INTRODUCTION According to estimation by FAO, global population will be around 9.1 billion by 2050 (Cohen, 2005) and around (Barrett, 2010). To feed all the population, challenges in current agriculture like climate change, shrinking available land for agriculture, higher use of chemical fertilizers, depleting soil properties, yield stagnation of crops etc. have to be reduced by adopting sustainable agriculture (Gomiero et al., 2011). A sustainable agriculture is one which depletes neither the people nor the land. Sustainable agriculture is known for environment protection, to maintain soil properties and to expand Earth’s natural resource base (Gold, 2016). The increasing demand of crop yield and food can be achieved by use of biofertilizers like Rhizobium, Azotobacter, Azospirillum and blue green algae (BGA) for the betterment of crops (Mishra et al.,2013) and even for the health of soil (Singh et al., 2014). Rhizobium fixes nitrogen symbiotically and stimulates plant growth by production of plant growth hormones (Tilak et al., 2006), vitamins, by solubilization of insoluble phosphates, induction of systemic disease resistance and enhancement in stress resistance (Lebrazi and Benbrahim 2014). Interaction between Rhizobium and legume crops has potential to increase agricultural productivity with less dependence on non-renewable inputs like artificial fertilizers (Peoples et al., 2009). Cowpea [Vigna unguiculata (L.) Walp], a member of Leguminosae family (Ng and Padulosi, 1991, Kumar et al., 2022) is a crop of great economic importance for low-income population in developing countries (Verdier et al., 1998; Singh, 1997) because it is good source of protein (Fatokun, 2002), carbohydrate, vitamins and minerals (Iqbal et al., 2006). Being a leguminous crop, it also fixes nitrogen symbiotically with biofertilizers (Eke-Okoro et al., 1999); although it requires nitrogen as a small basal dose for quick and better start because it is essential constituent of many enzymes, protein and chlorophyll. To ensure proper germination and growth of seedlings, there are different ways to apply biofertilizers to seeds of cowpea and seed pelleting with Rhizobiumis one of them. Seed pelleting is a mechanism of applying needed material in such a way that they affect the seed or soil at the seed-soil interface to ensure better performance of seed. Seed pelleting with Rhizobium can also reduce the negative effect on seed germination, seedling growth and plant growth in soil due to excessive use of urea (Bremner and Krogmeier, 1989). Pawar et al. (2014) reported that seed inoculation with Rhizobium show higher growth and yield in legumes when it is compared to application of Rhizobium in soil as biofertilizers. Besides, cowpea has inherent problems like flower shedding, shrinkable seeds, poor pod and seed setting due to deficiency of micronutrients, macronutrients, growth promoting substances and biotic stress and Rhizobium is known for providing plant growth promoting substances like auxin and to increase nutrient uptake. Keeping in view the above prospective, this study had been planned to determine the effect of seed pelleting with Rhizobium and nitrogen application on yield and quality parameters of cowpea crop. MATERIALS AND METHODS This experiment was conducted during Kharif season of 2015-16 at experimental farm of Dr. Y S Parmar UHF which is located at an altitude of 1250 meters above mean sea level with latitude of 35.5oN and longitude of 77.8oE in the mid- hill zone of Himachal Pradesh, India. Genetically pure seed of cowpea cv. Him Lobia 1 was used for experiment. Liquid and powder form of Rhizobium culture was obtained from Soil microbiology laboratory of Department of Soil Science and water management. Seeds were pelleted at CSIR-IHBT (Institute of Himalayan Bioresource Technology) Palampur, H.P., India. For seed pelleting clay and adhesive (45% Gum Arabica) was used. There were total 20 treatment combinations (4 level of seed pelleting i.e. P1-Control, P2-Rhizobium liquid + clay + adhesive, P3- Rhizobium powder + clay + adhesive, P4- Rhizobium liquid formulation + jaggary and 5 level of nitrogen application i.e. F1-0 % Nitrogen of Recommended dose of fertilizer, F2 -40% N of RDF, F3 -60% N of RDF, F4 -80% N of RDF, F5 -100% N of RDF) and each treatment was replicated three times so there were total 60 plots of 1.8m × 1.5m (i.e. 2.7 m2) size. There were total 40 plants in every plot and spacing was 45cm × 15cm. Urea is applied to these plots and recommended dose for cowpea is 45kg/hectare. Seed yield per plant and per hectare as yield parameters and germination %, speed of germination, seedling length, seedling dry weight, seed vigour index-I and seed vigour index-II as seed quality parameters were observed. RESULTS AND DISCUSSIONS Seed pelleting with Rhizobium (liquid and powder form) and jaggary affected significantly seed yield of crop. Seed yield per plant was increased by 15.74% over control (no pelleting) when seed were pelleted with Rhizobium liquid form. Maximum average seed yield per plant (22.49 g) was found when seed were pelleted with liquid form (P2) and minimum average yield per plant (19.43 g) was found in control (no pelleting) treatment. It might be due to that Rhizobium ensures proper nodulation in root zone which leads adequate nitrogen uptake (Vessey, 2003). Rhizobium also exhibits antibacterial and antifungal activities (Pawar et al., 2014) which allow seeds for healthy seedling rise. Similar findings were obtained by Bohra et al. (1990); (Patel and Jadav, 2010); (Mishra and Solanki, 1996) and Rajput (1994) in cowpea. (Khanam et al., 1994); (Albayrak et al., 2006); (Khalil et al., 1989) also found increased yield per plant in chick pea, Common Vetch (Vicia sativa L.) and mung bean respectively when seeds of these crops were inoculated with Rhizobium. Different dose of nitrogen application as application of urea also affected seed yield per plant significantly. Maximum average seed yield per plant (21.86 g) was found when 80% N of RDF was applied to plots and minimum (19.81 g) was found in control in which urea was not applied. Application of nitrogen in form of urea increased seed yield per plant because nitrogen helps in vegetative growth of plant and nitrogen also play a vital role to reduce nutritional deficiency especially at reproductive stage which leads to high number of pods per plant, seeds per pod and finally higher seed yield (Umeh et al., 2011); (Thies et al., 1991); (Pikul et al.,1997) also found increased yield in different legumes when seeds were treated with Rhizobium. (Upadhyay and Singh, 2016) also reported that recommended nitrogen dose increased seed yield in cowpea. The interaction effects due to seed pelleting and nitrogen application were found to be non-significant at 5% level of significance. Maximum average seed yield was found when 80% N of RDF (F4) applied and seeds pelleted with liquid form of Rhizobium (P2). Minimum average seed yield per plant was found in P1F1 (control + 0% N of RDF). Around 28% yield per plant was increased in P2F4 over control (P1F1). Kishan et al., (2002) also reported that seed pelleting with Rhizobium and nitrogen application increase seed yield in cowpea cv. Pusa Phalguni. Same findings were also obtained by Mishra and Solanki, (1996) in cowpea and Soni et al., (2021) in pigeonpea. Seed yield per hectare was significantly affected by different seed pelleting and nitrogen application treatments. Interaction effect of seed pelleting and nitrogen application was non-significant on seed yield per hectare though. When seeds were inoculated with liquid form of Rhizobium pelleting than total yield per hectare was increased by 20.1% over control. Among different doses of nitrogen application, 80% N of RDF gave maximum yield (23.96 q) which was 12% higher in comparison to control (0% N of RDF).Treatment combination of liquid Rhizobium pelleting (P2) and 80% N of RDF (F4) gave maximum (26.73 q) yield per hectare and minimum (19.39 q) was found in P1F1 (non-pellet seeds + 0% N of RDF). There was around 37% hike in seed yield per hectare when seeds were pelleted with Rhizobium liquid and 80% N of RDF were supplied to plots over control (non-pellet seeds + 0% N of RDF). Seed pelleting with Powder form of Rhizobium also increased the seed yield. The enhancement in seed yield per hectare due to seed pelleting with Rhizobium might be due to the carryover beneficial effects of pre sowing treatments with nutrients to the seeds which led to better plant growth during vegetative and reproductive phase and ultimately led to increased seed yield. Seed yield per hectare was increased linearly with the increasing levels of nitrogen fertilization with Rhizobium seed pelleting due to increase in plant height, number of branches per plant, number of pods per plant and number of seeds per pods. Harvested seeds from crop were analyzed for seed quality parameters like germination percentage, seedling length, seedling weight and vigour index and found that all the parameters were increased in comparison to seeds which were sown. Among different types of pelleting treatments, maximum germination (95.90%) was found with Rhizobium liquid pelleted seeds (P2) and minimum (91.85%) was found in non-pelleted seeds (P1). The application of different nitrogen doses had also exhibited significant effect on germination. Maximum germination (94.75%) was found with application of 80% N of RDF (F4) and found to be statistically superior to all other doses of nitrogen. However, minimum germination (92.75%) was found with the application of 0% N of RDF (F1).Interaction effect of seed pelleting and nitrogen application on germination percentage was non-significant buy germination percentage increased in every treatment and maximum (96.25%) was found in P2F4 and minimum (91.25%) was in control (P1F1). It might be due to freshly harvested seeds from plants which had uptake proper quantity of nutrients during their growth. Due to proper supply of nitrogen during mother plant growth, mother plants might be produced high content protein seeds and high content of protein in seeds in known for higher germination. Similar results of increased germination due to seed inoculation with Rhizobium and nitrogen application was reported by Yadav and Malik (2005) in cowpea. Both treatment; seed pelleting and nitrogen application had significant effect on speed of germination separately but interaction effect of both treatments was non-significant. In case of seed pelleting, maximum (58.66) speed of germination was found in P2 and minimum (56.67) was found in control. Among treatment of nitrogen application, maximum (58.97) speed of germination was found in F4 and minimum (57.10) was found in control (F1). The biofertilizers and nitrogen doses provide different micronutrients to the mother plant at early stages of growth that play vital role in producing good quality seed and good quality seeds led to higher speed of germination. Increased speed of germination due to seed pelleting was also recorded by Shashibhaskar et al. (2009); Masuthi et al. (2009). Different pelleting treatments and nitrogen application had significant effect on seed vigour index-I. Among different pelleting treatments, maximum (2774.08) SVI-I was found in P2 and minimum (2665.95) was found in non-pelleted seeds (P1). Among different nitrogen application, maximum (2835.38) SVI-I was found in F4 and minimum (2658.79) was found in F1. Interaction of seed pelleting and nitrogen application had also significant effect on SVI-I and maximum (2952.33) SVI-I was found in P2F4 and minimum (2556.70) was found in P1F2. Micronutrients provided to the mother plant during the early stages of growth helps to produce uniform, bold and vigorous seed that results in good germination and seedling length that led to enhanced SVI-I. Increased seed vigour index-I might be due to increased germination and seedling length. Similar findings of increased seed vigour index-I due to seed pelleting with Rhizobium and nitrogen application was reported by Kishan et al. (2001) in cowpea cv. Pusa Phalguni. Different types of pelleting and different doses of nitrogen had significant effect on seed vigour index-II in cowpea. Among different types of pelleting, maximum seed vigour index-II (7346.90) was found with Rhizobium (liquid form) pelleted seeds and minimum (6156.50) was found in the non-pelleted seeds (P1). The application of different nitrogen doses also exhibited significant effect on seed vigour index-II. Maximum seed vigour index-II (6823.56) was found with application of 80% N of RDF (F4) and found to be statistically superior to all other doses of nitrogen. However, minimum seed vigour index-II (6447.40) was found with the application of 0% N of RDF (F1). The interaction effects due to seed pelleting and nutrition management were found to be non-significant at 5% level of significance. Masuthi et al. (2009) reported that the seed pelleting provides the nutrient to the mother plant during early stages of growth which led to formation of bold and vigours seeds. The enhanced germination and seedling dry weight due to vigorous seeds led to enhanced SVI-II. The biofertilizers and nitrogen doses provide different micronutrients to the mother plant at early stages of growth that play vital role in seed set, seed size and quality. Higher seed quality might be due to well-developed seeds with higher thousand seed weight and additional supply of micronutrients due to seed pelleting to the mother plant which led to the production of bold and vigorous quality seeds. The good quality seeds led to higher speed of germination and seedling vigour (length and dry weight).The increased seedling length of seeds harvested from the crop raised from pelleted seeds has also been reported by (Masuthi et al., 2009) in cowpea. Seedling dry weight. Similar findings of increased seed vigour index-I due to seed pelleting with Rhizobium and nitrogen application was reported by Swaroop et al., (2001) in cowpea; Khatana et al. (2021) and in chickpea by Patil et al. (2002).