Effect of integrated organic nutrient management on growth and yield of summer groundnut (Arachis hypogaea L.)

Introduction

Groundnut (Arachis hypogaea L.) is one of the most important oilseed crops of India and plays a vital role in ensuring food, nutritional, and economic security. It is valued for its high edible oil and protein content and is often referred to as the "Queen of Oilseeds." India is among the leading groundnut-producing countries of the world, with Gujarat contributing the largest share of national production. Among the different growing seasons, summer groundnut consistently records higher productivity than the kharif crop due to favourable climatic conditions such as higher temperatures, longer sunshine hours, assured irrigation, and comparatively lower incidence of pests and diseases. Despite its high yield potential, groundnut productivity remains constrained by declining soil fertility, nutrient imbalance, and inefficient nutrient management practices, particularly under intensive cropping systems. Groundnut is a nutrient-exhaustive leguminous crop and requires relatively higher amounts of phosphorus because of its critical role in root development, nodulation, biological nitrogen fixation, and oil biosynthesis. Phosphorus deficiency leads to poor root growth, reduced nodulation, delayed flowering, impaired pod formation, and inferior seed quality, resulting in substantial yield losses. In most agricultural soils, the availability of phosphorus is limited due to fixation into insoluble forms, with only a small fraction of total soil phosphorus being accessible to plants. This low phosphorus use efficiency highlights the need for integrated phosphorus management strategies to improve nutrient availability and crop performance. Organic nutrient sources such as farmyard manure and vermicompost are key components of sustainable nutrient management systems. Their application improves soil physical properties, including aggregation, porosity, and water-holding capacity, while enhancing chemical properties such as cation exchange capacity and nutrient buffering. Additionally, organic amendments stimulate soil biological activity by increasing microbial biomass, enzyme activity, and nutrient mineralization. The organic acids released during decomposition reduce phosphorus fixation and increase the availability of native and applied phosphorus. Biofertilizers, particularly Rhizobium and phosphate-solubilizing bacteria, further enhance nutrient availability by fixing atmospheric nitrogen, solubilizing insoluble phosphorus, and producing plant growth-promoting substances that improve root development and nutrient uptake. The integrated use of organic manures and biofertilizers enhances nutrient use efficiency, improves yield stability, and sustains soil fertility while reducing dependence on chemical fertilizers. Such eco-friendly and biologically sound nutrient management practices minimize environmental degradation and support long-term productivity. Overall, adoption of integrated nutrient management approaches is essential for achieving sustainable groundnut production under both irrigated and rainfed conditions, while maintaining soil health and ensuring the resilience of groundnut-based cropping systems.

Materials and Methods

The present investigation was carried out by laying out a field experiment on groundnut with the application of inorganic fertilizer, organic manure (vermicompost and FYM) and biofertilizer to groundnut in summer season and levels of recommended dose of fertilizer apply in form of organic during two consecutive years, 2022 and 2023

Experimental Site

The field experiment was conducted at Block -F and Plot no -21, College Farm, Navsari Agricultural University, Navsari during summer and kharif seasons of 2022 and 2023. Geographically, university campus is situated at 20º 57' North latitude, 72º 54' East longitudes and has an altitude of 10 meters above the mean sea level. It is located 12 km away in the east from the great historical place 'Dandi' on the Arabian seashore.

Soil

The soil of south Gujarat is locally known as "Deep Black Soil". The soil of Navsari campus is classified under the order Inceptisols comprising of Afine montmorillonitic, isohyperthermic, family of Vertic ustrochrepts and soil series Jalalpur by the soil survey officer, Navsari, Department of Agriculture, Gujarat state, having poor drainage capacity and good water holding capacity. The soil cracks heavily on drying and expands on wetting. The experimental field has flat topography. A representative soil sample was drawn from 0-15 cm depth covering entire area before sowing of the groundnut crop. The samples were mixed thoroughly and then, the composite sample was analysed for desired physico-chemical properties of the soil.

Treatment details

The experiment was laid out in randomised block design with four replications. The main plot treatments T

Field preparations

The experimental plot was ploughed and fine seedbed was prepared by subsequent harrowing with tractor drawn harrow in both directions, followed by planking. Irrigation channels were prepared by V-ditcher. Layout and allotment of treatments as

Application of Fertilizer and Organic Manure

The application of manures and fertilizers were done as per treatments. The nitrogen was applied through urea (46 % N) whereas phosphorus was applied through single super phosphate (16 % P2O5) in treatment T2. Farm Yard Manure and vermicompost were applied in the required quantities and proportions as specified in the treatments and uniformly spread and mixed in particular plots before sowing to treatment T 3 to T 6 . All the manures were applied 09 days prior to sowing of crop while in treatments. The desired quantity of FYM and vermicompost was worked out as per treatments. By considering P content in Farm Yard Manure (FYM) and vermicompost. Nutrient content in manure analyzed as per standard laboratory method

Seed Treatment and Sowing

Summer Groundnut variety, GG 34 was used for this experiment. The required quantity of seeds was worked out for the experimental area. Inoculation of biofertilizer (Rhizobium 10ml kg -1 ) to the seeds was done in both the years before sowing. In the treatments T 2 to T 6 , Rhizobium and phosphate solubilizing bacteria (PSB) were applied. For this purpose, 100 ml of Rhizobium was used for seed treatment at the time of sowing and 100 ml of PSB was used. The inoculated seeds were dried under shade and were sown at recommended seed rate of 100 kg ha -1 . The seeds were sown manually in the furrows spaced at 30 cm and were covered with soil uniformly.

Results and Discussion

Growth parameter 3.1.1 Plant population

The plant population of summer groundnut recorded at 15 DAS and at harvest did not differ significantly due to different organic phosphorus management practices during 2022 and 2023 as well as in the pooled analysis (Table 1). Although numerical variations were observed, both initial and final plant population remained statistically non-significant across treatments. The integrated organic nutrient management treatment recorded numerically higher initial plant population (32.66 The control treatment recorded relatively lower initial and final plant population during both years and in pooled analysis; however, the differences were marginal and non-significant. The non-significant response of plant population to organic phosphorus management may be attributed to uniform seed rate and spacing, along with favourable soil moisture conditions at sowing, which ensured uniform germination and crop establishment. Similar results have been reported earlier, indicating that organic manures mainly improve soil physical properties without causing marked variation in plant population (Gaur, 1991; Sahrawat, 2006) [9,27] . Although biofertilizers such as Rhizobium and phosphate-solubilizing bacteria enhance early root growth and nutrient availability (Chetti et al., 1995; Khan et al., 2019) [5,14] , their effect on plant population was nonsignificant under the present experimental conditions.

Plant height

Plant height of summer groundnut at 60 DAS, 90 DAS and at harvest was significantly influenced by different organic nutrient management treatments during 2022, 2023 and on pooled basis (Table 2 [29,12] . Similar improvements in plant height of groundnut under integrated organic nutrient management have been reported earlier by Mahrous et al. (2015) [18] and Patel et al. (2019) [22] .

Number of leaves per plant

The number of leaves plant -1 of summer groundnut at 60 DAS, 90 DAS and at harvest was significantly influenced by different organic nutrient management treatments during 2022, 2023 and on pooled basis (Table 3 with Fig. 2). Across both the years and pooled analysis, the treatment T₅ (50% RDP through FYM + 50% RDP through vermicompost + seed treatment with Rhizobium + PSB) consistently recorded the highest number of leaves per plant at all growth stages At 60 DAS, T₅ recorded the highest number of leaves per plant (64. 35 Overall, the pooled results clearly indicated that integrated application of FYM and vermicompost along with biofertilizer seed treatment significantly enhanced leaf production compared to control and other treatments The enhanced leaf production and retention under integrated organic phosphorus management may be attributed to sustained nutrient release, improved phosphorus availability, and enhanced microbial activity, which collectively supported prolonged vegetative growth and delayed senescence. Similar findings have been reported by Bhardwaj and Omanwar (1994) [4] , Stevenson (1994) [30] , and Kejiya et al. (2019) [13] .

Number of branches per plant

The number of branches per plant of summer groundnut at 60 DAS, 90 DAS and at harvest was significantly influenced by different organic nutrient management treatments during 2022, 2023 and on pooled basis (Table 4 with Fig. 3). Across both the years and pooled analysis, the treatment T₅ (50% RDP through FYM + 50% RDP through vermicompost + seed treatment with Rhizobium + PSB) consistently recorded the highest number of branches per plant at all growth stages. At 60 DAS, T₅ recorded the highest number of branches per plant of 12.87 during 2022 and 13.52 during 2023, with pooled 13.20, which was at par with T₆ (12.77 and 13. 28 Overall, the pooled results indicated that integrated application of FYM and vermicompost along with biofertilizer seed treatment significantly enhanced branching in summer groundnut compared to control and other treatments. The superior branching observed under integrated organic phosphorus management may be attributed to improved phosphorus availability, sustained nutrient release from FYM and vermicompost, and enhanced microbial activity, which collectively supported better root development and vegetative growth. Similar findings on increased branching in groundnut under integrated organic nutrient management have been reported earlier by Akbari et al. (2002) [1] and Patel et al. (2019) [22] .

Yield parameter 3.2.1. Dry pod yield

The data presented in 5 and illustrated in Fig. 4 revealed that different organic phosphorus nutrient management treatments significantly influenced dry pod yield (kg ha⁻¹) of summer groundnut during 2022, 2023, and pooled analysis. The highest dry pod yield was recorded under treatment T₅ (50% RDP through FYM + 50% RDP through vermicompost + seed treatment with Rhizobium + PSB), producing 4181, 4092, and 4052 kg ha⁻¹ in 2022, 2023, and pooled data, respectively. Treatment T₆ (75% FYM + 25% vermicompost + seed treatment with Rhizobium + PSB) was followed with T₅, producing 3473, 3500, and 3486 kg ha⁻¹ in in 2022, 2023, and pooled respectively. The lowest yield was observed in T₁ (control) with 1510, 1559, and 1535 kg ha⁻¹ in 2022, 2023, and pooled respectively The higher yield under T₅ can be attributed to the synergistic effect of FYM and vermicompost, which ensured a balanced and sustained release of nutrients, improved soil structure, and enhanced microbial activity. The inclusion of Rhizobium and phosphate-solubilizing bacteria (PSB) facilitated biological nitrogen fixation and increased phosphorus availability, promoting better vegetative growth, root development, and pod formation (Brady and Weil, 2008; Patil, 2017; Mengel and Kirkby, 2001). Adequate phosphorus availability supported energy transfer, ATP synthesis, and reproductive development, enhancing peg penetration, pod setting, and seed filling (Jones and Murray, 2017; Smith et al., 2018) [12,29] . Overall, the results confirm that integrated organic phosphorus management (FYM + vermicompost + microbial inoculation) enhances nutrient use efficiency, improves source-sink relationships, and promotes physiological processes, resulting in higher dry pod yield in summer groundnut (Hegde and Sudhakara Babu, 2004; Mahrous et al., 2015) [18] .

Haulm yield

The data on haulm (stover) yield of summer groundnut as influenced by different organic phosphorus nutrient management practices are presented in Table .5 and illustrated in Fig. 4. The results revealed that haulm yield was significantly influenced by organic nutrient management practices during both the years (2022 and 2023) as well as in the pooled analysis. Among the treatments, application of 50% RDP through FYM + 50% RDP through vermicompost along with seed treatment of Rhizobium + PSB (T₅) recorded the highest haulm yield of 10,458 and 10,551 kg ha⁻¹ during 2022 and 2023, respectively, with pooled 10,505 kg ha⁻¹, and followed treatment T₆ (75% RDP through FYM + 25% RDP through vermicompost + seed treatment of Rhizobium + PSB) also produced higher haulm yield (8,909, 9,047 and 8,978 kg ha⁻¹ during 2022, 2023 and pooled, respectively. The lowest haulm yield was observed under T₁ (control) with 3,931, 4,117 and 4,024 kg ha⁻¹ during 2022, 2023 and pooled, respectively. The superior haulm yield under integrated organic phosphorus management, particularly in T₅, may be attributed to sustained nutrient release, improved soil physical and biological properties, enhanced nitrogen availability, and increased chlorophyll synthesis, resulting in vigorous vegetative growth and higher biomass accumulation. Similar findings have been reported by Singh et al. (2010) [35] and Yadav et al. (2017) [36] in leguminous crops.

Total Biomass Yield

The data on total biomass yield of summer groundnut as influenced by different organic phosphorus nutrient management practices are presented in Table .5 and Fig. 4. The results indicated that total biomass yield (kg ha⁻¹) was influenced by organic nutrient management during both the years (2022 and 2023) as well as in pooled analysis. The highest total biomass yield was recorded with application of 50% RDP through FYM + 50% RDP through vermicompost along with seed treatment of Rhizobium + PSB (T₅), registering 14,659 and 14,555 kg ha⁻¹ during 2022 and 2023, respectively, with pooled 14,507 kg ha⁻¹, and followed by treatment T₆ (75% RDP through FYM + 25% RDP through vermicompost + seed treatment of Rhizobium + PSB) also produced comparable biomass yield (12,758, 12,309 and 12,533 kg ha⁻¹ during 2022, 2023 and pooled, respectively). The lowest biomass yield was observed under T₁ (control) with 5501,5676 and 5588 kg ha⁻¹ during 2022, 2023 and pooled, respectively. The superiority of T₅ (50% RDP through FYM + 50% RDP through vermicompost along with seed treatment of Rhizobium + PSB) may be attributed to the balanced and sustained nutrient supply through integrated organic sources, improved soil physical and biological properties, and enhanced microbial activity, resulting in better crop growth and higher biomass accumulation. Similar improvements in total biomass under integrated organic nutrient management have been reported by Stevenson (1994) [30] and Lampkin (2002).

Conclusion

Application of T₅ (50% RDP through FYM + 50% RDP through vermicompost along with seed treatment of Rhizobium and PSB) showed non-significant differences in initial and final plant population, while it significantly enhanced growth parameters such as plant height, number of leaves and number of branches per plant at different growth stages during both years and on pooled basis. Consequently, treatment T₅ (50% RDP through FYM + 50% RDP through vermicompost along with seed treatment of Rhizobium and PSB) recorded the highest pod yield, haulm yield and total biomass yield of summer groundnut, proving its superiority over the remaining treatments during 2021-22, 2022-23 and in pooled analysis The results clearly demonstrate that partial substitution of organic phosphorus through FYM and vermicompost, coupled with biofertilizer inoculation, is an effective and sustainable nutrient management strategy for enhancing crop growth, yield and for sustainable groundnut production

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