Effect of weed management and growth hormones on growth, yield and economics of black wheat (Triticum aestivum L.) in the North East plain Zone

Introduction

Wheat (Triticum aestivum L.) is one of the most widely cultivated cereal crops and forms the backbone of food security in India, where it is grown over about 30 million hectares with an annual production of nearly 110 million tonnes. In recent years, attention has shifted from quantity to quality of food, and pigmented wheat varieties such as black wheat have gained importance because of their high anthocyanin and phenolic content. These compounds possess strong antioxidant properties, and black wheat additionally offers a comparatively lower glycemic index and higher fibre content, making it a promising functional food. Despite these advantages, the cultivation of black wheat is still limited, mainly due to the lack of region-specific agronomic recommendations. Among the various constraints in wheat production, weed infestation is a major factor that can reduce grain yield by 30-50% through competition for nutrients, moisture, light and space, the loss being most severe during early crop growth. Chemical control using herbicides such as metribuzin, metsulfuron-methyl and pendimethalin is popular because it is effective and less labour-intensive, although excessive reliance on a single herbicide can encourage resistant weeds and affect soil health. Hence integrated approaches combining chemical and manual methods are advocated. Plant growth regulators (PGRs) influence growth and development even at low concentrations. Gibberellic acid (GA₃) promotes cell elongation, leaf expansion and photosynthesis; indole-3-butyric acid (IBA) stimulates root development; and amino acids act as biostimulants supporting nitrogen metabolism. Combining effective weed management with judicious use of PGRs may therefore produce better results than either practice alone, particularly for black wheat where information is scarce. Keeping these points in view, the present investigation was undertaken with the following objectives: (i) to study the effect of weed management and growth hormones on the growth and yield of black wheat; and (ii) to work out the economics of the different treatment combinations.

Materials and Methods

The field experiment was carried out during the rabi season of 2025-26 at the Agricultural Research Farm, Prof. Rajendra Singh (Rajju Bhaiya) University, Prayagraj (U.P.), situated at 25°13′ N latitude and 81°46′ E longitude at an altitude of about 98 m above mean sea level. The soil of the experimental field was sandy loam in texture, slightly alkaline in reaction (pH 8.25), low in organic carbon (0.42%) and available nitrogen (181.60 kg ha⁻¹), medium in available phosphorus (16.50 kg ha⁻¹) and available potassium (230.47 kg ha⁻¹). The experiment was laid out in a Randomized Block Design (RBD) with twelve treatment combinations replicated three times, giving a total of 36 plots, each of 9 m² (3 m × 3 m). The black wheat variety NABI-MG was sown manually at a spacing of 20 cm × 3 cm using a seed rate of 100 kg ha⁻¹. Metribuzin @ 175 g a.i. ha⁻¹ and metsulfuron-methyl @ 4 g a.i. ha⁻¹ were applied as post-emergence herbicides, pendimethalin 30% EC was applied as a pre-emergence herbicide immediately after sowing, and hand weeding was carried out at 30 and 60 DAS. The growth regulators (IBA, GA₃ and amino acid) were applied as foliar sprays at the recommended concentrations using a knapsack sprayer. The treatment combinations were T₁-T₁₂ as shown in Table 1. Observations on plant height, leaf area index (LAI), dry matter accumulation, root length and number of tillers were recorded at 30, 60 and 90 DAS and at harvest. Yield attributes (number of ears m⁻², number of seeds plant⁻¹, ear length and test weight), seed yield, straw yield, biological yield and harvest index were recorded at harvest. Economics of treatments was worked out in terms of cost of cultivation, gross return, net return and benefit-cost (B:C) ratio. The data were statistically analysed by the analysis of variance technique for RBD, and treatment means were compared using the critical difference (CD) at 5% level of significance.

Yield attributes

The yield attributes were significantly influenced by the treatments, except test weight, which differed only numerically. The maximum number of ears (361.85 m⁻²), number of seeds per plant (44.83), ear length (9.67 cm) and test weight (36.89 g) were recorded under T₁₁ (Hand weeding + GA₃), closely followed by T₁₂ (Hand weeding + Amino acid), T₁₀ (Hand weeding + IBA) and T₉ (Pendimethalin + GA₃). The improvement in yield attributes under T₁₁ is the result of better weed control and the favourable effect of GA₃ on photosynthesis and assimilate translocation from source to sink during the reproductive phase. The minimum values were recorded under T₁ (Metribuzin + IBA).

Yield and harvest index

Seed yield, straw yield, biological yield and harvest index varied significantly among the treatments. The maximum seed yield (45.60 q ha⁻¹), straw yield (51.00 q ha⁻¹), biological yield (94.30 q ha⁻¹) and harvest index (48.36%) were recorded under T₁₁ (Hand weeding + GA₃), followed by T₁₂ (Hand weeding + Amino acid), T₁₀ (Hand weeding + IBA) and T₉ (Pendimethalin + GA₃). The higher seed yield under T₁₁ is a cumulative outcome of more ears per unit area, more seeds per plant, longer ears and better test weight, while the higher harvest index indicates more efficient partitioning of photosynthates towards the economic yield. The lowest seed yield (24.60 q ha⁻¹) and harvest index (22.75%) were recorded under T₁ (Metribuzin + IBA), reflecting poor growth and inefficient resource utilization.

Economics of treatments

The cost of cultivation ranged from ₹51,448 ha⁻¹ (T₁) to ₹66,545 ha⁻¹ (T₄), depending on the herbicide used, the growth regulator applied and labour requirement for hand weeding. The maximum gross return (₹2,65,792 ha⁻¹) and net return (₹2,02,499 ha⁻¹) were obtained under T₁₁ (Hand weeding + GA₃), owing to its superior seed and straw yields.

The benefit-cost ratio was highest under T₁₁ (3.20), followed by T₁₂ (3.08), T₁₀ (3.07) and T₉ (3.03), and lowest under T₁ (2.06). The high B:C ratio under T₁₁ indicates that every rupee invested generated the greatest return, confirming that hand weeding combined with GA₃ is the most remunerative practice for black wheat under the agro-climatic conditions of Prayagraj.

Conclusion

On the basis of one season of experimentation, it is concluded that the combination of hand weeding with foliar application of gibberellic acid, T₁₁ (Hand weeding + GA₃), proved to be the most effective treatment for black wheat, producing the highest growth, yield attributes, seed yield (45.60 q ha⁻¹), biological yield, harvest index and profitability (net return ₹2,02,499 ha⁻¹; B:C ratio 3.20). Therefore, T₁₁ may be recommended for achieving higher productivity and profitability of black wheat under the agroclimatic conditions of the North East Plain Zone. As the conclusions are drawn from a single year's data, the study should be repeated for at least one more season, and with additional combinations and concentrations of growth regulators, to confirm the findings.

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