Synergistic effect of iron and zinc on growth, yield, and economics of little millet (Panicum sumatrense Roth ex Roem. & Schult.) in the Chitrakoot region

Introduction

The global agricultural landscape is increasingly confronted with the dual food security for fast growing population is becoming more harder and mitigating the impacts of climate change, a context that has catalyzed a renewed interest in climate-resilient, nutrient-dense crops. Little millet (Panicum sumatrense), often referred to as 'Kutki', stands out as a quintessential underutilized crop with immense potential to contribute to sustainable agriculture and nutritional security due to its exceptional adaptability and nutritional profile (Goron & Raizada, 2015) [8] . Its grains are rich in phytochemicals and contain substantial amounts of iron (5-8 mg/100 g) and zinc (3-4 mg/100 g), values that are higher than those found in milled rice and refined wheat (Saleh et al., 2013) [16] . Despite its virtues, little millet cultivation in India is characterized by low productivity, averaging a stagnant 500 kg/ha (Directorate of Millets Development, 2022) [7] . This is particularly evident in tribal-dominated districts and the Bundelkhand region, including Chitrakoot, where the persistent low yield is primarily attributed to the use of local landraces and inadequate nutrient management (Yadav et al., 2021) [23,24] . The soils of Chitrakoot are semi-arid, often deficient in essential micronutrients like zinc and iron, which not only limits crop yield but also results in grains with low mineral content, exacerbating local nutritional deficiencies or "hidden hunger" (Singh et al., 2020) [18] . Iron is fundamental part of chlorophyll synthesis, respiration, and DNA synthesis (Briat et al., 2015) [3] , while zinc acts as a co-factor for over 300 enzymes regulating carbohydrate metabolism, protein synthesis, and auxin metabolism (Alloway, 2008) [2] . Research in other millets has demonstrated that foliar application of iron and zinc is a highly efficient method for increasing their content in grains, bypassing soil-related constraints common in semi-arid regions (Cakmak, 2008; Aciksoz et al., 2011) [4,1] . Therefore, this study was formulated with the following objectives: to study the effect of iron and zinc on the growth and yield of little millet, and to work out the economics of different treatment combinations.

Materials and Methods

Experimental Site and Climate

The experiment was carried out at Agriculture Research farm, Mahatma Gandhi Chitrakoot Gramodaya Vishwavidyalaya, Chitrakoot, Satna (M.P.), which lies in a semi-arid, sub-tropical region (25.148°N latitude, 80.855°E longitude). The soil of the experimental field was sandy loam in texture, slightly high (pH 7.3), low in organic carbon (0.25 %), and deficient in available iron (3.52 ppm) and zinc (0.48 ppm).

Experimental Design and Treatments

The trial was arranged in a Randomized Block Design (RBD) with 3 replications. Total Nine treatment combinations were tested, involving three levels of foliar iron (0, 2, and 3 ppm from FeCl₃) and three levels of soilapplied zinc (0, 20, and 30 kg ha⁻¹ from ZnSO₄), with a uniform application of 5.0 t ha⁻¹ of Farm Yard Manure (FYM) in all treated plots except the control. A uniform recommended dose of fertilizer (N:P₂O₅:K₂O @ 40:20:20 kg ha⁻¹) was applied to all plots. The little millet variety 'JK-4' was sown on 30th July 2024.

Data Collection and Analysis

Observations on growth parameters (plant height, number of leaves, number of tillers per meter row length) were recorded at 20, 40, and 60 Days After Sowing (DAS). At harvest, yield attributes like dry matter accumulation, panicle length, and test weight (1000-seed weight) were measured. Grain and straw yield were recorded from the net plot and converted to kg ha⁻¹. Economics were calculated based on prevailing input and output prices. The data were subjected to Analysis of Variance (ANOVA), and all treatments were evaluated at the 5% level of significance using the CD test.

Results and Discussion

Growth Parameters

The integrated application of Fe and Zn significantly influenced all growth parameters. Treatment T₉ [3 ppm Fe + 30 kg Zn ha⁻¹ + 5.0 t FYM] consistently resulted in the maximum plant height (104.37 cm at 60 DAS) and number of tillers per meter row length (11.2 at 60 DAS). The lowest values were recorded in the control treatment T₁ (Table 2).

Iron is a critical co-factor for enzymes involved in chlorophyll synthesis and electron transport, thereby enhancing photosynthetic efficiency (Briat et al., 2015) [3] . Zinc is essential for auxin synthesis, which regulates cell division and elongation (Alloway, 2008) [2] . Their synergistic interaction, facilitated by the improved soil health from FYM, likely enhanced meristematic activity and resource allocation, leading to better plant architecture, a finding consistent with Mandal et al. (2021) [12] . 3). Consequently, T₉ also produced the significantly highest grain yield of 12.44 q ha⁻¹, which was 22.7% higher than the control treatment T₁ (10.12 q ha⁻¹). Zinc plays a specific role in pollen development and viability, which is crucial for proper grain setting, while iron is vital for energy transfer during the grain filling process (Cakmak, 2008; Hafeez et al.,

] . The combination ensured efficient photosynthesis, translocation of assimilates, and seed development, a finding supported by Das et al. (2022) [5] .

Economics

Economically, Treatment T₉ [3 ppm Fe + 30 kg Zn ha⁻¹ + 5.0 t FYM], despite having the highest cost of cultivation (₹ 30,370 ha⁻¹), generated the maximum gross return (₹ 58,025 ha⁻¹) and net return (₹ 27,655 ha⁻¹) (Table 4). The higher yield in T₉ comfortably offset its increased input cost.

However, the most favorable B:C ratio of 2.02 was observed in T₇ [3 ppm Fe + 0 kg Zn ha⁻¹ + 5.0 t FYM], indicating that for farmers with capital constraints, foliar iron alone with FYM provides the highest return per rupee invested. The results align with Joshi et al. (2023) [10] , who reported that a combination of micronutrients and organic amendments significantly improved the profitability of millet cultivation.

Conclusion

The study conclusively demonstrates that the combined application of iron and zinc, along with FYM, significantly enhances the growth, yield, and profitability of little millet.

3 For farmers aiming for the highest economic efficiency per rupee invested, T₇ [3 ppm Fe + 5.0 t FYM] presents the most viable and economically sustainable alternative. The adoption of this integrated micronutrient management is a step towards precision nutrition, ensuring higher productivity, enhanced farm income, and improved nutritional output from little millet.

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