Optimizing grain and oil yields of sesame (Sesamum indicum L.) through variety selection and intra-row spacing in the Sudan Savanna, Nigeria

Introduction

Sesame (Sesamum indicum L.), commonly known as beniseed, is one of the most ancient oilseed crops known to humanity, with domestication dating back over 3,000 years (Ashri, 2017) [1] . Primarily a rain-fed crop, it is cultivated throughout the tropics and subtropics. While characterized as a short-day plant, it exhibits broad adaptability to long-day environments. Sesame is highly valued for its superior oil quality, often distinguished as the "queen of oilseeds" due to its stability and nutritional profile. Globally, sesame is ranked sixth in oilseed production and eighth in vegetable oil production (FAO, 2018) [2] . In 2018, global production reached approximately 6 million metric tons, with Myanmar, Sudan, and India leading as the primary producers (FAO, 2020) [3] . In the Nigerian context, sesame was introduced following World War II. While initially cultivated as a minor crop in the Northern and Central regions, it gained significant prominence as a major commercial crop after 1974 (Madina, 2020) [4] . Currently, it is a vital cash crop across several northern states, including Benue, Jigawa, Nasarawa, and Taraba, with additional production in Borno, Gombe, Kano, Katsina, Kogi, Plateau, and Yobe (Arora, 2024) [5] . Nigeria produces over 580,000 tonnes of sesame annually. As of the end of 2018, sesame seeds emerged as Nigeria's largest agricultural export, with the potential to generate over US$4 billion in annual revenue through expanded export activities (Stan, 2020) [6] . Nigeria possesses high potential for sesame production, driven by increasing domestic and international demand for the crop and its derivatives. Sesame is regarded as the "queen of oilseeds" due to its exceptional oil content and quality (Olawuyi et al., 2023) [7] . The popularity of sesame is attributed to its diverse health and industrial applications. Notably, the seeds contain a higher oil concentration than most other oilseed crops. Sesame oil is extensively utilized in the cosmetic industry for the formulation of lotions and creams. Furthermore, the oil possesses insecticidal and antifungal properties, allowing it to function as a surfactant and protective coating in agricultural formulations (Yahaya, 2023) [8] . The agronomic performance of sesame is influenced by climatic conditions, nutrient and water availability, inter-and intraspecific competition, and biotic stresses such as pests and diseases, alongside socioeconomic factors. Usman et al. (2021) [9] noted that traditional growers seldom utilize improved varieties; however, research indicates that improved cultivars significantly enhance yield potential. Additionally, inadequate spacing constrains the rhizosphere and photosphere, limiting the plant's ability to capture resources for growth. This restriction inhibits the development of growth parameters and hinders dry matter accumulation (Adesoji et al., 2020) [10] . Consequently, low sesame yields are frequently attributed to suboptimal plant density, improper planting dates, and high pest pressure (Yahaya, 2023). [8] Maximizing sesame productivity is essential for enhancing agricultural profitability and addressing food security challenges. A comprehensive understanding of how variety selection and intra-row spacing interact to influence performance enables the adoption of cultivation practices that optimize yield. Maximum light interception is achievable only when optimal plant spacing is provided from the early stages of vegetative growth (Rajesh et al., 2017) [11] . Furthermore, establishing an appropriate plant density is critical for the efficient utilization of growth factors-including water, light, nutrients, and carbon dioxide to maximize grain yield (Fetene and Alemayehu, 2016) [12] . According to Oloniruha (2021) [13] , planting geometry is a decisive factor in crop performance, as it dictates plant population and canopy architecture, which in turn affects solar radiation interception. To improve sesame yields in the study area, the integration of suitable varieties and precise spacing is necessary. Intra-row spacing directly modulates inter-plant competition for essential resources, thereby influencing resource-use efficiency. Identifying the optimal intra-row spacing for specific varieties allows for the minimization of resource wastage while enhancing dry matter accumulation and overall yield. Consequently, this research was conducted to evaluate the yield performance of sesame varieties as influenced by intra-row spacing within the Sudan Savanna of Nigeria, based on the hypothesis that varieties respond differentially to spatial arrangements.

Materials and Methods Experimental Site and Soil

The experiment was conducted during the 2025 wet season at two locations: the Teaching and Research Farm of the Basic Vocational Agriculture School, Tambu-Daura (12° 59' 34" N, 8° 16' 58" E; 549 m above sea level) and the Teaching and Research Farm of the College of Agriculture, Hassan Usman Katsina Polytechnic, Katsina (11° 49' N, 7° 23' E; 428 m above sea level). During the study period, the total annual rainfall was 412.4 mm and 398.1 mm for Tambu and Katsina, respectively. Prior to planting, composite soil samples were collected at a depth of 0-30 cm from both experimental sites and subjected to physical and chemical analyses using standard laboratory procedures. The soil textural classes were identified as sandy clay for Tambu and sandy loam for Katsina. The experimental treatments comprised three sesame varieties (EX-SUDAN, KENANA-4, and E8) and four intra-row spacings (10, 15, 20, and 25 cm). The trials were laid out in a split-plot design with four replications; varieties were assigned to the main plots, while intra-row spacings were allocated to the sub-plots.

Agronomic Practices

The experimental field was cleared, harrowed, and ridged prior to sowing. The field layout consisted of twelve main plots, each subdivided into four sub-plots. Each sub-plot comprised six ridges, with a gross plot size of 4m x 4.5m long (18m 2 ) and the net plot was 4m x 3m (12m 2 ). Each main plot contained four (4) sub-plots of 4 m x 4.5 m. Sesame seeds were sown according to the specified intra-row spacing treatments. At three stands per hole, the target plant populations were 399,000, 265,734, 199,500, and 159,600 plants ha -1 for the 10, 15, 20, and 25 cm spacings, respectively. Fertilizer was applied via side placement at a total rate of 60:30:30 kg ha -1 of N, P 2 O 5 , and K 2 O. A basal application of NPK 15:15:15 (providing 30:30:30 kg ha -1 ) at 3 weeks after sowing (WAS), followed by a top-dressing of 30 kg N ha -1 at 6 WAS, as recommended by Bassam (2024) [14] . Weed control was maintained through manual hoeing at 3, 6, and 9 WAS, with earthing-up carried out at 6 WAS. Harvesting was performed manually when the leaves and stems transitioned from green to yellow. Plants were cut at the base, bundled, and inverted over tarpaulins for two weeks to facilitate drying and minimize seed shattering.

Table 1: Summary of agronomic advantages of each variety

Verities

E8 EX-Sudan (NCRIBEN-04E) Kenana-4 (NCRIBEN-05E)

Performance primarily known for its high-yield potential high grain yield, high oil content and early maturity

The seeds are noted for their high fat/oil content.

Outstanding features i) combined performance in growth and yield-related traits. ii) exhibits favourable performance in several morphological traits, including days to germination, plant height, number of leaves, and number of branches. high potential grain yield, up to 1.2 tons per hectare. Source (Anon,2024) [15] Data Collection Data for the number of capsules, number of seeds per capsule, 1,000-seed weight, and seed yield per plant were obtained from five randomly tagged plants within each net plot. For seed yield per hectare, all plants within the net plot area were harvested, threshed, and weighed; the resulting net plot yields were then extrapolated to kg ha⁻¹. From the harvested seed lot, a 20 g representative sample was collected from each plot to determine oil and crude protein contents following AOAC (2012) [16] procedures. Seed oil content was determined gravimetrically using the Soxhlet extraction method with petroleum ether as the organic solvent. Following extraction, the solvent was evaporated, and the recovered oil was weighed. Crude protein was determined via the Kjeldahl method: seed nitrogen was digested with concentrated sulfuric acid to form ammonium sulfate. The ammonia released during distillation was trapped in boric acid and titrated against a standard acid solution. Total nitrogen was then multiplied by a conversion factor of 6.25 to calculate the crude protein percentage. Both oil and protein contents were recorded as percentages. Analysis was done at analytical laboratory of Soil Science Department, Bayero University, Kano, Nigeria.

Data Analysis

Data on yield and quality parameters were subjected to Analysis of Variance (ANOVA) following the procedures for a split-plot design as described by Gomez and Gomez (1984) [17] . All statistical analyses were performed using SAS software version 9.0 (SAS Institute, 2002) [18] . Significant differences among treatment means were separated using Duncan's Multiple Range Test (DMRT) at 5% and 1% levels of probability (P ≤ 0.05 and P ≤ 0.01) (Duncan, 1955) [19] .

Results

Soil Sampling and Analysis

The physico-chemical properties of the soil at the two experimental sites (Tambu and Katsina) are presented in Table 2. The results indicate that the textural class at both locations was sandy loam. Chemical analysis revealed soil values of 6.42 and 6.32 for Tambu and Katsina, respectively, indicating that the soils were slightly acidic at both sites. Total nitrogen (N) and organic carbon (OC) levels were higher in Tambu than in Katsina. Regarding exchangeable cations, Tambu exhibited higher concentrations of potassium (K), calcium (Ca), sodium (Na), and a higher Cation Exchange Capacity (CEC); however, magnesium (Mg) levels were higher at the Katsina site.

Capsule length

The impact of variety and intra-row spacing on the capsule length of sesame at Tambu and Katsina is presented in Tables 5.

Varietal differences were significant (P<0.05) at both locations.

In Tambu, EX-SUDAN and KENANA-4 performed similarly (statistically at par) but were significantly (P<0.05) superior to the E8 variety. However, in Katsina, EX-SUDAN significantly (P<0.05) outperformed all other varieties. The effect of intra-row spacing on capsule length was also significant (P<0.05) across both sites. Sowing at an intra-row spacing of 25 cm yielded significantly higher capsule lengths compared to the other spacing levels.

Number of seeds per capsule

The influence of variety and intra-row spacing on the number of seeds per capsule during the 2025 growing season at Tambu and Katsina is presented in Table 5. The varietal effect was significant (P<0.05) at both locations, with EX-SUDAN producing a significantly higher number of seeds per capsule (P<0.01) compared to the other varieties. Additionally, the effect of intra-row spacing was significant (P<0.05) at both sites; specifically, the 25 cm spacing produced a significantly greater number of seeds per capsule than the narrower spacing levels.

seed weight (SW)

The response of sesame 1,000-seed weight (1,000-SW) to variety and intra-row spacing during the 2025 growing season at Tambu and Katsina is presented in Table 6. The varietal effect was significant (P<0.05) at both locations, with EX-SUDAN recording a significantly higher 1,000-SW than the other varieties. Intra-row spacing also had a highly significant (P<0.01) influence on 1,000-SW across all sampling stages and locations. The results indicate that an intra-row spacing of 25 cm resulted in a significantly higher 1,000-SW compared to the other spacing treatments.

The response of seed yield per plant to variety and intra-row spacing during the 2025 growing season at Tambu and Katsina is presented in Table 6. The varietal effect was significant (P<0.05) at both locations, with EX-SUDAN producing a significantly higher seed yield per plant than the other varieties. Similarly, intra-row spacing significantly (P<0.05) influenced seed yield per plant at both sites. At both locations, sesame sown at an intra-row spacing of 25 cm resulted in significantly higher yields per plant compared to the narrower spacing treatments.

The response of seed yield per hectare to variety and intra-row spacing during the 2025 season at Tambu and Katsina is presented in Table 6. The varietal effect was significant (P<0.05) at both locations, with EX-SUDAN recording a significantly higher yield than the other varieties. Intra-row spacing also had a highly significant (P<0.05) influence on seed yield per hectare at both sites; specifically, sowing at 25 cm resulted in significantly higher yields compared to all other spacing levels.

The interaction effect between variety and intra-row spacing on seed yield per hectare at Tambu is presented in Table 7. The results indicate that the EX-SUDAN variety sown at 25 cm produced the highest seed yield (P<0.05), while the lowest yield was recorded for E8 at 10 cm (539.27 kg). Similarly, the significant interaction at Katsina is shown in Table 8. Here, EX-SUDAN at 25 cm again produced the highest seed yield (P<0.01), whereas the lowest yield was observed in KENANA-4 sown at 10 cm (490.55 kg).

The influence of variety and intra-row spacing on the seed oil yield of sesame during the 2025 growing season at Tambu and Katsina is presented in Table 9. The varietal effect was significant (P<0.05), with EX-SUDAN achieving a significantly higher oil yield than the other varieties. Intra-row spacing had a highly significant (P<0.05) influence on oil yield at both locations. The results demonstrate that an intra-row spacing of 25 cm resulted in a significantly higher oil yield compared to the other spacing levels

The influence of variety and intra-row spacing on the crude protein content of sesame during the 2025 growing season at Tambu and Katsina is presented in Table 9. The varietal effect was significant (P<0.05) across both locations, with EX-SUDAN recording significantly higher crude protein levels than the other varieties. Intra-row spacing also significantly (P<0.05) affected crude protein content at both sites. In Tambu, the 25 cm and 20 cm spacings were statistically at par. However, in Katsina, sowing sesame at an intra-row spacing of 25 cm resulted in a highly significant (P<0.05) increase in crude protein compared to all other spacing treatments. Means followed by the same letter(s) within the same column and treatment are not significantly different at 5% level of probability using DMRT. Means followed by the same latter(s) within the same column and treatment are not significantly different at 5% level of probability using DMRT: Not-significant. CPT: Crude protein.

Discussion

Appropriate soil quality and adequate moisture are vital for the growth and development of sesame in the Sudan Savanna. The sandy loam texture of the experimental sites is suitable for sesame cultivation; however, the soils were deficient in organic carbon, total nitrogen, available phosphorus, and CEC. These deficiencies are characteristic of Savanna soils, which are typically low in primary nutrients and exchangeable cations (Singh, 1987) [20] . Consequently, the split application of NPK fertilizer at 3 and 6 weeks after sowing was essential to support crop growth. This aligns with the observations of Adesoji et al. (2020) [10] , who noted that Nigerian Savanna soils rarely support viable crop production without fertility enhancement through organic or inorganic amendments.

The results of this study revealed that varietal effects were significant across all measured yield parameters, likely due to inherent genetic variations. This is consistent with Audu et al.

(2021) [21] , who attributed sesame development to improved genetic composition. The EX-SUDAN variety significantly outperformed KENANA-4 and E8 in terms of capsule number, capsule length, 1,000-SW, seed yield per plant, total seed yield, and oil and protein content. The superiority of EX-SUDAN is characterized by its high yield potential and early maturity, with potential yields of 1.3 t ha⁻¹ compared to 1.2 and 1.0 t ha⁻¹ for KENANA-4 and E8, respectively (Anon, 2024) [15] . These findings corroborate those of Mohammed et al. (2019) [22] , who reported that EX-SUDAN was superior to local varieties such as TUMKUR and GULBARGA. Similarly, Ibrahim et al. (2016) [23] and Rufai et al. (2024) [24] observed that EX-SUDAN consistently recorded higher yield components including capsule counts and grain yield than KENANA-4 and E8.

The intra-row spacing significantly influenced performance, with the 25 cm spacing outperforming narrower options. This was evidenced by significant increases in the number of capsules, seeds per capsule, seed yield per plant, yield per hectare, and oil and crude protein contents.

These results indicate that at lower plant populations, the efficiency of light, moisture, and nutrient utilization was improved, allowing the sesame crop to maximize resource capture at both experimental sites. These findings corroborate the results of Fetene and Alemayehu (2016) [12] , who reported that increase in intra row spacing from 5 to 25 cm, plant height (cm), primary branches per plant, capsules per plant, seed yield per plant (g), 1000-seed weight (g

Acknowledgement

AcknowledgementsI must acknowledge the Tertiary Education Trust Fund (TETFUND) for sponsoring this research from start to finish. Furthermore, I would like to thank the principle and staff of the College of Vocational Agriculture Tambu-Daura as well as the management of the College of Agriculture Hassan Usman Katsina Polytechnic for offering me with the lands used for the research. Additionally, I am grateful to Katsina State Agriculture and Rural Development Authority (KTARDA) for providing me with meteorological data for this research.

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