Impact of improved agronomic approaches on yield and quality of soybean [Glycine Max (L.) Merrill] under northern transition zone of Karnataka

Introduction

Soybean (Glycine max), a primary oilseed crop originating from East Asia, plays critical role in India's agriculture. Beyond its global standing, soybean's significance in India is underlined by its nutritional richness, featuring 40 % protein, 20 % oil and 6.4 % lysine content, accompanied by essential vitamins and minerals Chauhan et al. (2005) [1] . This crop serves not only as a nutritional powerhouse but also contributes ecologically by fixing atmospheric nitrogen (35-140 kg ha -1 ), reducing the need for synthetic fertilizers and enhancing soil fertility. Its versatility in acclimating to various climatic conditions establishes it as a significant contender well-matched for the evolving environmental dynamics in this specific region. Globally, soybean takes the lead as the primary oilseed crop, contributing 61 % to the total oilseeds production. While Brazil leads in production, India's 3 % contribution underscores its indispensable role in the nation's agricultural fabric. In Karnataka, where soybean spans 0.43 million hectares, yielding 0.44 million tonnes (Annon., 2022) [2] . The cultivation of oilseeds, particularly soybean, holds critical significance for India's edible oil production. Our study integrates scientific insights, emphasizing the testing of soybean varieties that demonstrate resilience and adaptability to the changing climatic conditions of the northern transition zone of Karnataka. The challenges identified, such as the failure by farmers in the northern transition zone of Karnataka to cultivate adapted varieties with proper row spacing, hinder optimal production. The low productivity of the crop is due to several constraints; among them genotypes and their spacing are important (Dhaliwal et al., 1995) [3] . Achieving an optimal plant density becomes imperative, maximizing resource utilization such as water, nutrients, light and CO 2 resulting in higher crop productivity. Acko et al. (2009) [4] reported that optimal row spacing and cultivar selection are crucial for attaining high yield and producing quality soybean seeds. Cultivating resistant, high-yielding varieties with appropriate planting geometry is crucial for unlocking the maximum yield potential of soybean crops, particularly in the context of the changing climatic conditions of the northern transition zone of Karnataka. Optimizing plant population and adopting suitable agronomic practices emerge as pivotal factors influencing growth and yield enhancement (Billore et al., 2000) [5] . Early and medium maturity with stress-resistant genotypes, known for their adaptability to diverse farming conditions, offer promising solutions for changing climatic conditions. This research aims not only to contribute to the general understanding of soybean production but also to provide region-specific insights crucial for sustainable and optimized cultivation practices in the face of evolving climates.

Material and Methods

To investigate how various plant geometries impact the growth and yield of soybean varieties, an experiment conducted during kharif 2022 season at the Main Agricultural Research Station of the University of Agricultural Sciences in Dharwad (latitude of 15°29′ North and longitude of 74°58′ East), Karnataka, India under rainfed condition. During the crop growth period, the total rainfall received at Main Agricultural Station, Dharwad was 574 mm in 37 rainy days. Mean monthly relative humidity of 87.1, 86.55, 82, 76.7 and 58 respectively were observed during July, August, September, October and November months which was congenial for crop growth. While, mean maximum temperature ranged from 26.6-29.5 ˚C and minimum temperature varied from 16.5-20.5 ˚C which fall within the range of optimum temperature (15-32 ˚C) requirement of soybean crop. The experimental field was laid out in the split-plot design in 4.5 × 5.0 m 2 gross plot size with twelve treatment combinations comprising three varieties, M 1 -DSb 21, M 2 -KDS 726 and M 3 -KDS 753 as main plot and four geometries S 1 -22.5 × 10 cm, S 2 -30 × 10 cm, S 3 -37.5 × 10 cm and S 4 -45 × 10 cm as sub-plot. The soil of the experimental field was clayey, with pH of 7.1, EC of 0.33 dS m -1 , organic carbon (0.45 %). Farm yard manure at recommended dose of 6.25 t ha -1 was applied uniformly and incorporated into the soil before 15 days of soybean sowing. Urea, di-ammonium phosphate (DAP) and muriate of potash (MOP) were used as sources of N, P 2 O 5 and K 2 O at recommended doses of 40:80:25 kg ha -1 , respectively. Applied entire doses as basal. On July 22, 2022, the crop was planted with seeds treated with rhizobium and PSB culture @ 150 grams per 10 kilograms of seeds, employing geometry levels. Pre-emergence herbicide application of Pendimethalin 30 EC @ 3.25 l ha -1 was sprayed after sowing in order to keep the field free from weeds during initial crop growth. Later, hand weeding followed by inter cultivation were carried out at 45 and 60 days after sowing, the inter-cultivation was carried out using cycle weeder and blade hoe. Five plants chosen randomly within the net plot area were tagged and utilized for observing various growth parameters throughout the crop's growth stages, as well as for assessing yield parameters at the time of harvest. The data obtained from the experiment was analyzed statistically using the Analysis of Variance (ANOVA) method, following the methodology recommended by Gomez and Gomez et al., 1984 [6] . The 'F' test will be conducted at a 5% level of significance to determine the significance level. The standard error of the mean and coefficient of variability were calculated for the set of observations for each characteristic at the 5 % level of significance.

Results and Discussions

Yield and yield parameters Varieties

The experiment evaluated the performance of three soybean varieties, namely DSb 21, KDS 726 and KDS 753, with a focus on understanding genetic variability and its influence on key yield parameters. Throughout the study, KDS 753 and KDS 726 consistently demonstrated superior performance compared to DSb 21 across various growth and yield parameters, underscoring the impact of specific genotype on enhanced traits. Regarding the seed yield, KDS 753 (21.88 q ha -1 ) and KDS 726 (20.86 q ha -1 ) significantly outperformed over DSb 21, which recorded the lowest seed yield (18.17 q ha -1 ). Additionally, KDS 753 exhibited significantly higher values in 100-seed weight (15.85 g), number of pods per plant (50.63) and seed yield per plant (21.57 g) compared to DSb 21, but it was on par with the variety KDS 726 indicating that the genetic traits of KDS genotypes contributed to superior pod development, seed weight and overall crop yield. These findings align with prior studies by Pawar et al.

(2015) [7] and Nayak et al. (2020) [8] . Furthermore, the genotypes exerted noticeable influences on yield components, with KDS 753 displaying superiority in yield per plant, seed yield per hectare and biological yield per hectare. KDS 726 closely followed KDS 753 in performance, indicating that their genetic characteristics contribute to efficient resource utilization and allocation, resulting in increased overall biomass and yield production. The observed higher pod numbers, seed weight and biomass accumulation in these specific cultivars are consistent with genetic traits influencing yield potential, as supported by studies conducted by Raghuwanshi et al. (2017) [9] , Anusha et al. (2021) [10] and Smith et al. (2022) [11] . This comprehensive analysis highlights the significance of genetic factors in shaping soybean cultivar performance and yield outcomes, providing valuable insights into the completed experiment.

Planting geometry

Top of Form

The crop geometry with dimensions of 45 × 10 cm exhibited significantly higher seed yield (22.67 q ha -1

) and straw yield (26.37 q ha -1 ). In contrast, the narrowest spacing of 22.5 × 10 cm yielded the lowest seed yield (16.70 q ha -1

) and straw yield (20.64 kg ha -1

). This rise in seed yield can primarily be attributed to an increased number of pods per plant and higher seed weight per plant. Similar findings were also documented by Angadi (2016) [12] and Anusha et al. (2021) [10] . As the row spacing increased from 22.5 × 10 cm to 30 × 10 cm, 37.5 × 10 cm and finally to 45 × 10 cm, there was a notable and significant rise in both the number of pods per plant and seed yield per plant. Among the different spacing, the arrangement of 45 × 10 cm stood out with the highest recorded number of pods per plant (52.09) and seed yield per plant (15.64 g). The variations observed in pods per plant could potentially be attributed to the corresponding variations in the number of branches. The wider row spacing, as evident in the 45 × 10 cm arrangement, allowed each plant ample room for robust vegetative and reproductive growth. This, in turn, led to a higher count of branches per plant, facilitating an enhanced capacity for pod bearing. The advantage of wider spacing includes reduced plant competition and improved availability of light, moisture and nutrients, all contributing to a more favourable source-sink relationship. This environment ultimately results in an increased number of pods per plant and consequently a higher seed yield per plant. These findings resonate with the results reported by Malek et al. (2012) [13] , Sivakumar et al. (2018) [14] and Keisham et al. (2021) [15] . The increase in pods plant-1 with respect to increase in row-to-row spacing was also reported by Khubele (2015) [16] and Angadi (2016) [12] . Upon evaluation, the results pertaining to the weight of 100 seeds were determined to be statistically non-signifi cant across various spacing configurations. However, it is important to note that the spacing of 45 × 10 cm recorded a numerically higher test weight (15.64 g). These findings lend support to those previously reported by Singh (2011) [17] and Patel et al. (2022).

Interactions

The interaction between soybean varieties and planting geometries showed significant impact on the performance of soybean. Among the treatment combinations, the variety KDS 753 along with the planting geometry of 45 × 10 cm performed best on several key parameters including seed yield (24.98 q ha -1 ) and straw yield (28.54 q ha -1 ) which was statistically on par with the same variety at 37.5 × 10 cm. While, the variety DSb 21 sown with the geometry level of 22.5 × 10 cm had lowest seed yield (15.34 q ha -1

). Similar results were also reported by Angadi (2016) [12] . Significantly higher seed yield was recorded in the treatment involving the KDS 753 genotype when planted with spacing configuration of 45 × 10 cm, outperforming other treatment combinations. This increase in yield can be attributed to the inherent advantage of this particular genotype in achieving an optimal yield across different spacing conditions. Although narrower spacing led to a higher plant population per unit area, this approach failed to surpass the yield obtained from the lower population under wider spacing. This discrepancy can be attributed to the significantly lower yield attributes recorded at closer spacing, which were unable to compensate adequately for the superior yield attributes generated per individual plant at the lower population within wider spacing. In the context of all three varieties, including DSb 21, KDS 726 and KDS 753, an intriguing pattern emerges when considering the influence of plant spacing on seed yield. As plant spacing widens, there is significant increase in seed yield per hectare. This phenomenon suggests that all varieties derive benefits from expanded plant spacing, potentially facilitating improved light penetration and mitigating competition for essential resources among neighbouring plants.

Table 1. Yield and yield attributes of soybean as influenced by varieties and geometries

Treatments

Number of pods plant-1 100 Seed weight (g) Seed yield plant-1 (g) Seed yield (q ha -1 ) Straw yield (q ha -1 )

Quality parameters

Varieties

With respect to oil and protein content, the oil content of the three varieties, DSb 21, KDS 726 and KDS 753 was found to be 16.54 %, 17.68 % and 18.15 %, respectively. KDS 753 showed significantly higher oil content with an increase of 1.47 % compared to DSb 21.

The elevated oil content exhibited by KDS 753 could be attributed to its genetic makeup, likely favouring a heightened lipid biosynthesis pathway. This aligns with prior research, including the work of Rani (2000) [18] and Vyas et al. (2014) [19] which illuminated the genetic traits capability of boosting both oil content and yield. However, oil content of all the genotypes were lower than its potential due to late sowing and heavy rainfall occurred at pod development and maturity stages. Among the varieties, KDS 753 exhibited the highest protein content (38.88 %). In contrast, DSb 21 had the lowest protein content (36.41 %). However, the differences in protein content between varieties were not statistically significant. The protein yield, which represents the actual amount of protein obtained per hectare, varied significantly among the varieties. Comparable result was noticed by Meshram et al. (2014) [20] . The heightened protein content witnessed in KDS 753 suggests the presence of advantageous genetic traits, these collective insights underscore the dominant role genetics plays in shaping protein related characteristics in soybean crops.

Planting geometry

Spacing did not exert significant influence on protein and oil content. Nevertheless, it is important to highlight that the wider spacing of 45 × 10 cm exhibited notably higher protein yield (868 kg ha -1 ) and oil yield (399 kg ha -1 ). The higher protein and oil yield achieved under this treatment can be attributed to the higher seed yield, as it directly contributes to the higher protein and oil yield. Remarkably similar results were also documented by Halvankar et al. (1999) [21] , Vyas et al. (2014) [19] and Patel et al. (2022).

Interactions

Among the treatment combinations, the variety KDS 753 when sown with the planting geometry of 45 × 10 cm recorded significantly higher oil yield (456 kg ha -1 ) and protein yield (981 kg ha -1 ) compared to other treatments which was statistically comparable with the same variety at planting geometry of 37.5 × 10 cm. These increase in protein and oil yield can be attributed directly to the higher seed yield.

Conclusions

In conclusion, the comprehensive analysis of soybean cultivation strategies reveals the significant performance of the KDS 753 variety, particularly when paired with the optimal spacing of 45 × 10 cm. This combination showcases higher seed yield and superior quality.

Highlighting the significance of customized cultivation methods, incorporating KDS 753's genetic attributes, optimal spacing and resource efficiency. In essence, KDS 753 emerges as a promising option for soybean cultivation, effectively balancing yield improvement and economic viability.

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22. How to cite this article: Dewangan I, Somanagouda G, Salakinkop S, R C. Impact of improved agronomic approaches on yield and quality of soybean [Glycine Max (L.) Merrill] under northern transition zone of Karnataka. International Journal of Research in Agronomy. 2026;9(10):348-352. doi: https://www.do i.org/10.33545/2618060X.2026.v9.i10e.6807