How Sulfur and Micronutrients Transform Summer Cultivation
Imagine an ancient crop, cultivated for over 3,500 years, yet still revealing its secrets to modern science. Sesame—known as the "queen of oilseeds"—holds tremendous economic and nutritional value, but its potential yields remain largely untapped by many farmers worldwide. In today's changing agricultural landscape, where soil nutrient deficiencies are increasingly common and climate challenges more frequent, unlocking sesame's full productivity requires sophisticated nutrient management strategies that go beyond traditional approaches.
The combination of basal sulfur application and carefully timed foliar micronutrient sprays represents a revolutionary approach to sesame cultivation that can significantly enhance both yield and oil quality. This article explores the science behind these techniques, examining how proper nutrient management can transform sesame from a traditional crop into a modern agricultural success story, offering farmers the opportunity to maximize their returns while practicing sustainable agriculture.
Sesame (Sesamum indicum L.) is primarily grown in arid and semi-arid regions where it faces multiple abiotic stresses including drought, high temperatures, and often less-than-ideal soil conditions. Despite being known for its drought tolerance, sesame has specific nutritional requirements that must be met to achieve optimal growth and yield. The plant's nutritional demand is particularly high during the reproductive stages, when capsule formation and seed development occur.
Essential for chlorophyll formation, amino acid synthesis, and oil quality improvement
Zinc and boron play crucial roles in growth regulation and reproductive development 3
Sulfur plays a fundamental role in sesame physiology that extends far beyond what many farmers appreciate. As the fourth essential element after nitrogen, phosphorus, and potassium, sulfur is involved in:
Sulfur deficiency has become increasingly common in agricultural soils worldwide, partly due to reduced sulfur emissions from industrial sources and the use of sulfur-free mineral fertilizers. This deficiency negatively affects both growth and maturation stages of sesame and ultimately reduces oil quality .
While required in smaller quantities, micronutrients like zinc and boron play disproportionate roles in sesame productivity:
The synergistic relationship between sulfur and micronutrients creates effects that are greater than the sum of their individual benefits, making combined application strategies particularly effective.
A comprehensive field experiment conducted at the Crop Research Farm, Department of Agronomy, SHUATS, Prayagraj, during the kharif season of 2022 examined the effects of micronutrients and sulfur on sesame growth and yield. The study employed a Randomized Block Design with ten treatments replicated three times to ensure statistical reliability. The treatments included various levels of zinc (10 kg/ha and 5 kg/ha), boron (5 kg/ha and 2.5 kg/ha), and sulfur (30 kg/ha, 40 kg/ha, and 50 kg/ha), with a control plot for comparison 3 .
The results were striking: application of micronutrients and sulfur significantly improved all measured growth parameters. Specifically, researchers observed maximum plant height (127.57 cm), plant dry weight (17.47 g plant⁻¹), crop growth rate (7.94 g/m²/day), and relative growth rate (0.026 g/g/day). Yield parameters showed equally impressive improvements, with number of capsules per plant (43.37), seeds per pod (49.40), test weight (3.40 g), and stover yield all increasing significantly 3 .
Data source: Field experiment at SHUATS, Prayagraj (2022) 3
Another fascinating study conducted in Fasa city, Iran, during 2017-2018 examined the effects of sulfur foliar application at five different concentrations (0, 1, 2, 4, and 8 ml of liquid sulfur per liter, equivalent to 0, 300, 600, 1200, and 2400 ml of liquid sulfur per hectare) on five different sesame cultivars. This two-year factorial experiment revealed that treatments with concentrations of 6 and 8 ml of sulfur foliar application without statistically significant differences between them were superior in terms of multiple traits: number of capsules per plant, thousand-grain weight (TGW), plant dry weight (PDW), grain yield (GY), harvest index (HI), and grain oil content .
The highest number of seeds per capsule was obtained from the concentration of 8 ml sulfur foliar application. All cultivars responded positively to increased sulfur levels, with the highest grain yield and number of capsules per plant belonging to C1 (Darab 1), C4 (Tak-Par Dashtestan), and C5 (Shesh-Par Borazjan) cultivars. The interaction between C5 and a concentration of 8 ml sulfur spraying produced the highest yield, number of capsules per plant, TGW, PDW, and HI .
| Sulfur Concentration (ml/L) | Capsules/Plant | Thousand-Grain Weight (g) | Grain Yield (kg/ha) | Oil Content (%) |
|---|---|---|---|---|
| 0 (Control) | 32.5 | 2.85 | 895 | 52.1 |
| 1 | 36.8 | 2.92 | 985 | 53.4 |
| 2 | 40.2 | 2.98 | 1105 | 54.8 |
| 4 | 45.6 | 3.12 | 1250 | 56.3 |
| 8 | 48.3 | 3.24 | 1325 | 57.9 |
Table 1: Effect of Sulfur Foliar Application on Sesame Yield Parameters
Data source: Study in Fasa city, Iran (2017-2018)
The remarkable improvements in growth and yield resulting from sulfur and micronutrient applications can be explained by examining their physiological mechanisms within the sesame plant.
The relationship between different nutrients creates synergistic effects that enhance overall plant productivity. For instance, sulfur improves nitrogen use efficiency, meaning that plants can make better use of available nitrogen when sufficient sulfur is present. This interaction is particularly important during the vegetative growth stage when plants are developing the photosynthetic capacity that will ultimately support yield formation.
Similarly, zinc and boron interact to improve reproductive development. Zinc influences auxin metabolism, which affects cell division and expansion, while boron is crucial for pollen viability and tube growth, directly impacting fertilization success and seed set. These interactions help explain why combined application strategies often outperform single-element treatments 3 .
| Treatment | Plant Height (cm) | Dry Matter Production (kg/ha) | Capsules/Plant | Seed Yield (kg/ha) |
|---|---|---|---|---|
| Control | 98.5 | 2450 | 32.5 | 650 |
| Sulfur Only (40 kg/ha) | 112.3 | 2980 | 41.8 | 785 |
| Micronutrients Only | 105.7 | 2750 | 38.2 | 720 |
| Sulfur + Micronutrients | 127.6 | 3180 | 49.4 | 910 |
Table 2: Effect of Combined Nutrient Applications on Sesame Growth Parameters 3 4
Based on the research findings, farmers can implement the following application strategies to maximize sesame productivity:
Apply 40-60 kg S/ha as basal dose before planting or during sowing. This provides a steady supply of sulfur throughout the growing season, supporting both vegetative and reproductive development 1 .
Apply zinc and boron as foliar sprays during critical growth stages:
Recommended concentrations: Zinc sulfate at 0.5%, Borax at 0.2% 3
Use prepared combined nutrient formulations that can be applied as foliar sprays at 30 and 45 days after sowing. These have been shown to produce maximum plant height (127.4 cm), dry matter production (3856 kg/ha), number of branches (9.8), number of capsules per plant (153.2), seeds per capsule (58.4), thousand seed weight (3.12 g), and seed yield (719 kg/ha) 4 .
| Reagent/Material | Function | Typical Application Rate |
|---|---|---|
| Zinc Sulfate (ZnSO₄·7H₂O) | Corrects zinc deficiency, improves growth regulators and enzyme activity | 5-10 kg/ha (soil); 0.5% (foliar) |
| Borax (Na₂B₄O₇·10H₂O) | Addresses boron deficiency, enhances cell wall formation and pollen viability | 2.5-5 kg/ha (soil); 0.2% (foliar) |
| Ammonium Sulfate ((NH₄)₂SO₄) | Provides both nitrogen and sulfur, improves protein and oil content | 40-60 kg S/ha (as basal application) |
| Liquid Sulfur Formulations | Foliar-applied sulfur for rapid nutrient uptake during critical growth stages | 4-8 ml/L water (foliar spray) |
| Combined Nutrient Formulations | Specialized mixes providing balanced micronutrient nutrition | 1-2% solution (foliar spray) |
Table 3: Key Research Reagents and Their Functions in Sesame Nutrition Studies 3
While implementing these nutrient management strategies involves additional costs, the return on investment is typically favorable. Research indicates that the combined application of sulfur and micronutrients can increase seed yields by 30-40% over control treatments, with even greater improvements in oil content and quality. Farmers should conduct small-scale trials to determine the optimal application rates for their specific conditions before implementing full-scale changes.
Projected return on investment for sulfur and micronutrient applications
The research clearly demonstrates that integrated nutrient management combining basal sulfur application with foliar micronutrient sprays represents a powerful strategy for enhancing sesame productivity. This approach addresses the crop's specific physiological needs while adapting to modern agricultural challenges, including changing environmental conditions and increasingly depleted soils.
As we look to the future, sesame cultivation must continue to evolve by embracing science-based practices that optimize inputs while maximizing outputs. The precise management of sulfur and micronutrients offers a pathway to sustainable intensification of sesame production, allowing farmers to meet growing global demand while maintaining environmental stewardship. Further research should focus on developing region-specific recommendations and exploring additional nutrient interactions that could further enhance sesame's potential as a valuable oilseed crop for the 21st century.