Effect nitrogen, sulphur and biofertilizers on growth and yield of Indian mustard [Brassica juncea (L.) Czern & Coss]

Introduction

Indian mustard [Brassica juncea (L.) Czern. & Coss.] is one of the most important oilseed crops cultivated in India and ranks next to soybean and groundnut in terms of economic significance. India is among the leading producers of rapeseed-mustard in the world, second only to China. According to the Directorate of Economics and Statistics (DES, 2024) [10] , rapeseed-mustard contributes about 8.32 million tonnes to the country's total oilseed production of 31.31 million tonnes. Out of the total edible oil production of approximately 7.36 million tonnes, rapeseedmustard accounts for nearly 2.58 million tonnes. Mustard oil cake, a valuable by-product, contains about 5.10% nitrogen, 1.80% phosphorus and 1.20% potassium, along with nearly 40% protein. However, the presence of glucosinolates restricts its wider utilization as feed (Bhinda et al., 2025) [4] . Among the mustard-growing states of India, Rajasthan occupies the leading position, contributing nearly 46% of the national production. During 2024-25, the state produced about 4.20 million tonnes of mustard, followed by Haryana and Madhya Pradesh. Besides these states, mustard is also cultivated in Uttar Pradesh, Gujarat and several non-traditional regions such as Karnataka, Tamil Nadu and Andhra Pradesh. The crop is grown under both irrigated and rainfed ecosystems, with a larger share under irrigation. Because mustard responds favourably to nutrient application, irrigated cultivation generally results in higher productivity and profitability (DES, 2024) [10] . In recent decades, continuous cultivation of high-yielding varieties and intensive cropping systems have led to depletion of essential plant nutrients from agricultural soils. The increasing pressure on limited land resources to meet the food and oil requirements of a growing population has further aggravated nutrient deficiencies.

Consequently, mustard is often cultivated under suboptimal nutrient conditions, which adversely affects its growth, development and productivity (Chandel et al., 2025) [5] . Rising fertilizer costs, gradual reduction in fertilizer subsidies and concerns regarding environmental pollution caused by excessive fertilizer use have highlighted the need for balanced nutrient management. An integrated nutrient management approach involving chemical fertilizers, organic manures and biofertilizers offers a sustainable solution for maintaining soil fertility while improving crop productivity and environmental quality. Nitrogen is one of the most essential nutrients required for plant growth and development. It plays a key role in metabolic activities, energy transfer, synthesis of proteins, nucleic acids, chlorophyll and protoplasm. Adequate nitrogen supply promotes chlorophyll formation, enhances photosynthetic efficiency and increases dry matter accumulation, ultimately resulting in higher biomass production and yield (Sahu et al., 2025) [35] . Sulphur is another important nutrient for Indian mustard because of its direct involvement in protein synthesis and oil formation. It contributes to the production of sulphur-containing amino acids, vitamins and enzymes and is necessary for chlorophyll development and several metabolic processes. Sulphur also improves nutrient availability and soil health when supplied in appropriate quantities. Since oilseed crops have a comparatively higher sulphur requirement, its deficiency can significantly reduce seed yield and oil content. Approximately 41% of Indian soils are reported to be deficient in sulphur. Deficiency symptoms usually appear first on young leaves as pale green or yellow coloration. Adequate sulphur nutrition is therefore indispensable for realizing the yield and quality potential of mustard, particularly in sulphurdeficient soils (Singh and Singh, 2018) [39] . Biofertilizers have emerged as an important component of sustainable agriculture. These preparations contain beneficial microorganisms that colonize the rhizosphere or plant tissues and enhance plant growth through various mechanisms. They improve nutrient availability by fixing atmospheric nitrogen, solubilizing phosphorus, oxidizing sulphur and producing plant growth-promoting substances (Verma et al., 2019) [51] . Among the beneficial microorganisms, Azotobacter is a free-living aerobic nitrogen-fixing bacterium that contributes significantly to crop growth and productivity. It synthesizes growth-promoting substances such as auxins, cytokinins and gibberellins and helps plants tolerate various biotic and abiotic stresses (Bhattacherjee and Dey, 2014) [3] . Similarly, Azospirillum has gained considerable importance in mustard cultivation due to its ability to associate with plant roots and improve nitrogen availability. It stimulates root growth, enhances nutrient uptake and increases chlorophyll content, leading to better plant vigor and productivity. Moreover, Azospirillum produces phytohormones such as indole acetic acid, gibberellins and cytokinins, which positively influence plant growth and development (Kumar et al., 2018) [21] . Seed inoculation with Azospirillum has been reported to improve germination, growth parameters, yield attributes and oil content in mustard. Its integrated use with inorganic fertilizers can reduce nitrogen fertilizer requirements while improving soil biological activity and long-term soil fertility (Dubey et al., 2021) [11] . Considering the importance of nitrogen, sulphur and biofertilizers in enhancing crop growth, nutrient use efficiency, yield and quality of Indian mustard, their optimum management is essential for achieving sustainable productivity. Therefore, the present field experiment was undertaken to evaluate the effect of different nitrogen levels, sulphur levels and biofertilizer inoculation on the growth, yield and quality of Indian mustard.

Materials and Methods

The field experiment was carried out at the Agronomy Research Farm, School of Agricultural Sciences, Jaipur National University, Jaipur, Rajasthan during kharif season of 2025. The experimental site is situated in semi-arid eastern plains of Rajasthan and lies between 26 92' North latitude, 75 78' East longitude and at an altitude of 430 meters from the mean sea level. The soil of the experimental field was sandy in texture and slightly alkaline in reaction with PH 7.58, organic carbon (OC) (0.43%), available nutrient (nitrogen 217.30 kg ha -1 ; phosphorus 20.28 kg ha -1 and potassium 219.20 kg ha -1 ). The experiment was laid out in factorial randomized block design with three replications. The field trial consisted four nitrogen levels viz., (i) control, (ii) 30 kg N ha -1 , (iii) 60 kg N ha -1 and (iv) 90 kg N ha -1 ; three sulphur levels viz., (i) control, (ii) 40 kg S ha -1 and (iii) 50 kg S ha -1 and three biofertilizers inoculation (i) control, (ii) Azotobacter and (iii) Azospirillum. The Indian Mustard variety 'Radhika (DRMR 2017-15)' was sown @ 5 kg seed ha -1 with spacing of 30 cm x 10 cm. The two irrigations are applied. All agricultural practices were kept uniform in all the plots.

Results and Discussion

Growth Parameters 3.1.1 Effect of nitrogen levels

Result indicated that the highest growth parameters viz. plant height (cm), DMA (g/plant) at 60, 80, 100 DAS, at harvest, Number of primary and secondary branches plant -1 at 80, 100 DAS and at harvest and crop growth rate at 40-60 DAS, 60-80 DAS, 80-100 DAS and 100 DAS-at harvest of the Indian mustard were recorded with the application of 90 kg N ha -1 and it was at par with the application of 60 kg N ha -1 (Table 1). These findings align with observations of Hera et al. (2017) and Meena et al.

(2019) [15,27] , who attributed increased plant height under adequate nitrogen supply to enhanced cell elongation, accelerated meristematic activity, and greater internode elongation driven by improved photosynthetic efficiency. Increased availability of nitrogen promotes biosynthesis of indole acetic acid (IAA), a phytohormone directly responsible for cell elongation, which explains the progressive height response to nitrogen increments. Nitrogen's role in chlorophyll synthesis ensures a greater photosynthetically active leaf area, which in turn channels more assimilates towards branch development. The positive response of DMA to nitrogen was attributed to enhanced leaf area development, improved canopy architecture, and greater sink activity. These results are in conformity with those reported by Patel and Jadav (2018) and Sharma et al. (2020) [33,36] in Brassica juncea, who observed that nitrogen-driven improvements in photosynthetic capacity directly translated into higher dry matter production.

Effect of sulphur levels

The sulphur levels significantly enhanced the growth parameters of Indian mustard. The highest growth parameters viz. plant height (cm), DMA (g plant -1 ) at 60, 80, 100 DAS, at harvest, Number of primary and secondary branches plant -1 at 80, 100 DAS and at harvest and crop growth rate at 40-60 DAS, 60-80 DAS, 80-100 DAS and 100 DAS-at harvest of the Indian mustard were recorded with the application of 50 kg S ha -1 and it was at par with the application of 40 kg S ha -1 (Table 1). Sulphur-induced enhancement in chlorophyll content and photosynthetic rate facilitates more efficient carbon assimilation, thereby supporting greater vegetative growth. Sulphur-mediated improvement in branching to enhanced auxin metabolism and stimulated lateral bud development. These findings are in agreement with Tripathi and Singh (2018), Yadav and Kumar (2019), Meena et al. (2019) and Mishra et al. (2020) [49,54,27,31] .

Effect of biofertilizers inoculation

The biofertilizers inoculation significantly enhanced the growth parameters of Indian mustard. the maximum growth parameters viz. plant height (cm), DMA (g/plant) at 60, 80, 100 DAS, at harvest, Number of primary and secondary branches plant -1 at 80, 100 DAS and at harvest and crop growth rate at 40-60 DAS, 60-80 DAS, 80-100 DAS and 100 DAS-at harvest of the Indian mustard were recorded with sed inoculated by azotobacter (Table 1). Azotobacter contributes significantly to nitrogen availability in the rhizosphere, thereby supporting enhanced vegetative growth. Azospirillum, as an associative nitrogen-fixer, similarly benefits plant growth through root morphology improvement and hormone production, though generally to a lesser extent than Azotobacter (Vessey, 2003) [53] . Biofertilizer-induced improvement in DMA and CGR is linked to enhanced availability of mineral nutrients, improved water-use efficiency, and augmented photosynthetic capacity, as elaborated by Tilak et al. (2005) and Goswami et al. (2016) [45,13] .

Yield attributes and yield 3.4.1 Effect of nitrogen levels

The highest Yield attributes and yield viz., length of siliqua, number of silique plant -1 , number of seeds siliqua -1 , test weight and yield viz., seed yield, stover yield, biological yield and harvest index recorded with the application of 90 kg N ha -1 and it was significantly at par with 60 kg N ha -1 (Table 2). These improvements are attributed to the role of nitrogen in promoting greater photosynthetic activity, extended leaf area duration, and enhanced partitioning of assimilates to reproductive structures. These findings are consistent with those of Jat et al. (2019) and Choudhary et al. (2021) [17,6] , who reported that adequate nitrogen supply during reproductive growth significantly enhanced siliqua number and seed filling efficiency in mustard. These results are in close conformity with similar findings reported by Verma et al.

Effect of sulphur levels

The highest yield attributes and yield viz., length of siliqua, number of silique plant -1 , number of seeds siliqua -1 , test weight and yield viz., seed yield, stover yield, biological yield and harvest index recorded with the application of 50 kg S ha -1 and it was significantly at par with 40 kg S ha -1 (Table 2). These improvements are attributed to sulphur critical role in the synthesis of glucosinolates and sulphur-containing amino acids which are involved in pollen viability and fertilization efficiency, ultimately contributing to better seed set and seed filling (Ganeshamurthy et al., 2021) [12] . The findings conform with results reported by Kumar and Sharma et al. (2020), Jat et al.

(2020) and Verma and Choudhary (2021) in Brassica juncea [54,36,17,50] .

Effect of biofertilizers Inoculation

The maximum yield attributes and yield viz., length of siliqua, number of silique plant -1 , number of seeds siliqua -1 , test weight and yield viz., seed yield, stover yield, biological yield and harvest index recorded with seed inoculated by Azotobacter (Table 2). This improvement is attributed to better nutrient acquisition, improved soil structure through exopolysaccharide production, and enhanced symbiotic associations that collectively support better plant establishment and productivity and the superior performance of Azotobacter over Azospirillum in improving yield attributes may be attributed to its additional mechanisms of phosphate solubilization and production of growth-promoting metabolites that enhance reproductive efficiency. These results are in close conformity with similar findings reported by Yadav et al., (2022) [56] .

Conclusion

Based on a one-year field study on cluster bean, it may be concluded that: The application of 90 kg N ha -1 + 50 kg S ha -1 + azotobacter was suitable to attain the higher growth parameters, yield attributes and yield of Indian mustard and it was followed by 60 kg N ha -1 + 40 kg S ha -1 + azotobacter.

Acknowledgement

The authors express their gratitude to the School of Agricultural Sciences, Jaipur National University, Jaipur, and the Rajasthan Agricultural Research Institute, Durgapura, Jaipur, for their support in conducting the field experiments and for providing meteorological data.

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