Effect of bioinoculants on growth promoting attributes and yield of chickpea

Introduction

Chickpea (Cicer arietinum L.) is an important pulse crop all over the world covering Asia, Africa, Europe, Australia, and North America and South Amrica continents. India's chickpea production during 2021-22 was 13.75 million tonnes from an acreage of 10.91 million ha, with a productivity of 12.6 q/ha (DES 2023, MOAF&W, GoI) [1,3] . In India, chickpea has highest area in Maharashtra, Madhya Pradesh and Rajasthan. It contains 21 percent protein, 61.5 percent carbohydrates, 4.5 percent fat and is also rich in calcium, iron and niacin. It leaves substantial amount of residual nitrogen for subsequent crops and adds plenty of organic matter to maintain and improve soil health and fertility. Enhancing the production while keeping the environment safe is one of the major challenges in the 21 st century (Berg, 2009) [2] . The seed inoculation with various microbial isolates significantly increased the available nutrient status and grain yield in legumes (Kamble et al., 2023) [5] . Promoting sustainable farming practices and reducing dependence on chemical fertilizers as they are costly, deplete soil health and disrupt nutrient balance require a thorough understanding about Plant Growth-Promoting Rhizobacteria (PGPR) that can biologically fix nitrogen, solubilize phosphorus, and produce substances such as organic acids and indole acetic acid, which contribute to improved chickpea growth. PGPR are heterogeneous group of bacteria that are found in the rhizosphere, at root surfaces and in association with roots, which improve the extent or quality of plant growth directly or indirectly. These microorganisms play an important role in increasing the availability of N, P and K. Chickpea is capable of fixing atmospheric nitrogen with the help of Rhizobium residing in the root nodules. Rhizobium enhances the biological nitrogen fixation of the plant which not only improves the nitrogen nutrition of inoculated chickpea but also reduces the dependence on inorganic nitrogen fertilizers (Namvar et al., 2011) [9] . Phosphorus is an essential macronutrient crucial for the growth and development of plants. Phosphorus requirement of legume crops is higher due to higher energy consumption during the process of symbiotic nitrogen fixation (Schulze et al., 2006) [12] . Phosphate solubilizing microorganisms (PSM) have ability to dissolve insoluble inorganic phosphorus and make them available to plants by various mechanisms such as production of organic acids and phosphatase enzymes (Shaikh et al., 2016) [13] . Pseudomonas promotes plant growth by mechanisms such as production of plant growth regulators and vitamins, enhancement of plant nutrient uptake and suppression of pathogenic or deleterious organisms (Glick, 1995) [4] . Potassium is essential for maintaining the ionic environment required for metabolic processes in the cytosol. It is essential for protein synthesis. Potassium solubilizing bacteria solubilize K bearing minerals and increase its availability due to the production of some weak organic acids such as citric, tartaric, etc. which causes increase in plant growth and yield (Maurya et al., 2014) [8] . The preparations containing living or latent cells of efficient strains of microorganisms called biofertilizers. Seed or soil treatment of biofertilizers help in enhancing biological nitrogen fixation through nodule formation, phosphorus solubilisation, production of phytohormones like cytokinins, gibberellins and indole acetic acid (IAA) (Verma et al., 2013) [19] and also show antagonism against phytopathogens by production of siderophores, celluloses and antibiotics in chickpea (Kaur and Sharma, 2013) [6] . Biofertilizers, when applied as a consortium significantly enhance plant growth and help for maintaining soil fertility (Woo and Olimpia, 2018) [22] . Considering this, the present investigation was conducted to evaluate the effect of Mesorhizobium (AKCR-1), Pseudomonas fluorescence, Phosphate solubilizing bacteria (PSB), and Potassium solubilizing bacteria (KSB) on growth and yield of chickpea.

Material and Methods

The field experiment was conducted during rabi 2023-24 at Pulses Research Unit, Dr PDKV, Akola. The experiment was laid out in a Randomized Block Design (RBD) with nine treatments including control and three replications. Chickpea seeds were inoculated as per the treatment with Mesorhizobium (AKCR-1), Pseudomonas fluorescence, PSB and KSB prior to sowing using 25 g/kg of seed. Treatment wise dose of N, P 2 O 5 and K 2 O was applied at the time of sowing. Each treatment has gross plot size 3.00× 2.40 m 2 and net plot size 2.80 × 1.80 m 2 and replicated thrice with JAKI-9218 chickpea variety. The treatment consisted with different bioinoculants and four levels of recommended dose of fertilizers (RDF). The data on root length, shoot length, plant height, plant dry weight and nodulation was recorded at 45 DAS from five randomly selected plants from each plot. Seed yield was also recorded after harvesting the chickpea crop. Data collected on various parameters of crop were subjected to statistical analysis by following the method of analysis of variance (ANOVA) given by Panse and Sukhatme (2000) [10] to draw valid conclusion.

Results and Discussion

Root and shoot length

The root length were recorded in the range from 8.48 to 18.57 cm at 45 DAS. The highest root length of chickpea was recorded in the combined treatment of Mesorhizobium (AKCR-1) + Pseudomonas + PSB + KSB + 100% RDF i.e. 18.57 cm, which was statistically at par with the treatment of Mesorhizobium (AKCR-1) + Pseudomonas + PSB + KSB + 75% RDF i.e. 17.14 cm and significantly higher than all other treatments. Seed treatment with Mesorhizobium (AKCR-1) + Pseudomonas + PSB + KSB + 100% RDF recorded highest shoot length i.e. 22.86 cm followed by the treatment of Mesorhizobium (AKCR-1) + Pseudomonas + PSB + KSB + 75% RDF i.e. 21.35 cm. The minimum shoot length was recorded in control. The data pertaining to root and shoot length is presented in Table 1. The results are in agreement with the findings of Vishwas et al., (2017) [21] , who demonstrated that seed biopriming with Rhizobium and Pseudomonas at 10% for 12 hours significantly improved germination (87%), speed of germination (77.11), shoot length (20.33 cm), root length (16.14 cm), seedling length (24.91 cm) compared to control and Rhizobium alone @ 10% for 12 hours.

Plant height

Difference in plant height due to different treatments was found statistically significant. Highest plant height was recorded in the combined application of Mesorhizobium (AKCR-1) + Pseudomonas + PSB + KSB + 100% RDF (32.11 cm) followed by the treatment of Mesorhizobium (AKCR-1) + Pseudomonas + PSB + KSB + 75% RDF (30.94 cm). Lowest plant height was recorded in control treatment (21.10 cm). These results are in agreement with the observations made by Rinku et al., (2020) [11] who observed that plant height was highest in the combined application of Rhizobium + PSB + 100% RDF, which was closely followed by Rhizobium + PSB + 75% RDF. The combined application of Mesorhizobium (AKCR-1) + Pseudomonas + PSB + KSB + 100% RDF (87.31 mg/plant) recorded maximum nodule dry weight followed by Mesorhizobium (AKCR-1) + Pseudomonas + PSB + KSB + 75% RDF (85.02 mg/plant) and found superior to remaining all other treatments. The similar finding was reported by Tagore et al., (2013) [17] , who observed that the combination of Rhizobium and PSB was the most effective treatment, resulting in the increased nodule number, nodule fresh weight, nodule dry weight, shoot dry weight and grain yield.

Uninoculated control

Bioinoculants with 100% RDF Plate 1: Effect of bioinoculants on nodulation of chickpea

Plant dry weight

The data on plant dry weight as affected by different treatments is presented in Table 2. The maximum plant dry weight was recorded in the treatment of Mesorhizobium (AKCR-1) + Pseudomonas + PSB + KSB + 100% RDF) (5.23 g/plant), which was followed by Mesorhizobium (AKCR-1) + Pseudomonas + PSB + KSB + 75% RDF (4.98 g/plant), while minimum dry weight was found in control (3.18 g/plant). Similarly, Bansal R.K. (2009) [1] and Singh et al., (2015) [16] reported that presowing inoculation of pulses seeds with different inoculants (Rhizobium, PGPR, and PSB), either individually or in combination, significantly increased plant height, root length, dry matter production, nodule number per plant, nutrient uptake, and seed yield compared to the uninoculated control.

Grain yield

The yield study revealed that among all the treatments, combined application of Mesorhizobium (AKCR-1) + Pseudomonas + PSB + KSB + 100% RDF recorded highest yield (23.6 q/ha), which was statistically at par with the treatment of Mesorhizobium (AKCR-1) + Pseudomonas + PSB + KSB + 75% RDF (22.31 q/ha). Singh et al., (2004) [14] reported increment in the average growth and yield of green gram as influenced by bio-fertilizer and phosphorus application. Similar results was reported by Verma et al., (2019) [20] and Singh et al., (2018) [15] , who recorded the improved yield attributes of chickpea with integration of synthetic fertilizers and biofertilizers. The present study is in agreement with Tejasree et al., (2024) [18] who recorded comparable findings of seed bio-priming with Rhizobium, PSB, and KMB with 100% RDF of NPK, yielding the highest values across various plant growth parameters and grain yield, which were statistically similar with seed biopriming using Rhizobium, PSB, and KMB with 75% RDF of NPK.

Conclusion

The present study concluded that seed inoculation with different (biofertilizers) bioinoculants [Mesorhizobium (AKCR-1) + Pseudomonas + PSB and KSB]+ 100% RDF recorded maximum nodulation, root and shoot length, plant height, plant dry weight and grain yield and it was statistically at par with the treatment of Mesorhizobium (AKCR-1) + Pseudomonas + PSB + KSB + 75% RDF. Hence the high dose of inorganic biofertilizers for the maximum production of chickpea can be reduced upto 25% and keep safe the environment.

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