This experiment was carried out from June to November 2022 at the agricultural farm of Hohai University, Nanjing (31°57′N, 118°50′E), China. The weather of this zone is categorized as humid subtropical with four seasons. The annual mean temperature is 15.9°C, the maximum and the minimum temperatures are 43°C and −16.9°C, and the mean annual rainfall is 1,062 mm (Yang et al., 2018). The soil was collected from the topsoil layer (0 cm–15 cm), dried by sunlight, and passed through a 5-mm screen. The used soil was classified as loam-textured soil, which was characterized as follows: soil pH was 7.02 ± 0.47, the soil organic matter was 6.43 ± 0.37 g·kg⁻¹, the total phosphorus (TP) content was 0.47 ± 0.012 g·kg⁻¹, the available phosphorus (AP) content was 14.75 ± 1.36 mg·kg⁻¹, the available nitrogen (AN) content was 32.41 ± 6.12 mg·kg⁻¹, and the available potassium (AK) content was 123.46 ± 15.02 mg·kg⁻¹.

This study was carried out using a randomized complete block design using three repetitions ( Figure 1 ). The first factor was saline water used for irrigation, which imposed three levels with an electrical conductivity (EC) of 0.5 dS/m as control, 2.5, and 5.5, representing WS_0.5, WS_2.5, and WS₅, respectively. The addition made the saline irrigation of 50% sodium chloride (NaCl) and 50% calcium chloride (CaCl₂) by weight in well water. NaCl was supplied to water used for irrigation to attain the proposed irrigation water salinity levels (WS2.5 and WS5.5) (melting 0.5843 g of NaCl in 1 liter of water increased the EC by 1 dS/m).

The second factor was calcium lignosulfonate (CLS) in addition to three levels: CLS₀ (0%), CLS₅ (5%), and CLS₁₀ (10%) on a weight basis. A group of 27 PVC vessels were installed in an uncontrolled shelter roofed with elastic film. Every experimental vessel (depth: 40 cm, diameter: 25 cm) had tiny holes at the bottom and was occupied with 10 kg dry soil ( Figure 1 ).

Later, CLS amounts were supplied and homogenized with the soil. The quantity of CLS at 5% (CLS₅) was calculated on a weight basis, supposing the soil bulk density of 1 g/cm³. The quantity of CLS at the level of 10% (CLS₁₀) enlarged twice to accomplish the rate of 10% (CLS₁₀), whereas no CLS was added to the rate of 0% (CLS₀).

After filling the pots with the soil mixed with the corresponding rates of CLS, the superphosphate (12%, P₂O₅), urea (46% N), and potassium chloride (60% K₂O) as chemical fertilizers were added to the mixture according to the soil test. The pot moisture holding capacity was measured for each rate of CLS. Then, the maize variety, so-called Xianyu 335, was used. The seeds were sown in soil peat moss at three seeds per plug tray cell and thinned to one plant per hole 3 weeks after the germination. Then, the seedlings were transplanted to the pots and irrigated to 100% of pot water-holding capacity every other day for a week. Afterward, irrigation water salinity treatments were implemented every other day, and water amounts were determined based on the water quantity needed to increase the moisture content to 100% of the pot water-holding capacity.

For chemical investigation, the soil samples were obtained from the topsoil layer (0 cm–20 cm). A pH meter estimated soil acidity (pH) in soil/water extract (1/2.5). The EC of soil was assessed by measuring the extract through an EC meter. Some samples were placed in a fridge at 4°C to estimate the dissolved organic carbon (DOC). Additional samples were also saved to measure soil easily oxidative carbon (EOC) and soil total organic carbon (TOC). The TOC amount was computed by the titration of ferrous ammonium sulfate and the potassium dichromate oxidation (Lu, 1999). The soil DOC level was computed in the soil/water extract at 25.5°C after shaking for 1 h (Jiang et al., 2006) and rotating at 4,500 r·min⁻¹ for 15 min (Bankó et al., 2021). The occasioning supernatant was passed through a 0.45-mm screen, and the attained blend was measured by the titration of ferrous ammonium sulfate and the oxidation of potassium dichromate. The EOC amount was estimated by reacting finely dried samples with 333 mmol·L⁻¹ KMnO₄ through shaking at 60 r·min⁻¹ for 60 min (Blair et al., 1995). After that, the resultant was centrifuged for 5 min at 2,000 r·min⁻¹. The obtained mixture was diluted, and its absorbance was noted at 565 nm using a spectrophotometer. Subsamples were added to a blend of salicylic acid and selenium sulfate to measure the ion contents of potassium (K⁺), calcium (Ca⁺⁺), and sodium (Na⁺) in the soil. The mixture was transferred to the ingestion cylinders, which were heated for 30 min at 100°C. The temperature was then raised to 380°C for 180 min using a hotplate (YKM-36, Shanghai, China) (Jackson, 2005). Soil K⁺, Ca⁺⁺, and Na⁺ contents were identified by the flame photometer method (FB640N, Wincom, Hunan, China) (Ghosh, 1993).

At physiological maturity (R6), plants were collected, partitioned into grains, stems, and leaves, positioned in the oven for 3 days at 75°C, and balanced to get dry weights. Plant samples for each plant part were milled, sieved using a 1-mm mesh, and kept in the paper bags for further analysis. The soil/root tubes for each treatment were collected, and roots were isolated by carefully washing the soils. The plant roots were dried with paper tissues, and the fresh root mass was determined. The methylene blue dyeing method estimated the root active adsorption area (RAAA) using fresh root samples (Zhang et al., 1994). The root dry weight (RDW) was measured from the fresh root biomass and the water amount of the dried root.

During the vegetative (tassel, VT) and reproductive (dent, R5) growth stages, data regarding plant height (PH, cm), stem diameter (SD, cm), leaf number per plant (NL), and leaf length (LL, cm) were recorded in triplicate. The PH was identified from the soil surface unit at the shoot’s top. The SD was identified through a digital caliper (CD 7303V, China). The NL per plant was counted, and LL was measured using a meter tap.

The photosynthesis level (Pn, µmolCO₂ m²/S) of the leaf was measured through an opened-flow gas exchange apparatus. The Pn rate was measured in three replications of leaves between 08:40 and 10:50 on a sunshiny day through a moveable photosynthesis apparatus (LI-6400XT, LI-COR, USA). The leaf deoxyribonucleic acid (DNA) content was measured at the reproductive (milk, R3) growth stage and detected by flow cytometry analysis. Leaf subsamples were separated into tiny slashes and placed in 50 mM KCl, 5 mM HEPES, 1 mg/mL dithiothreitol (Sigma, St. Louis, MI, USA), 0.2% Triton X-100 (nucleus isolation buffer), and 10 mM MgSO₄. The samples were passed over a 33-mm net. The nuclei were positioned in paraformaldehyde (4%) for half an hour, sedimented (200 g, 10 min, 4u C), and then suspended in a separation buffer (Sheteiwy et al., 2021a).

At physiological maturity (R6), the root glutamine synthetase [RGS, μmol/(g·h)] ability was assessed using a standard method by Chen et al. (2021). The nitrate reductase [RNR, µg/(g·h)] activity of the root was assessed by the investigation blend, including 1-g fresh roots sited in 25 mM K₃PO₄ buffer, 10 mM KNO₃, 0.2 mM NADH, 5 mM NaHCO₃, and 5-μL extract in a final quantity of 0.5 mL. The attained reaction was suspended by delivering 50 μL of 0.5 M Zn(CH₃COO)₂. Then, 50 μL of 0.15 mM phenazine methosulphate was delivered to oxidize the excessive NADH. The mixture was centrifuged for 5 min at 10.000× g. The quantity of NO₂₋ was detected by blending 500 μL of supernatant with 250 μL of 1% sulfanilamide obtained in 1.5 N HCl and 250 μL of 0.02% N-(1-naphthyl) ethylene-diamine dihydrochloride. The absorbance was logged at a 540-nm wavelength using the spectrophotometric method (Ogawa et al., 1999).

At the vegetative (tassel, VT) and reproductive (dent, R5) growth stages, subsamples (0.5 g) of the ground flag were frozen in liquid N. They were then placed in a mixture of 15% glycerol, 1 mM EDTA, 0.1% Triton X-100, 1 mL Tris–HCl (pH 7.8), and 14 mM 2-mercaptoethanol. The consequent blend samples were rotated for 12,000× g at 4°C for 10 min. The glutamine synthetase [LGS, µmol/(g·h)] activity of the leaf was identified by identifying glutamyl hydroxamate formation in the mixture at 540 nm after reaction with FeCl₃ (10%): TCA (24%): HCl (6 mol/L) at 1:1:1 ratio. The leaf nitrate reductase [LNR, µg/(g·h)] activity was identified through a standard method by Baki et al. (2000). Briefly, 0.2 g of the crushed leaf was kept for 30 min at 30°C in a dark place with 0.2 M KNO₃, 9 mL of medium consisting of 25% isopropanol, and 0.1 M sodium phosphate buffer (acidity 7.2). The spectrophotometer detected the discharged nitrite at a wavelength of 540 nm.

The leaf’s malonaldehyde (MDA) amount was identified by a standard method of Zhou and Leul (1999). Briefly, a flag tissue sample (0.25 g) was added to liquid N by supplying 10% (w/v) TCA (5 ml). The resulting mixture was rotated at 4,000× g for 15 min at 4°C. Later, the supernatant (2 mL) was submitted to 0.67% (w/v) thiobarbituric acid (2 mL), persisted at 100°C for 30 min, and finally transmitted to an ice bath. The subsequent samples were rotated at 4°C at 2,000× g for 5 min. The spectrophotometer recorded the supernatant absorbance at 532-nm, 600-nm, and 450 nm wavelengths. The hydrogen peroxide (H₂O₂) level of the supernatant was logged at 390 nm by the spectrophotometer. The leaf’s relative water content (RWC, %) was estimated by drying samples at 75°C for 2 days in the oven, where dry mass was achieved afterward by sealing the targeted leaf for 2 days in deionized water. Then, the leaves were dried before reaching the turgid mass (Sheteiwy et al., 2019).

The wet digestive tubes for the seed, stem, leaf, and root were arranged to measure plant tissues’ K, Ca, and Na nutrient concentrations (%). The digestive tubes were supplied with 0.5 g of each plant part powder. A 1-g selenium reagent mixture was placed in the tube and supplied with 10 mL of concentrated H₂SO₄ (Jackson, 2005). The K, Ca, and Na percentages in the tissues of root, stem, leaf, and grain were measured by the flame photometry technique (Tandon, 1993). The amounts of K, Ca, and Na nutrients in crop removal were estimated by the following equations (Mosier and Syers, 2004; Bandaogo et al., 2015):

where NAG is the nutrient accretion in grain (mg/plant), NCG is the nutrient concentration in the grain (%), GDW is the grain dry weight (g/plant), NCL is the nutrient concentration in the leaf (%), LDW is the leaf dry weight (g/plant), NAS is the nutrient accretion in the stem (mg/plant), NCS is the nutrient concentration in the stem (%), SDW is the dry weight (g/plant), NAL is the nutrient accretion in leaf (mg/plant), NAR is the nutrient accretion in the root (g/plant), NCR is the nutrient concentration in root tissues (%), and RDW is the root dry weight (g/plant).

As proposed by Maas and Hoffman (1977), the model of salt tolerance was employed in corn yield as a development factor to standardize the level of decline of the factor with increasing salt stress, as indicated by its ECe (excluding the threshold value for assumed salinity and soil amendment). With yield used as a development factor, the salt resistance model (Maas and Hoffman, 1977) is given by the following equation:

where Y_a is the average achieved corn yield for a given CLS addition and saline irrigation treatment (g); Y_m is the average highest corn production (grain yield) achieved by the CLS₀ control treatment (g) for the relevant CLS addition; EC_e is the soil salinization threshold value (dS m⁻¹); ECe is the soil salinization excluding the threshold value (dS m⁻¹); and b is the slope value denoting the degree of decreasing yield with rising ECe excluding the threshold value.

To identify differences in corn embryo ultramorphology for the different treatments, a scanning electron microscope was employed following a standard protocol (Wei et al., 2009). The sonication in dehydrated alcohol dehulled a grain sample (0.1 g) for 5 min. Then, grains were sliced by carpet tape to get cross sections sputter-coated to a thinness of 30 nm with a gold object in a vacuum-coating device. Silver dye was enclosed to the bottom of the seed cuts to avoid the charge on its surface. The seed endosperm ultramorphology engaged to the scanning electron microscope (JEOL JSM-1300) was checked on the core endosperm of a transverse unit at a 15-kV accumulating voltage, and the pictures for each sample were skimmed. The seed chemical structure was identified by calculating the percentages of protein, fat, and starch, according to Pan et al. (2013), using an infrared grain analyzer (FOSS, Hilleroed, Denmark). The seed’s digestive tubes were used where nutrient contents in the grains were determined using the spectrophotometer through the indophenol-blue protocol for N (Novozamsky et al., 1974) and the Barton protocol for P (Jones, 2001). Silicon level (%) was measured using a standard protocol by Zhao et al. (2019).

The collected data were processed by the IBM-SPSS-19 statistical package, employing the analysis of variance (two-way ANOVA) and performing the process of the general linear model. Once the P values were significant, the obtained mean values were compared at the 0.05 significance level using Duncan’s multiple range test. All collected values are the averages of three replications.

ANOVA results exhibited that under the similar calcium lignosulfonate (CLS) addition rate, increasing the water salinity (WS) stress during WS_0.5, WS_2.5, and WS_5.5 considerably enlarged the soil EC, pH, and Na contents while decreasing EOC, DOC, TOC, K, and Ca contents ( Table 1 ). Under similar salinity stress, CLS₀, CLS₅, and CLS₁₀ led to a large decline in the soil EC, pH, and Na⁺ content and a gradual enlargement in the DOC, EOC, TOC, K⁺, and Ca⁺⁺ levels in the soil. Due to the interactive effect, treatment WS_0.5 × CLS₁₀ exhibited the lowest values of EC (3.85 and 3.00), pH (7.28 and 7.11), and Na⁺ (0.23 and 0.08, g/kg) and the highest EOC (6.30 and 4.23 g/kg), DOC (368.1 and 284.1 mg/kg), TOC (15.64 and 13.58 g/kg), K⁺ (0.167 and 0.139 g/kg), and Ca⁺⁺ (0.39 and 0.19 g/kg) contents of the soil at the layers of 10 cm and 20 cm, respectively. However, treatment WS_5.5 × CLS₀ showed the greatest values of EC (15.03 and 14.37), pH (8.56 and 8.02), and Na⁺ (1.01 g/kg and 0.67 g/kg) and the lowest values of EOC (1.82 g/kg and 1.02 g/kg), DOC (172.3 mg/kg and 88.6 mg/kg), TOC (10.67 g/kg and 8.85 g/kg), K⁺ (0.120 g/kg and 0.101 g/kg), and Ca⁺⁺ (0.15 g/kg and 0.08 g/kg) contents of the soil at the depths of 10 and 20 cm, respectively.

At physiological maturity (R6), the RAAA, RDW, RNR, and RGS of roots were reduced by increasing the salinity stress during WS_0.5, WS_2.5, and WS5_5.5 whereas the RAAA, RDW, RNR, and RGS of roots enlarged with increasing CLS addition rate during CLS₀, CLS₅, and CLS₁₀, respectively. In addition, the highest RAAA (6.54 m²/plant), RDW (2.61 g/plant), RNR [14.07 µg/(g·h)], and RGS (3.58 mg/g/FW/h) values in CLS₁₀ were detected under WS_0.5. However, the lowest RAAA (2.38 m²/plant), RDW (1.74 g/plant), RNR [5.87 µg/(g·h)], and RGS (1.38 mg/g/FW/h) values in CLS₀ were detected under WS_5.5 ( Table 2 ).

Significant variations in K, Ca, and Na contents in the root tissues were detected among salinity treatments. Under a similar CLS application rate, the root tissues’ K and Ca contents decreased gradually, whereas Na content increased during WS_0.5, WS_2.5, and WS5_5.5, respectively. Under the similar salinity treatment, K and Ca root contents increased gradually while decreasing Na root content during CLS₀, CLS₅, and CLS₁₀. The highest K (0.73%) and Ca (0.38%) contents and the lowest Na (0.07%) content in the root tissues were recorded by the treatment WS_5.5 × CLS₁₀. However, the lowest K (0.23%) and Ca (0.11%) contents and the highest Na (0.34%) content in the root tissues were recorded by the treatment WS_0.5 × CLS₀ ( Table 2 ).

The results of the flow cytometry investigation presented that CLS addition and salinity stress considerably alerted the cell cycle’s progress at exact stages ( Figures 2A–I ). The findings revealed that each treatment influenced the plant cell progression differently. Maximum values of side-scattered (SSC) light and forward-scattered (FSC) light signals were discovered in maize grown in the CLS₁₀ exposed to minor salinity stress under WS_0.5, signifying superior cell division, size, and granularity ( Figures 2A–C ).

Enhanced values of SSC and FSC were recognized in maize grown in CLS₅, specifying an enhanced cell division, size, and granularity, with lessening salinity stress during the WS_2.5 treatments. Thus, the cells’ development was slightly motivated by the variations in the cell’s progress when growing maize in CLS₅ with decreasing salinity stress during the WS_2.5 ( Figures 2D–F ). Minimum values of SSC and FSC were noted in maize grown in CLS₁₀, demonstrating a negligible developed cell size division and granularity while maximizing salinity stress during the WS_5.5. Thus, cell progression was noticeably reduced, parallel to changes in cell development when growing maize in CLS₁₀ with lightning salinity stress during WS_0.5 ( Figures 2G–I ).

During the vegetative (tassel, VT) and reproductive (dent, R5) growth stages, CLS addition significantly enhanced the RWC and Pn in all salinity stress treatments. This impact improved as the amount of CLS added increased. Under the same CLS application level, the salinity stress treatments impacted the RWC and Pn differently, where their values were increased by decreasing salt-stress during the WS_5.5, WS_2.5, and WS_0.5 treatments. Regarding the interaction of the factors, the greatest Pn (13.13 µmol m⁻² s⁻¹ and 8.63 µmol m⁻² s⁻¹) and RWC (48.93% and 36.73%) were recorded by WS_0.5 × CLS₀ at vegetative (tassel, VT) and reproductive (dent, R5) growth stages, respectively. However, the lowest Pn (7.65 µmol m⁻² s⁻¹ and 4.90 µmol m⁻² s⁻¹) and RWC (10.86% and 7.99%) values were observed with WS_5.5 × CLS₁₀ ( Figures 3A, B ).

Given significant differences between different factors, CLS application significantly improved the LGS and LNR under salinity stress treatment. Under the same CLS rate, the salinity stress displayed a varied effect on the LGS and LNR, where their values were improved by reducing salt-stress during the WS_0.5, WS_2.5, and WS_5.5. Given the interaction of the factors, the greatest LGS [827.7 µmol/(g·h) and 953.9 µmol/(g·h)] and LNR [29.12 µmol/(g·h) and 40.59 µg/(g·h)] were recorded by WS_0.5 × CLS₀ at the vegetative (tassel, VT) and reproductive (dent, R5) growth stages, respectively. However, the lowest LGS [471.6 µmol/(g·h) and 573.4 µmol/(g·h)] and LNR [14.25 µg/(g·h) and 20.86 µg/(g·h)] were recorded values were observed with WS_5.5 × CLS₁₀ ( Figures 3C, D ).

The MDA and H₂O₂ contents decreased significantly with increases in CLS addition amounts, whereas the increasing salinity stress increased MDA and H₂O₂ contents. Given the interaction of factors, WS_5.5 × CLS₀ resulted in the maximum values of MDA (7.26 µmol/g and 11.41 µmol/g) and H₂O₂ [5.71 mmol/(m²·S) and 7.11 mmol/(m²·S)] contents at the vegetative (tassel, VT) and reproductive (dent, R5) stages, respectively. However, the minimum MDA (3.34 and 6.57 µmol/g) and H₂O₂ [3.05 mmol/(m²·S) and 4.91 mmol/(m²·S)] values were recorded by WS_0.5 × CLS₁₀ ( Figures 3E, F ).

As displayed in Figures 4A–D at the vegetative growth phase, NL, LL, PH, and SD were unfavorably declined by salinity stress. WS_5.5 led to lower NL, LL, PH, and SD values under all salt-stress treatments, whereas WS_0.5 resulted in the greatest values of PH, SD, NL, and LL.

The CLS application showed a substantial augmentation in LL, NL, PH, and SD values under the salt stress treatments. CLS₁₀ resulted in greater PH, SD, NL, and LL values under all salt-stress treatments. Regarding interactive effects of the factors, the greatest PH, SD, NL, and LL mean values were recorded by WS_0.5 × CLS₁₀ (105.3 cm, 3.73 mm, 6 leaves/plant, and 78.3 cm), whereas the lower mean values were noticed with WS_5.5 × CLS₀ (42 cm, 0.93 mm, 14 leaves/plant, and 34.5 cm).

Similar to the previous phase, salinity stress reduced the growth parameters of maize during WS_0.5, WS_2.5, and WS_5.5. However, CLS addition exhibited a major enhancement in these parameters during CLS₀, CLS₅, and CLS₁₀, during the vegetative (tassel, VT) and reproductive (dent, R5) growth stages ( Figures 3A–D ). Therefore, the highest PH, SD, NL, and LL values were detected in WS_0.5 × CLS₁₀ (152.5 cm, 4.86 mm, 18 leaves/plant, and 96.6 cm), whereas the smallest values were noted by WS_5.5 × CLS₀ (81.2 cm, 2.16 mm, 10 leaves/plant, and 58.3 cm).

The variations in biomass production of corn for various CLS addition rates under salt stress were significant. The biomasses for seeds, leaves, stems, and thus shoot biomass improved with CLS rate increasing during CLS₀, CLS₅, and CLS₁₀, respectively. Meanwhile, increasing salinity stress considerably reduced the masses of grains, leaves, and stems, and thus shooting. Moreover, the highest biomasses for seeds, leaves, stems, and thus shoot biomass were noticed in WS_0.5 × CLS₁₀ [51.55, 87.06, 164.21 (g/plant)]. However, the lowest values were watched in WS_5.5 × CLS₀ [19.31, 42.86, 71.25 (g/plant)] ( Table 3 ).

Significant changes (P<0.05) in the ion contents in maize plants’ seeds, stems, and leaves were detected across salinity stress treatments. The maize plants were more reactive with K under WS_0.5 than WS_5.5 conditions through the season. The K and Ca percentages in stems, leaves, and grains enlarged when the CLS addition rate increased during CLS₀, CLS₅, and CLS₁₀, respectively. Due to interaction, the maximum values of K and Ca amounts in leaves (1.71% and 0.54%), stems (1.51% and 0.84%), and grains (0.84% and 0.68%) were obtained under the WS_0.5 × CLS₁₀. However, the lowest K and Ca concentrations in leaves (0.76% and 0.11%), stems (0.52% and 0.37%), and grains (0.29% and 0.22%) were achieved under the WS_5.5 × CLS₀ ( Table 3 ). Unlike the K and Ca concentrations, the Na percentages in the stems, grains, and leaves of maize were considerably increased by increases in salinity stress and reductions in CLS addition rates. Moreover, the highest Na levels in maize grains, stems, and leaves were obtained under WS_5.5 × CLS₀ (0.37%, 0.52%, and 0.56%). However, the lower values were witnessed in WS_0.5 × CLS₁₀ (0.06%, 0.11%, and 0.17%) ( Table 3 ).

The findings specified that different CLS addition rates under salinity stress treatments affected Na, K, and Ca accumulation in the leaf, stem, root, and grain. The accumulation of K and Ca in the root, leaf, stem, and grain declined with increasing salinity stress during the WS_0.5, WS_2.5, and WS_5.5, respectively. However, the Na accumulation in the stem, root, grain, and leaf improved during the WS_0.5, WS_2.5, and WS_5.5 ( Table 4 ), unlike the K and Ca accumulation trend in root, leaf, stem, and grain, which were realized during CLS₀, CLS₅, and CLS₁₀. However, the Na uptake in leaf, stem, root, and grain declined with increasing CLS addition rates during CLS₀, CLS₅, and CLS₁₀, respectively. Due to interaction, the highest K and Ca uptake while the lowest Na uptake in the root (19.1 mg, 10 mg, and 1.83 mg), leaf (881.5 mg, 278 mg, and 30.9 mg), stem (1,314 mg/plant, 731 mg/plant, and 95.8 mg/plant), and grain (1,330.1 mg, 1,117 mg, and 279.2 mg) were recorded by the WS_0.5 × CLS₁₀ treatment. However, the lowest K and Ca uptake while the highest Na uptake in the root (6.7 mg, 1.1 mg, and 3.81 mg), leaf (146 mg/plant, 21 mg/plant, and 71 mg/plant), stem (201 mg, 159 mg, and 230 mg), and grain (206 mg, 157 mg, and 399 mg) were recorded by the WS_5.5 × CLS₀ treatment ( Table 4 ).

The salt resistance index for the maize plant is presented as a function of grain yield against the reached ECe mean values for every CLS addition rate ( Table 5 ). For CLS₀, no reduction until 2.09 dS/m of the threshold value was detected in the grain yield. However, surpassing the standard value, corn production declined by 27.78% for each unit enlargement in the salt-stress degree. Regarding the CLS₅, a substantial rise in the ECe value to 4.02 dS/m was witnessed; however, the slope value was reduced to 14.92%. Moreover, under CLS₁₀, a substantial enlargement in the ECe value of 5.96 dS/m was detected; however, the slope value was reduced to 7.34% ( Table 5 ).

The ultramorphology of maize seed embryo altered significantly under different treatments ( Figures 5A–I ). The maize seed embryo exposed to CLS₀ exhibited many circular starch grains of smaller size and a plethora of unformed starch particles with untidy-edge starch granules. The ultramorphology of maize seed embryo also showed a large increase in the content of protein matrix at the periphery, increasing the injury to the seeds compared with CLS₀ and WS_0.5 by increasing salinity stress in the order of WS_0.5 > WS_2.5 > WS_5.5 ( Figures 5A–C ).

However, the ultramorphology of maize grain embryo exposed to CLS₅ was boosted by enhancements in crystallization and size for starch particles with an obvious drop in protein matrix over reducing salinity stress in the order of WS_5.5 > WS_2.5 > WS_0.5 ( Figures 5D–F ). The positive development in the ultramorphology of maize grain embryos exposed to CLS₁₀ developed greater with a greater size for starch grains, well-built starch particles with sharply bounded starch particles. Furthermore, the protein matrix declined, preventing the injury to maize grains compared with CLS₀ and CLS₁₀ by reducing salinity stress in WS_5.5 > WS_2.5 > WS_0.5 ( Figures 5G–I ). Considerable differences in the maize grain’s quality and chemical composition signs were found through different treatments ( Table 6 ). Under a similar calcium-sulfonated lignin addition rate, WS_0.5 boosted proteins, fatty acids, starch, Si, P, and N percentages in the maize grains. During the similar salinity stress, the smallest proportions of protein, fat, starch, Si, P, and N were realized in CLS₀, followed by CLS₅, while the greatest percentage was detected in SL₁₀.

Due to the combination, the WS_0.5 × CLS₁₀ treatment showed the greatest proportions of protein, fat, starch, Si, P, and N in the maize grains. Conversely, the WS_5.5 × CLS₀ treatment exhibited the smallest proportions of protein, fat, starch, Si, P, and N in the maize grains.