Impact of genotypes, fertilizer levels and cutting management on growth and yield of hybrid Napier

Introduction

Agriculture remains the backbone of the Indian economy, with the livestock sector playing a vital role in rural livelihoods, employment, income generation and nutritional security, particularly for small and marginal farmers (NAAS, 2024) [10] . India has emerged as the world's leading milk producer, with milk production reaching 230.58 million tonnes during 2022-23, reflecting the continued growth and importance of the dairy sector in the national economy (DAHD, 2024; NAAS, 2024) [10] . Livestock production also contributes substantially to the food and nutritional security of rural households and provides an important source of regular income. However, despite India's large livestock population and leading position in milk production, productivity per animal remains relatively low, mainly because of inadequate availability and quality of feed and fodder, limited genetic potential and insufficient adoption of scientific feeding, breeding and management practices (Kona, 2025) [8] . The shortage of quality green fodder is particularly important because cultivated fodder occupies only a small proportion of the total cultivated area, while crop residues and other available feed resources are often nutritionally poor. Therefore, improving the availability of high-quality fodder, along with better genetic resources, balanced nutrition and scientific dairy management, is essential for increasing livestock productivity, improving farm income and ensuring sustainable livestock production in India (NAAS, 2024; Kona, 2025) [10,8] .

Materials and Methods

The field experiment was conducted during 2023-24 and 2024-25 in consecutive two years at Post Graduate Institute Farm, Mahatma Phule Krishi Vidyapeeth, Rahuri, Dist. Ahilyanagar (Maharashtra State). The soils of the experimental field were clayey in texture. The soil was low in available Nitrogen (193.25 kg ha -1 ), medium in available phosphorous (15.75 kg ha -1 ) and very high in potassium (288.36 kg ha -1 ). The soil organic carbon content, pH and EC was 0.48 per cent, 8.27 and 0.39 dSm -1 respectively. The soil moisture constants viz., field capacity (34.42%), permanent wilting point (17.43%), bulk density (1.31 g cm -3 ) and porosity (47.94%) indicate that soil was good in water retention capacity. The field experiment was laid out in spilt-split plot design. The experiment was laid out in a split-split plot design with three replications and twenty seven treatments combinations comprising three genotypes G1-Phule Gunwant, G2-Phule Jaywant and G3-BNH-10 as main plot treatments; three fertilizer levels F1-150% RDF, F2-125% RDF and F3-100% RDF as sub plot treatments and three cuttings C1-75 Days interval, C2-60 Days interval and C3-45 days interval as a sub-sub plot treatments. The gross plot and net plot size were 6.00 m x 5.40 m and 5.80 m x 3.60 m, respectively. The experiment was conducted during two years on fixed site without changing the randomization. The periodical observations on growth studies, growth analysis and yield contributing characters and yield were recorded at 45, 60 and 75 days interval. The growth parameters viz., plant count, plant height (cm), number of tillers per bunch -1 , number of leaves plant -1 ; physiological parameters viz., chlorophyll content (%); Yield contributing characters viz., green fodder yield (t ha -1 ) and dry matter yield (t ha -1 ). The land was ploughed twice by a tractor with chisel ploughing followed by harrowing in the experimental field. The field was brought to fine tilth and laid out in to proper plot size (m). The Hybrid Napier fodder slips were planted at 90 x 60 cm spacing and the first irrigation was done on the same day of planting and thereafter as and when required. The necessary after care operations such as hand weeding were done as per the requirement. Also 5 plants were tagged in each plot initially on 15th day to study the growth parameters of the fodder crop on 60 days after planting (DAP) as first cut and subsequent cut as per treatments. The growth and yield observations were recorded from the net plots. The data collected on growth parameters between treatments were subjected to Analysis of Variance (ANOVA) by split-split plot design to find the significant difference between treatments and interpretation of data was done as per the procedure described by Gomez and Gomez (1984) [4] .

Results and Discussion

The results of the experiment were presented based on the pooled data of 2020, 2021 and 2022.The data on growth components viz., plant height, number of leaves, number of tillers and number of leaves/ tillers as well as yield components i.e., per plant yield and total yield (t/ha/year) as influenced by different treatments were presented in Table 1 and 2 respectively.

Effect of Genotypes

The genotypes included in the present investigation were G₁-Phule Gunwant, G₂-Phule Jaywant and G₃-BNH-10. However, the growth and yield parameters differed significantly among the genotypes. Phule Gunwant (G₁) recorded significantly higher plant height (191.79 cm), maximum tillers per plant in (47.39), and higher number of leaves per bunch (414.24). BNH-10 (G₃) recorded the highest leaf: stem ratio (1.04), while Phule Jaywant (G₂) recorded the lowest values for most growth parameters. The superior vegetative growth of Phule Gunwant resulted in significantly higher total green forage yield (262.17 and 286.11 t ha⁻¹; pooled 274.14 t ha⁻¹) and total dry matter yield (52.56 and 56.11 t ha⁻¹; pooled 54.34 t ha⁻¹), followed by BNH-10, whereas Phule Jaywant produced the lowest yields. The superior performance of Phule Gunwant may be attributed to its inherent genetic potential for vigorous vegetative growth, efficient nutrient utilization, greater leaf area development and enhanced photosynthetic efficiency, which resulted in greater internodal elongation and stem growth. Genotypes possessing greater vegetative vigour generally exhibit higher tillering potential, resulting in increased forage productivity. Genotypic variation in forage crops plays a significant role in determining morphological characters such as leaf production, tiller number and overall biomass accumulation. The higher L:S ratio observed in BNH-10 may be attributed to its greater leaf production relative to stem biomass, indicating a more desirable forage morphology. Since leaves contain higher concentrations of digestible nutrients than stems, genotypes with a higher L:S ratio generally possess superior forage quality and nutritive value. The higher L:S ratio observed in BNH-10 may be attributed to its greater leaf production relative to stem biomass, indicating a more desirable forage morphology. Since leaves contain higher concentrations of digestible nutrients than stems, genotypes with a higher L:S ratio generally possess superior forage quality and nutritive value. Similar genotypic differences in Hybrid Napier grass have been reported by Tessema et al. (2010) [15] , Turano et al. (2016) [18] . The higher green forage yield of Phule Gunwant may be attributed to its superior genetic potential, greater plant height, higher tiller production, increased leaf number and overall better vegetative growth, resulting in greater biomass accumulation. The superior dry matter yield of Phule Gunwant may be attributed to its higher green forage yield, greater plant height, higher tiller production and increased leaf production, which contributed to greater biomass accumulation and dry matter production. Similar findings were reported by Tessema et al. (2010) [15] , Kumar et al. (2012) [9] , Aruna et al. (2024) [1] and Tomar et al. (2024) [17] .

Effect of Fertilizer Levels

Growth and yield parameters were significantly influenced by fertilizer application. Application of 150% RDF (F₃) recorded the highest plant height (186.88 cm pooled), maximum tillers per plant (50.28), highest number of leaves per bunch (445.09), total green forage yield (270.89 t ha⁻¹) and total dry matter yield (54.63 t ha⁻¹). It was followed by 125% RDF (F₂), while 100% RDF (F₁) recorded the lowest values for these parameters. In contrast, the highest leaf: stem ratio (1.06) was recorded under 100% RDF (F₁) and was at par with 125% RDF (F₂), whereas 150% RDF (F₃) recorded the lowest leaf: stem ratio (0.82). Overall, application of 150% RDF promoted vigorous vegetative growth and produced the highest forage and dry matter yields, demonstrating its superiority over lower fertilizer levels. The increased plant height under higher fertilizer application may be attributed to greater availability of nitrogen, phosphorus and potassium, which enhanced chlorophyll formation, photosynthetic activity, cell division, cell elongation and protein synthesis, thereby promoting rapid vegetative growth. Nitrogen, being a major constituent of chlorophyll and amino acids, plays a vital role in stem elongation and biomass production. The increase in tiller production with higher fertilizer levels may be attributed to enhanced availability of nitrogen and other essential nutrients, which promoted rapid cell division, increased bud initiation, improved root development and greater photosynthetic activity. Adequate nitrogen supply stimulates the emergence and development of basal buds, resulting in increased tillering capacity and higher vegetative growth. The reduction in L:S ratio under higher fertilizer application may be attributed to enhanced stem elongation and increased stem biomass resulting from vigorous vegetative growth, which proportionally exceeded the increase in leaf biomass. Although higher fertilizer levels substantially improved overall biomass production, stem growth was relatively greater, thereby reducing the leaf: stem ratio. Similar findings have been reported by Ubi and Omaliko (2006) [19] , Damame et al. (2017) [2] , Patil et al. (2024) and Sutar et al. (2024) [14] in forage grasses. The increase in green forage yield with higher fertilizer application may be attributed to the enhanced availability of essential nutrients, particularly nitrogen, which promoted vigorous vegetative growth, increased tillering, greater leaf area, enhanced photosynthetic activity and efficient utilization of solar radiation, ultimately resulting in higher biomass production. Similar findings were reported by Kumar et al. (2012) [9] , Shalini et al. (2020) [12] and Aruna et al. (2024) [1] who concluded that increasing fertilizer application enhanced morphological development and forage accumulation, resulting in significantly higher green forage yield. The increase in dry matter yield with increasing fertilizer levels may be attributed to improved nutrient availability, particularly nitrogen, which enhanced vegetative growth, leaf area development, photosynthetic efficiency and biomass accumulation. Increased nutrient uptake promoted higher assimilate production and dry matter partitioning, resulting in greater dry matter yield. These findings are in close agreement with those reported by Pathan (2013) [11] and Damame et al. (2017) [2] .

Effect of Cutting

The different cutting intervals had no significant effect on the initial and final plant population, indicating uniform crop establishment and plant survival under all cutting management practices. However, growth and yield parameters were significantly influenced by cutting interval. The 75-day cutting interval (C₃) recorded the highest height (181.16 cm pooled), maximum tillers per plant (44.30) and highest number of leaves per bunch (396.78), whereas the 45-day cutting interval (C₁) recorded the highest leaf: stem ratio (1.11). In contrast, the 60-day cutting interval (C₂) produced the highest total green forage yield (277.59 t ha⁻¹) and total dry matter yield (53.03 t ha⁻¹), followed by the 45-day cutting interval, while the 75-day cutting interval (C₃) recorded the lowest forage and dry matter yields. Overall, the 60-day cutting interval proved to be the most suitable cutting management practice for maximizing forage productivity of hybrid Napier under the experimental conditions. The higher plant height observed under longer cutting intervals may be attributed to the availability of a longer growth period before harvest, allowing continuous photosynthesis, greater accumulation of assimilates, increased internodal elongation and enhanced stem development. Frequent harvesting at shorter intervals restricted vegetative growth by reducing the time available for canopy development and reserve carbohydrate accumulation. Similar observations have been reported by Damame et al. (2017), Shalini (2020) [12] , Tomar et al. (2024) [17] and Sutar et al. (2024) [2] [14] . The higher number of tillers under the longer cutting interval may be attributed to the availability of a longer recovery period between successive harvests, allowing greater accumulation of carbohydrate reserves, enhanced root growth and improved development of axillary buds. Frequent cutting at shorter intervals limits reserve accumulation and suppresses the emergence of new tillers. Similar observations have been reported by Shalini et al. (2020) [12] , Hindoriya et al. (2021) [5] and Sutar et al. (2024) [14] . The increase in leaf production with higher fertilizer levels may be attributed to improved nutrient availability, particularly nitrogen, which enhanced chlorophyll synthesis, photosynthetic efficiency, leaf initiation and expansion, thereby promoting vigorous vegetative growth. Enhanced nutrient supply also favours rapid cell division and differentiation, resulting in the production of more leaves. Similar findings have been reported by Kumar et al. (2012) [9] , Damame et al. (2017) [2] and Singh et al. (2018) [13] . Increasing cutting interval significantly enhanced leaf production and forage yield of Napier grass due to prolonged vegetative growth. Similar findings have been reported by Pathan et al. (2013) [11] and Sutar et al. (2024) [14] . The higher L:S ratio under shorter cutting intervals may be attributed to the harvesting of younger forage, which contains a greater proportion of leaves and less stem development. As the crop matures with increasing cutting intervals, stem elongation and lignification become more pronounced than leaf development, resulting in a progressive decline in the leaf: stem ratio. This finding is consistent with the well-established relationship between forage maturity and morphological composition. Similar observations were reported by Tessema et al. (2003) [16] . The superior forage yield recorded under the 60 day cutting interval may be attributed to an optimum balance between vegetative growth and harvesting frequency. Harvesting at 60 day intervals provided sufficient time for regeneration and biomass accumulation while permitting more harvests during the year than the 75 day interval. In contrast, longer cutting intervals reduced the number of harvests, leading to lower cumulative annual forage yield despite greater plant maturity at each harvest. Similar findings were reported by Ishrath (2018) [6] , Shalini et al. (2020) [12] and Tomar et al. (2024) [17] who concluded that cutting frequency is one of the most important management practices influencing forage productivity, with intermediate cutting intervals producing maximum annual biomass while maintaining satisfactory forage quality. The higher dry matter yield obtained under the 60-day cutting interval may be attributed to an optimum balance between forage maturity and frequency. This interval allowed sufficient time for biomass accumulation and dry matter deposition while maintaining a greater number of harvests during the year. In contrast, the 75-day cutting interval reduced the cumulative annual dry matter production due to fewer harvests despite greater maturity of individual plants. These findings are in conformity with the results reported by Jagdeesh et al. (2017), Shalini et al. (2020) [12] and Sutar et al. (2024) [14] .

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