plant drought tolerance29. Understanding the water-related mechanisms in different agricultural practices can help balance yield growth and sustainable use of resources in dry-land agricultural systems.

We assume that in semi-arid regions, the application of various tillage management practices combined with plant growth regulators can reduce the risk of corn lodging and promote yield formation. To confirm these assumptions, this experiment determined the effects of different tillage management practices combined with plant growth regulators on the physicochemical properties of corn stems, the morphological characteristics of roots, the molecular structure of vascular bundles, the content of endogenous hormones in root bleed sap, and yield. This study aims to provide a theoretical basis for corn lodging resistance and yield increase in semi-arid areas. The results of plant growth regulators are more conducive to agricultural production management.

Materials and methods

Site description

This field trial was conducted during the years 2021 and 2022 in Huan, China, which is located at a longitude of 107°21′ E and latitude of 36°20′ N. The annual average rainfall was 419 mm yr−1, and the temperature was 5.9 °C, while in July–September 59% of the precipitation occurred. The 40-year (1980–2020) average monthly precipitation and the monthly distributions of precipitation and temperature during the two years are shown in (Fig. 1). The soil at the experimental site was classified as light silt loam. The soil had 1.02 g kg−1 organic carbon, 1.70 g cm−3 bulk density, 21.84% field capacity (FC), respectively. The soil chemical properties are shown in Table 1.

Fig. 1
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Monthly rainfall distribution and air temperature during the maize-growing seasons in 2021and 2022 at the experimental site.

Table 1 The chemical properties of experimental site of the soil layers (0–20 cm).
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Field management

The field study adopted a randomized complete block design (RCBD) with three replications, and each plot area was 200 m2 (40 × 5 m). The field study included three tillage management measures: D: rotary tillage, R: conventional tillage, and B: reduced tillage. Rotary tillage included a rotary tillage depth of 15 cm, conventional tillage included a tillage depth of 25 cm, and reduced tillage included a surface tillage depth of 15 cm. There were two plant growth regulators, the Chinese trade name was E: Jindeli and the key active components were ethephon and cycocel, the dosage was 450 ml ha−1, the concentration was 2 ml EC/11H2O, and it was sprayed three times at the VT period. Y: Yujinhuang (a mixture of 27% ethephon and 3% DTA-6) (provided by Fujian Haolun Co., Ltd.) was used as a plant growth regulator, and it was sprayed three times during the VT period. CK: conventional tillage with water spraying (Table 2). Total nitrogen 180 kg ha−1 was continuously supplied to the field during the sowing, jointing, and flowering stages. The recommended PK 90 and 30 kg ha−1 apply at the day before sowing. Planting corn variety Dafeng No. 30 with a plant population of 75,000 plants ha−1, while sowing time is May 29, 2021, and June 1, 2022, with a row spacing of 60 cm. No irrigation water is supplied, but manual weeding is controlled. Wheat crop is grow before maize planting and supply recommended fertilization, irrigation with conventional tillage operations.

Table 2 Details of different number of treatments combination in experiment treatments details
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Maize canopy structure and stalk microstructure

Concerning the method of He et al.34, five plants were randomly selected from each plot at the dough stage to determine the center of gravity, panicle height, and panicle coefficient. To grasp the lodging rate in the field, all lodging plants in each plot were counted. Plants with an angle between the stem and the vertical axis exceeding 30° and straight and uninterrupted were root lodging, and plants with broken stems were stem lodging. The lignin content of the third basal internode (BN) was determined at various growth stages. The lignin content was analyzed according to the method of Wang et al.35. Concerning the method of Bian et al.36, at the dough stage to determine the ratio of ear height. The cross-sectional area, vascular bundles, stem microstructure, and cortical thickness, were determined by using a BX51 microscope from Beijing Olympus Corporation. The stem segment of 2 cm from the middle of the second basal internode was incised using a blade and subsequently immersed in a fixing solution (formaldehyde: acetic acid: 70% ethanol [1:1:18]) for preservation. The tissue slices were cut lengthwise with a blade and stained with 1% ferruginous red, and the large and small vascular bundles were quantified under a BX51 microscope from Beijing Olympus Corporation.

Root sampling and nutrients concentration in root-bleeding sap

The roots of each soil core of each treatment were then scanned using a scanner (Epson V700, Indonesia). These root images were further analyzed using WinRHIZO software version 5.0. According to Yang et al.37, the root bleeding sap collection method is most suitable for the collection of maize root sap. According to the study of Ali et al.29, the transport rate was expressed as ml h−1 root−1. The NH4+ and NO3− in the exuded root fluid were measured by an AA3 continuous flow analytical system.

Quantitative analysis of the beta model

Root growth rate and duration were calculated by beta model Yin et al.38

$$\begin{aligned} w = & w_{\max } \left( {1 + \frac{{t_{e} - 1}}{{t_{e} - t_{m} }}} \right)\left( {\frac{t}{{t_{e} }}} \right)^{{t_{e} /(t_{e} - t_{m} )}} \quad {\text{with}}\;0 \le 1 \\ & < 2t_{e} - t_{m} \quad {\text{and}}\quad 0 < 2t_{m} < t_{e} \\ \end{aligned}$$
(1)

Using this model, the average root growth rate (Ć) in the growth period was calculated by the following equation:

$$c = \frac{{w_{\max } }}{{t_{e} }}$$
(2)

The maximum root growth rate (cm) was determined by Yin et al.38.

$$c_{m} = \frac{{2t_{e} - t_{m} }}{{t_{e} \left( {t_{e} - t_{m} } \right)}}\left( {\frac{{t_{m} }}{{t_{e} }}} \right)^{{t_{m} /(t_{e} - t_{m} )}} w_{\max }$$
(3)

Morphological index of brace root

At the ear formation stage, five plants were selected from each plot, and the roots were excavated at the center of the plant, with row spacing of 1/2 the plant width and 1/2 the length. After rinsing the roots, the surface moisture was absorbed with tissue paper, and the number of root layers was counted. Fresh coltsfoot roots were dried at 80 °C to constant weight and the dry weight was measured. The flux of endogenous hormones was measured by using enzyme-linked immunosorbent assay (ELISA) Wang et al.35.

Statistical analysis

The experiments were carried out under a randomized complete block design (RCBD) with four replications. Data were pooled and the means and standard errors (SE) for the 2 years were calculated. Means were compared by analysis of variance (ANOVA) to test for significant differences (P < 0.05) between samples with different tillage management practices and plant growth regulators by using SPSS 19.0 software. Means were compared by using the least significant difference (LSD) test. Microsoft Excel 2010 was used to draw the figures (Fig. 2).

Fig. 2
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Effects of various tillage management practices combined with plant growth regulators on the lignin content (LC, mg g−1 FM) of the third basal internode (3rd BI) at the silking stage, grain filling stage and physiological maturity stage of maize during 2021 and 2022. Note: ED: Jindele spraying with rotary tillage; ER: Jindele spraying with conventional tillage; EB: Jindele spraying with minimum tillage; YD: Yuhuangjin spraying with rotary tillage; YR: Yuhuangjin with conventional tillage; YB: Yuhuangjin with minimum tillage; EYD: Jindele + Yuhuangjin spraying with rotary tillage; EYR: Jindele + Yuhuangjin spraying with conventional tillage; EYB: Jindele + Yuhuangjin with minimum tillage; CK: water spraying with conventional tillage. Vertical bars represent the standard error of the mean (SEM) (n = 3). Lowercase letters indicate significant differences at P ≤ 0.05 (LSD test).

Results

Lignin content and stem microstructure

Cortical thickness, small and large vascular bundles changed considerably (Table 3). Cortical thickness, cross-sectional area, large and small vascular bundles in the EYD treatment were 43.9%, 52.6%, 27.7%, and 36.1% greater than those in the CK treatment, respectively. Small vascular bundles were densely packed and big vascular bundles were well established in the EYD treatment. Cortical thickness, cross-sectional area, small and large vascular bundles all significantly improved in the rotary tillage and kindler growth regulator application treatments. Cortical thickness, cross-sectional area, small and large vascular bundles significantly improved in the EYD treatment than in the CK treatment. Cross-sectional area considerably increased by 36.9%, 49.8%, 22.5%, and 33.6%, respectively. Furthermore, the area of ​​ small and large vascular bundles could be improved when a plant growth regulator was applied under rotary tillage or conventional tillage conditions.

Table 3 Effects of various tillage management practices with plant growth regulators on stalk microstructure of maize during 2021–2022ab
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Ion composition and rate of root-bleeding sap

In the two study years, at several growth stages of corn, different tillage management practices combined with plant growth regulators had a significant impact on root wound sap flow (Fig. 3). In 2021, under the EYD treatment, the root injury and flow rates at 25, 50, 75, 100, and 125 DAP were considerably greater. At each growth stage, there was no substantial variance in root injury and flow rate between ER and EYR treatments and YB and EYB treatments. A similar trend of root injury and flow rate was observed in the 2022 study year. The root injury and flow rate of EYD was significantly greater than that of CK treatment at each growth stage. The root injury and flow rate of YD, YR, EYD, and EYR treatments were considerably higher at 125 DAP. In addition, the root injury and sap rates under YD and EYD treatments at 25 and 125 DAP were considerably greater than those in other treatments.

Fig. 3
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Effects of various tillage management practices combined with plant growth regulators on rates of root bleeding sap during the maize growing periods in 2021–2022. Vertical bars represent the standard error of the mean (SEM) (n = 3). Lowercase letters indicate significant differences at P ≤ 0.05 (LSD test).

Mineral nutrients in root juice varied greatly during the study years 2021 and 2022, showing changes under different tillage management practices combined with plant growth regulators at different growth stages of corn (Table 4). Since almost all nitrogen, such as NO3− and NH4+, is absorbed by the roots, it is transported through the xylem to the aboveground, where different tillage managements combined with plant growth regulators can considerably alter NH4+ and NO3− conveying rate. At different growth stages, the emission rates of NO3− and NH4+ in the EYD were considerably greater than that of EYR and EYB treatments. The NH4+ content in the EYD was considerably greater at the V7 (rapid growth phase and stem elongation begin) and grain-filling stages, whereas the ED, ER, and YR treatments were not considerably diverse at the V7 and GF stages. Thus, the emission rates of NO3− in the EYD treatment were considerably greater at the V7 and GF stages. Moreover, in the study year 2022, the NO3− and NH4+ in the EYD were considerably more than that of ED and YD treatments.

Table 4 Changes of the nutrient concentrations (µg h−1 root−1) in root bleeding sap under the various tillage management practices with plant growth regulators during 2021–2022 growing seasons.
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In the 2021 and 2022 study years, various tillage management practices combined with plant growth regulators affected the delivery rates of Zn, Fe, Ca, P, Mg, and K. At diverse growth stages, the transport rates of Zn, Fe, Ca, P, Mg, and K in the EYD treatment were considerably higher than those in the other treatments. Than that of EYR and EYB treatments, the EYD treatment considerably improved the Zn, Fe, Ca, P, Mg, and K transport rates at each growth period. However, there was a non-considerable variance in the transport rates of P and K between the EYD and EYR treatments at the V7 and GF stages. Than that of CK treatment, the EYD had greater transport rates of Zn, Fe, Ca, P, Mg, and K at the V7 and GF stages. In the V7 stage and the filling stage, the Zn and Fe in the EYD and EYR treatments were considerably reduced.

Comparison of secondary root establishment characteristics and model

There were substantial differences in the secondary root growth parameters of TRDW, TRL, and ARD under various tillage management practices combined with PGRs in the 0 to 100 cm soil layers (Table 5). Throughout both study years, tm, Ć, Wmax, te, and cm of TRL, ARD, and TRDW, under various tillage management practices combined with PGRs showed similar profiles: EYD > EYR > YD > ED > EYB > YR > ER > EB > YB > CK treatments, respectively. Compared with CK treatment, tm of TRL and TRDW in EYD treatment was delayed. tm of ARD, TRL, and TRDW in EYD treatment was delayed by 59.4 days, 56.3 days, and 16.4 days, respectively, than that of CK treatment. The tm and te of ARD in EYD treatment were accelerated than that of CK treatment. Likewise, te and tm of ARD in EYR treatment were accelerated compared with EYB treatment.

Table 5 Effects of various tillage management with plant growth regulators on secondary growth parameters of the root system of maize during 2021–2022 growing seasons
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Root diameter (cm), RWD and RVD

Several tillage management practices combined with PGR considerably influenced the root diameter of corn (Fig. 4). Maize root diameter improved slowly during the early growth stage, quickly during the middle growth stage, and slowly reduced during the late growth stage. In the EYD treatment, maize root diameter was considerably larger by 26.7%, 42.1%, 40.0%, 50.0%, and 34.8% at 25, 50, 75, 100, and 125 DAP than that of CK treatment. The RWD and RVD are one of the most significant parameters for evaluating root traits. RVD and RWD were considerably affected by various tillage management practices combined with plant growth regulators and improved slowly with the variation of maize growth stages (Fig. 5). With rotary tillage and application of Jindele + Yuhuangjin plant growth regulator, RWD and RVD of corn were significantly improved than that of CK treatment at several growth stages. Significant variation was observed among all treatments from 25 DAP onwards. From 50 to 125 DAP, under EYD and EYR treatments, maize crops had considerably higher RVD and RWD compared to EYB treatment. At 25, 50, 75, 100 and 125 DAP, RWD of EYD was 33.3%, 70.6%, 54.1%, 67.2% and 47.6% higher than CK treatment, and EYR treatment was 20.0%, 66.7%, 57.5%, 58.3% and 40.3% higher than CK treatment (Fig. 6). At 25, 50, 75, 100, and 125 DAP, RVD under EYD was 50.0%, 55.6%, 54.5%, 60.0%, and 45.8% higher than under CK treatment, respectively, and under EYR treatment was 40.0%, 42.9%, 58.3%, 52.9%, and 35.0% higher than under CK treatment, respectively.

Fig. 4
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Effects of various tillage management practices combined with plant growth regulators on root diameter at the soil depths of 0–100 cm during 2022. Vertical bars represent the standard error of the mean (SEM) (n = 3). Lowercase letters indicate significant differences at P ≤ 0.05 (LSD test).

Fig. 5
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Effects of various tillage management practices combined with plant growth regulators on root volume density at the soil depths of 0–100 cm during 2022. Vertical bars represent the standard error of the mean (SEM) (n = 3). Lowercase letters indicate significant differences at P ≤ 0.05 (LSD test).

Fig. 6
Fig. 6The alternative text for this image may have been generated using AI.
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Effects of various tillage management practices combined with plant growth regulators on root weight density at the soil depths of 0–100 cm during 2022. Vertical bars represent the standard error of the mean (SEM) (n = 3). Lowercase letters indicate significant differences at P ≤ 0.05 (LSD test).

Brace root, endogenous hormones from corn root bleeding sap, and ear traits

Several cultivation management practices combined with plant growth regulators had a significant influence on the morphological features of reinforced roots at the tassel stage (Table 6). In the EYD and EYR treatments, root diameter, volume, angle, and dry weight of reinforced roots improved, with the maximum values ​​shown under rotary tillage with the application of Jindele + Yuhuangjin plant growth regulators. Application of plant growth regulators improved root diameter, volume, angle, and dry weight of reinforced roots throughout both study years. Than that of CK treatment, plants treated with EYD, EYR, and EYB had considerably higher numbers of reinforced root layers in 2021. But, there was non-considerably variance in the study year 2022.

Table 6 Effects of different treatments on morphological trait of brace root of maize during 2021–2022.
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Various tillage management practices combined with PGR had considerably influenced GA, IAA, and CTK, in both study years (Table 7). The flux of GA, IAA, and CTK from root bleeding sap was diverse among various tillage practices combined with two sprays of plant growth regulators. Under the EYD, the flux of IAA, GA, and CTK improved, but the endogenous hormones of the CK treatment reduced to changing degrees. After the plant growth regulators were sprayed, the endogenous hormones of rotary tillage, conventional tillage, and minimum tillage changed considerably. Taking rotary tillage as an example, the flux of IAA, GA, and CTK under Jindele + Yuhuangjin spraying of plant growth regulators increased respectively. Combining different tillage practices with PGR application had considerable influence on CTK/GA, GA/IAA, and CTK/IAA in both study years. PGR application affected the ratios of endogenous hormones to different degrees. In different treatments, CTK/IAA and CTK/GA ratios increased considerably, while GA/IAA ratios decreased considerably. PGR application altered the balance between endogenous hormones.

Table 7 Effects of different treatments on the endogenous hormones of root bleeding sap of maize during 2021–2022.
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In treatments, EYD and EYR, EH, EHC, and CG were significantly higher in the 2021 and 2022 years (Table 8). Various tillage practices considerably improved CG and EH, combined with Jindele + Yuhuangjin PGR spraying which increased EHC. In 2016, in EYD and EYR treatments, EH, EHC, and CG were not significant during both study years. In EYD and EYR treatments, EH, EHC, and CG were considerably more associated with the rest of the other treatments, as a result, the lodging rate of corn is improved.

Table 8 Effects of different treatments on ear height (EH, cm), ear height coefficient (EHC, %), centre of gravity (CG, cm), stem lodging rate (SLR, %), root lodging rate (RLR, %), total lodging rate (TLR, %), root Lodging/total lodging (RL/TL, %) and grain yield (GY, t ha−1) of maize during 2021–2022.
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Maize lodging characteristics and production

The lodging rates of shoots and roots under the EYD treatment were considerably higher than the rest of the other treatments during both years (Table 8). The average data show that under EYD treatment, SLR decreased by 97%, RLR decreased by 65%, and TLR decreased by 74%, then that of CK treatment, respectively. The results indicated that spraying plant growth regulators improved the RLR of maize; the lodging of corn is more significant at the CK. The mean of the data represents that under ED, ER, and CK treatment, SLR, RLR, and TLR increased, respectively. The average of the data shows that EYD treatment considerably reduces the lodging rate characteristics of corn and as a result, directly increased 53% the corn grain yield.

Discussion

Compared with other cultivation measures, plant growth regulators can adjust crop growth according to production needs21, regulate plant morphology, and improve lignin content, plant hormones and yield39. It is well known that plant growth regulators are characterized by low input costs18. At present, compared with the CK treatment, the lignin of the 3rd basal internode is greater in the EYD treatment. The lignin content was considerably positively correlated with endogenous hormone signaling activity, which is consistent with the results of earlier research40,41. Improvement in lodging resistance is mainly due to the increased content of lignin, cellulose, carbohydrates, anatomical structural factors such as cortex thickness, vascular bundles and degree of lignification34,42,43,44. In this study, the thickness, and the vascular bundles of the maize cortex under the EYD treatment were greater. In the EYD treatment, small vascular bundles were densely packed and large vascular bundles were developed. Plant vascular bundles are also important for water and nutrient conduction45. The carrying capacity of the conducting tissues in maize crops is positively correlated with vascular bundles42. Under EYD treatment, compared with CK treatment, SLR was reduced by 97%, RLR was reduced by 65%, and TLR was reduced by 74%.

The pathway of interaction is primarily through root sap bleeding and endogenous hormone contents32. In the EYD treatment, the root bleeding rates at various plant growth stages were considerably higher than in all other treatments. There were non-significant variances in root bleeding rates between the ER and EYR and the YB and EYB treatments at each growth stage. Furthermore, the root bleeding rates in the YD and EYD treatments at 25 and 125 DAP were significantly higher than all other treatments. Tillage methods have a considerable influence on the intensity of root sap bleeding. Rotary tillage significantly increases the root bleeding sap, thereby significantly increasing root absorption capacity and yield46. At the V7 and grain-filling stages, the transport of NO3− and NH4+ under the EYD was considerably greater than all other treatments. At diverse growth stages, the transport of ion composition of root-bleeding sap under EYD was considerably greater. Plant vascular bundles are also essential for the transport of water, nutrients and photosynthesis34. The transport tissues in maize plants are positively correlated with vascular bundles38.

Root lodging is related to root diameter, and angle47. Furthermore, increasing maize root length, root absorption, and dry weight can coordinate productivity, and increase grain yield48,49. The tm of TRDW and TRL in the EYD treatment was slower, and the te of TRDW, ARD, and TRL in the EYD was slower than that in the CK treatment (59.4 days, 56.3 days, and 16.4 days, respectively). The te and tm of ARD in the EYR treatment were also earlier than that in the EYB treatment. Specifically, as density of root can increase the maize root system, and effective root absorption area, and the increasing trends became more pronounced as the growing season proceeded50,51. Conventional tillage and RT significantly increased root diameter, RVD, and RWD. This is consistent with the results of earlier studies47,52. At various growth stages, the maize root diameters under the EYD were considerably higher. Under the conditions of rotary tillage and application of Jindele + Yuhuangjin growth regulator, the RVD and RWD of maize crops at all growth stages were considerably greater. At 50–125 DAP; the RVD and RWD of maize crops in the EYD and EYR were significantly greater. The root structure plays an essential role in to uptake of water and nutrients throughout the maize growth stages. The root number and bending strength of maize with 120 kg ha−1 nitrogen application are higher than those without nitrogen application52,53.

Improvement of stem strength and root morphological characteristics increases plant water, nutrient, and photosynthetic conduction, thereby positively affecting the seed-filling stage35,54. Under EYD and EYR treatments reached the maximum value root parameters under rotary tillage with Jindler + Yuhuanghuang sprayed PGR. The root layers in the EYD, EYR, and EYB treatments increased significantly in 2021, but there was no significant difference in 2022. PGR can improve the absorption capacity of roots by improving root morphology55. It is the relative content of various hormones, not the absolute content of a particular hormone that determines the physiological effect50. Under the different tillage methods combined with PGR, the fluxes of GA, CTK, and IAA in the root wound fluid were changed. In the EYD, the fluxes of GA, CTK, and IAA improved, while, the fluxes of endogenous hormones decreased to different degrees in the CK treatment. The PGR affected the proportions of endogenous hormones to different degrees, and the interaction pathway was mainly through the wound fluid. In each treatment, the CTK/IAA ratio and the CTK/GA ratio improved considerably, and the GA/IAA ratio reduced considerably. The PGR changes the balance between endogenous hormones. The PGR regulates the endogenous hormone of plants through exogenous application, thus affecting plant development and growth28. The RT planting system increases the yield of corn, which can be attributed to the improvement of soil fertility38,56, thereby increasing root biomass57. The EYD treatment considerably reduced the lodging rate characteristics of corn, thereby directly increasing the yield of corn kernels. Various farming practices and plant growth regulators are actual measures to maintain high yield levels39,58. The increase in RLD, ARD, and RDWD under EYD treatment helps develop the root system and improves the soil water content and nutrient uptake, thereby considerably improving lodging resistance and is an effective technique to reduce the risk of corn productivity in semi-arid areas. Study finding suggest these techniques are promising tools for farmers in semi-arid regions to sustain high maize yields while reducing lodging-related losses. However, further investigations are needed to explore plant growth regulators in combination tillage management practices, and control mechanisms for various maize varieties.

Conclusions

The application of plant growth regulators in combination tillage management practices significantly reduces the risk of lodging stress, where this reduction is attributed to the higher mechanical strength of culm. Our results showed that under the Jindele + Yuhuangjin spraying with rotary tillage considerably decreased lodging percentage, improved root distribution and dry weight, enhanced stalk microstructure, lignin content, morphological trait of brace root, and maize production. Under the EYD treatment considerably improved root growth, lignin content and stem mechanical strength, while considerably reducing lodging percentage. Furthermore, the NO3- and NH4+ under EYD treatment were considerably higher than those under ED and YD treatments. Under the EYD and EYR, the Zn, Fe, K, Mg, P, and Ca delivery rates were significantly maximum. The EYD treatment increases the root angle, dry weight volume, and diameter, of the brace roots. The Ć, cm, and Wmax of TRDW, ARD, and TRL, under the EYD and EYR treatments, were considerably greater as compared with those under the ED and YD treatments. The increase in RLD, ARD, and RDWD under EYD treatment helps develop the root system and improves the soil water content and nutrient uptake, thereby considerably improving lodging resistance and is an effective technique to reduce the risk of corn productivity in semi-arid areas. Study finding suggest these techniques are promising tools for farmers in semi-arid regions to sustain high maize yields while reducing lodging-related losses. However, further investigations are needed to explore plant growth regulators in combination tillage management practices, and control mechanisms for various maize varieties.