Assessment of nitrogen content, uptake, quality and economics of finger millet (Eleusine coracana G.) as influenced by nitrogen levels and selected varieties

Introduction

Millets are small-grained coarse cereals traditionally cultivated by smallholders and tribal farmers in tropical regions and are among the oldest crops grown in India (Maitra, 2020) [16] . They are broadly classified into major and minor millets. Finger millet (Eleusine coracana G.) is an allotetraploid cereal (2n = 4x = 36, AABB) belongs to the Poaceae family and adapted to semi-arid regions due to its C₄ photosynthetic system. Its gluten-free grains are widely used in food and beverages, while the straw serves as feed and thatching material. The crop has excellent storage quality (Ceasar et al., 2018) [4] and a rich nutritional profile, containing high levels of Ca, Fe, Zn, K, Mg, Mn, dietary fibre, phenolic compounds and essential amino acids such as cystine, methionine and tryptophan (Backiyalakshmi et al., 2023) [2] . Finger millet products are reported to reduce blood cholesterol and blood pressure and possess anti-cancer, anti-ageing, anti-diabetic, anti-obesity and anti-anaemic effects. Owing to these benefits, finger millet is considered a "superfood" for combating malnutrition (Gebreyohannes et al., 2024) [9] . The crop is ecologically resilient (Prasanna Kumar et al., 2019) [22] , highly responsive to nutrient application (Ramya et al., 2020) [24] and contributes to agro-biodiversity due to its rich varietal base (Brahmachari et al., 2018) [3] . The low productivity of finger millet is mainly attributed to the use of local varieties, poorquality seed, weak crop establishment under direct sowing and faulty agronomic practices (Maitra et al., 2020) [16] . Although several improved cultivars in India have the potential to yield 3.5-4.0 t ha -1 (Prabhakar et al., 2017) [21] , their wider adoption is essential to enhance overall production. Significant variation in yield attributes, grain yield and nutrient uptake among varieties has been documented (Simion et al., 2020) [27] . Likewise, efficient nutrient management plays a crucial role in improving finger millet productivity. Nitrogen is an essential macronutrient required in large quantities for plant growth (Dhhwayo and Whhgwin, 1984) [8] . It is often the most yield-limiting nutrient in crop production and is widely applied in annual crops. As a key component of proteins, nitrogen plays a vital role in plant metabolic processes, thereby influencing both productivity and quality in finger millet. Adequate nitrogen application has been reported to enhance growth, dry matter accumulation and yield, particularly under dry or rainfed conditions (Hari Prasanna, 2016) [12] . In view of these factors, a field experiment was conducted during the kharif, 2019.

Materials and Methods

The field experiment was conducted at the Instructional Farm, Pacific College of Agriculture, Udaipur, Rajasthan (24°35' N; 73°42' E). The area falls under Agro-climatic Zone IV-A ("Subhumid Southern Plains and Aravalli Hills"). The climate is subhumid with hot summers, humid monsoon and cold winters. The region receives about 640 mm annual rainfall, 70-80% during July-September. During kharif 2019, total rainfall was 835.9 mm. The soil was "clay loam" (35.6% sand, 37.4% silt and 26.3% clay) with bulk and particle densities of 1.30 and 2.65 Mg m⁻³ and porosity of 50.94%. It had pH (8.20), EC (0.77 dS m⁻¹) and 0.61% organic carbon. Available nutrients were: N (248.10 kg ha⁻¹), P (20.60 kg ha⁻¹) and K (355.90 kg ha⁻¹). The experiment included nine treatment combinations of three varieties (Local, GNN-7 and GN-8) and three nitrogen levels (0, 30, 60 kg N ha⁻¹) in a factorial RBD with three replications. Twenty-seven plots were laid out (4.3 x 3.3 = 14.19 m 2 gross; 4 x 3 = 12 m 2 net plot size). Furrows were opened at 25 cm spacing and sowing was done manually at a depth of 2-3 cm using a uniform seed rate of 8 kg ha⁻¹. Seeds were obtained from verified sources and treatments were imposed as per standard procedures.

The protein content (%) in grains was determined by multiplying grain nitrogen content (%) with a conversion factor 6.25 (A.O.A.C.).

Total N uptake by the crop: The total uptake of N by the crop was estimated by using the following formula:

Net returns: To find out the most profitable treatment, economics of different treatments was worked out in terms of net returns by subtracting the cost of treatment and the cost of cultivation from gross income obtained. Net returns (Rs. ha -1 ) = Gross returns -Total cost of cultivation Benefit-cost ratio: This was calculated by dividing net returns with cost of cultivation for each treatment to see the economic viability of the treatments.

Statistical analysis:

Data collected during the present investigation were subjected to statistical analysis by adopting appropriate method of analysis of variance as described by Cochran and Cox (1967) [7] . Wherever the variance ratio (Fvalues) were found significant at 5 percent level of probability, the critical difference (CD) values were computed for making comparison among the treatment means. To assess the relationship between various characters, correlation coefficient was worked out in order to establish cause and effect relations. All the statistical estimates were computed by standard statistical procedures (Panse and Sukhatme, 1995) [20] .

Results and discussion Protein Content in Grain

Protein content varied significantly among varieties (Table 1). GN-8 recorded the highest protein content (7.08%) followed by the GNN-7 over local variety. The superior protein content in GN-8 can be attributed to its higher nitrogen accumulation in grains as the protein content is directly influenced by grain N concentration. The strong positive correlation between protein content and grain N content (r = 0.991) further supported this relationship. Similar varietal differences were reported by Kumari et al., (2018) [15] . Application of significantly increased protein content over the control and 30 kg N ha⁻¹ remained at par. The increase in protein content under higher N supply is due to enhanced synthesis of amino acids, continued nitrogen availability during grain filling and subsequent protein accumulation. These findings align with those of Rao et al. (1989) [25] , who observed increased protein content with nitrogen fertilization.

Nitrogen Content in Grain and Straw

Varieties did not differ significantly in N content of grain. However, GN-8 recorded significantly higher N content in straw (Table 1). Increased nitrogen content in GN-8 may be linked to its greater biomass accumulation and improved nutrient absorption efficiency. Similar type of variation in N content was noted by Maitra et al. (1999) [17] , Gupta et al. (2012) [11] and Radha et al. (2020) [23] . Nitrogen levels had a consistent positive effect on N content in both grain and straw. Increasing N from 0 to 60 kg ha⁻¹ significantly enhanced N content, better nitrogen nutrition and assimilation in plants. Similar increases in tissue N content due to nitrogen fertilization have been reported by Rao et al. (1986) [26] , Jagathjothi et al. (2010) [13] , Pallavi et al. (2015) [18] and Radha et al. (2020) [23] .

Nitrogen Uptake by Grain and Straw

Varieties GN-8 and GNN-7 were at par and recorded significantly higher N uptake by grain and straw compared to the local variety (Table 1). The higher uptake in GN-8 is associated with its greater dry matter production as nutrient uptake is a function of biomass and nutrient concentration. The results are in close conformity with the findings of Pallavi et al. (2015) [18] , Radha et al. (2020) [23] and Panda et al. (2021) [19] . This relationship supported by the strong correlation between dry matter accumulation and total N uptake (r = 0.997). Nitrogen uptake increased significantly with higher nitrogen levels. Application of 30 kg N ha⁻¹ increased N uptake by grain by 53.29%, while 60 kg N ha⁻¹ further enhanced uptake by 9.64% over 30 kg N ha⁻¹. Straw N uptake increased by 79.83% at 60 kg N ha⁻¹ over control. These improvements can be attributed to increased nitrogen availability, enhanced root activity and greater vegetative growth. A positive correlation between grain yield and N uptake (r = 0.905) supports the role of applied nitrogen in boosting uptake efficiency by Singh (2015) [29] and Panda et al. (2021) [19] .

Economics

Variety GN-8 recorded the highest net returns (₹59,954.11 ha⁻¹) and B:C ratio (2.53) due to its higher yield and nutrient uptake efficiency, aligning with the findings of Giribabu (2010) [10] . Among nitrogen levels, 60 kg N ha⁻¹ produced the maximum net returns (₹60,825 ha⁻¹) and the highest B:C ratio (2.56), performing significantly better than the control and at par with 30 kg N ha⁻¹, consistent with Chandraprabha et al. (2024) [5] .

Treatment

Yield (q ha -1 ) Nitrogen content (%) N uptake (kg ha -1 ) Total N uptake (kg ha -1 ) Protein content (%) Net returns (Rs. ha - Grain yield (kg ha -1 ) Plant height at harvest (cm) 0.899* 6.

Grain yield (kg ha -1 ) Number of tillers m -1 row length at harvest 0.974* 7.

Grain yield (kg ha -1 ) DMA (g plant -1 ) at harvest 0.942* 8.

Grain yield (kg ha -1 ) Effective tillers m-1 row length 0.907* 9.

Grain yield (kg ha -1 ) Ear length(cm) 0.996* 10.

Grain yield (kg ha -1 ) Ear weight (g) 0.907* 11.

Grain yield (kg ha -1 ) No. of grains per ear 0.987* 12.

Grain yield (kg ha -1 ) Test weight 0.907* 13.

Grain yield (kg ha -1 ) N uptake by grain (%) 0.907* * Significant at 5 percent level of probability Grain yield (kg ha -1 ) N content in grain (%) 0.985* 2.

Grain yield (kg ha -1 ) N uptake in grains (kg ha -1 ) 0.905* 3.

Protein content (%) N content in grain (%) 0.991* 4.

Total N uptake by the crop Biological yield (kg ha -1 ) 5.

Number of effective tillers m -2 Number of grains spikes -1 0.998* * Significant at 5 percent level of probability

Conclusion

The study clearly demonstrated that both variety selection and nitrogen fertilization play a crucial role in enhancing the productivity, quality and profitability of finger millet under semi-arid conditions. Among the tested varieties, GN-8 consistently outperformed GNN-7 and the local variety in terms of protein content, nitrogen content, nitrogen uptake, net returns and B:C ratio, highlighting its superior genetic potential and nutrient use efficiency. Application of nitrogen significantly influenced quality and nutrient dynamics, with 60 kg N ha⁻¹ recording the highest nitrogen content in grain and straw, maximum total N uptake and the most favorable economic returns. The strong positive correlations between nitrogen availability, dry matter accumulation, N uptake and grain quality further the importance of adequate nitrogen supply. Based on the findings, the combination of variety GN-8 with 60 kg N ha⁻¹ is recommended for achieving higher productivity, better grain quality and improved economic returns in finger millet cultivation under semi-arid conditions.

Acknowledgement

AcknowledgmentThe authors thank the Department of Agronomy, Pacific College of Agriculture Udaipur, for providing all facilities during the course of this study.

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