Influence of biofertilizers and nutrient levels on growth and productivity of hybrid indian mustard (Brassica juncea L.)

Introduction

Oilseeds hold a significant position in Indian agriculture, ranking behind cereals. They are among the most important crops in the country, offering high returns per unit area and demonstrating strong adaptability to diverse agroclimatic conditions. India has the fourth-largest vegetable oil economy globally, following the USA, China, and Brazil. In the Indian agricultural economy, oilseeds are the second-largest contributor after cereals. As the third-largest producer of rapeseed mustard (21.1%) after Canada and China, India plays a crucial role in the global rapeseed mustard industry (FAOSTAT, 2022) [4] . The country exported mustard seeds worth US$ 45.4 million, with a total export volume of approximately 51.6 million kg. India is a key exporter of mustard oilseeds, meals, and flour, ranking as the third largest mustard seed exporter in 2022. Rapeseed mustard is a vital component of the Indian oilseed sector. In the 2023-24 period, it ranked first among oilseeds in terms of production, contributing 33.24% to India's total oilseed output. The overall oilseed production stood at 39.59 million metric tons, with rapeseed mustard accounting for 13.16 mt (ICAR-DRMR Bharatpur, 2024) [6] . The leading oil-producing states in India include Rajasthan, Madhya Pradesh, Gujarat, Maharashtra, Haryana, Uttar Pradesh, West Bengal, Karnataka, Tamil Nadu, and Telangana. Among these, Rajasthan, Madhya Pradesh, Haryana, and Uttar Pradesh are the top producers in 2021-22, contributing approximately 47%, 14%, 12%, and 9% of the total production, respectively (MoA&FW, GOI, 2023). Mustard production in India varies owing to a multitude of influencing factors. As a significant oilseed crop, mustard is primarily cultivated for its oil content, which is extensively utilized in culinary and food production applications. Production levels are subject to fluctuations resulting from variables, such as climatic conditions, soil fertility status, nutrient recommendations, irrigation availability, pest infestations, and market prices. Recent initiatives have aimed to enhance mustard cultivation to decrease dependency on imports and satisfy domestic oil demand. Nutrient management plays a pivotal role in mustard production by directly affecting the plant's growth, development, and yield. Nitrogen, phosphorus, potassium, and sulphur are essential for the growth and development of Indian mustard. The application of these nutrients significantly influences crop productivity, nutrient uptake, and soil health. Rana et al. (2018) found that different phosphorus fertilizers helped Indian mustard use phosphorus better and recover more nitrogen and potassium, leading to higher yields and better use of resources. Optimal application of N, P, K, and S is crucial for maximizing Indian mustard productivity. Integrated nutrient management, which combines organic and inorganic sources, has demonstrated promising results in enhancing soil fertility, microbial activity, and crop yield (Basak et al., 2017) [2] . Biofertilizers play several vital roles in soil fertility, crop productivity, and agricultural production, as they are ecofriendly. However, they cannot replace chemical fertilizers, which are indispensable for achieving the maximum crop yields (Sharma et al., 2018) [15] . Biofertilizers with phosphatesolubilizing bacteria (PSB) have proven to be very effective in helping plants grow better and absorb more nutrients in different crops, such as Indian mustard. PSB can convert insoluble phosphorus into plant-available forms, thereby increasing phosphorus availability in the soil (Aliyat et al., 2022) [1] . Indian mustard (Brassica juncea L.) plays a crucial role in the agricultural sector as a valuable oilseed crop. Its significance lies not only in providing high-quality edible oil but also in its potential for improving farmers economic conditions. The cultivation of improved varieties, particularly hybrid strains, has become increasingly important in maximizing crop productivity. These advanced cultivars are specifically developed to withstand various environmental stresses, exhibit enhanced disease resistance, and produce higher yields compared to traditional varieties (Thakur et al., 2021) [16] . The success of growing mustard relies on many factors, such as choosing the right types of mustard seeds, using the best planting methods, practicing good crop rotation, and managing pests and diseases effectively. Additionally, the availability of irrigation facilities and the ability to adapt to prevailing climatic conditions significantly influence crop performance. The development of conventional breeding programs has led to the introduction of varieties with improved yield potential and higher oil content, thereby expanding cultivation opportunities.

Materials and Methods

The study was conducted on Gangetic Alluvial soil (Inceptisols) characterized by a sandy clay loam texture, slight alkalinity, and low levels of organic carbon and nitrogen, at the Agricultural Research Farm, Banaras Hindu University, during the winters of 2021-22 and 2022-23. The experiment was conducted using a split-plot design to evaluate the effects of different fertility levels (Nitrogen, phosphorus, potassium and sulphur), Indian mustard hybrids, and biofertilizer applications on soil nutrient dynamics and plant performance. The main plot treatments consisted of a factorial combination of three fertility levels and two mustard hybrids. The fertility levels included F1: 75% RDF (90, 45, 45, 30 kg NPKS ha⁻¹), F2: 100% RDF (120, 60, 60, 40 kg NPKS ha⁻¹) and F3: 125% RDF (150, 75, 75, 50 kg NPKS ha⁻¹). These were combined with two hybrids, H1: 'Pro Agro Hybrid Mustard-5222' and H2: 'Pioneer Hybrid Mustard-45S46' resulting in six main plot treatment combinations (3 fertility levels × 2 hybrids). Each main plot was further subdivided into three sub-plots to which different biofertilizer treatments were applied: B1 (Controlno biofertilizer), B2 (PSB + SDB, where PSB is phosphate solubilizing bacteria and SDB is sulphur dissolving bacteria), and B3 (NPK consortia comprising beneficial microbes that aid in nitrogen fixation, phosphorus solubilization, and potassium mobilization) Half of the nitrogen dose and full doses of phosphorus, potassium, and sulphur were applied as basal dressing, with the remaining nitrogen topdressed at 30 and 55 DAS. During the first year, the mean maximum and minimum temperatures were 32.9 °C and 6.7 °C, respectively, with an average temperature of 19.8 °C. The total rainfall received was 69.2 mm, with an average relative humidity of 75.53%, wind speed of 1.76 km hr -1 , 5.92 sunshine hours day -1 , and evaporation rate of 1.89 mm day -1 . In the second year, slightly lower maximum temperature (32.3 °C), lower minimum temperature (4.8 °C), and average temperature (18.5 °C), relative humidity (69.89%) were recorded. Although rainfall (2.2 mm) and were lower than the previous year, sunshine hours (6.7 hours day -1 ) and evaporation (2.12 mm day - 1 ) were marginally higher, along with wind speed (2.31 km hr -1 ). Under assured irrigation, where moisture was not limiting, the improved sunshine duration, enhanced temperature amplitude, and lower humidity likely created a more conducive environment for photosynthesis, nutrient assimilation, and overall crop metabolism. These factors possibly contributed to the better growth and yield performance observed in the second year. Three irrigations were administered, adhering to standard crop management practices. Weather conditions in the second year were more conducive to mustard cultivation. Growth parameter such as plant height (cm), number of primary and secondary branches plant -1 , CGR, RGR at intervals of 30-60 DAS and 60-90 DAS and seed yield (kg ha -1 ) were recorded during the 2-year experimentation. The collected data were subjected to statistical analysis as outlined by Gomez and Gomez (1984) [5] . The interpretation of treatment effects was conducted using Fisher's critical difference at the p=0.05 significance level.

Where, W1 and W2 are plant dry weight per plant at time t1 and t2, respectively. S is the plant spacing in squire meter Where, ln is the natural log

Results and Discussion

Fertility levels

The data showed that (Table 1.) application of 125% RDF (150, 75, 75, 50 kg NPKS ha -1 ) recorded significantly higher plant height (183, 193 cm), number of primary branches plant -1 (8.30, 8.85), number of secondary branches plant -1 (14.9, 15.8) and seed yield (2710, 2824 kg ha -1 ) over the 75% RDF NPKS during both years of the experiment (Fig 1 .). Balanced nutrition especially N, P, K and S helps in regulating the cytokinin-auxin balance as well as homeostasis in plant, which promotes growth of lateral buds that ultimately, develop as branches. Formation of auxiliary and lateral branches is physiologically a case of tissue differentiation that is one of the main roles of nitrogen (Prasad et al., 2022) [13] . These results are close conformity with (Kumar et al., 2018; Mandal et al., 2018) [7,10] . Application of 125% RDF NPKS recorded highest CGR and RGR at intervals of 30-60 and 60-90 DAS (Table 2). Higher fertility level, the crop acquired greater shoot dry weight subsequently increased the CGR, AGR, RGR and NAR. This increase in these morphophysiological characters might be due to the maintenance of higher levels of auxin in the plant tissues thereby greater synthesis of food in the leaves with better water relation (Majid and Simpson, 1997; Mondal et al., 2017; Sahoo et al., 2025) [9,12] .

Hybrid varieties

As shown in (Table 1.) in-between hybrid varieties 'Pioneer Hybrid Mustard-45S46' recorded significantly higher plant height (cm), number of primary and secondary branches plant -1 , seed yield (kg ha -1 ), CGR at 30-60 DAS over the 'Pro Agro Hybrid Mustard-5222' during both years of study. CGR at 60-90 DAS failed to touch the level of significance (Table 2.). However, RGR at 30-60 and 60-90 DAS failed to touch the level of significance similar trend was followed in second year. The varietal difference in plant height were also reported by Thakur et al. (2021) [16] the findings of the experiment indicated that the growth parameters of the Indian mustard cv. '45S35' included plant height, primary branches per plant, dry weight, and crop growth rate.

Biofertilizers

Two years of experiment revealed that application of NPK consortia resulted significantly higher plant height, number of secondary branches plant -1 , seed yield (kg ha -1 ) it was followed by PSB+SDB. Number of secondary branches plant -1 recorded highest with application of NPK consortia with percentage increment of (11.8%, 8.9%) over the control plot (Table 1.). However, CGR at intervals of 30-60 and 60-90 DAS resulted significantly higher with application of NPK consortia and it was statistically at par with PSB+SDB in first year of the experiment while in second year trial NPK consortia recorded highest over the control plot. Meanwhile RGR at intervals of 30-60 DAS recorded significantly higher with application of NPK consortia and it was followed by PSB + SDB during both years of the experiment and however intervals of 60-90 DAS failed to touch the level of significance during both years of the experiment (Table 2.). Kumar et al. (2017) [8] reported that mustard seeds treated with Azotobacter and PSB showed faster emergence and stronger early growth due to improved nutrient mobilization at the root-soil interface.

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