Legume Research

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Legume Research, volume 44 issue 9 (september 2021) : 1109-1117

Appraisal of Seed Priming with Liquid Microbial Inoculants on Growth and Yield Attributes of Forage Cowpea

S. Ramya1, Gulab Pandove2,*, Anu Kalia3, Sukhdeep Kaur2, Harpreet Oberoi4, Brijesh Kumar Yadav2
1Department of Microbiology, Punjab Agricultural University, Ludhiana-141 004, Punjab, India.
2Regional Research Station, Punjab Agricultural University, Bathinda-151 001, Punjab, India.
3Electron Microscopy and Nanoscience Laboratory, Department of Soil Science, Punjab Agricultural University, Ludhiana-141 004, Punjab, India.
4Department of Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana-141 004, Punjab, India.
  • Submitted23-07-2019|

  • Accepted08-11-2019|

  • First Online 17-03-2020|

  • doi 10.18805/LR-4201

Cite article:- Ramya S., Pandove Gulab, Kalia Anu, Kaur Sukhdeep, Oberoi Harpreet, Yadav Kumar Brijesh (2021). Appraisal of Seed Priming with Liquid Microbial Inoculants on Growth and Yield Attributes of Forage Cowpea . Legume Research. 44(9): 1109-1117. doi: 10.18805/LR-4201.
Inadequate and nutritionally unbalanced supply of forage results in low productivity of livestock. There is an urgent need of burgeoning forage supply by amalgamating organic and inorganic components in integrated manner.Thereupon, the present investigation was carried out to evaluate the potential of liquid microbial inoculants on growth and yield of forage cowpea.The field experiments were conducted during kharif season (2018) at Punjab Agricultural University, Regional Research Station, Bathinda and Department of Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana, Punjab respectively. The experiment was laid out in randomized complete block design with a total of eleven treatment combinations of liquid microbial inoculants (Burkholderia seminalis, Burkholderia sp. and Bradyrhizobium sp.) with 75% and 100% RDF and replicated thrice. Results indicated that the treatment T10 (75% RDF + Burkholderia sp. + Burkholderia seminalis) significantly (p<0.05) enhanced vine length (210.47 and 205.33 cm), leaf length (11.77 and 11.53), leaf breadth (8.97 and 9.14 cm) and dry matter yield (40.13 and 38.18 q/ha) at Ludhiana and Bathinda respectively. Moreover, the percentage increase in green fodder yield (q/ha) with T10 treatment over T1 (control) was 13.21% at Ludhiana and 12.50% at Bathinda. Accordingly, it can be concluded that liquid microbial inoculants could play a predominant role in integrated nutrient management of forage cowpea for enhanced productivity.
Livestock being an integral part of Indian agriculture plays a crucial role in bucolic economy. The prime aspect for bettered animal production on sustainable basis is balanced nutrition and requisite feeding of animals. However, mounting pressure and preferred demand for commercial and food crops have resulted in decline in the scope of increasing the area under forages (Backiyavathy et al., 2006). Cowpea can make a relevant contribution towards livestock forage and supply nitrogen to the soil. Thus, acting as binal purpose crop. It is largely cultivated in arid and semi-arid tropics of India and it is believed to be originated in Africa, the largest producer. Cowpea is also recognized for good regeneration potential. Approximately 6.2 million tonnes of cowpea was produced across the globe on about 11.3 million hectares of area in the year 2013 (faostart.org updated in Aug 2015). In India, it had production of 2.21 million tonnes with 3.9 million hectares area under cultivation and national productivity of 683 kg/ha in 2013 (Mandal et al., 2009).
 
In Punjab, cowpea is predominantly grown for fodder starting from March to July. Due to its fast growing nature, it supplies nutritious and palatable fodder during kharif when there is scarcity of green fodder. The area under fodder crops in the state is approximately 0.9 million hectares and the annual production is about 70 million tonnes of green fodder (Anonymous, 2014). Nonetheless, each animal gets fodder supply of about 30.5 kg per day, whereas per capita prerequisite of green fodder is 40 kg per animal. To meet this per capita fulfillment of green fodder per adult animal per day, 90 million tonnes of green fodder will be required (Mann et al., 2014). The suitable strategy to meet the growing demand for forage crop available in the country is to increase the production per unit area per unit time.
 
Cowpea requires good quantity of nutrients throughout the growth periods essentially phosphorus for great development of roots, better nodulation and nitrogen fixation. Modern agriculture based on chemical fertilizers is not a viable technology because of array of tribulations associated with it such as surface and ground water pollution, associated plant nutrient losses and loss of soil productivity from excessive erosion (Joshi et al., 2016). Neither the fertilizers nor the organic sources in isolation can achieve a sustained production under intensive cropping system. Thus holistic approach is required. Integrated nutrient management includes application of organic, inorganic and biological component in an integrated manner. Microbial inoculant emerged as one of the integral component of INM. Microbial inoculants are cost effective, ecofriendly and renewable source of plant nutrients. Plant growth promoting rhizobacteria have been used worldwide as microbial inoculants for increasing crop productivity, soil fertility and for sustainable agriculture (García-Fraileet_al2015). The relationship between PGPR and their host can be rhizospheric or endophytic.

Endophytic bacteria colonizing internal plant tissues, benefit plants by using various traits, synthesis of phytohormones (Beneduzi et al., 2012), exopolysaccharides, osmoprotectants, (Berg et al., 2013) and antifungal metabolites (Gond et al., 2015). The use of bacterial endophytes in agriculture has immense potential to reduce the environmental impacts caused by chemical fertilizers, especially nitrogen fertilizers. Endophytic bacteria have the ability of biological nitrogen fixation and potential to produce 1-aminocyclopropane-1-carboxylate (ACC deaminase). In addition, endophytic colonization can results in increased plant vigour, tolerance to biotic and abiotic stresses, enhanced drought tolerance and ameliorated phosphorus utilization (Yadav et al., 2014). The majority of endophytic strains isolated were identified as Burkholderia, Curtobacterium, Rahnella, Pseudomonas, Acinetobacter, Pantoea, Rhodotorula and Rhizobium species. Endophytic Burkholderia reside inside the plant tissues without doing substantive harm and increases the growth of rice plants from 42–64% under gnotobiotic conditions (Govindarajan et al., 2008). Results also showed that Bradyrhizobium sp. and Herbaspirillum sp. instantly colonize the interior of rice roots when rice is grown in rotation with a legume crop (Guong et al., 2012).
 
In present study, we have evaluated the effects of liquid microbial inoculants on growth and yield attributes of forage cowpea.
Experimental conditions
 
The field experiment was conducted during Kharif  2018 at Punjab Agricultural University, Ludhiana (30.9°N latitude and 75.85°E longitude with average elevation of 244 metres above sea level) and Punjab Agricultural University, Regional Research Station, Bathinda (30° 09'36" N latitude, 74° 55'28" E longitude and at an altitude of 211 m above sea level). The field experiment was laid out in RCBD design and replicated thrice. There were eleven treatments, viz. T1: Recommended dose of fertilizer (RDF), T2: RDF + liquid microbial inoculant of Burkholderia sp., T3: RDF +  Liquid microbial inoculant of Burkholderia seminalis, T4: RDF + Liquid microbial inoculant of  Bradyrhizobium sp., T5: RDF + Liquid microbial inoculant of Burkholderia sp. and Burkholderia seminalis, T6: RDF + Liquid microbial inoculant of Burkholderia sp. and Bradyrhizobium sp. respectively, T7: 75% of RDF + liquid microbial inoculant of Burkholderia sp.,T8: 75% of RDF +  Liquid microbial inoculant of Burkholderia seminalis, T9: 75% of RDF + Liquid microbial inoculant of  Bradyrhizobium sp., T10: 75% of RDF + Liquid microbial inoculant of  Burkholderia sp. and Burkholderia seminalis and T11: 75% of RDF + Liquid microbial inoculant of Burkholderia sp. and Bradyrhizobium sp. The land preparations were done mechanically with proper care to avoid mixing of soil from adjacent plots. Cowpea variety ‘CL-367’ was sown at the rate 25kg/acre as per treatment schedule at an inter-row spacing of 30 cm with the gross plot dimensions of 5m ´ 3m. Nitrogen and phosphorus were applied as per the treatments through urea and single super phosphate. Seed bacterization was done with liquid microbial inoculants of Burkholderia seminalis, Burkholderia sp. and Bradyrhizobium sp. as per treatments @ 100ml/ acre. Inoculated seeds were then air dried in shade and planted within 2 hours. Weeding and hoeing was done to avoid weeds and suitable control measures were taken to prevent insects and pests. Other cultural operations and plant protection measures were followed as per the recommendations. During the study period, at Ludhiana location, mean monthly minimum and maximum temperatures during the crop season ranged from 31.28 to 34.21°C and 16.61 to 27.31°C respectively. The mean monthly relative humidity ranged from 38.31 to 88.96%. The total rainfall received during the crop season was 444.1 mm. At Bathinda location, mean monthly maximum and minimum temperatures during the crop season ranged from 35.5 to 32.23°C and 26.1 to 17.1°C respectively. The mean monthly relative humidity ranged from 40.2 to 84.8%. The total rainfall received during the crop season was 242.0 mm.
 
Growth and yield attributes
 
At 70-72 days after sowing (DAS) green fodder yield per net plot was recorded and dry matter yield was calculated on the basis of dry matter content obtained by drying known quantity of green forage from each plot in hot air oven at 70°C. Likewise, data on vine length, leaf length, leaf breadth, stem girth, number of leaves/ branch, number of branches/ plant, leaf stem ratio, green fodder yield and dry matter yield was recorded from five random plants/ plot in the net plot area at harvesting.
 
Soil microbial studies
 
Soil samples were collected from rhizospheric soil at 30, 60 DAS and at harvest. Total viable bacterial, fungal and actinomycetes counts from soil samples were estimated through dilution spread plate method. Collected moist soil sample (10 grams) was weighed and added to the water blank for obtaining first dilution. The 1 ml suspension was transferred to 9 ml of water blank. Similarly, the serial dilution was made up to the highest dilution of 10-7. Then, 1 ml aliquots of the appropriate dilutions were spread plate on Nutrient agar, Glucose yeast extract and Starch casein agar media for bacterial, fungal and actinomycetes count respectively.
 
Soil characteristics
 
Soil samples were collected from rhizospheric soil and air dried, ground and sieved through 2 mm sieve. Determination of organic carbon content (Walkley and Black, 1934),  available nitrogen by alkaline permanganate method (Subbiah and Asija, 1956), available phosphorus by 0.5N Sodium bicarbonate extraction method (Olsen et al., 1954) and available potassium by neutral normal ammonium acetate extraction by flame photometer (Jackson, 1973) was done separately for each plot.
 
Statistical analysis
       
The experimental data collected on various aspects of investigation were statistically analyzed with the procedure as described by Cochran and Cox, (1950). The comparisons were made at 5% level of significance.
The productivity of our livestock often remains low due to inadequate and nutritionally unbalanced supply of feed and fodder. Increasing human population and reduction in land availability for cultivation are the two threats for agricultural sustainability (Shahbaz and Ashraf, 2013). Forage is the cheapest source of animal feed which need to be properly managed, fertilized and harvested at proper stage of growth. In view of these facts, there is an urgent need of increasing good quality forage supply by adopting improved agronomic techniques such as liquid microbial inoculants. Integrated nutrient management is propounded as a promising strategy for addressing such challenges. Microbial inoculants being an important component of INM are eco-friendly and economical sources of nutrient. The use of microbial inoculants in agriculture has substantially increased during the past two decades. Thereupon, the objective of the current study was to evaluate the potential of liquid microbial inoculants to improve growth and yield of cowpea under field conditions. The results obtained from the present investigation as well as pertinent discussion have been summarized under following heads.
 
Growth characteristics
 
The data on growth parameters viz. vine length (cm), leaf length (cm), leaf breadth (cm), stem girth (cm), number of branches per plant, number of leaves per branch and leaf: stem ratio were recorded at harvest.
 
Vine length (cm)
 
Vine length is a reliable growth index of the plant particularly fodder crops, which represents the infrastructure build-up over a period of time. It can also be considered as important factor to judge the vigour of plant.
 
Liquid microbial inoculants showed statistically significant effect on vine length of shoot. Maximum vine length of shoot was observed in treatment T10 (210.47 and 205.33 cm) followed by T5 (200.41 and 202.22 cm), T11 (198.96 and 200.27 cm), T6 (196.31 and 190.62 cm), T8 (194.50 and 185.75 cm), T7 (189.12 and 187.75 cm), T9 (187.14 and 184.60 cm), T3 (184.46 and 186.17 cm), T2 (183.56 and 185.26 cm), T4 (182.73 and 179.33 cm) and T1 (181.05 and 176.90 cm) at Ludhiana and Bathinda respectively (Table 1 and 2). Improvement in vine length might be due to more development and branching of roots due to secretion of plant growth promoting hormones by Burkholderia seminalis, Burkholderia sp. and Bradyrhizobium sp. This in turn must have helped in improved uptake of nutrients and enhanced plant vigour. These findings were similar with those of El-Waraky and Kasem, (2007) who pointed out that inoculation of cowpea seeds cv. Kafer El-Sheikh-1 with biofertilizer (Halex-2: a biofertilizer containing a mixture of non-symbiotic Nitrogen-fixing bacteria of the genera Azospirillum, Azotobacter and Klebsiella) significantly increased plant height, number of leaves and branches. Similarly, Singh et al., (2006) reported that inoculation of rhizobium to seeds @ 0.5 kg/ha, VAM (vesicular arbuscular mycorrhiza) inoculated to soil @ 5 kg/ ha, or Rhizobium + VAM) resulted in the highest number of leaves, vine length and number of nodules per plant of cowpea cv. Narendra Lobia-2.
 
Leaf length (cm)
 
Leaf length of plant indicates the biomass of plant. Productivity and photosynthetic activity is also correlated with the leaf area. The maximum leaf length was exhibited by treatment T10: 75% of RDF + Burkholderia sp. Burkholderia seminalis (11.77 and 11.53 cm) and minimum at T1: RDF (10.48 and 10.19 cm). All treatments with liquid inoculants showed significant improvement in leaf length at both locations (Table 1 and 2). The possible reason for improved leaf length might be due to increase in phosphorus availability due to phosphate solubilizing activity of cultures that gives rapid and vigorous start to plant and thus, enhanced growth parameters. Our findings were similar with Fernandes and Bhalerao (2015) who reported that the plants treated with biofertilizer (Rhizobium japonicum) showed significant improvement in the growth parameters like the length of leaves, breadth of leaves, shoot length and root length. Azospirillum inoculation also significantly increased the growth in terms of length and breadth of leaf and fresh and dry weight/ plant of rice plant as reported by Hossain et al., (2015).
 
Leaf breadth (cm)
 
Leaf breadth serves as a reliable criterion to assess leaf area which in turn relates to green fodder yield. Liquid microbial inoculants significantly improved leaf breadth at both the locations. Maximum leaf breadth (8.97 and 9.14 cm) was observed with treatment T10 which was at par with treatment on T5 (8.94 and 9.09cm) in both the locations (Ludhiana and Bathinda) respectively. Minimum leaf breadth was recorded with treatment T1 (8.52 and 8.03 cm) across Ludhiana and Bathinda respectively (Table 1 and 2). This increase in leaf breadth might be due to application of liquid microbial inoculants which might have enhanced the availability of nitrogen and phosphorus by biological nitrogen fixing and phosphate solubilizing ability of Burkholderia seminalis, Burkholderia sp. and Bradyrhizobium sp. in addition to secretion of  plant growth promoting hormones like IAA, GA and Cytokinins. These findings were similar with those of Sharma et al., (2018) who reported that the combined application of 100 per cent RDF + biofertilizers + vermicompost resulted in maximum leaf length (61.80 cm), leaf width (22.53 cm), curd yield per hectare (35.97 tonnes/ha) and dry matter content (9.88%) in broccoli [Brassica oleracea (L.) var. italica].
 
Stem girth (cm)
 
Stem girth is an important vigour contributing component which corresponds to structural build-up of plant. The maximum stem girth was shown by the treatment T10: 75% of RDF + Burkholderia sp. + Burkholderia seminalis (2.13 and 2.27 cm) and minimum values in T1: RDF (2.00 and 1.96 cm) at Ludhiana and Bathinda respectively (Table 1 and 2). These results were supported by Nadeem et al., (2016) who reported that combined inoculation of seed with Rhizobium + phosphate solubilizing bacteria along with 40 kg phosphorus/ ha (P2) significantly increased the stem girth (1.84 cm) in cowpea over rest of treatment combination. Thus, increase in stem girth with treatments of liquid microbial inoculants might be due to increase in availability of nitrogen which in turn involves cell division, enlargement, elongation and differentiation.
 
Number of leaves/branch
 
Productivity of crop depends on the process of photosynthesis, which in turn depends on number of leaves in plants. Liquid microbial inoculants significantly affected the number of leaves per branch. However, maximum number of leaves per branch was observed in the plants supplemented with T10: 75% of RDF + Burkholderia sp. Burkholderia seminalis (42.38 and 41.99) followed by T5: RDF + Burkholderia sp. + Burkholderia seminalis (41.78 and 41.63) at both the locations respectively (Table 1 and 2). The increase in number of leaves per branch might be due to more availability of nutrients such as nitrogen and phosphorus due to treatments of cowpea seeds at the time of sowing with liquid microbial inoculants. These results are in conformity with the findings of Nkaa et al., (2014) who reported that phosphorus fertilizer significantly enhanced growth and yield characters of cowpea varieties such as number of leaves and number of branches in all the weeks of measurement. The number of leaves also increased in combined inoculation of liquid biofertilizer treatments such as Rhizobium + Azospirillum + Azotobacter (T7) at 60th day (27.6±3.2) followed by other treatments as reported by Uma Maheswari and Elakkiya, (2014).
 
Number of branches/plant
 
Number of branches/ plant is one of the quantitative character determining the total fodder yield. Liquid microbial inoculants non-significantly affected the number of branches/ plant. However, numerically maximum number of branches/plant was observed in treatment T10: 75% of RDF + Burkholderia sp. + Burkholderia seminalis (4.27 and 4.16) followed by T5: RDF + Burkholderia sp. + Burkholderia seminalis (4.22 and 4.07) at both the locations respectively. Minimum number of branches /plant was noted in the T1: RDF (3.63 and 3.67) at Ludhiana and Bathinda respectively (Table 1 and 2). These observations are in conformity with the works of Abdel-Hady, (2009) who demonstrated that fertilizing cowpea cv. Kaha with combination of FYM and Biofertilizer (Phosphorine + Rhizobacterien) and 1/2 NPK (recommended doses) produced the highest number of branches/plant, highest pod length, highest number of seeds /pod, highest pod filling and protein contents when compared to the control untreated plants.
 
Leaf stem ratio
 
The leaf stem ratio is an important yield contributing parameter and has a direct effect on final green and dry fodder yield of cowpea. However, maximum leaf stem ratio was observed with treatment T10: 75% of RDF + Burkholderia sp. + Burkholderia seminalis (0.493 and 0.489) followed by treatments T5: RDF + Burkholderia sp. + Burkholderia seminalis (0.487 and 0.480) in both the locations (Table 1 and 2). The improvement in leaf stem ratio might be attributed to the rapid expansion of dark green foliage due to increase nitrogen availability by Burkholderia seminalis, Burkholderia sp. and Bradyrhizobium sp. due to biological nitrogen fixation. Similar results were studied by Verma et al., (2017) who have reported that growth parameters like leaf stem ratio, plant height, number of leaves, fresh weight of leaf, fresh weight of stem, fresh weight of plant, LAI, dry matter accumulation on leaf, stem and plant and CGR improved significantly with 100% RDN @ 60 kg ha-1 + ST with Azotobacter + Azospirillum as compare to other treatments.
 
Green fodder yield (q/ha)
 
Green fodder yield represents the total biomass of plant organs and effective absorption of nutrient elements. Application of liquid microbial inoculants of Burkholderia seminalis, Burkholderia sp. and Bradyrhizobium sp. have no significant effect on biological yield of forage cowpea. However, the maximum green fodder yield was obtained with treatment T10: (285.71 and 267.85 q/ha) followed by T5 :(RDF+ Burkholderia sp. + Burkholderia seminalis) (280.95 and 264.28 q/ha), T8: 75% of RDF + Burkholderia seminalis (277.81 and 263.09 q/ha), T11: 75% of RDF+ Burkholderia sp+ Bradyrhizobium sp., (277.19 and 263.90 q/ha), T7: 75% of RDF + Burkholderia sp. (276.19 and 255.95 q/ha), T6: RDF + Burkholderia sp.+ Bradyrhizobium sp. (276.38 and 263.09 q/ha), T9: 75% of RDF + Bradyrhizobium sp. (273.81 and 257.14 q/ha), T3: RDF + Burkholderia seminalis (269.04 and 254.76 q/ha), T2: RDF + Burkholderia sp. (266.66 and 253.57 q/ha), T4: RDF + Bradyrhizobium sp (263.09 and 251.19 q/ha) and minimum green fodder yield was observed with T1: RDF (252.38 and 238.09 q/ha) at Ludhiana and Bathinda, respectively (Table 3).
Similar results were reported by Ramanjaneyulu et al., (2010) who reported green and dry fodder yield of sorghum to be highest with half RDF (30 kg N+15 kg P2 O5 ha-1) and biofertilizers (Azotobacter + phosphate solubilizing bacteria). Prasad et al., (2013) also reported that phosphorus along with Rhizobium proved to be beneficial in increasing the shoot and root biomass. Similarly, Khan et al., (2017) reported that application of Burkholderia sp. and Pseudomonas aeruginosa with 50% of recommended nitrogen, phosphorus and potassium fertilizers produced equivalent or higher grain yield of rice compared to the control grown with full recommended fertilizer doses, which suggests that these strains may have the potential to be used as bioinoculants for sustainable rice production.
 
The increase in biological yield might be because of several factors such as release of growth promoting substances like IAA, GA and control of pathogens in addition to nitrogen fixation and phosphate solublization by liquid microbial inoculants (Burkholderia seminalis, Burkholderia sp. and Bradyrhizobium sp).
 
Dry matter yield (q/ha)
 
Dry matter yield is usually determined on dry matter basis, which is weight of plant material after the moisture within the plant material has been extracted. Liquid microbial inoculants showed statistically significant effect on dry matter yield. Dry matter yield attained with treatment T10 was highest (40.13 and 38.18 q/ha) followed by T5 (40.08 and 38.00 q/ha), T11 (39.38 and 35.79 q/ha), T(39.36 and 37.51 q/ha ), T8  (38.58 and 37.51 q/ha),T7 (38.09 and 35.02 q/ha), T9 (36.94 and 34.69 q/ha), T3 (36.54 and 34.29 q/ha),T2 (37.07 and 32.72 q/ha) and T4 (35.21 and 31.94 q/ha) and minimum dry matter yield was observed at T1 (34.92 and 31.76 q/ha) at Ludhiana and Bathinda respectively (Table 3).
 
These results were supported by Prasad et al., (2017) who reported that the inoculation of Rhizobium and phosphate solubilizing bacteria along with 20 kg N/ha through vermicompost significantly increased the growth i.e. plant dry weight, crop growth rate. The increase in dry matter yield with liquid inoculant treatments indicated the favourable response of forage cowpea to seed treatment with liquid inoculants of Burkholderia seminalis, Burkholderia sp. and Bradyrhizobium sp.
 
Soil chemical and microbial properties
 
In present study application of liquid microbial inoculants treatments have non-significant effect on organic carbon, available nitrogen, available phosphorus and available potassium in comparison to control (T1) (Fig 2). This might be due to the fact that inoculated bacterial cultures were endosymbiotic in origin and involved preferential invasion of the host tissues followed by inhabitation of the root nodules. Therefore, such bacteria can affect the host plant by exhibiting direct exchange of the PGP substances and other compounds via bacteria-plant cell membrane interfaces particularly the bacteria-secreted phytohormones alter the hormonal homeostasis of the plant and lead to higher growth of the root tissue and thus increase the surface area for the absorption and uptake of the water and nutrients from the rhizosphere. However, the impact on the rhizosphere soil remains marginally low to negligible due to the preference of these bacteria to remain closely adhered to or invade the host tissues and thus exist in low numbers in the rhizosphere soil. Further, the improvement in plant yield might be attributed to increased availability of nutrients in direct vicinity of plant’s roots.
 
Similar to no or negligible change in the soil nutrient contents, a little numerical improvement in the total bacterial, fungal and actinomycetes count of the rhizospheric soil was recorded (Fig 3). This might be due to the fact that applied bacterial inocula moved inside the plant tissues resulting in probably no release of the molecules in the rhizosphere for the elicitation of the native microbial population. Further, the existing diversity of the native microbial communities get buffered or balanced such that the total viable counts of microbial populations remain same. Microbes which are favourable for plants get increased and others get decreased. Kennedy, (1999) reported that the modification in bacterial community structure caused by inoculation could be buffered by ecosystem resilience, which is driven by the level of diversity and interactions of the plant-soil-biota.
 
It is believed that for improving soil health by use of inoculants, recurrent inoculations with highly competitive strains over a period of several years is required. As native strains give tough competition to inoculated strains (applied in the form of inoculants). Thus, bulk inoculation of soil in addition to seed inoculation is need of hour for improving soil health as these could play significant role in decomposition of organic component and myriad of biogeochemical cycles.
Liquid microbial inoculants of Burkholderia seminalis, Burkholderia sp and Bradyrhizobium sp. individually and in various combinations along with 100% and 75% recommended dose of fertilizer in integrated manner were found to escalate growth and yield attributing characters of forage cowpea through various mechanisms. Nonetheless, maximum growth and yield attributing traits of forage cowpea were observed with 75% of RDF + Burkholderia sp. + Burkholderia seminalis. Accordingly, these liquid microbial inoculants could play a predominant role in integrated nutrient management of forage cowpea for enhanced productivity.

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