Indian Journal of Agricultural Research

  • Chief EditorV. Geethalakshmi

  • Print ISSN 0367-8245

  • Online ISSN 0976-058X

  • NAAS Rating 5.60

  • SJR 0.293

Frequency :
Bi-monthly (February, April, June, August, October and December)
Indexing Services :
BIOSIS Preview, ISI Citation Index, Biological Abstracts, Elsevier (Scopus and Embase), AGRICOLA, Google Scholar, CrossRef, CAB Abstracting Journals, Chemical Abstracts, Indian Science Abstracts, EBSCO Indexing Services, Index Copernicus

Impact of Plant Growth Promoting Rhizobacteria in Restoring Soil and Crop Attributes

Anshika Singh1, Rajani Srivastava1,*
1Environmental Science (Environmental Technology), Institute of Environment and Sustainable Development, Rajiv Gandhi South Campus, Banaras Hindu University, Varanasi-221 003, Uttar Pradesh, India.
Background: To evaluate the effect of selected plant growth promoting rhizobacteria (PGPR) (Paenibacillus polymyxa, Pseudomonas putida and Azospirillum brasilense) and Trichoderma sp. in the restoration of selected attributes of soil fertility and the crop productivity in Indian Vindhyan semi-arid region. 

Methods: An experiment was conducted at the Rajiv Gandhi South Campus, Banaras Hindu University, with test crop brinjal (Solanum melongena L.). Fourteen treatments: four mono-inoculants (T1 to T4), six bi-inoculants (T5 to T10), two tri-inoculants (T11 and T12), one tetra-inoculant (T13) and control (T14) were included in the present study. Paenibacillus polymyxa, Pseudomonas putida, Trichoderma sp. and Azospirillum brasilense were used in single or in combination in all treatments. 

Result: The results showed a positive increment in organic C and total N in all treatments. This increase was maximum in T13 (Paenibacillus polymyxa + Pseudomonas putida + Trichoderma sp. + Azospirillum brasilense) treatment followed by T11> T12> T8> T9> T5> T6> T10> T2> T3> T4> T1 compared to control. Positive increment in plant height, number of leaves and flowers were also noted in T13, T11 and T12 treatments. Maximum above-ground biomass and below-ground biomass were recorded in tetra inoculant treatment. Improved nutrient acquisition in T13 (tetra-inoculant) and T11 and T12 (tri-inoculant) treatments is due to increasing nutrient uptake of N from nitrogen-fixing bacteria and uptake of P from phosphate mineralizing. Thus, for restoration of selected soil and crop attributes through PGPR and Trichoderma sp. especially through tetra-inoculants or tri-inoculantsis considered to be a good technique.
The semi-arid soil of the Indian Vindhyan region is degrading because of various reasons like drought, soil erosion, deforestation, desertification etc. Globally, land degradation negatively impacts about 3.2 billion people depending directly or indirectly on this resource. For fulfilling the requirement of several sustainable development goals (SDGs), like SDG 2 (Zero hunger), SDG 13 (Climate Action), SDG 15 (Life on land) and SDG 17 (Partnerships for the Goals), it is important to reverse the effect of degradation. So, the restoration of ecosystem attributes is important. It was reported that nutrient use efficiency, N uptake and productivity in dryland agroecosystem can be enhanced by the application of multipurpose tree leaves (Srivastava and Singh, 2013; 2019; Srivastava, 2019). They are known to improve plant growth in many ways when compared to synthetic fertilizers, insecticides and pesticides (Saha et al., 2020; Sani et al., 2020). Many Rhizobacteria and fungal species, archaea, fungi, algae, insects, annelids and other invertebrates can be utilized as Plant Growth Promoting Rhizobacteria (PGPR) or biofertilizers (Zhou et al., 2016; Singh et al., 2020). The implication of PGPR for restoring agricultural land sustainability have gained worldwide importance, as now the emphasis has shifted from chemical to biological approach in the agricultural system (Srivastava and Singh, 2017; Oleńska et al., 2020).

The direct mechanisms of PGPR include biological nutrient uptake and solubilization (Oleńska et al., 2020), nitrogen fixation, phosphate solubilization (Yadav et al., 2014), siderophore production and iron uptake (Zhou et al., 2016) and phytohormone synthesis. In past, various researches have been carried to study the effect of rhizospheric bacteria on the growth of different crops including legumes, vegetables and spices (Verma et al., 2014; Sellitto et al., 2019). There is a scarcity of information about the application of PGPR for the restoration of soil fertility and crop productivity in the semi-arid Vindhyan region. In this view, the current study was carried out to evaluate the effect of PGPR and Trichoderma sp. alone and in combinations with each other’s on the restoration of selected attributes of soil fertility (like soil organic carbon, nitrogen) and the crop productivity (test crop-brinjal) in Indian Vindhyan semi-arid region.
The experiment was carried out at the Rajiv Gandhi South Campus, Banaras Hindu University, Barkachha, Mirzapur which is situated in the Vindhyan region of district Mirzapur (25°10’ latitude, 82°37’ longitude and altitude of 427 meters above mean sea level). The soil of this region is sandy loam red laterite in texture with low drainage made from Vindhyan rocks, invariably poor fertility status. The soil is slightly acidic in reaction (5-6 pH), poor in nitrogen as well as phosphorus and moderate in potash. The soil had a poor amount of organic carbon below 0.5% (Srivastava and Singh, 2002; Srivastava et al., 2020).

The pot experiments were conducted over one crop period (from December 2018-April 2019) with the incorporation of PGPR of Siliguri variety. The test crop selected for the experiment was brinjal (order Sonales and family Solanaceae) because of its versatile nature and adaptation to different agro-climatic regions. Four sterilized seeds of brinjal were taken separately in the test tube and added total volume of 5ml broth cultures of microbial consortia. After this, same four seeds of brinjal were sown in different pot, treatment-wise. The PGPR culture was collected from the IESD, BHU. Initially, the blocks of soil were broken down, homogenized, sieved and filled in the pots (diameter of pots, 7 cm and height 15 cm). Total 70 pots (5 replicates for each treatment x 14 treatments) were prepared and irrigated with tap water to maintain the moisture in the soil to support plant growth. All pots were placed in an experimental area that was covered with nylon net at the top and sides to prevent litter blown from external sources or the bird herbivory. After few days of germination, thinning was done in each pot (reduced up to 1 in each pot) for further experiment. Three bacterial strains (Paenibacillus polymyxa, Pseudomonas putida and Azospirillim brasilense) and one fungal species (Trichoderma sp.) were selected for consortia development. The treatments were: first four mono-inoculants (T1 to T4); Paenibacillus polymyxa (T1), Pseudomonas putida (T2), Trichodermasp. (T3), Azospirillum brasilense (T4), next six bi-inoculants (T5 to T10); Paenibacillus polymyxa + Pseudomonas putida (T5), Paenibacillus polymyxa + Trichoderma sp. (T6), Paenibacillus polymyxa + Azospirillum brasilense (T7), Pseudomonas putida + Trichoderma sp.(T8), Pseudomonas putida + Azospirillum brasilense (T9), Trichoderma sp.+ Azospirillum brasilense (T10), next two are tri-inoculants (T11 and T12); Paenibacillus polymyxa + Pseudomonas putida + Trichoderma sp. (T11), Paenibacillus polymyxa + Pseudomonas putida + Azospirillum brasilens (T12) and one tetra-inoculants Paenibacillus polymyxa + Pseudomonas putida + Trichoderma sp.+ Azospirillum brasilense (T13) and one control (T14). Test plants were monitored continuously after every 25-30 days interval for vegetative analysis (including measurement of plant height, no. of leaves, no. of buds, etc.). Determining the above and below-ground biomass of brinjal in different treatments was done after crop harvest. The initial and final soil samples were also drawn for physical and chemical analysis. Soil moisture analysis was determined by oven drying at 105°C. Soil pH was done by a digital pH meter. The water holding capacity of the soil was measured by the brass cup method (Piper, 1966). Soil organic carbon (OC) was estimated by Walkley and Black method (Walkley and Black, 1934) and total nitrogen (TN) by the Micro-Kjeldahl method (Jackson, 1958).

Statistical analysis in the present paper was done using the SPSS package (version 16, U.S.A.) All the values are expressed as mean ± standard error. Mean values were compared by using the least significant difference (LSD) range test procedure at the 5% level of significance. Two-tailed Pearson correlation coefficients between soil properties and crop productivity parameters under different PGPR treatments were calculated to observe the impact of change in soil properties on crop productivity.
The experiment showed differences in physico-chemical properties in soil and crop growth attributes in brinjal due to the application of varied quality of Plant Growth Promoting Rhizobacteria (PGPR). Initial holding capacity (WHC), Organic C (0.4%) and total N (0.03%) were scarce in soil showing degraded conditions. pH was neutral to slightly alkaline (Table 1).

Table 1: Changes in selected soil physico-chemical properties and vegetative characteristics of test crop (brinjal) after application of different PGPR strains in form of single (T1- T4), bi-(T5-T10), tri-(T11-T12) and tetra-(T13) inoculants.

In the present experiment, there were increases in fertility status of soil after 3-4 months of the incorporation of PGPR culture. Compared to control; soil moisture increased was a minimum of 6% in T1 treatment and a maximum of 135% in T13 treatment. The water holding capacity was recorded highest in T13 (18.5) followed by T11, T12, T8, T9, T5 and was lowest in T1. Enhancement in WHC was varied from 6% to 89% under different PGPR treatments. The value of pH varied from slightly alkaline to neutral or slightly acidic. The most effective combination applied for soil restoration in this study was tetra inoculants (T13) and after that tri inoculants (T11 and T12). These treatments significantly increased plant growth, biomass and nutrient uptake as compared to mono and bi inoculant treatments and control. Soil moisture and WHC were showed little increase in mono inoculant treatments (T1 to T4) and maximum upto 90% in tetra inoculant treatment (T13).  Pseudomonas sp. is reported to improve soil texture by increasing the water holding capacity of the soil (Tewari and Arora, 2014; Naseem and Bano, 2014). According to Grover et al., (2011), Azospirillum sp. is also responsible for increased water circulation between soil and plants. Zhang et al. (2020) also reported that the strains of Pseudomonas and Bacillus sp. are efficient in eliminating drought stress and promoting plant growth. Synergistic effects of bacterial strains used in tetra or tri inoculants in this study (like in T13, T11 and T12) had the maximum values for WHC, soil moisture, OC, TN and plant biomass. Single and bi inoculants showed minimum improvement as promotion of only a few metabolisms in the plant that could not produce synergistic effect. The presence of microbial culture in soil enhances the biodegradation of organic matter, improving the pH, improving the nutrient availability for plants and also increasing the fertility of the soil (Adeleke et al., 2017).

The increase in organic carbon (C) and total nitrogen (N) content in soil was evident after the treatment with PGPR culture (Table 1). This increase was maximum in T13 followed by T11> T12> T8> T9> T5> T6> T10> T2> T3> T4> T1 treatment and control. T13 showed an increase in the OC content of soil (1.3) which is about 189% more than the control (0.45), facilitating the accumulation of a large amount of organic matter promoting the significant growth of the plant. The values of total N content in soil was also found maximum in T13 treatment (0.14) followed by T12, T11, T8 and T9 (0.13 in each)> T10 and T5 (0.12)>T6 (0.11)> T7 and T2 (0.09)> T3(0.07) and T1 and T4 (0.06) treatments in comparison to control (0.042). T13 (tetra inoculants) treatment showed 2.8 times greater OC and 3.3 times higher total N as compared to control (Table 1). Improved nutrient acquisition in T13 (tetra-inoculant) and then T11 and T12 (tri-inoculant) treatments was due to increased nutrient uptake of N from nitrogen-fixing bacteria, uptake of P from phosphate mineral solubilizing bacteriaand uptake of iron from siderophore producing bacteria (Pseudomoas putida and Trichoderma sp.) and suppressing plant diseases (Verma et al., 2016; Jaiswal et al., 2019). It was also reported by Sani et al., (2020) that Trichoderma sp. improved soil fertility and promoted the growth of rhizosphere microbes, which eventually led to higher tomato yields and increases in antioxidants and minerals. In the present study, the T13 treatment and other treatments were these two species Pseudomoas putida and Trichoderma sp. showed benefits.

Vegetative growth of test crop (brinjal) also showed improvement under different PGPR treatments. The pattern was more distinct as crops reach maturity (Table 1). The maximum number of leaves has been recorded at 80 days after transplanting DAT in T13 (13 leaves) treatment, followed by T11=T12 (11 leaves)> T2=T4=T5=T8 (10 leaves) > T3=T6=T7=T9=T10 (9 leaves) and minimum in T1 (8 leaves) and control (7 leaves). In all treatments, T13 showed increased shoot growth and the increase was more pronounced at 80 DAT. T13 treatment showed about 2 times more plant leaves and 1.6 times greater shoot height as compared to control.

Application of mono, bi, tri and tetra PGPR inoculant showed variation in above-ground and below-ground biomass and also in the number of flowers per plant per pot (Fig 1).

Fig 1: (A) Variations in number of flowers (per plant/pot) (B) above-ground biomass (g/plant/pot) and below-ground biomass g/plant/pot) of test crop under different PGPR treatments. Values are means of ±SE.

Maximum above ground (4 g) and below-ground biomass (1.7 g) were recorded in the T13 treatment. However, the treatments such as T10, T6, T7, T3, T4 and T1 (2.4, 2.3, 2.4, 2.3, 1.4 and 1.3 g, respectively) showed comparatively lesser enhancement in biomass comparison to control. Maximum 6 flowers were produced in T13 treatment whereas only 2 flowers per plant were reported in T2, T3 and control. Various studies revealed that Pseudomonas putida have a multifunctional role in plant growth promotion and development. It was reported that this species help in biocontrol and produce secondary metabolites and also used for production of IAA, ammonia and increased nutrient uptake (Verma et al., 2014). Pseudomonas sp. is also reported to regulate protein synthesis, seed germination, siderophore production and phyto-beneficial traits (Zhang et al., 2019, Dhawi, 2020). Previous studies have also revealed that combined inoculation of A. Brailense with Pseudomonas sp. and P. polymyxahad significantly increased grain yield and dry matter content, N and P uptake (Silva et al., 2015). Benmati et al., (2020) investigated the effects of Azospirillum brasilense, Bacillus sp. and Frankia CcI3 on durum wheat under water deficit conditions also. Their studies confirm the significant abilities of PGPR under water stress conditions for maintaining growth and plant survival. Azospirillum sp. is reported to improve plant growth by N fixation and production of IAA, cytokinin and gibberellins (Steenhoudt and Vanderleyden, 2000). Tetra and tri inoculants involving P. putida and Azospirillum sp. showed the highest values in terms of biomass production and vegetative characteristics compared to other treatments and control. It was reported that Pseudomonas and Trichooderma sp. showed inhibition of soil-borne phytopathogens (Fusarium and Rhizoctonia) by HCN, siderophore production (Gupta and Gopal, 2008) and lytic enzymes (Verma et al., 2014).

Different soil fertility and productivity parameters of the brinjal crop were correlated and assessed under different treatments (Table 2).

Table 2: Pearson’s correlation coefficient analysis showing relationship among soil quality indicators and crop productivity parameters.

All soil quality indicators (soil moisture, water holding capacity, organic C and total N) were positively correlated with crop vegetative growth. Greater degrees of correlation were observed in the case of the plant above ground biomass and below-ground biomass with soil organic C (0.93 and 0.85) and total N (0.93 and 0.82).The overall performance of inoculated treatments revealed that seed treatment of Brinjal with tetra and tri inoculants, each bestowed with specific functions such as nitrogen fixer, phosphate solubilizers, antagonist, etc, could give significantly better performance in all respect of plant growth, yield, biomass and nutrients uptake as compared to individual treatments.
It can be concluded that the most effective treatment to enhance plant growth, biomass and nutrient uptake were tetra (T13, Paenibacillus polymyxa + Pseudomonas putida + Trichoderma sp.+ Azospirillum brasilense) and tri inoculants (T12, Paenibacillus polymyxa + Pseudomonas putida + Azospirillum brasilen and T11, Paenibacillus polymyxa + Pseudomonas putida + Trichoderma sp.). Significant increments were not only seen in plant growth but also in the soil physico-chemical properties. The findings thereby confirm that application of microbial consortia (PGPR) in three or more combinations may produce more profound effects in terms of restoration of soil fertility and crop productivity and yield in Vindhyan dry tropical soil.

  1. Adeleke, R., Nwangburuka, C., Oboirien, B. (2017). Origins, roles and fate of organic acids in soils: A review. South African Journal of Botany. 108: 393-406. 

  2. Benmati, M., Mouellef, A., Belbekri, N., Djekoun, A. (2020). Effects of Durum wheat (Triticum durum Desf.) inoculation with PGPR (Azospirillum brasilense, Bacillus sp and Frankia CcI3) and its tolerance to water deficit. Indian Journal of Agricultural Research. 54: 437-444.

  3. Dhawi, F. (2020). Plant growth promoting rhizobacteria (PGPR) regulated phyto and microbial beneficial protein interactions. Open Life Sciences. 15(1): 68-78. biol-2020-0008.

  4. Grover, M., Ali, S.Z., Sandhya, V., Rasul, A. and Venkateswarlu, B. (2011). Role of microorganisms in adaptation of agriculture crops to abiotic stresses. World Journal of Microbiology and Biotechnology. 27(5): 1231-1240. 10.1007/s11274-010-0572-7.

  5. Gupta, A. and Gopal, M. (2008). Siderophore production by plant growth promoting rhizobacteria. Indian Journal of Agricultural Research. 42: 153-156.

  6. Jackson, M.L. (1958). Soil Chemical Analysis. Prentice Hall, Inc.

  7. Jaiswal, D.K., Verma, J.P., Krishna, R., Gaurav, A.K. and Yadav, J. (2019). Molecular characterization of monocrotophos and chlorpyrifos tolerant bacterial strain for enhancing seed germination of vegetable crops. Chemosphere. 223: 636- 650.

  8. Naseem, H. and Bano, A. (2014). Role of plant growth-promoting rhizobacteria and their exopolysaccharide in drought tolerance of Maize. Journal of Plant Interactions. 9(1): 689-701.

  9. Oleñska, E., Ma³ek, W., Wójcik, M., Swiecicka, I., Thijs, S., Vangronsveld, J. (2020). Beneficial features of plant growth-promoting rhizobacteria for improving plant growth and health in challenging conditions: A methodical review. Science of the Total Environment. 743: 140682. j.scitotenv.2020.140682.

  10. Piper, C.S. (1966). Soil and plant analysis: A laboratory manual of methods for the examination of soils and the determination of the inorganic constituents of plants. Bombay: Hans Publisher, pp. 366

  11. Saha, I., Datta, S., Biswas, D. (2020). Exploring the role of bacterial extracellular polymeric substances for sustainable development in agriculture. Current Microbiology. 77(11): 3224-3239.

  12. Sani, M.N.H., Islam, M.N., Uddain, J., Chowdhury, M.S.N., Subramaniam, S. (2020). Synergistic effect of microbial and nonmicrobial biostimulants on growth, yield and nutritional quality of organic tomato. Crop Science. 60(4): 2102-2114. 

  13. Sellitto, V.M., Golubkina, N.A., Pietrantonio, L., Cozzolino, E., Cuciniello, A., Cenvinzo, V., Florin, I., Caruso, G. (2019). Tomato yield, quality, mineral composition and antioxidants as affected by beneficial microorganisms under soil salinity induced by balanced nutrient solutions. Agriculture. 9(5): 110.

  14. Silva, V.Nd, Silva, L. EdS. Fd, daSilva, A.J. Nd, Macedo, G. Rd. (2015). Biofertilizers and performance of Paenibacillus in the absorption of macronutrients by cowpea bean and soil fertility. Revista Brasileira de Engenharia Agrícola e Ambiental. 19(12): 1136-1142. 1807-1929/agriambi.v19n12p1136-1142.

  15. Singh, T.B., Sahai, V., Goyal, D., Prasad, M., Yadav, A., Shrivastav, P., Ali, A., Dantu, P.K. (2020). Identification, characterization and evaluation of multifaceted traits of plant growth promoting rhizobacteria from soil for sustainable approach to agriculture. Current Microbiology. 77(11): 3633-3642.

  16. Srivastava, R. (2019). Enhancing N uptake and agronomic efficiency of rice in tropical dry land agroecosystem by regulating decomposition of multipurpose tree leaves. Indian Journal of Ecology. 46 Special Issue (7): 15-19.

  17. Srivastava, R. and Singh, A. (2017). Plant growth promoting rhizobacteria (PGPR) for sustainable agriculture. International Journal of Agricultural Sciences. 7(4): 505-510.

  18. Srivastava, R. and Singh, K.P. (2002). Variations in soil organic C and total N storage due to cultivation practices in the Gangetic plain, India. International Journal of Ecology and Environmental Sciences. 28(3): 193-199.

  19. Srivastava, R. and Singh, K.P. (2013). Implications of multipurpose tree leaf application on wheat productivity in dry tropics. Journal of Forestry Research. 24(4): 777-782. https://

  20. Srivastava, R. and Singh, K.P. (2019). Impact of Tree Leaf Application on Microbial Biomass and Productivity in Tropical Dryland rice Microcosm. Proceedings of the National Academy of Sciences, India Section B. 89(2): 685-693. https://

  21. Srivastava, R., Mohapatra, M., Latare, A. (2020). Impact of land use changes on soil quality and species diversity in the Vindhyan dry tropical region of India. Journal of Tropical Ecology. 36(2): 72-79. 467419000385.

  22. Steenhoudt, O. and Vanderleyden, J. (2000). Azospirillum, a free- living nitrogen-fixing bacterium closely associated with grasses: Genetic, biochemical and ecological aspect. FEMS Microbiology Reviews. 24(4): 487-506. https://

  23. Tewari, S. and Arora, N.K. (2014). Multifunctional exopolysaccharides from Pseudomonas aeruginosa PF23 involved in plant growth stimulation, biocontrol and stress amelioration in sunflower under saline conditions. Current Microbiology. 69(4): 484-494.

  24. Verma, J.P., Jaiswal, D.K., Maurya, P.K. (2016). Screening of bacterial strains for developing effective pesticide-tolerant plant growth-promoting microbial consortia from rhizosphere soils of vegetable fields of eastern Uttar Pradesh, India. Energy, Ecology and Environment. 1(6): 408-418. https:/ /

  25. Verma, J.P., Yadav, J., Tiwari, K.N., Jaiswal, D.K. (2014). Evaluation of plant growth promoting activities of microbial strains and their effect on growth and yield of chickpea (Cicer arietinum L.) in India. Soil Biology and Biochemistry. 70: 33-37.

  26. Walkley, A. and Black, I.A. (1934). An examination of the degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method. Soil Science. 37: 29-38.

  27. Yadav, J., Verma, J.P., Jaiswal, D.K. Kumar, A. (2014). Evaluation of PGPR and different concentration of phosphorus level on plant growth, yield and nutrient content of rice (Oryza sativa). Ecological Engineering. 62: 123-128.

  28. Zhang, M., Yang, L., Hao, R., Bai, X., Wang, Y., Yu, X. (2020). Drought-tolerant plant growth-promoting rhizobacteria isolated from jujube (Ziziphus jujuba) and their potential to enhance drought tolerance. Plant and Soil. 452(1-2): 423-440.

  29. Zhang, Y., Zhou, C.M., Pu, Q., Wu, Q., Tan, S., Shao, X., Zhang, W., Xie, Y., Li, R., Yu, X.J., Wang, R., Zhang, L., Wu, M., Deng, X. (2019). Pseudomonas aeruginosa Regulatory Protein AnvM Controls Pathogenicity in Anaerobic Environments and Impacts Host Defense. mBio. 10(4): e01362-19. doi: 10.1128/mBio.01362-19. Erratum in: mBio. 2020 Oct 13; 11(5): PMID: 31337721; PMCID: PMC6650552.

  30. Zhou, C., Guo, J., Zhu, L., Xiao, X., Xie, Y., Zhu, J., et al. (2016). Paenibacillus polymyxa BFKC01 enhances plant iron absorption via improved root systems and activated iron acquisition mechanisms. Plant Physiology and Biochemistry. 105: 162-73.

Editorial Board

View all (0)