Integrated nutrient management for enhancing growth and productivity of chickpea (Cicer arietinum L.)

Introduction

Pulses occupy a paramount position in global agriculture, playing a fundamental role in addressing food security and malnutrition. Globally, India stands out as a major pulsegrowing country, accounting for a dominant share of the total world area under pulse cultivation and roughly one-fourth of global production. Within the domestic food basket, pulses serve as an indispensable dietary component, fulfilling more than 30% of the daily protein requirement of the population (John et al., 2021) [5] . Among these food legumes, chickpea (Cicer arietinum L.), commonly referred to as gram, Bengal gram, chhola, or garbanzo bean is the most vital Rabi (winter) crop, valued widely for its high consumer acceptability and multi-purpose utilities. Nutritionally, chickpea seeds are an excellent source of plant-based protein (23-24%), carbohydrates (61.5%) and crude fat (4.5%), supplemented by essential minerals like calcium and phosphorus and dietary fiber (Jukanti et al., 2012) [6] . The crop exhibits a favorable amino acid profile, supplying key constituents such as lysine (0.49%), methionine (0.11%) and tryptophan (0.04%) that complement cereal-based diets (Wallace et al., 2016) [22] . Furthermore, a relatively low concentration of anti-nutritional factors such as trypsin inhibitors enhances its protein digestibility and biological value (Wood and Grusak, 2007) [23] . Consequently, chickpea serves as a highly nutritious, costeffective protein source for human dietary supplementation and livestock feed formulations (Merga and Haji, 2019) [13] . Chickpea belonging to the sub-family Papilionaceae of the family Fabaceae, is historically recognized as one of the earliest grain legumes domesticated by humans in the Old World (Maesen, 1972) [11] . Its origin is closely linked to Western Asia, from where it gradually spread across the Indian subcontinent and other parts of the world (Zhang et al, 2024) [24] . In India major production landscapes are concentrated in states like Madya Pradesh, Maharashtra, Rajasthan, Andhra Pradesh, Uttar Pradesh and Karnataka (Kumari and Malik, 2024) [9] . However, despite holding the status of the world's largest producer, India's aggregate supply frequently struggles to fulfill its surging internal market demands. A primary challenge preventing the crop from achieving its full genetic yield potential is inadequate and skewed crop nutrition. While macronutrients like nitrogen (N), phosphorus (P) and potassium (K) are critical for robust metabolic activity, photosynthetic capacity and enzymatic operations (Hernandez et al., 2024) [4] , the intensive and indiscriminate utilization of chemical fertilizers over the decades has precipitated severe land degradation, environmental pollution and widening multi-nutrient deficiencies. Although chemical nitrogen application provides a vital initial starter boost (e.g., 20 kg N ha -1 ) that triggers early root development and nodule formation before biological nitrogen fixation kicks in, sole reliance on synthetic NPK inputs threatens long-term production stability.

To bridge this productivity gap while restoring ecological integrity, the adoption of Integrated Nutrient Management (INM) has become a modern agricultural imperative. The core philosophy of INM revolves around adjusting soil fertility and plant nutrient reserves to an optimum level, sustaining high yields via the combined exploitation of mineral fertilizers, organic amendments, and microbial inoculants (Krishna et al., 2025) [8] . Mixing graded doses of Recommended Dose of Fertilizers (RDF) with organic matrices like vermicompost and microbial formulations provided superior yield stability (Upadhayaya and Chapai, 2024, Meena and Suman, 2025) [21] . Organic additions improve soil physical properties and offer balanced nutrition, while biofertilizers like Rhizobium actively fix atmospheric nitrogen. Concurrently, Phosphate Solubilizing Bacteria (PSB) synthesize organic molecules (e.g., citric, succinic and malic acids) that unlock fixed, insoluble soil fractions into plant-available orthophosphates (Laxmi et al., 2002; Tarafdar, 2008) [10,19] . Keeping these factors in view, the present field investigation was structured to systematically evaluate the synergistic effects of chemical fertilizers alongside organic manures and microbial inoculants for maximized chickpea output and sustained soil vitality.

Materials and Methods

The field experiment was conducted during the Rabi season of 2017-2018 at the instructional farm of the BFIT Group of Institutions, Department of Agronomy, Suddhowala, Dehradun (Uttarakhand), India. The site is located in the transitional Bhabar and Tarai Zone at 29°58' N to 31°02' N latitude, 77°34' E to 78°18' E longitude and an elevation of 648 meters above mean sea level. Pre-sowing mechanical and chemical analysis of the initial 0-15 cm soil layer revealed a sandy loam texture (50.58% sand, 28.50% silt and 11.12% clay) with a neutral pH of 6.67, normal electrical conductivity (0.38 dS m -1 ) and 0.91% organic carbon. The baseline soil fertility was low in available nitrogen (228.60 kg ha -1 ), high in available phosphorus (36.34 kg ha -1 ) and low in available potassium (267.73 kg ha -1 ). The experiment was laid out in a Randomized Block Design (RBD) with 14 treatments replicated three times (Table 1). Chickpea variety Pant G-114 was sown at a seed rate of 60-70 kg ha -1 with a crop geometry of 30 cm row-to-row and 8-10 cm plant-to-plant spacing. Biometric growth parameters and yield attributes recorded were processed through analysis of variance (ANOVA) for RBD as outlined by Panse and Sukhatme (1957) [15] , using a critical difference (CD) at a 5% level of significance (P = 0.05). Seed treatment with 5g Rhizobium (RC) culture kg -1 seeds T3

Seed treatment with Phosphorus solubulizing bacteria (PSB) @ 5g kg -1 seeds T4

Seed treatment with Rhizobium and PSB culture @ each 5 g kg -1 seeds T5 100% Recommended dose fertilizers (RDF) @ 25: 50: 20 kg ha -1 T6

Seed treatment with 5g Rhizobium (RC) culture kg -1 seeds + Vermicompost (VC) @ 2 t ha -1 T7

Seed treatment with Phosphorus solubulizing bacteria (PSB) @ 5g kg -1 seeds + Vermicompost (VC) @ 2 t ha -1 T8

Seed treatment with Rhizobium and PSB culture @ each 5 g kg -1 seeds + Vermicompost (VC) @ 2 t ha -1 T9 50% RDF + Rhizobium and PSB culture @ each 5 g kg -1 seeds + Vermicompost (VC) @ 2 t ha -1 T10 50% RDF + seed treatment with Rhizobium culture @ 5 g kg -1 seeds T11 50% RDF + seed treatment with PSB @ 5 g kg -1 T12 50% RDF + seed treatment with Rhizobium and PSB @ each 5 g kg -1 seeds T13 50% RDF + Vermicompost (VC) @ 2 t ha -1 T14 Control (C)

Results and Discussion

Growth parameters Plant height

The statistical analysis revealed that the variation in plant height was non-significant (NS) at the early vegetative steps of 30 DAS and 45 DAS, as well as at the terminal harvest stage (Table 2). However, a significant treatment response was recorded at 60 DAS, aligning with the peak vegetative expansion phase of the legume. At 60 DAS, the maximum plant height of 60.33 cm was observed under T 9 (50% RDF + RC + PSB + VC), displaying an increase of 7.92% over the absolute control (T 14 55.90 cm). Treatment T 9 was statistically at par with T 5 (100% RDF: 59.78 cm), T 8 (RC + PSB + VC: 59.00 cm), T 12 (50% RDF + RC + PSB: 59.00 cm) and T 13 (50% RDF + VC: 59.00 cm). The significant expansion in plant height at 60 DAS under T 9 is due to the sustained, balanced synchrony of synthetic nitrogen, phosphorus and potassium combined with organic carbon from vermicompost. Vermicompost acts as a steadyrelease matrix of macr and micronutrients, while dual bio-inoculation with Rhizobium and PSB facilitates early nitrogen fixation and phosphorus solubilization. This combined approach drives enhanced cell division and internodal elongation during peak growth phases, a finding supported by the work of Doğan and Çığ (2023) [2] .

Number of branches plant -1

Branching determines the final canopy structure and the number of operational fruiting nodes in grain legumes. The number of branches plant -1 varied significantly across all observation intervals (Table 3). At 30 DAS, the highest number of branches was recorded in T 5 (100% RDF: 11.00), which was statistically at par with 50% RDF + RC + PSB (10.66) and 50% RDF + PSB (10.33). By 60 DAS and final harvest, the maximum values were achieved under 50% RDF + RC + PSB + VC (13.00 and 15.00 branches, respectively) and 50% RDF + VC (13.00 and 15.00 branches, respectively). This lateral development indicates that the organic matter in vermicompost, coupled with synthetic NPK, improves soil physical architecture and moisture retention. This improvement facilitates the continuous lateral translocation of nutrients like potassium, which regulates the cellular turgor required for auxiliary bud development (Sohu et al., 2015) [17] . [14] . Conversely, the integrated approach supplies a minimal starter dose of chemical nitrogen alongside a steady release of organic carbon, fostering an optimal rhizosphere environment for Rhizobium colonization. Furthermore, the inclusion of PSB solubilizes fixed soil phosphorus via organic acid production, providing the high ATP energy required by the nitrogenase enzyme complex for biological nitrogen fixation (Tarafdar, 2008; Tagore et al., 2013) [19,18] .

Yield attributing characters

The integrated nutrient management regimes significantly improved all yield-attributing components. The maximum number of pods plant -1 (63.33) was achieved under 50% RDF + RC + PSB + VC, which was statistically at par with 100% RDF (63.00) and significantly superior to all other remaining setups. This reflects a 104.29% increase in pod production over the control. In case if grains per pod, Treatment 50% RDF + RC + PSB yielded the highest grain count of 1.66 grains pod -1 , which was statistically at par with 50% RDF + RC + PSB + VC (1.60) and 100% RDF (1.59). Whereas the maximum 100-seed weight of 18.00 g was produced under both 50% RDF + RC + PSB + VC and 50% RDF + PSB, outperforming the control value of 13.00 g. These structural increases indicate that combining mineral inputs with bio-organic matrices expands source-to-sink efficiency. Available phosphorus drives primordial flower initiation and pod setting, while potassium optimizes carbohydrates and amino acid translocation into developing seeds, resulting in higher seed indices (Kemal et al., 2018) [7] . Similar effect of INM practices on yield attributes of chickpea was observed by Tiwari et al. (2022) [20] ; Sodavadiya et al. (2023) [16]

Grain yield, straw yield and harvest Index

The highest grain yield (20.66 q ha -1 ) and straw yield (24.33 q ha -1 ) were recorded under 50% RDF + Rhizobium + PSB + Vermicompost which was statistically at par with 100% RDF (20.00 q ha -1 of grain and 23.80 q ha -1 of straw yield). This integrated approach resulted in a 98.08% increase in grain yield and an 87.15% increase in straw yield over the absolute control, which recorded the lowest overall yields (10.43 q ha -1 grain and 13.00 q ha -1 straw yield). Similarly, the highest harvest index of 50.00% was achieved under T 9 , outperforming the control value of 40.00% (Tale 5).

The superior grain and straw yield observed under T 9 confirms that substituting 50% of synthetic mineral fertilizers with vermicompost and microbial inoculants delivers balanced crop nutrition. Vermicompost slowly releases secondary and micronutrients while improving soil structure, which extends root architecture. Concurrently, Rhizobium and PSB maximize nutrient availability in the root zone. This combined effect maintains high chlorophyll levels and photosynthetic rates, promoting dry matter accumulation and efficient translocation into the final grain sink (Boreddy et al., 2019; Dotaniya et al., 2022) [1,3] . These findings confirm that INM strategies can reduce reliance on chemical fertilizers by 50% while improving agronomic yield.

No. Treatments

Grain yield (q ha -1 ) Straw yield (q ha -1 ) Harvest index (%) T1 Vermicompost (VC) @ 2 t ha - 1 13.00 15.00 47.00 T2 Rhizobium Culture (RC) @ 5 g kg -1 12.00 14.00 40.87 T3 PSB Culture @ 5 g kg -1 11.00 14.53 39.00 T4 RC + PSB @ each 5 g kg -1

Conclusion

The field experiment demonstrates that an integrated nutrient management strategy effectively secures high agronomic productivity in chickpea (Cicer arietinum L.) while simultaneously preserving chemical inputs. The combined application of 50% Recommended Dose of Fertilizers (10 kg N + 30 kg P 2 O 5 + 10 kg K 2 O ha -1 ) paired with vermicompost 2 t ha -1 and dual biofertilizer seed inoculation with Rhizobium culture and Phosphate Solubilizing Bacteria, each @ 5 g kg -1 seed) optimized plant vegetative architecture, enhanced biological root nodulation by 211.11% at 60 days after sowing and achieved a remarkable 98.08% increase in grain yield and 87.15% increase in straw yield over the unfertilized absolute control. Replacing 50% of the mineral fertilizer requirement with organic amendments and targeted microbial inoculants provides an excellent, highly productive method for maintaining crop yields, optimizing resource utilization and fostering sustainable soil fertility.

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