INTRODUCTION Cabbage (Brassica oleracea L. var. capitata), belonging to family cruciferae is one of the most important cool season leafy vegetable growing all over the world. It is believed to have originated in Western Europe which was the first cole crop to be cultivated. Prior to cultivation and use as food, cabbage was mainly used for medicinal purposes. Cabbage contains a range of essential vitamins, minerals, small amount of protein and carbohydrates. It is an excellent source of Vitamin C (36.6 mg). In addition to containing some vitamins, cabbage supplies minerals like Potassium 170 mg, Calcium 40 mg, Phosphorus 26 mg and Magnesium 12 mg per 100 gram of the diet. In India, it is grown in an area of 4.01million ha producing 9.27 million tons with the productivity of 23.12mt/ha (Anonymous, 2020). Maximum cabbage producing states are West Bengal followed by Orissa, Madhya Pradesh, Bihar, Assam, Gujarat, Chhattisgarh, Haryana Jharkhand, and Uttar Pradesh. Among the various factors involved in cabbage production, nutrients play major role in enhancing the yield with its quality. Experimental evidences showed that cabbage responds positively to nitrogen application and moderately to phosphorus application. Importance of organic and inorganic fertilizer on the productivity and nutritional quality of cabbage has been reported by several researchers. Recently soil management practices have changed dramatically, including an increased use of synthetic fertilizers and pesticides to increase the crop yield. The cultivation of crop requires balanced supply of plant nutrients whereas most of the farmers are applying only chemical fertilizer for fetching maximum yield. Inadequate soil management using only chemical fertilizers has caused a global problem of nutrition depletion in soil and has made the pH of the soil acidic that caused reduction in crop yield (Hungria et al., 2005). As an attribute to the chemical fertilizers, plant growth promoting bacteria (PGPB) were used as first described by Kloepper and Schroth (1978) that can directly or indirectly enhance the plant growth. Direct mechanisms include production of plant hormones such as indole acetic acid (IAA), gibberellins and cytokines (Glick et al., 1999) along with a symbiotic N2 fixation as well as solubilization of phosphates. On the other hand, indirect mechanisms are the production of iron chelators, siderophores, as well as cyanides which act as antagonists to plant pathogens (Glick, 2012). All these traits of PGPB increase seedling emergence, vigor as well as yield (Kloepper et al., 1989). There is an immediate need to replace the use of chemical fertilizers by alternative biological fertilizers. The use of microorganisms with the aim of improving soil fertility by maintaining biogeochemical cycles for nutrition management in the soil is necessary for agriculture. Hence the aim of study is to determine the influence of three different fertilization systems (NPK) on cabbage growth and yield in presence and absence of Pseudomonas aeruginosa for the recommendation of bio fertilizer application in cabbage. MATERIAL AND METHODS The present study was conducted in the Department of Industrial Microbiology (IM), Jacob Institute of Biotechnology and Bioengineering (JIBB), Sam Higginbottom University of Agriculture, Technology and Sciences (SHUATS), Allahabad during 2018-2019. Phosphate solubilization assay: Sterilized NBRIP medium (National Botanical Research Institute’s phosphate medium pH-7.0) was poured in sterilized petriplates and P. aeruginosa strain was spot inoculated at the center of NBRIP using sterile inoculating loop and incubated at 28±2º C. Further the colony diameter was observed for the visible halo zone around the colony after 2, 4, 6, 8 and 10 days intervals. Phosphate solubilization index and efficiency was calculated by the following formula: Zinc solubilization assay: Zinc solubilization was assayed by preparing 100ml Pikovskaya’s agar medium containing 0.1% insoluble zinc compounds viz., ZnO, ZnS and ZnCO3. The sterilized Pikovskaya’s agar media (pH-7.0) was poured in sterilized petriplates and the P. aeruginosa strain was spot inoculated at the center of the medium using sterile inoculating loop. Un-inoculated plate was used as control. Plates were incubated at 28±2ºC for 24, 48 and 72 hours and observed for the diameters of visible clearing zone around the colony as discrossed center (Saravanan et al., 2007). Potassium solubilization assay: The sterilized Aleksandrov media (pH-7.0) having mica powder (insoluble form of potassium) was poured in sterilized petriplates and the P. aeruginosa strain was spot inoculated at the center of the medium using sterile inoculating loop. Plates were incubated at 28±2ºC. Detection of potassium solubilization by culture was based upon the ability of solubilization zone formation (Parmar and Sindhu 2013). Qualitative assay for production of IAA: King’s B broth (pH-7.2) was prepared with and without L-Tryptophan (0.5%) and sterilized, further it was grown in 50 ml conical flask containing 25 ml King’s B broth (King et al., 1954) with and without L-Tryptophan (0.5%) solution and incubated at 28±2ºC for 24 hours on a shaker then the culture was centrifuged at 4000 rpm for 20 minutes. One ml of culture supernatant was dropped in a test tube and mixed with 2 ml Salkowski reagent A (2% of 0.5M FeCl3 in 35% perchloric acid) and 4 drop of Orthophosphoric acid. After 25 minutes of incubation, light pink color observation indicated positive reaction for IAA production. Seed treatment, sowing and measurement of growth attributes: Cabbage seeds (Brassica oleracia L.) were surface sterilized with 95% ethanol for 5 min and washed with sterilized water. Seeds were grown in three replications in a field containing sterilized soil and non-sterilized soil (control). The plots were watered regularly to maintain optimum moisture and other routine care was taken to protect the plants from pests and diseases. Three plants in each treatment were randomly selected and tagged with a label for recording various growth parameters (fresh weight of the head plant height, leaves per plant, root length, number of lateral roots, stem diameter, shoots length and leaf length) at 20, 40, 60, 80 and 100 days after sowing. Vigor index: Seedling vigor index (SVI) was calculated by multiplying the germination percentage and seedling length in centimeter. Harvest index: It is the net head weight to the gross head weight taken at marketable stage. RESULTS AND DISCUSSION The observations recorded on screening and characterization of test bacteria (Pseudomonas aeruginosa MCCB 0035) for PGPR traits, various growth parameters, yield of cabbage, and influence of combination of NPK with Pseudomonas aeruginosa MCCB 0035 during the experiment. Further the recorded data were analyzed statistically and discussed. The P-solubilizing activity was determined by the microbial biochemical ability to produce and release organic acids through their carboxylic group chelates and cations (mainly Ca) bound to phosphate, converting them into the soluble forms. In the current study, it was reaffirmed that the phosphate solubilization by different PSBs was involved with the production of organic acids (Rashid et al., 2004). The inverse relationship observed between the pH and soluble-P concentration which indicated that organic acid production by these PSB strains plays a significant role in the acidification of the medium, facilitating the Phosphate solubilization (Table 1). Similar inverse relationship between pH and soluble phosphate was reported earlier by (Illmer and Schinner 1995). The bacteria Pseudomonas aeruginosa MCCB 0035 was helpful in phosphate solubilization in vitro after a time period of 10 days. Several parameters such as halo zone diameter 01.90cm, colony diameter 0.50cm, Phosphate solubilization index (PSI) of 4.80cm and Phosphate solubilization efficiency (PSE) of 280.00% was observed. These P solubilizing soil bacteria could serve as efficient bio fertilizers for improving the P-nutrition of crop plants. The advantage of using natural soil isolates over the genetically manipulated or the one which has been isolated from a different environmental set up is the easier adaptation and succession when inoculated into the plant rhizosphere. Phosphate solubilizing microbes play important role in improving the growth and yield of a variety of crops through organic phosphorus mineralization (Alori et al., 2017). Preliminary experiments on Zn solubilization by plate assays revealed effective solubilization of Zn compounds by Glucanoacetobacter diazotrophicus strains and expressed high levels of solubilized Zn existing as free Zn2+ ions as well as Zn chelates (Alloway, 2004). Zinc solubilization was observed having halo zone diameter of 1.70cm, colony diameter 0.60mm, zinc solubilization index (ZSI) 3.83cm, zinc solubilization efficiency (ZSE) 183.33%. Observations revealed that the isolate was found to be positive for zinc solubilization (Table 2). Several researchers have tested the ability of Pseudomonas aeruginosa to produce IAA and consequently, considered as IAA producing rhizobacteria. It also have been studied that IAA biosynthesis is greatly influenced by L-TRP precursor. Addition of L-TRP (an auxin precursor) to the media increased the auxin production by several folds (Frankenberger and Arshad 1995). Here the production of IAA by Pseudomonas aeruginosa MCCB 0035 after a time period of 24 hours, L-tryptophan produced light pink color (positive) and without tryptophan produced light yellow color. After a time period, shelf-life determination of Pseudomonas aeruginosa MCCB 0035 was analyzed. During the entire sampling period, gram negative rod shape bacteria were observed, without any contamination and cfu/ml count. Influence of Pseudomonas aeruginosa MCCB 0035 with different doses of NPK revealed the highest germination percentage in the treatments T5- NPK (full dose) + P. aeruginosa MCCB 0035, with 73.33% as compared to T0 treatment 53.33%. Whereas highest vigour index (56.66%) was also noticed in the same treatment T5. Similar results have also been reported by Lucy et al. (2004) during the treatment combinations. Among the different treatments, the maximum number of leaves, maximum shoot length of 30.0cm (Table-4) and maximum plant height of 30.86cm was observed in the treatment T5 {NPK (full dose) + P. aeruginosa (carrier based Full dose)}. Treatment T5, recorded 88.17% increase in plant height, compared to control T0 at 100 DAT. The plant height in treatment T5, was found to be significant, when compared with T1, T2, T3, T4, T6, T7, and T8 treatments, respectively (Table 3). The similarity in results has also been earlier reported by Ibukunoluwa Moyin-Jesu (2015). Among all the treatments, highest value (87.28%) of lateral roots per plant of cabbage at harvesting was observed in treatment T5. The least value (18.33cm) of number of lateral roots per plant of cabbage was observed in control having no treatment. The highest value of fresh head weight (1583.33g) of cabbage at harvesting was observed in treatment T5. The least value of number of fresh head weight (383.33g) of cabbage was observed in control having no treatment. Dry root weight (g) of cabbage was measured at harvesting where T5- NPK (full dose) + P. aeruginosa MCCB 0035 (Carrier based Full dose) was observed to be the most effective among all other treatments, showing the highest values of dry root weight (9.50g) of cabbage at harvesting. The least value of number of dry root weight (3.92g) of cabbage was observed in control which received no treatments. The dry root weight obtained in T5 treatment was found to be significant, when compared with T1, T2, T3, T4, T6, T7, and T8 treatments, respectively. Dry stem weight of cabbage was measured at harvesting. Treatment T5, (NPK full dose + P. aeruginosa MCCB 0035 Carrier based full dose) was observed to be the most effective among all other treatments, showing the highest values of dry stem weight (22.08g) of cabbage. Krestini et al. (2020) evaluated microbial consortium with NPK fertilizers resulting in maximum yield plant height and plant population. The least value of dry stem weight (7.65g) of cabbage was observed in control which received no treatments. Treatment- T5 recorded 96.30% increase in dry stem weight of cabbage plant as compared to control (T0) at 100 DAT. The dry stem weight of T5 was found to be significant, when compared with treatments T1, T2, T3, T4, T6, T7, and T8 respectively. Baeshen, (2016) reported some plant growth promoting pigments like pyocyanin produced by some strain of Pseudomonas aeruginosa that may significantly increase their height. Head diameter of cabbage was measured at harvesting. Treatment, T5- NPK (full dose) + P. aeruginosa MCCB 0035 (Carrier based Full dose) was observed to be the most effective among all other treatments, showing the highest values of head diameter (17.80cm) of cabbage at harvesting. The similar findings were also reported by Singh and Pandey (2010) where they found significant cabbage head yield with application of NPK in combination with biofertilizer. The least value of head diameter (9.33cm) of cabbage was observed in control having no treatment. Harvest index of cabbage was measured after harvesting. Among the different treatments, the harvest index of 756.93% of T5 was found to be significant, when compared with treatments T1, T2, T3, T4, T6, T7, and T8 respectively. The least value of harvest index (368.47%) of cabbage was observed in control. Treatment T5, recorded 48.67% increase in harvest index as compared to control at 100 DAT (Table 6). Verma and Maurya (2013) have also confirmed the finding while using NPK with Pseudomonas fluorescens. In the present study it was observed that Pseudomonas aeruginosa MCCB 0035 was found to be positive for phosphate solubilization efficiency (280.00%), zinc solubilization efficiency (183.33%) and positive result for IAA production with observance of light pink color. Strain Pseudomonas aeruginosa MCCB 0035 supported a population of 8.0 × 10-8 cfu/ml after 35 days. This strain Pseudomonas aeruginosa MCCB 0035 and NPK exhibited a germination percentage of 73.33% and vigor index of 56.66%. Similarly Rizvi et al. (2013) reported enhanced root nodulation in Phosphate solubilizing bacteria Pseudomonas fluorescens treatments. The performance of microbial consortium copulated with Pseudomonas spp. was always beneficial in respect to yield and soil health (Soumya, 2020). Field experiment with cabbage plants suggested that treatment T5, NPK full dose + P. aeruginosa (carrier based full dose) exhibited highest plant height (30.86cm), maximum number of leaf (23.33), maximum number of unfolded leaf (25.00), maximum shoot length (30.00cm), highest stem length (Table-5) (28.66cm), maximum number of lateral root / plant (60.33), maximum root weight (7.81g), maximum stem weight (22.08), maximum head weight (1583.33g), maximum head diameter (17.80 cm) and maximum harvest index (756.93g). Fitriatin et al. (2021) also studied about combined application of biofertilizers with NPK combination, resulting in enhanced growth and yield of the crop. It was concluded that treatment T5 (NPK full dose + P. aeruginosa carrier based full dose) was better than other treatments and this treatments T5 can be recommended for the growth of cabbage under field condition. Verma et al. (2014) and (2017) reported highest nutrient values and highest physicochemical properties as pH, EC, Organic carbon when the plants were treated with Pseudomonas spp.