Influence of liquid biofertilizer seed treatments on the seed quality parameters of soybean (Glycine max (L.) Merrill.)

Introduction

Seed quality is fundamental to the success of soybean production because high germination and vigorous seedlings are required for rapid and uniform establishment. In seed-production programmes, evaluation of harvested seed quality is therefore necessary in addition to measuring field yield. Germination percentage reflects the capacity of a seed lot to produce normal seedlings, while vigour indices provide a broader indication of seedling performance under test conditions. Biofertilizers may affect harvested seed quality indirectly through improved nutrition, root development, nodulation, photosynthetic activity and assimilate supply during seed filling. Rhizobium is particularly important in soybean because biological nitrogen fixation supports nitrogen nutrition. PSB can improve phosphorus availability, and KSB can increase potassium availability. Other beneficial microorganisms can influence root growth, nutrient acquisition and plant physiological efficiency. Consequently, biofertilizer-treated plants may produce seed with improved germination and seedling vigour. The literature reviewed in this paper provides substantial support. Lakshmi et al. (1997) [1] reported improved nodulation, root development and plant growth with Rhizobium treatment. Siddaraju et al. (2018) [2] observed improved germination, seedling length, dry matter and vigour in soybean seed harvested from inoculated plots. Joshi et al. (2018) [3] reported strong seed-quality responses to PSB treatment. Bazzo et al. (2020) [4] showed that microbial inoculation and co-inoculation could improve physiological seed quality. Ghadge et al. (2020) [5] recorded high germination and plant vigour with a Rhizobium + PSB + KMB consortium. Dalvi et al. (2021) [6] also found improved germination and vigour under bioagent-based seed coating. However, a treatment that is highly productive in the field does not necessarily have to be the treatment that produces the most vigorous harvested seed. The present investigation therefore focused specifically on the physiological quality of seed produced under eleven liquid biofertilizer treatments and compared the response of germination and two vigour indices.

Objective

To study the effect of liquid biofertilizers on seed quality of soybean.

Materials and methods

The field experiment was conducted during kharif, 2025-26 at the Seed Technology Research Unit, VNMKV, Parbhani, Maharashtra, using soybean cv. MAUS-612. The trial followed randomized block design with three replications and eleven treatments. Gross plot size was 2.7 × 4.0 m, net plot size was 1.8 × 4.0 m, spacing was 45 × 5 cm, seed rate was 65 kg ha -1 and fertilizer was applied at 30:60:30 kg N:P:K ha -1

. Sowing was performed on 3 July 2025. The treatments were T 1 control; T 2 Rhizobium; T 3 Rhizobium + KSB; T 4 EM culture; T 5 PSB; T 6 KSB; T 7 Azospirillum; T 8 Pseudomonas; T 9 Rhizobium + PSB; T 10 Rhizobium + PSB + KSB; and T 11 VNMKV Biomix. Liquid inoculants were applied at 20 ml kg -1 seed.

After harvest, 100 seeds per replication were tested by the rolled towel paper method. Germination was evaluated under controlled conditions, with first count on day 5 and final count on day 8. Vigour Index-I was calculated as standard germination (%) × seedling length (cm), and Vigour Index-II as standard germination (%) × seedling dry weight (mg), following the methodology stated in the thesis and ISTA procedures.

Treatment differences were assessed using analysis of variance according to Panse et al. (1954) [7] , with standard error and critical difference at 5% probability used for mean comparison.

Results and discussion

Treatment effects were highly significant (P = 0.01) for germination, Vigour Index-I and Vigour Index-II. Replication effects were non-significant, indicating reasonable experimental uniformity.

Germination percentage

Germination ranged from 87.00 to 95.86%, with a mean of 91.72%. T 2 Rhizobium recorded the highest germination (95.86%), followed by T 9 Rhizobium + PSB (94.00%) and T 5 PSB (93.66%). These three treatments were therefore the best performers for germination. T 10 recorded 93.00%, while the control was lowest at 87.00%. The 8.86 percentage-point advantage of T 2 over the control indicates a substantial improvement in the physiological quality of harvested seed. The superiority of Rhizobium is consistent with its role in nodulation and biological nitrogen fixation. Better nitrogen nutrition during seed formation can support protein synthesis, seed development and the production of physiologically competent seed. The present observation agrees with Bazzo et al. (2020) [4] , who found higher physiological quality following microbial inoculation, and Siddaraju et al. (2018) [2] , who reported improved germination in inoculated soybean. Joshi et al. (2018) [3] reported particularly high germination with PSB treatment, which is also reflected in the strong ranking of T 5 in the present study. Dalvi et al. (2021) [6] and Dhutmal et al. (2025) [8] likewise reported improved germination under bioagent and liquid-biofertilizer treatments.

Vigour Index-I

Vigour Index-I ranged from 1696.20 to 2122.47, with a mean of 1868.48. T 2 was highest (2122.47), followed by T 9 (2094.73) and T 5 (1988.80). T 10 recorded 1877.93 and the control had 1696.20. The same three treatments that ranked highest for germination also ranked first, second and third for Vigour Index-I. This consistency strengthens the evidence that T 2 , T 9 and T 5 produced physiologically superior harvested seed rather than merely increasing the germination percentage. Because Vigour Index-I incorporates seedling length, the high values under T 2 and T 9 indicate that the resulting seedlings were not only capable of germination but also developed greater length under the test conditions. Manjanagouda et al. (2025) [9] reported higher vigour indices after liquid-biofertilizer biopriming, while Shewale et al. (2024) [10] observed improved seedling vigour under a multifunctional bioconsortium. Ghadge et al. (2020) [5] also recorded strong seedling performance under Rhizobium + PSB + KMB inoculation.

Vigour Index-II

Vigour Index-II ranged from 2687.17 to 3569.50, with a mean of 2929.81. T 2 recorded the highest value (3569.50), followed by T 9 (3362.80) and T 5 (3033.73). The control recorded 2687.17. Thus, the same three treatments remained the top performers when seedling dry weight was incorporated into the vigour assessment. The advantage of T 2 over control was 882.33 index units, showing a strong difference in seedling biomass production. Siddaraju et al. (2018) [2] specifically identified Rhizobium as an effective inoculant for improving soybean seed physiological quality. Dhutmal et al. (2025) [8] reported enhanced germination and vigour in Rhizobium-and KSB-treated plots, while Lakshmi et al. (1997) [1] linked Rhizobium treatment with improved nodulation and plant development. These reports provide a biological basis for the present superiority of Rhizobium-treated seed lots.

The three best treatments

Rhizobium (T 2 ) was the clear overall leader, ranking first for germination, Vigour Index-I and Vigour Index-II. Rhizobium + PSB (T 9 ) ranked second for every quality parameter, making it the most consistent combined treatment. PSB (T 5 ) ranked third for all three parameters and therefore also deserves attention where seed physiological quality is the primary criterion. The uniformity of this top-three ranking is stronger than the treatment ranking observed for field yield, where several treatments were traitspecific leaders. The strong performance of T 2 may be associated with effective nodulation and biological nitrogen fixation during crop growth, while the response of T 9 suggests that combining nitrogen fixation with phosphorus solubilization can support seed development and seedling performance. T 5 also performed strongly, in agreement with the literature reviewed in the thesis. Nevertheless, the mechanism cannot be established directly from the present data because microbial population, nutrient uptake and seed biochemical composition were not measured.

Overall interpretation and seed-production relevance

Taken together, the three quality indicators demonstrate that liquid biofertilizer seed treatment can improve the physiological quality of harvested soybean seed relative to untreated control. The response was especially pronounced with Rhizobium and Rhizobium + PSB. This is consistent with the broader concept that beneficial microorganisms can improve plant nutrition and physiological efficiency during seed development. Therefore, assessment of seed quality is desirable when selecting biofertilizer treatments for seed-production systems.

Conclusion

Liquid biofertilizer seed treatments significantly influenced germination and seed vigour of soybean cv. MAUS-612. Rhizobium (T 2 ) was the best treatment for all three quality indicators, followed by Rhizobium + PSB (T 9 ) and PSB (T 5 ). The untreated control was consistently inferior. The results support the use of liquid microbial seed treatment as a promising approach for producing physiologically superior soybean seed, but treatment selection should consider both seed yield and seed quality. Further multi-season and multi-location studies should confirm the stability of these responses.

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