Seed Rate and Row Spacing Effects on Yield and Quality of Sorghum Maturity Groups Under Central European Conditions

Abstract

Efficient and climate-resilient Sorghum bicolor L. cultivation is increasingly important under Central European conditions. This study evaluated two hybrids across two locations in 2023–2024 with row spacings of 25, 45, and 75 cm and four sowing densities of 210,000–300,000 seed ha⁻¹. Row spacing, year, and genotype exerted a strong and consistent effect on grain yield and quality, with multiple instances reaching high statistical significance (p < 0.001). In contrast, seed rate had no significant main effect, influencing results only via site- and season-specific interactions. At a 45 cm row spacing, sorghum exhibited the highest grain yield (8.59 t ha⁻¹), the lowest seed moisture content (13.59%), and the greatest protein yield (1.094 t ha⁻¹). The 25 cm spacing with higher density produced with 0.46 t ha⁻¹ higher yields than 75 cm and the highest protein content (13.35%), but 0.48 t ha⁻¹ lower yield than the 45 cm treatment. The 75 cm spacing generally gave 12.29% lower yield and 6.72% lower quality despite higher tillering. TKW was highest at 45 cm row spacing (31.12 g), 23.3% greater than at 75 cm (25.25 g). The 45 cm row spacing provided the most stable yield, superior quality, and balanced agronomic performance, representing the most practical configuration for sustainable sorghum production under Central European conditions.

1. Introduction

The productive area available for plants is one of the most important factors influencing the intensity of plant development and ultimately the crop yield [1,2]. Therefore, both the number of plants and the row spacing act as crucial determinants for successful crop production [3,4]. Similarly to maize, sorghum (Sorghum bicolor L.) yield is highly responsive to variations in plant density [5,6,7]. Establishing the right planting density and row spacing is a critical component of crop management, directly influencing early crop development, stand uniformity, and final yield outcomes [8]. Farmers often face difficulties in maintaining optimal planting density. An excessively low number of seedlings usually results in increased weed pressure, ultimately reducing yield [9,10]. Manipulating row spacing in row crops can significantly influence weed control and crop development [11].

Studies indicate that in some crops, wider row spacing can lead to increased tillering and potentially higher yields; however, the effects may vary depending on species and environmental conditions [12,13]. In contrast, Plants grown in narrow rows are generally more evenly spaced, which reduces competition among individual plants for light, water, and nutrients, resulting in higher yields compared with wider row arrangements. In addition to yield benefits, narrow row spacing can improve weed suppression, enhance crop development, and reduce soil erosion [14,15], lowering evaporative water loss [16] and suppressing weeds due to earlier canopy closure that shades the soil surface more quickly [17]. Tillering, an important morphological characteristic, is closely associated with the efficient use of resources like light and water, and it directly affects the potential crop yield. Studies have shown that as plant populations increase, the number of tillers per plant often decreases. Furthermore, higher density can lead to reductions in plant height and stem thickness, although yield per unit area typically increases due to the higher number of plants occupying the field [18,19,20,21].

The correct determination of plant number and row spacing is influenced by several factors, including genotype, maturity, water availability (irrigation or rainfall), nutrient supply (soil fertility and nutrient availability), and sowing time [22,23]. Agronomic performance varied by cultivar and nutrient supply, and optimal planting density and row spacing are key determinants of yield and quality [24]. Appropriate row spacing improves the microclimate around plants, facilitating better light interception and CO₂ uptake, which favorably affects yield and internal quality traits such as protein content and hectoliter weight [25,26,27]. Determining the optimal plant number and row spacing is therefore essential for regional production recommendations and achieving maximum yield [28].

This study aimed to determine the influence of different row spacings on the yield, morphological traits, and internal quality parameters of two sorghum (Sorghum bicolor L.) hybrids, RGT Icebergg (early) and RGT Huggo (mid-early), adapted to current climatic conditions. The specific objectives were to assess the effects of varying row spacing on grain yield and key morphological parameters, to evaluate changes in grain quality traits such as protein content and test weight, and to compare the hybrids’ responses to different plant spatial arrangements. It was hypothesized that narrower row spacing would enhance yield performance through improved resource utilization and weed suppression (H₁), whereas wider spacing would increase tillering but potentially reduce yield per unit area (H₂). Higher planting densities were expected to decrease individual plant size yet increase total yield (H₃). Furthermore, it was assumed that row spacing would influence grain quality traits by modifying the microclimate within the canopy (H₄), and that the two hybrids would differ in their responses due to genotype-specific adaptation strategies (H₅).

2. Materials and Methods

2.1. Description of the Studied Areas

The study was conducted for 2 year (2023 and 2024) in the immediate vicinity of Győr (northwestern part of Hungary). Regarding the soil types of Győr and its surroundings, the area is typically characterized by heavy clay loam, sandy loam, and heavy meadow soils [29]. Due to natural variability in soil properties even within small geographic areas, a single experimental site would not have been sufficient to provide representative data. Therefore, two sites were selected to capture differences in soil texture, nutrient content, and pH, while also avoiding monoculture and taking into account practically agronomical considerations. This approach ensures that the results are robust, scientifically valid, generalizable, and applicable across a wider range of regional agricultural conditions. The first year in 2023 the trial was in Töltéstava location (latitude: 47°37′48.1″ N, longitude: 17°45′50.2″ E), which is located in the north-western region of Hungary. The second year in 2024 the trial was in Pázmándfalu location (latitude: 47°33′22.9″ N, longitude: 17°47′39.2″ E), which is located in the north-western region of Hungary. The soils at the experimental sites are classified as sandy clay loam for Töltéstava and as sandy loam for Pázmándfalu [30,31]. Based on accredited laboratory analyses of the 0–30 cm soil horizon [32] and in accordance with Hungarian standard criteria [33,34,35,36,37], the soils at Töltéstava exhibit good organic matter content (2.84% w/w), adequate nitrogen levels (7.2 mg/kg), high phosphorus content (155 mg/kg), medium potassium levels (150 mg/kg), and slightly alkaline pH (7.75), whereas the soils at Pázmándfalu show low organic matter content (1.8% w/w), low nitrogen levels (2.53 mg/kg), good phosphorus content (131 mg/kg), good potassium levels (134 mg/kg), and a neutral pH (7.2). These classifications are also consistent with several international references [38,39,40,41,42,43,44].

2.2. Experimental Design and Treatments

During both years, the experiment was arranged in a randomized complete block design with three replications (Table S1). A randomized complete block design (RCBD) was selected to minimize the effect of environmental heterogeneity across the experimental field and to ensure that the treatment effects could be reliably compared. This design is widely used in agronomic experiments to control spatial variability and improve the accuracy of statistical analysis [45]. The row spacings examined were 25, 45, and 75 cm, while the seeding rates investigated were 210,000, 240,000, 270,000 and 300,000 seed ha⁻¹.

In both years, sowing was performed in a single-row configuration using the Wizard’s Own Turbine Vacuum Precision Seeder (distributor of Temple kft., Tiszakécske, Hungary), model WZ-A10. In 2023, the results from three replicates of plots sized 3 m × 7.5 m with an intermediate 1.5 m × 7.5 m (11.25 m²) were averaged. In 2024, plots measuring 3 m × 8 m with intermediate sizes of 1.5 m × 8 m (12 m²) were used. Field plot sizes between 10 and 15 m² are widely used in agronomic research as they provide a good balance between statistical reliability and practical feasibility, allowing precise measurement of treatment effects without excessive resource demand. Additionally, harvesting only the inner rows of plots is a common approach to minimize border effects—plants at the edges often experience different growing conditions (light, competition, microclimate) compared to those in the center—thus ensuring that yield data more accurately reflect the treatment rather than edge artifacts [46].

Two hybrid sorghums of different ripening groups were used for the experiment. One of them, RGT Icebergg, is a white-seeded, early-maturing hybrid. Its flowering begins at 900 °C, and full ripening requires 1830 °C. Its thousand-seed weight is 28–30 g, and its plant height ranges from 115 to 135 cm. It was registered in Italy in 2018 by RAGT 2n. They started trading in Hungary in 2020. They are unique on the Hungarian market due to their special white seed color. The other hybrid, RGT Huggo, is a orange colored seed, mid-early maturing variety that begins flowering at 915 °C and requires a heat sum of 1860 °C for full maturity. Its thousand-seed weight ranges from 32 to 35 g, and its plant height is between 115 and 125 cm. RGT Huggo was registered by RAGT in 2014. It was started to be traded in Hungary in 2018. It has now become a popular hybrid among grain sorghums [47,48]. The seeds used were taken from the field demo plot experimental bags of RAGT Vetőmag Kft (Budaörs, Hungary).

2.3. Experimental Plots Management

The fields were sown under no-till after two passes of cultivators, with sowing on 11 May at 3 cm depth. In 2023, tillage included autumn fertilization with 45–45–45 kg ha⁻¹ NPK, followed by 13th of May application of 4 L ha⁻¹ terbuthylazine + s-metolachlor (Gardoprim^® Plus Gold, distributor of Syngenta Kft., Budapest, Hungary) and 22nd of June application of 0.3 L ha⁻¹ dicamba (Banvel^® 480 S/480 g L⁻¹, distributor of Syngenta Kft., Budapest, Hungary)—an integrated approach well-supported in the literature for optimizing sorghum and corn yield [49,50]. Weed management strategies similar to Amini et al. (2024) were also applied to maximize crop performance [51]. In early summer, this was followed by the application of 90 kg ha⁻¹ of nitrogen (active ingredient) on 10 June. The area was free from pests.

In 2024, autumn fertilization also consisted of 45–45–45 kg ha⁻¹ NPK, and the preceding crop was winter wheat, as in the previous year (2023). The fields were sown under no-till conditions after two passes of cultivators, with sowing on 3 cm depth. Two days before sowing (on 9 May), a pre-emergent herbicide treatment was applied using 4 L ha⁻¹ of Gardoprim^® Plus Gold (containing S-metolachlor + terbuthylazine). This was followed by the application of 90 kg ha⁻¹ of nitrogen (active ingredient) on 10 June. Additionally, a post-emergent herbicide treatment was carried out using 0.5 L ha⁻¹ of Banvel^® 480 S (dicamba) on 12 June, followed by manual weeding on 15 June. Pre-emergent applications of S-metolachlor and terbuthylazine have been proven effective for weed control in sorghum, improving selectivity and yield [52,53]. The 2024 growing season was characterized by lower-than-average precipitation, with only 297.8 mm falling during the vegetation period, resulting in slow and heterogeneous sorghum development.

2.4. Harvesting and Data Collection

In our study, the number of days from sowing to harvest differed substantially between 2023 and 2024 due to variable weather conditions. A similar approach was adopted by Gao et al. (2022) who evaluated phenological variation among sorghum genotypes under different environmental conditions, though their study did not involve year-on-year comparisons or specific calendar dates [54]. The time from sowing to harvest varied between the two stands due to wetter and drier weather conditions. In 2023, harvest took place 186 days later on 13th of November. In 2024, harvest took place 145 days later on 3rd of October.

Growth vigor from germination to the five-leaf stage was scored on a scale from 1 (weak) to 5 (excellent). Morphological measurements were collected from a randomly selected 1 m² area within the inner two rows of each plot. Borrell et al. (2014) conducted similar morphometric analyses on bioenergy sorghum, although their focus was primarily on biomass traits in genetically modified lines [55]. The total plant height is measured in centimeters from the soil surface to the end of the bud. The length of the bud was measured from the lower branch to the tip. Subsequently, the number of bugs per square meter and the number of tillering were quantified in the examined plot. The inner rows were harvested with a plot combine. Seed yield was adjusted to a storage moisture content of 14%. During the harvest, 1 kg samples were analyzed, from which the thousand-grain weight and the content parameters (hectoliter weight, protein content) were examined. Based on the product of the measured seed yield and protein content, we also determined the protein yield available per hectare. The seed quality and compositional analyses were conducted using the Mininfra SmarT SW (distributor of Infracont Kft., Pomáz, Hungary), a near-infrared, hopper-type analyzer with a hectoliter weight module, which enables rapid and accurate assessment of grains, oilseeds, and flours, simultaneously determining test weight and internal quality parameters. Grain samples from the sorghum hybrids were analyzed for hectoliter weight, and protein content using a Mininfra SmarT SW near-infrared (NIR), hopper-type analyzer. The instrument allows rapid, protein content, hectoliter parameters simultaneously. Measurements were conducted by filling the hopper with representative grain samples from each plot, and the device recorded the NIR spectra, which were processed using the built-in calibration models to predict the protein content and other quality traits. The method is based on principles demonstrated in previous studies on sorghum, where single-seed or bulk NIR spectral data provided accurate and reliable estimates of key grain quality parameters [56].

This approach enabled consistent and efficient evaluation of grain quality across all treatments in both 2023 and 2024, supporting comparisons of hybrid performance under different row spacing and plant density conditions. The thousand-seed weight of sorghum grains was determined individually for each plot to accurately reflect hybrid and treatment-specific characteristics. Measurements were performed using a grain counter (distributor of Sadkiewicz Instruments, Bydgoszcz, Poland) and the TKW values were calculated on a 14% moisture basis to ensure comparability across samples. This approach provides rapid reproducible measurements of seed mass, in line with previously reported protocols for diverse sorghum germplasm [57].

2.5. Data Analysis

For each parameter studied, data from three replicates were averaged and statistically analyzed. The effects of the main factors and their interactions on grain yield were evaluated using a multifactorial analysis of variance (ANOVA), considering the mean yield data of the two experimental years. The model included four independent variables: row distance, seed rate, year, and hybrid. Both main effects and two-, three-, and four-way interactions were examined to explore potential relationships among the factors.

The ANOVA was performed using ARM software (Analysis of Range Models, version 4.1), and the significance of main effects and interactions was tested using the F-test at the 5% probability level (p < 0.05). When significant differences were detected, mean comparisons were conducted using the Student–Newman–Keuls (SNK) and Tukey’s Honestly Significant Difference (HSD) post hoc tests. In addition, the Least Significant Difference (LSD) was calculated to determine the minimum statistically significant difference between treatments. Grouping letters (e.g., a, ab, bcd … j) indicate that means sharing the same letter are not significantly different from each other, while means with different letters differ significantly.

The standard deviation (SD) and coefficient of variation (CV) were also reported to assess the precision and reliability of the experimental results. While the LSD represents the statistical threshold for significance, the SD and CV provide complementary information on data variability and consistency. This combined analytical approach is widely recognized for its robustness in agricultural research [58,59] and has been successfully applied in similar crop performance studies, including sorghum and maize [60]

3. Results

3.1. Growing Conditions

As illustrated in Figure 1, local precipitation measurements in 2023, together with historical data from the Hungarian Meteorological Service the Győr region [61], indicate that rainfall during the sorghum growing season was substantially above the 1991–2020 average, particularly in May, July, and August. Temperature data show a mixed pattern, because mean maximum temperatures were generally close to or slightly above the long-term average, with July being warmer and May slightly cooler. Minimum temperatures were consistently higher than the long-term average, especially in July, August, and September, supporting favorable growing conditions for sorghum.

In contrast, the summer of 2024 exhibited an extreme precipitation distribution, with drier conditions compared to historical average. This led to unfavorable growing conditions and induced forced ripening of the plants. Such fluctuations in precipitation and temperature are well known to influence the development, yield potential, and stress tolerance of the crops [62,63].

In 2024, the weather conditions during the sorghum growing season showed considerable deviations from the 1991–2020 long-term averages, as shown in Figure 2. Precipitation patterns were highly variable, with excessive rainfall in May (115.1 mm) and September (124.6 mm), nearly twice the long-term mean for these months. In contrast, July and August were markedly dry, receiving only 13.9 mm and 31 mm of rainfall, respectively, compared with long-term averages of 71 mm and 65 mm.

Temperature data also indicated warmer-than-average conditions. Maximum temperatures in July and August (32.3 °C and 33 °C, respectively) exceeded the 1991–2020 means by 4–5 °C, while minimum temperatures were also consistently higher throughout the growing season. Even during the cooler months of May and October, both daytime and nighttime temperatures remained above the long-term averages. Overall, the 2024 season was characterized by a combination of heat stress and uneven precipitation distribution, which likely influenced crop development and water availability during critical growth stages.

The recorded weather data from the study locations in 2024 also revealed notable temperature variations among the sites. Compared to 2023, the warming trend was more pronounced, with temperatures rising rapidly and reaching their peak in August—approximately 1 °C higher than the 2023 average. From September onward, a gradual cooling was observed, although temperatures remained above the values recorded in the previous years. These temperature shifts, particularly during reproductive stages, are critical, as they can shorten grain filling duration and reduce final yield [64].

Meteorological data recorded at the Töltéstava and Pázmándfalu experimental sites revealed substantial differences between the 2023 and 2024 growing seasons, with significant implications for the development and productivity of grain sorghum.

In 2023, the total annual precipitation amounted to 1019.8 mm, compared to only 655.1 mm in 2024, reflecting a markedly wetter season. The good precipitation during May (130.0 mm) and June (93.2 mm) in 2023 supported rapid vegetative growth and ensured optimal canopy development. Conversely, the same months in 2024 were substantially drier, with only 115.1 mm and 59.1 mm of rainfall, respectively, which likely imposed early-season water stress during the critical period of biomass accumulation [65]. In terms of reproductive development and grain filling, rainfall during July and August 2023 (111.1 mm and 133.6 mm, respectively) provided ideal conditions for kernel development and grain filling.

In contrast, 2024 was characterized by severe drought stress in the same months, with precipitation dropping to just 13.9 mm in July and 31.0 mm in August. These deficits coincided with prolonged periods of elevated temperatures, with mean maximum daily temperatures reaching 32.3 °C and 33.0 °C in July and August 2024, respectively—significantly higher than the 28.7 °C and 27.9 °C observed in 2023. Under such high-temperature stress, sorghum and other C4 crops often exhibit accelerated senescence, reduced photosynthetic activity, and lower seed yields [66,67,68,69]. While both years had identical mean annual minimum temperatures (8.7 °C), the average maximum temperature was slightly higher in 2024 (17.8 °C) than in 2023 (16.9 °C), primarily due to the extreme summer heat events. Notably, the high rainfall in September 2024 (124.6 mm) likely arrived too late to positively influence final yield, as most hybrids had already reached physiological maturity or were under advanced drought-induced senescence.

These climatic contrasts explain the observed inter-annual variability in grain sorghum performance. The combination of ample rainfall and moderate temperatures in 2023 created ideal conditions for both vegetative development and grain filling, resulting in superior yield and quality outcomes. In contrast, the pronounced water deficit and high thermal load during the critical reproductive stages in 2024 led to stress-induced yield reduction and higher treatment variability [70].

3.2. Yield and Harvest Moisture Content

Based on the results of the multifactorial analysis of variance, the effects of various agronomic factors on grain yield were evaluated, considering the mean values across the two experimental years. Among the main effects, row distance, year, and hybrid significantly influenced yield (p < 0.05).

A highly significant effect of row distance (p < 0.001) indicated that changes in plant density and spatial arrangement substantially affected grain yield, with distinct mean yield levels observed among different row spacing treatments. The effect of year was the most pronounced (p < 0.001), suggesting that the contrasting weather and environmental conditions of the two growing seasons had a decisive impact on yield performance. The hybrid also exhibited a significant effect (p = 0.017), implying that hybrids differing in growth duration responded differently to the environmental conditions of each season. In contrast, the main effect of seed rate was not significant (p = 0.316), indicating that varying the seeding density alone did not result in statistically verifiable yield differences.

Among the interactions (Figure 3), only the row distance × year interaction (p = 0.002) was significant, suggesting that the effect of row spacing varied between the two years—in other words, the optimal row distance was dependent on the specific growing season.

Non-significant (trend-level) relationships were observed for the row distance × hybrid (p = 0.096) and row distance × seed rate × year (p = 0.084) interactions. All other two-, three-, and four-way interactions were non-significant (p > 0.1), indicating that these factors acted independently in influencing yield.

The results demonstrate that, when averaged over the two years, grain yield was primarily affected by seasonal variation (year effect) and row distance, while the hybrid had a smaller but still statistically significant influence. The seed rate and most interaction effects were not significant, suggesting that under the conditions of this study, these factors did not independently or jointly exert a substantial impact on yield outcomes.

In cause of row distance, year, and hybrid had significant effects on grain moisture at harvest (p < 0.05). The effect of row distance was highly significant (p < 0.001), indicating that plant spacing influenced the rate of grain drying. The year effect (p = 0.032) reflected strong environmental variation between the 2023 and 2024 seasons, while hybrid (p = 0.029) showed that hybrids with different growth durations differed in moisture content at harvest.

The seed rate had no significant effect (p = 0.373). Among interactions, row distance × year and year × hybrid were highly significant (p < 0.001), suggesting that the influence of row spacing and hybrid maturity on grain moisture depended on yearly climatic conditions (Figure 4). All other interactions were non-significant (p > 0.05).

The results from the 2023 and 2024 growing seasons demonstrated that grain sorghum yield and harvest moisture content were significantly influenced by row spacing, and hybrid maturity, while climatic variability between years played a decisive role in determining yield levels. Based on the two-year average, the lowest grain moisture content was recorded at the 45 cm row spacing (13.59%), which did not differ significantly from that observed at the 25 cm spacing (13.73%). In contrast, the 75 cm spacing resulted in a significantly higher moisture content of 14.29%, representing an increase of 0.7% compared to the 45 cm spacing.

Figure 5 shows in 2023, a relatively better weather conditions, yields ranged from 9.91 to 11.88 t ha⁻¹. The highest yield being recorded for the medium-early hybrid at 270,000 seed ha⁻¹ and 25 cm spacing, while the lowest was obtained for the early hybrid at 210,000 seed ha⁻¹ with the same spacing.

In contrast, the 2024 season, characterized by drought stress, produced markedly lower yields (4.63–7.19 t ha⁻¹), where significant treatment differences emerged; notably, both the highest and lowest yields occurred at 240,000 seed ha⁻¹, underscoring the strong influence of row spacing and hybrid type.

Across the two years (Figure 6), average yields at 210,000 (7.98 t ha⁻¹) and 300,000 seed ha⁻¹ (8.29 t ha⁻¹), were similar, differing by only 0.31 t ha⁻¹. The largest year-to-year yield gap (5.10 t ha⁻¹) was recorded at 270,000 seed ha⁻¹, whereas 240,000 seed ha⁻¹ proved most stable with only a 4.82 t ha⁻¹ gap (yield difference ≈ 0.28 t ha⁻¹). This indicates that depending solely on sowing seed rate, yield differences between a wetter and a drought year may reach 46.9% (yield difference ≈ 4.98 t ha⁻¹).

Row spacing exerted a substantially stronger influence on grain yield than seeding rate. At 25 cm row spacing, the yield was 8.11 t ha⁻¹, at 45 cm spacing the best result was 8.59 t ha⁻¹, while at the wide 75 cm spacing the lowest average yield of 7.65 t ha⁻¹ was observed (Figure 7).

Across both years, the average yields of the early and medium-early hybrids were nearly identical (8.09–8.14 t ha⁻¹), but their responses differed. The medium-early hybrid was more sensitive to density and spacing, achieving its maximum yield (11.063 t ha⁻¹) at 300,000 seed ha⁻¹ in 2023 but declining to 10.523 t ha⁻¹ at 210,000 seed ha⁻¹ (difference 0.54 t ha⁻¹), with the gap widening to 0.735 t ha⁻¹ in 2024, while the early hybrid showed minimal sensitivity, as yields at 210,000 and 300,000 seed ha⁻¹ differed by only 30 kg ha⁻¹ in 2023 and in 2024 the gaps were slightly increased (0.203 t ha⁻¹).

Both hybrids responded best to 45 cm spacing. Statistical groupings confirmed that 25 and 45 cm treatments, particularly with early hybrids, consistently fell into the highest-yielding categories (“a” or “ab”), while 75 cm spacing was predominantly associated with lower-yielding groups (Table S2). Harvested seed moisture content ranged from 13.5% to 15.4%, with early hybrids showing generally lower levels, reducing post-harvest drying needs. Sowing seed rates also had a minor effect, as 300,000 seed ha⁻¹ averaged 0.22% lower moisture than 210,000 seed ha⁻¹, which had the highest values. Moisture differences were smaller in 2024 than in 2023 and rarely exceeded the year-specific significance threshold of 0.98%, indicating that under severe drought, climatic stress masked treatment-specific effects. Reliability was confirmed by low coefficients of variation (4.37% in 2023 and 3.26% in 2024), indicating the stability of the measurements.

3.3. Hectoliter Weight and Protein Content

For the hectoliter weight, year and hybrid had highly significant main effects (p < 0.001). Moreover, significant interactions were observed between row spacing × year and year × hybrid (p < 0.001), indicating that the effects of spatial arrangement and hybrid maturity on test weight varied markedly between the two growing seasons.

In addition, the interaction between row spacing × year × hybrid was statistically significant (p = 0.022), and the row spacing × seed rate × year × hybrid interaction also showed significance (p = 0.006). These findings suggest that test weight was jointly influenced by plant spatial configuration, seeding density, seasonal conditions, and hybrid maturity, reflecting the complex interaction between environmental and agronomic factors.

Protein content revealed a highly significant interaction between row spacing × year (p < 0.001), indicating that the effect of spatial arrangement on grain protein concentration differed markedly between the two growing seasons. In addition, the three- and four-way interactions row spacing × seed rate × year (p = 0.052), row spacing × year × hybrid (p = 0.043), seed rate × year × hybrid (p = 0.042), and row spacing × seed rate × year × hybrid (p = 0.051) were near the threshold of statistical significance. These results suggest that grain protein content was influenced not only by environmental conditions but also by complex interactions among planting density, hybrid maturity, and spatial configuration, reflecting the multifactorial nature of protein accumulation in sorghum grain. The analysis of hectoliter weight and protein content, revealed distinct patterns across years and treatments. In the 2023 season, no statistically significant differences were observed in hectoliter weight at the LSD 0.05 level, indicating that maturity groups, row spacing, and sowing seed rate did not significantly affect this parameter.

In contrast, small but statistically significant differences were found in protein content, with values ranging between 11.81% and 12.61%. In 2024, hectoliter weight values ranged from 68.13 to 74.57 kg hl⁻¹, with significant differences detected at the LSD 0.05 level (Figure 8). The highest hectoliter weight (74.57 kg hl⁻¹) was recorded in the early maturity group at 75 cm row spacing and 210,000 seed ha⁻¹, while the lowest value (68.13 kg hl⁻¹) was measured in the same maturity group at 25 cm row spacing and 270,000 seed ha⁻¹. In average of the two year data 45 and 75 cm row spacing tended to produce higher hectoliter weights, whereas lower values were more frequent at 25 cm spacing.

Regarding protein content, a noticeable difference was observed between the two years, with the average protein content measuring 12.30% in 2023 and 13.67% in 2024. Previous studies have confirmed that yield reductions caused by drought lead to a more concentrated protein content, resulting in higher percentage values [71,72]. Protein content in 2024 ranged between 13.04% and 14.77%, with significant differences across treatments. The highest protein content (14.77%) was observed in the early maturity group at 25 cm row spacing and 270,000 seed ha⁻¹, while the lowest (13.04%) was recorded in the early group at 45 cm row spacing and the same seed rate (Figure 9). Overall, the early maturity group tended to have higher protein content, especially at narrow row spacing. Combined results from the two years showed the highest average protein content 13.24% in the 25 row spacing.

At 45 cm row spacing, the 210,000–240,000 seed per hectare exhibited superior average protein content of 13.04% relative to the higher-density treatment at the same spacing, while at 75 cm, the same density similarly outperformed the denser configuration, achieving 12.84%. Previous Brazilian field studies have demonstrated that reducing row spacing enhances seed nutritional quality—especially protein concentration [73]. Singh et al. (2005) investigated possibilities for increasing corn protein content, which ranges between 5.7% and 11% [74]. During our experiment, sorghum protein content ranged from 11.81% to 14.77%, representing an average increase of 4.94% compared to corn.

Although both sorghum genotypes exhibited similar average protein levels, their responses to row spacing and seeding rates differed. The early hybrid consistently produced high protein content across all row spacings and seeding rates, while the mid-early hybrid showed more limited responses to treatments. In the two-year average results show that increasing row spacing showed an increasing trend for hectoliter weight, whereas increasing seeding rate had the opposite effect, leading to a pronounced decrease.

The two-year average showed no substantial difference in hectoliter weight between 45 cm (73.02 kg hl⁻¹) and 75 cm (73.08 kg hl⁻¹) row spacings, while the 25 cm spacing was lower, at 72.75 kg hl⁻¹. However, at 45 cm spacing, a density of 240,000 seed ha⁻¹ produced stable and high results in both years, averaging 74.20 kg hl⁻¹. It is the same values were recorded at 75 cm spacing with 270,000 seed ha⁻¹. The coefficient of variation for hectoliter weight ranged between 0.97% and 2.35%, while for protein content it varied between 1.52% and 2.76%, reflecting the variability and precision of measurements (Table S3). LSD values indicated that statistical significance was more pronounced for protein content than for hectoliter weight, where differences were generally smaller.

3.4. Protein Yield and Thousand Kernel Weight

Thousand kernel weight (TKW) and protein yield were significantly influenced by key agronomic and genetic factors, although the magnitude and pattern of effects varied between the two parameters.

For TKW, highly significant main effects were detected for row spacing, seed rate, and hybrid (all p < 0.001), while the year effect was not significant (p = 0.240). This indicates that kernel development was mainly governed by planting geometry and hybrid characteristics rather than by interannual environmental differences. In contrast, for protein yield, the year effect was the most dominant (F = 1166.78; p < 0.001), reflecting the strong influence of environmental and climatic variability between the two growing seasons. Row spacing (p < 0.001) and hybrid (p = 0.003) also had significant effects, whereas the influence of seed rate was not significant (p = 0.180), suggesting that seeding density had a limited role in determining protein productivity under the tested conditions.

Significant interaction effects were observed for both traits, highlighting the complexity of factor interdependence. In the case of TKW, strong interactions such as Row distance × Seed rate, Row distance × Year, and Seed rate × Year (all p < 0.001) demonstrated that both plant density and environmental conditions modulated the expression of kernel mass. Higher-order interactions, including row distance × seed rate × year × hybrid (p < 0.001), indicated complex genotype–environment–management relationships affecting grain formation. For protein yield, a significant Row distance × Year interaction (p < 0.001) confirmed that the influence of spatial configuration on protein accumulation varied between years, while a weaker row distance × Hybrid interaction (p = 0.041) suggested genotype-specific responses to row spacing (Figure 10).

Results in Table S4 consistently demonstrate that row spacing had a significant impact on both protein yield and TKW. The 45 cm row spacing proved to be the most productive setting for all sowing seed rate combinations (1094 t ha⁻¹). In the wetter year, protein yields at planting densities of 210,000–240,000 seed ha⁻¹ ranged between 1.23 and 1.43 t ha⁻¹, whereas in the drier year they varied from 0.81 to 0.98 t ha⁻¹.

Across the two-year average, the yield reached 1.12 t ha⁻¹, representing the best performance. Over the two growing seasons, the early hybrid produced the highest average yield at 45 cm row spacing with a sowing seed rate of 210,000 seed ha⁻¹, reaching 1.16 t ha⁻¹. In 2023, the 25 cm row spacing achieved protein yields on a similar scale (1.23–1.43 t ha⁻¹) as the 45 cm spacing. The differences primarily originated from the 2024 season, when the 45 cm spacing produced yields ranging between 0.78 and 0.98 t ha⁻¹, while the 25 cm spacing resulted in lower values of 0.72–0.85 t ha⁻¹.

Figure 11 illustrates that the most favorable outcomes were obtained at the higher seed densities of 270,000–300,000 seed ha⁻¹, which delivered an average protein yield of 1.06 t ha⁻¹ across the two years. In contrast, the widest row spacing (75 cm) consistently resulted in the lowest protein yields. In 2023, values ranged between 1.24 and 1.36 t ha⁻¹, while in 2024 they were only between 0.61 and 0.77 t ha⁻¹. Averaged over the two years, this corresponded to a mean yield of 0.97 t ha⁻¹, which was achieved primarily at the lower planting densities of 210,000–240,000 seed ha⁻¹. These findings suggest that excessively wide spacing may reduce protein accumulation due to less efficient radiation interception and increased interplant competition within rows.

Considering the two-year average, the highest thousand-kernel weight (TKW) was achieved at the 45 cm row spacing for both hybrids. At this spacing, the TKW averaged 31.12 g, compared to 27.21 g at 25 cm and 25.25 g at 75 cm, representing an increase of 5.87 g, or approximately 23.3%, over the 75 cm spacing. Within the 45 cm spacing, planting densities of 210,000–240,000 seeds ha⁻¹ proved optimal, resulting in an average TKW of 31.47 g (Figure 12). In 2023, TKW ranged between 27.85 and 35.16 g, while in 2024—even despite the less favorable weather—it ranged between 30.61 and 34.52 g. The highest average values were produced by the early hybrid at both 210,000 and 240,000 seed ha⁻¹ planting densities, with TKWs of 34.2 g and 34.52 g, respectively. In contrast, both the narrowest (25 cm) and widest (75 cm) row spacings led to lower TKW values. Over the two-year average, at 25 cm spacing—particularly under high planting densities—TKW dropped to 24.46–27.94 g, while the 75 cm spacing resulted in a lower range of values and also performed more poorly in the higher-density plots. Across both years the highest average TKW was recorded at 45 cm row spacing, with values generally exceeding those at 25 cm and 75 cm. Specifically, 45 cm spacing averaged around 31.1 g, compared to 27.2 g at 25 cm and 25.2 g at 75 cm, indicating that a moderate row spacing supports better grain filling.

Regarding sowing seed rate, lower to moderate densities (210,000–240,000 seed ha⁻¹) tended to result in higher TKW values than the highest density (300,000 seed ha⁻¹), where kernel weight often decreased. This trend was most apparent at 75 cm spacing, where TKW dropped below 22 g at the highest seed rate, whereas at 45 cm spacing and 210,000 seed ha⁻¹, values reached up to 34.7 g. These trends indicate that 45 cm row spacing offers an optimal balance between plant competition and resource availability, fostering more efficient grain filling and kernel development. Although there were some differences in absolute values between 2023 and 2024, the treatment trends remained consistent across both years.

This suggests that the effects of row spacing, sowing seed rate, and hybrid type were robust and largely independent of annual climatic variation. However, inter-annual differences were likely influenced by year-specific weather conditions, such as temperature and precipitation patterns during flowering and grain-filling periods, which may have affected the magnitude of protein deposition and kernel weight.

3.5. Plant Height and Panicle Length

Plant height and panicle length were significantly influenced by multiple experimental factors, with strong year and genotype (hybrid) effects.

For plant height, the year exerted the most pronounced effect (p < 0.001), indicating that environmental conditions such as temperature and precipitation played a decisive role in vegetative growth. The hybrid also had a significant main effect (p < 0.001), suggesting that genotypic differences contributed markedly to height variation. A significant interaction between row distance × seed rate (p = 0.026) and between year × hybrid (p < 0.001) was observed, highlighting that planting density and environmental conditions jointly affected height expression. Furthermore, the row distance × year × hybrid interaction (p = 0.007) indicates that hybrid-specific responses to spacing varied between years.

Regarding panicle length, the hybrid type again showed a highly significant effect (p < 0.001), reflecting inherent genotypic differences. The year factor was also strongly significant (p < 0.001), underlining the impact of annual climatic variability. Significant effects were detected for row distance (p = 0.003) and for the interaction row distance × seed rate (p < 0.001), demonstrating that spatial arrangement significantly influenced panicle development. Additional significant interactions included row distance × year (p < 0.001), seed rate × year (p < 0.001), and seed rate × hybrid (p = 0.005), suggesting that both environmental and management factors interacted with genotypic characteristics in determining reproductive growth patterns.

The results over the two years, shown on Figure 13, demonstrated a noticeable year effect, with plant stands in 2023 growing significantly taller than those in 2024, likely due to more favorable weather conditions such as higher rainfall and more stable temperatures.

Low and uneven precipitation during the vegetation period can lead to early-season drought stress in sorghum, which significantly slows development and causes heterogeneous crop stands [75,76]. There were marked differences between maturity groups. Mid-early hybrids generally attained greater plant height compared to early types.

In 2023, the difference was especially pronounced under narrow row spacing combined with higher planting densities (270,000–300,000 seed ha⁻¹). Table S5 data also showed that plant height decreased with increasing row spacing and decreasing seed rate, possibly due to competition between plants for light. In such spatial arrangements, mid-early hybrids often was under 150 cm in height, indicating improved light interception and reduced intra-stand competition. In contrast, the growth of early hybrids was notably constrained under narrow row distance arrangements. Under these conditions, early hybrids typically reached only around 125–130 cm in height, suggesting a higher sensitivity to intensified competition, particularly under limited light and nutrient availability. Row spacing and seeding quantity had different effects in the case of the two hybrids. Similar results of row spacing on plant height have been reported by others [77,78].

Based on the data from the two years, the development of panicle lengths showed notable differences, mostly because of genotype and year condition (Figure 14).

In the wetter year, panicle lengths ranged between 22.5 and 30.9 cm. In contrast, in the drier year the values proved to be on average more than 5% higher, with panicle lengths ranging between 24.9 and 31.23 cm.

Overall mid-early hybrid showed an advantage in this trait, especially under wider row spacing. Considering the two-year averages, panicle length was 28.23 cm at a row spacing of 25 cm, 27.81 cm at 45 cm, and 28.36 cm at 75 cm. In contrast, the early hybrid produced panicle lengths of 27.72 cm at 25 cm, 26.20 cm at 45 cm, and 26.75 cm at 75 cm. In 2024, observations showed that early hybrid is able to produce the longest panicles under lower seed rate combined with wider row spacing. Interestingly, even under dry conditions, these early hybrids outperformed in terms of panicle length, surpassing other treatments and even showing an advantage compared to the generally better-yielding mid-early hybrid. This indicates that the formation of generative organs in early hybrid is more stable and resilient when exposed to drought stress.

The shortest panicles were generally observed in the 45 row spacing and the highest seed rate, particularly among early hybrid treatments. The observed differences reflect genuine biological variation, which was confirmed by statistical analysis. For plant height and panicle length the differential plasticity and adaptive capacity of the hybrids played a dominant role in shaping the outcome under varying spatial arrangements and year-specific environmental conditions.

3.6. Tillering and Panicle Density

Tillering and the number of panicles per square meter are strongly influenced by multiple factors. In both traits, agronomic factors—particularly row distance and seeding rate—had a significant effect (p < 0.001), and the growing season also played an important role. For tillering, the maturity group was also significant, whereas for panicle number, the maturity group alone did not show a notable effect (p = 0.635).

In both cases, interactions revealed a complex pattern, two-, three-, and four-way interactions were significant (p < 0.01–0.001). Notable interactions included row spacing × seeding rate × year, row spacing × seeding rate × hybrid, and row spacing × year × hybrid. These findings indicate that optimal row spacing and plant density cannot be generalized but are instead contingent on genotype and year, as hybrids respond differently to climatic conditions and agronomic adjustments. Both tillering and panicle number are highly multifactorial and interactive traits, regulated by the combined effects of agronomic, genetic, and environmental factors. The findings suggest that optimizing tiller formation and panicle number can only be achieved by considering genotype, seasonal conditions, and agronomic practices together, with significant synergistic interactions among them.

In the experiment the tillering was primarily determined by row spacing and seed rate. Wider spacing (75 cm), even at high seed rate, increased light availability between the rows, promoting lateral shoot development and resulting in higher tillering values. Figure 15 shows that the highest values (up to 2.3 tillers plant⁻¹) were recorded in early maturity groups sown at 75 cm row spacing and 300,000 seed ha⁻¹. In contrast, narrow spacing (25 cm) and high density limited the plants ability to produce tillers due to stronger intra-specific competition for light, water, and nutrients, leading to lower tillering values (typically between 0.7 and 1.78).

The average number of panicles per square meter in the rows also showed significant differences. It was unanimously true for the two hybrids that, on average, the highest seed quantity had the most panicles, which decreased as the seed quantity decreased. Based on the two-year averages, the highest panicle number was recorded at the 25 cm row spacing with 22.21 panicles per square meter, followed by 45 cm with 21.40 panicles per square meter, while the lowest was observed at 75 cm with 20.33 panicles per square meter (Figure 16).

The highest values were observed at 25 cm row spacing and 300,000 seed ha⁻¹, particularly in the early maturity group. In 2024, these treatments not only supported high plant populations but also ensured efficient reproductive development, reaching up to 26.08 panicles per square meter—statistically classified in the strongest homogeneous group (a), and also representing the highest panicle number on the two-year average (Table S6). Across maturity groups, early hybrids exhibited comparatively higher panicle densities, particularly under narrower row spacing and higher planting densities. Although mid-early types demonstrated slightly reduced tillering and panicle density, these differences did not translate into yield penalties relative to the early hybrids.

4. Discussion

This study investigated the effects of row spacing, seed rate, and hybrid maturity on sorghum (Sorghum bicolor L.) grain yield, harvest moisture, quality, and morphological traits across two growing seasons, providing a comprehensive evaluation of the interplay between agronomic management, genotype, and environmental conditions. Similar methodologies were applied by Dinberu & Mengasha (2023) also investigated various row spacings in sorghum cultivation, confirming that narrower row spacings significantly influence grain yield [79].

In the study the grain yield was strongly influenced by row spacing (p < 0.001) and growing season (p < 0.001), with hybrid contributing moderately but significantly (p = 0.017). Narrower row spacings of 25–45 cm consistently produced the highest yields, with 45 cm spacing outperforming the conventional 75 cm spacing by ~12.3% across the two years. The 25 cm spacing also increased yield relative to the 75 cm arrangement b—ut was slightly less productive than 45 cm, confirming H₁ that narrower spacing enhances yield through improved resource utilization and weed suppression. The row spacing × year interaction was significant (p = 0.002), indicating that the optimal spacing varied with seasonal conditions. Seed rate alone did not significantly affect yield (p = 0.316), while other interactions, such as row spacing × hybrid (p = 0.096) and row spacing × seed rate × year (p = 0.084), showed trend-level significance, suggesting that plant density and genotype effects are partially context dependent.

These findings align with recent results in grain sorghum. Herrera et al. (2024) reported similar yield increases with narrower row spacing, confirming the positive effect of optimized inter-row distance [80]. In our study, grain yield increased by ~12 % under narrower spacing. Similarly, some other research demonstrated that narrower row spacing combined with optimal plant populations enhanced grain sorghum yield by optimizing light interception and plant resource use [81]. In the results confirm this, as higher planting densities with narrower rows produced greater panicle densities despite lower tillering per plant.

Harvest moisture content was significantly affected by row spacing (p < 0.001), hybrid (p = 0.029), and growing season (p = 0.032). Highly significant interactions were observed for row spacing × year and year × hybrid (p < 0.001), indicating that the effects of spatial arrangement and hybrid maturity on grain drying were season-specific. Narrower row spacings facilitated faster grain drying, and medium-maturing hybrids exhibited greater height and longer panicles, while early-maturing hybrids showed higher protein content and enhanced tillering, supporting H₅ regarding genotype-specific responses. These trends are consistent with Dos Santos et al. (2023), who observed that hybrid-specific growth responses varied with row spacing and seasonal conditions, although their study focused on grazing sorghum and measured slightly lower moisture differences [82].

Grain quality traits were shaped by complex interactions among row spacing, seed rate, hybrid, and season. Thousand-kernel weight (TKW) was highly influenced by row spacing, seed rate, and hybrid (all p < 0.001), whereas the year effect was not significant (p = 0.240), indicating that kernel development is largely governed by genotype and management. Lower to moderate seed rates (210,000–240,000 seeds ha⁻¹) generally produced higher thousand-kernel weight (TKW) than the highest rate (300,000 seeds ha⁻¹), particularly at 75 cm spacing, where TKW dropped below 22 g. In contrast, 45 cm spacing at 210,000 seeds ha⁻¹ reached up to 34.7 g, indicating that intermediate spacing optimizes plant competition and resource use, enhancing grain filling. These results are consistent with Berenguer and Faci (2001) and Fernandez et al. (2012), who showed that moderate densities and row spacing improve kernel weight by reducing intra-plant competition [83,84]. Protein yield, in contrast, was strongly season dependent (F = 1166.78; p < 0.001), with additional contributions from row spacing (p < 0.001) and hybrid (p = 0.003). Significant interactions included row spacing × seed rate × year × hybrid (p < 0.001) for TKW and row spacing × year × hybrid (p = 0.043) for protein content, highlighting the multifactorial regulation of grain quality. The 25 cm row spacing at moderate density achieved the highest protein content (13.35%), while 45 cm spacing produced the highest protein yield (1.118 t ha⁻¹), confirming H₄ that row spacing affects grain quality through modification of the canopy microclimate. These results are in agreement with Nieman et al. (2024), who found that narrower spacing increased protein concentration, although our protein yield was higher due to combined effects of hybrid selection and seasonal conditions [85].

Morphological traits, including plant height and panicle length, were significantly affected by year (p < 0.001) and hybrid (p < 0.001), with additional significant interactions such as row spacing × seed rate (p = 0.026), year × hybrid (p < 0.001), and row spacing × year × hybrid (p = 0.007), indicating that both environmental conditions and genotypic differences shape vegetative growth, and suggesting that the genetic background of the hybrid exerts a stronger influence on plant morphology than row spacing or seeding rate. The results of this study, showing that plant height decreased with increasing row spacing and decreasing seed rate, are in contrast to Gondal et al. (2018), who reported that higher seeding rates and narrower plant spacing stimulated plant height due to internode elongation, highlighting that the effect of plant density on height can vary depending on genotype and environmental conditions [86]. Reproductive traits, including tillering and panicles per square meter, were strongly influenced by row spacing and seeding rate (p < 0.001), with significant two-, three-, and four-way interactions, including row spacing × seed rate × year, row spacing × seed rate × hybrid, and row spacing × year × hybrid. Ther results shows the wider row spacing (75 cm) with high seeding rates promoted maximum tillering (up to 2.3 tillers plant⁻¹), whereas narrow spacing (25 cm) and high density limited tiller production (0.7–1.78 tillers plant⁻¹). This is consistent with Liu et al. (2020), who found that light transmission within the canopy is reduced under denser and narrower row spacing, leading to intensified competition and limited tiller development [87]. These findings support H₂ and H₃, indicating that wider spacing increases tillering but reduces per-area yield, while intermediate spacing balances individual growth and total production. Similar patterns were observed by Gao et al. (2024), although our study quantified both morphological and grain quality parameters simultaneously [88]. The two-year averages indicate that narrower row spacings enhanced panicle density, with the highest number recorded at 25 cm (22.21 panicles m⁻²), followed by 45 cm (21.40 panicles m⁻²), and the lowest at 75 cm (20.33 panicles m⁻²), suggesting that closer spacing promotes greater reproductive site density despite potential limitations in individual tiller development. Previous research has shown that the combination of narrower row spacing (35 cm) and low seeding rate (220,000 seed ha⁻¹) resulted in the highest panicle productivity, due to better utilization of the available area [89]. The study confirms that optimizing row spacing and seeding rate significantly affects the number of panicles, grain weight, and overall yield. Benson et al. (2025) reported that under variable water supply, sorghum plants at lower densities do not fully compensate for reduced plant numbers, as the increase in tillers, plant per panicle, and grain weight is limited [90]. Similarly, Garba et al. (2025) highlighted that genotype × environment interactions influence sorghum yield gaps, indicating that compensation mechanisms may vary under different conditions [91]. Yan et al. (2023) further showed that the interaction of genotype, ecological type, and plant spacing affects yield responses under variable water supply [92]. Consistent with these findings, our two-year results show that for both maturity groups, panicle number decreases significantly as row spacing increases. Although wider row spacing promoted higher tillering per plant, it did not fully compensate for the lower number of plants per unit area, resulting in reduced overall panicle density. This pattern was consistent across maturity groups. Furthermore, no correlation was found between the number of panicles and the yield, which is also supported by previous studies [93,94].

The study demonstrates that sorghum productivity, harvest moisture, quality, and morphological traits are regulated by the inter-dependent effects of row spacing, seeding rate, hybrid, and growing season, and that single-factor manipulations are insufficient for consistent optimization. The results confirm that all experimental objectives were achieved and that the hypothesized relationships (H₁–H₅) are largely supported by the data, highlighting the importance of integrated, context-specific management for maximizing yield, grain quality, and crop resilience.

Nevertheless, when benchmarked against the 45 cm spacing, the 25 cm arrangement proved less efficient, producing on average 0.48 t ha⁻¹ lower yields, which slightly limits its overall agronomic advantage. For future cultivation practices, we recommend adopting 45 cm row spacing combined with moderate plant densities, especially in regions prone to climatic variability and extreme weather events. In current large-scale farming, sorghum is typically sown at 75–76 cm because the available machinery is set up for this spacing. Since the same equipment is used for sowing and harvesting sunflower and maize, no time is lost for machine adjustments, which is particularly critical during the harvest. Among the advantages of the row spacing of 25 and 45, it should be mentioned that seed drills are available for these technologies, which have already been proven in practice. Harvesting 45 cm row spacing remains challenging, as using a cereal cutting table requires additional adjustment time, otherwise currently there is no machinery available that is compatible with both 45 cm and 75 cm row spacings, making it a special procedure that farmers are unlikely to use in for sorghum cultivation.

However, experimental evidence shows that such wide row spacing is not agronomically optimal for sorghum, and for growers aiming for serious cultivation, investing in improved technology can result in yields that are up to half a ton or even one ton higher per hectare. In addition, it is important to emphasize that in the case of 45 cm row spacing, there is a good opportunity to use effective row cultivation. Row cultivation improves soil aeration, which enables more dynamic root and shoot development of the plants. This effect becomes particularly advantageous under drought conditions, as better-aerated soils enhance water infiltration and root activity, thereby improving the crop’s resilience and performance during prolonged dry periods. In addition, in the case of sorghum—where options for chemical weed control are limited—this factor is also highly significant for effective weed management. Cultivators equipped with row control optics have a large area capacity and good efficiency [95].

5. Conclusions

The 45 cm row spacing provides an optimal balance for maximizing yield, protein concentration, and seed quality, confirming that moderate narrowing of row spacing improves resource utilization, enhances microclimatic conditions, and supports weed suppression (H₁ and H₄). Higher planting densities increase total yield despite slightly reduced individual plant size (H₃), while wider spacing promotes tillering but limits per-area productivity (H₂). Differential responses of the two hybrids highlight genotype-specific adaptation strategies (H₅), emphasizing the importance of selecting appropriate hybrids under variable environmental conditions. Implementing these agronomic strategies alongside precise water management and stress-tolerant cultivars can enhance climate resilience, particularly under drought-prone conditions. From a practical perspective, adopting 45 cm row spacing with moderate seeding rates offers clear agronomic advantages, including improved panicle density, more efficient light interception, enhanced soil aeration through row cultivation, and better weed suppression. These benefits are particularly relevant for regions prone to climatic variability, such as prolonged droughts, and can contribute to more stable and higher yields in commercial sorghum production. Furthermore, the findings provide a framework for adjusting sowing equipment and row spacing technologies to optimize field operations without sacrificing productivity. For future research, these results indicate several promising directions: (i) testing the performance of additional sorghum hybrids under similar row spacing and density combinations to explore genotype × environment × management interactions; (ii) evaluating the long-term effects of row spacing on soil health, nutrient use efficiency, and water utilization; (iii) integrating precision agriculture tools and sensor-based management to dynamically adjust plant density and spacing according to seasonal conditions; and (iv) exploring the combined effect of row spacing and intercropping or cover cropping on sorghum productivity and resilience.