Bio-formulation in combination with inorganic fertilizer improves crop growth, productivity and economics of kharif groundnut (Arachis hypogaea L.) in Red and Laterite soils

ABSTRACT Indiscriminate application of inorganic chemicals has resulted in soil health deterioration and decline in crop produce in nutrient poor Alfisols of India. We conducted an experiment to find out the influence of different level of inorganic fertilizer and bio-formulations on nutrient uptake, crop growth and productivity of kharif groundnut in the Red and Laterite soils during 2018, 2019 and 2020. It was hypothesized that judicious application of inorganic fertilizer and bio-formulation would result in better nutrient uptake, improving nut yield and net income. We found that higher dose of inorganic fertilizer along with liquid bio-formulations yielded better results in terms of nutrient uptake, crop growth, yield and quality in groundnut. An increase of 43.2% and 57.5% in haulm and kernel N uptake; 67.6 and 98.1% in haulm and kernel P uptake; 47.4% and 57.6% in haulm and kernel K uptake was recorded, respectively, when 100% recommended dose of NPK (F4) was coupled with liquid NPK bio-formulation + Zn-solubilizing bacteria (B2) over control and was most economical (higher B:C ratio, 2.73). Groundnut being an exhaustive crop, responded well to higher levels of inorganic fertilizer and bio-formulations.


Introduction
Groundnut (Arachis hypogea L.) is an important oilseed crop cultivated in India and throughout the world, next to soyabean and mustard.Groundnut belongs to family Leguminosae and subfamily Papilionaceae.It is rich source of edible oil (42-52%), vegetable protein (22-30%) and carbohydrate (20%).Groundnut is also an important source of several essential fatty acids, vitamins and minerals like phosphorus, calcium, magnesium and potassium necessary for human nutrition (Kamara et al. 2011).
Though India ranks first in area coverage, average productivity of groundnut is quite low (ranks third in production, after USA and China).A major part of groundnut is cultivated in tropical and subtropical climatic zone of India.The soils are much weathered, acidic in reaction and low in organic matter and nutrients reserve, limiting groundnut production (Basu et al. 2008).As the crop is exhaustive in nature, it removes huge quantity of macro-and micronutrient from the soil.Implementation of intensive agriculture without proper nutrient management in these soils has led to deterioration of soil health, rather decline in crop production, and increasing cost of cultivation.Nevertheless, fertile soils are prerequisite for higher crop yield.Thus, judicial and balanced application of fertilizers is the key to maintain soil health and groundnut production.
Integrating inorganic source of nutrients with organics and bio-fertilizers improves soil health and increases crop production in a sustainable manner (Dasgupta et al. 2017;Ojha et al. 2018;Haldar et al. 2019).The inorganic fertilizers are concentrated source of nutrients and required only in lesser amount (Chen 2006).Though their requirement is less, they are reported to deteriorate soil health (Khan et al. 2008) and increases deficiency of secondary and other micronutrient (Panwar and Munda 2007) when used in excess and unscientific manner.Whereas, organics and bio-fertilizers not only supply the nutrients but also improves soil health by increasing soil organic carbon content and soil microbes population, that helps to mineralize unavailable form of nutrient to readily soluble form in soil (Kumar et al. 2015;Sarkar and Bandyopadhyay 2018;Hafez et al. 2021;Sen et al. 2021).
Rhizospheric soil contain diverse group of beneficial soil microorganisms, which helps in nutrient transformation in soil (Sen et al. 2021).Certain microorganisms have the capability to convert atmospheric nitrogen into a usable form (Wakarera et al. 2022), while others possess the ability to generate organic acids (Fasim et al. 2002;Tariq et al. 2007), thereby enabling the solubilization of insoluble Phosphorus (Khan et al. 2013), Potassium (Padhan et al. 2019) or Zinc (Dinesh et al. 2018, Yasmin et al. 2021).The easily soluble nutrients are available to plants for uptake, enhancing crop growth and production.The utilization of these beneficial microorganisms as bio-fertilizers on legumes with inorganic fertilizers have been reported to enhance plant growth, nodulation, dry matter accumulation and crop yield elsewhere (Basu et al. 2008;Caliskan et al. 2008;Mondal et al. 2020;Kundu et al. 2022).
Alfisols of Red and Laterite Zone of West Bengal (Subgroup-Typic Haplustalf) are poor in nutrient reserve with poor fertility status.These soils contain lesser amount of organic carbon, nitrogen, phosphorus and potassium.Soils are sandy in nature, low in CEC and suffers from high nutrient leaching losses (Basu et al. 2008;Patra and Bhattacharya 2009;Kundu et al. 2022).Thus, there is a dire need to find out suitable nutrient management practices for sustainable agriculture in this zone.
The main objective of the present study was to evaluate effect of different levels of inorganic fertilizers alone and in combination with bio-formulations on nutrient uptake, groundnut growth, yield, seed quality and economics in an acidic Red and Lateritic soil of West Bengal, India.We hypothesized that recommended dose of inorganic fertilizer with bio-formulation would enhance crop nutrient uptake, improve growth, yield and quality of the crop.

Site description
The field experiment was conducted during the kharif seasons (June-October) of 2018, 2019 and 2020 at the experimental plot of Regional Research Station (R & L Zone), Bidhan Chandra Krishi Viswavidyalaya, Jhargram, West Bengal, India (22.46°N, 87.01°E, elevation 81 above mean sea level).The mean monthly temperature varies between 11.6°C to 26.9°C in winter and 25.3°C to 40.2°C in summer.The site receives an average rainfall of 1300-1500 mm per annum.The South-West monsoon (July, August and September) contribute more than 70% of the annual rainfall.Month-wise variation in temperature (°C), rainfall (mm), relative humidity (%) and sunshine hour (hr) during the experiment at our experimental site is displayed in Figure 1.The soil of experimental site was characterized by red coloured, sandy loam textured (76.3% sand, 7.0% silt and 16.7% clay) and acidic in reaction (pH 5.5).Organic carbon content in soil is invariably low (0.4%) with low CEC (9.2 cmol(+) kg −1 ), low available NP (125.5 kg ha −1 N and 8.8 kg ha −1 Olsen P respectively) and medium available K (147.6 kg ha −1 ) content.The field was medium in slope having well irrigation facility.

Experimental design and treatment details
The experiment was laid out in split-plot design and replicated thrice.The main-plot consisted of four level of inorganic fertilizer, viz.F 1 : 25% recommended dose of fertilizer (RDF), F 2 : 50% RDF, F 3 : 75% RDF and F 4 : 100% RDF.The sub-plot contained different level of bio-formulations, viz.B 1 : no bioformulation, B 2 : liquid NPK bio-formulation + Zn-solubilizing bacteria and B 3 : Bio-grow.The liquid NPK bio-formulation is the consortia of three different bacteria i.e. nitrogen (N 2 ) fixer Azotobacter sp., P-solubilizer Paenibacillus sp. and K-solubilizer Bacillus sp.The liquid NPK bio-formulation and Zn solubilising bio-fertilizer (Bacillus sp.) were obtained from SSMP unit of Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India.Bio-grow contains several strains of Bacillus sp. and Pseudomonas sp.improving phosphorus solubilization, IAA and siderophore production (https:// www.nbaim.icar.gov.in).During each experimental year, same layout was followed.Each plot had a total area of 15 m 2 (3 m × 5 m) and separated by 0.5 m bund.

Crop management
Prior to sowing, the field was ploughed thoroughly, levelled and recommended doses of fertilizer was applied as basal at the rate of 20 kg ha −1 Nitrogen (N), 60 kg ha −1 phosphorus (P) and 40 kg ha −1 potassium (K) in the form of urea, single super phosphate and muriate of potash, respectively.Groundnut seeds were treated with 500 ml liquid NPK bio-formulation, 250 ml Zn-solubilizing bacteria and 500 ml Bio-grow per hectare as per the treatment prior to sowing.The uninoculated seeds were treated with 63% mancozeb + 12% (WP) carbendazim formulation at 3 g kg −1 of seed kernel to avoid seed-borne diseases.Variety TG 51 was used as a seed material which is a mutant derivative of TG26 × Chico, having early maturity with high yielding capacity.The seeds were sown at a depth of 3-4 cm manually with a seed rate of 150 kg ha −1 during the second fortnight of June of each experimental year at a row-to-row spacing of 30 cm and seed-to-seed spacing of 10 cm.The crop was irrigated through 1.5 HP diesel pump immediately after sowing for securing uniform crop establishment.Later irrigations were given each 6-8 days according to field capacity of soil and two additional irrigation at each critical crop water requirement stages (flowering, pegging and pod formation).Pre-emergence application of pendimethalin 30% EC at 0.75 kg a.i.ha −1 was done 2 days after sowing to control weed population.Two additional hand weeding were done at 20 and 40 days after emergence (DAE).For maintenance of standard plant population thinning operation was done at 30 DAE.Application of chlorpyriphos 20 EC at 3 ml L −l of water was done at 35 and 50 DAE to control sucking pest.The crop was harvested manually by uprooting of the whole plant upon physiological maturity and dried under sun.

Growth and yield attributes
Five plants from each plot were selected randomly during harvest and plant height was measured from the base to the tip of the main branch using measuring tape.Number of branches per plant was recorded from those same plants.Five plants were uprooted at 45, 60 and 75 DAE from each plot for counting the nodule number per plant.The roots of the plants were washed carefully in running tap water and then nodules were separated from each plant roots and kept separately.Thenumber of nodules were then counted and recorded.For dry matter accumulation measurement, an area of 1 m 2 was marked by a quadrant.Uprooted plants from this area were oven dried and the dry weight were recorded.Leaf area index was measured by dividing the total leaf area of plants with the respective area (Watson 1947).Ten leaflets were collected randomly; the margins of these leaves were traced on a graph paper (mm scale) and area was calculated.Leaflets were then dried and their dry weights were recorded.The Leaf area index (LAI) was then calculated using the area-weight relationship (Watson 1947).Crop growth rate (CGR) was calculated according to equation (1) according to Watson (1958), where W 1 and W 2 are the final and initial dry weight of plant material per unit area at times T 1 (initial time) and T 2 (final time), respectively.
Number of pegs and pods were counted from 5 randomly selected plants within each plot at the time of maturity.The peg to groundnut pod conversion percentage was calculated using equation (2): Hundred kernels were selected at random from 5 samples of each plot and their weight was recorded after drying.The sound mature kernel ratio (SMK) was calculated using the following equation (3): After recording the dry weight of pods, 100 pods were selected at random and shelled and the shelling percentage was calculated using following equation (4):

Nutrient assessment in plant
The collected plant samples were oven dried at 60°C for 72 h, ground in agate mortar, passed through 0.5-mm sieve and analyzed following standard methods.Total nitrogen (N) concentration in plant was determined by modified Kjeldahl method (Jackson 1973).For P and K, plant samples were first digested in a tri-acid (HNO 3 :H 2 SO 4 :HClO 4 = 10:1:4) mixture and then measured with a spectrophotometer and flame photometer, respectively (Jackson 1973).Crop nutrient uptake (kg ha −1 ) was calculated by multiplying the concentration of nutrients to the crop yield or dry matter yield (kg ha −1 ) using the following equation ( 5),

Quality assessment
Protein content in groundnut was determined using a near-infrared transmittance spectrophotometer with a silicon detector (model Trebor 99 Composition Analyzer manufactured by Trebor Industries, USA) following Misra et al. (2000).Oil content of the kernel was determined by solvent extraction method using Soxhlet apparatus (AOAC 1990).

Economic analysis
Cost of cultivation, gross and net return generated were calculated on the basis of the market price of the input, output and services.Cost of cultivation included expenditure on land preparation, seed materials, fertilizers, manures, sowing, weeding, thinning and gap filling, pesticides, fungicides, irrigation and harvesting, etc., of crop under different treatments.Gross return was calculated by multiplying groundnut minimum support price with pod yield.Net return was calculated after subtracting cost of cultivation from gross return.The benefit-to-cost ratio (BCR) for each treatment was computed using the following equation ( 6),

Statistical analysis
All the variables were subjected to ANOVA analysis meant for split-plot design (Gomez and Gomez 1984) using SPSS (v21.0)software.The standard error of mean (SEM±) and the value of critical difference (CD) at 5% level of significance were indicated in the tables and figures to compare the difference between the mean values.Different letters were assigned to each parameter columnwise to show significant difference at p < 0.05 following Duncan's multiple range test.
Table 1.Effect of different nutrient management practice on nutrients (NPK) uptake in groundnut haulm.

Crop nutrient uptake under different treatment
Variation in nutrient uptake in different parts of groundnut, i.e. the kernel and haulm, are reported in Tables 1 and 2. The N uptake in groundnut haulm varied from 65.3 to 86.3 kg ha −1 and 72.1 to 77.7 kg ha −1 in the main and sub-plot, respectively (pooled data).Whereas it varied from 81.5 to 117.6 kg ha −1 and 92.8 to 100.5 kg ha −1 in groundnut kernel.Highest haulm and kernel N uptake (avg.86.3 and 117.6 kg ha −1 , respectively) was found when higher dose of inorganic fertilizer was applied to the crop (100% RDF, F 4 ) in the main-plot and was significantly different from the rest of the treatment.Similarly, higher N uptake was recorded (77.7 and 100.5 kg ha −1 in haulm and kernel, respectively) when liquid NPK bio-formulation and Znsolubilizing bacteria was added to the crops (B 2 ) followed by Bio-grow treated plot (B 3 ) in the sub-plot.The variation in crop P uptake closely followed N uptake.Higher haulm and kernel P uptake (7.6 and 25.4 kg ha −1 , respectively) were recorded when higher dose of inorganic fertilizers were added to plots (F 4 ) followed by F 3 (6.1 and 21.2 kg ha −1 , respectively).Similarly, in case of bio-formulation, highest P uptake was found in B 2 (6.5 and 21.3 kg ha −1 in haulm and kernel, respectively) followed by B 3 (6.1 kg ha −1 and 20.0 kg ha −1 , respectively).Statistical analysis revealed that P uptake in F 4 and B 2 was significantly higher than other treatments in the main and sub-plot, respectively.Potassium (K) uptake in haulm and kernel varied from 47.3 to 63.7 kg ha −1 and 14.9 to 21.2 kg ha −1 in the main-plot and 52.6 to 57.0 kg ha −1 and 16.5 to 18.3 kg ha −1 in the sub-plot, respectively.Higher K uptake was found in plots receiving higher dose of inorganic fertilizer (F 4 ) along-with bio-formulations (B 2 ).However, the difference among treatments were not significant in the sub-plot.Two-order interaction effect between level of inorganic fertilizer (F) and bio-formulation (B) were found to be non-significant with respect to N and K uptake in groundnut haulm and kernel, indicating minimal combined or joined effect on N and K uptake.However, they both have positive effect on P uptake in haulm as indicated by significant interaction effect between F and B. Higher dose of inorganic fertilizer and bio-formulation have resulted in higher nutrient supply and their uptake in groundnut kernel and haulm.A similar observation was recorded by Mondal et al. (2020) and Kundu et al. (2022).Better nutritional environment in the rhizosphere under the treatment has resulted in enhanced nutrient uptake and their translocation within plant parts.Alongside, incorporation of Zn-solubilizing bacteria might have led to quick release of more readily plant-available inorganic forms of nutrients from soil through production of several organic acids, increasing their availability and uptake (Wang et al. 2014;Schütz et al. 2018).Thus, higher uptake of NPK nutrients from soil might be attributed to their greater concentration in groundnut, and higher pod and haulm yields (Basu et al. 2006).

Groundnut growth attributes
Influence of different nutrient management practices on various crop growth attributes are presented in Figures 2 and 3. Plant height at harvest varied from 44.8 to 47.5 cm in the main plot.Plant height was maximum (47.5 cm) in F 4 main plot, where 100% RDF was applied, followed by F 3 .However, their variation was not significant during the experimental years, except during the first year of the experiment (2018).
Plant height in different sub-plot recorded comparable results, whether the plots received bio-formulation received or not.Number of branches plant −1 at harvest varied from 8.7 to 14.0 in our experiment.
Maximum number of branches were found in F 4 main-plot and B 2 sub-plot receiving higher fertilizer dose and bio-formulations respectively.Lower no. of branches was recorded in plots receiving lower level of fertilizer.Higher dose of fertilizer resulted into higher crop nutrient uptake, increasing plant height and no. of branches plant −1 .Increased plant height and branch no. with higher dose of chemical fertilizer and  bio-fertilizer was reported elsewhere (Caliskan et al. 2008;Mondal et al. 2020;Kundu et al. 2022).The increase in plant height and no. of branches with higher level of fertilizer application was possibly due to higher nutrient uptake and their efficient utilization.Co-application of liquid NPK bio-formulation and Znsolubilizing microorganism with inorganic fertilizer was found to increase availability of several nutrients.Zinc stimulates several plant enzymes and plant growth hormones like auxin which helps in multiplication of more plant cells that ultimately improve vegetative growth and escalate canopy cover of the plant (Ved et al. 2002).Higher nutrient uptake has possible influences in activities of meristematic tissues of the plant and, number and size of the cell.Nutrient availability also has significant influences on activation of auxiliary bud, which is responsible for branching (Sarade et al. 2016).Similar results were reported byMondal et al. ( 2020).The two-order interaction effect between level of inorganic fertilizer and bioformulation (F × B) were found to be non-significant in respect of plant height , meaning minimal or no combined effect of inorganic fertilizer and bio-formulations on groundnut height in our experiment.
The average no. of nodules per plant ranged from 65.1 to 73.8, 89.6 to 99.6 and 113.5 to 131.5 at 45 days after emergence (DAE), 60 DAE and 75 DAE, respectively, in the main plot.Whereas, it varied from 64.6 to 75.8, 89.6 to 96.9 and 115.0 to 125.8 at 45 DAE, 60 DAE and 75 DAE, respectively, in the sub-plot.Generally, nodulation was higher during later stage of crop growth (75 DAE).Higher no. of nodules was found in F 4 and B 2 treatment in main and sub-plot, respectively.Higher nutrient uptake in plots receiving higher dose of fertilizer (F 4 ) and bio-formulations (B 2 ) has resulted in greater root lengths, increasing no. of nodules in groundnut.Similar results were reported elsewhere (Sagare and Bhalkar 1986;Basu and Bhadoria 2008).
Aboveground biomass of groundnut varied significantly throughout growth stage and fertilizer management practice (Figure 4).Groundnut dry matter was found to increase with increasing fertilizer level and maximum result was obtained when bio-formulations (B 2 ) were added along-with higher dose of inorganic fertilizer (F 4 ).It varied from 65.3 to 74.7, 142.4 to 168.6, 177.0 to 237.1 and 237.6 to 334.2 g m −2 at 45, 60, 75 DAE and at harvest, respectively, in the main plot, whereas it ranged from 68.5 to 70.1, 154.2 to 158.2, 202.4 to 210.9 and 272.9 to 295.0 g m −2 in the sub-plot at 45, 60, 75 DAE and at harvest respectively.Highest accumulation was found in the plots receiving higher dose of fertilizer (F 4 ) and bio-formulations (B 2 ) in all the years.However, changes in dry matter production with different treatment was not significant even with increasing the level of inorganic fertilizer or bio-formulation during initial stage.Variation in average aboveground dry matter accumulation between treatments increased as the growing stage advanced and the differences among the treatments was significant only during the later stage of crop development.Level of inorganic fertilizer (main plot) has greater impact on groundnut dry matter accumulation than application of bio-formulation (sub-plot) as we noticed in the experiment.Better nutrient uptake and increased photosynthetic activities due to enhanced plant vigour have resulted in greater accumulation of carbohydrates in body parts, increasing dry matter accumulation in plots receiving higher level of inorganic fertilizer (F 4 ) and bio-formulations (B 2 ).It is also reported that biofertilizer uninoculated crops tends to expense more energy towards collecting nutrient from soil and converting them in plant usable form, whereas in inoculated plants, nutrients are already in the organic reduced form and, hence, more readily available for plant metabolism, resulting in more dry matter accumulation in inoculated crops (Sogut 2006).Similar results were also reported elsewhere (Mathenge et al. 2019).The two-order interaction effect between level of inorganic fertilizer and application of bioformulation (F × B) were found to be significant in respect of dry matter accumulation in groundnut during later growth stages, indicating possible combined effect of both inorganic-and bio-fertilizer on dry matter accumulation in our experiment.

Groundnut physiological attributes
The effect of fertilizer treatments on various physiological traits is listed in Figures 5 and 6.The result revealed that leaf area index (LAI) and crop growth rate (CGR) were significantly influenced with the different level of inorganic fertilizer and application of bio-formulations during all growth stages.Groundnut LAI and CGR during different growth stage was found to increase with increasing inorganic fertilizer level and it was found maximum when bio-formulations (B 2 ) was added along-with higher dose of inorganic fertilizer (F 4 ).The LAI was found to vary from 0.97 to 1.13, 2.02 to 2.34 and 3.06 to 3.54 at 45, 60 and 75 DAE, respectively, in the main-plot and 1.03 to 1.07, 2.13 to 2.22 and 3.16 to 3.23 in the sub-plot.Maximum LAI during different growth stage was recorded under treatment F 4 .However, LAI was comparable under B 2 and B 3 in the sub-plot without any significant difference.Generally, CGR was highest in between 60 to 75 DAE and lowest during early (45 to 60 DAE) and later stage of development (75 DAE to harvesting).The CGR varied from 0.17 to 0.26, 0.25 to 0.42 and 0.20 to 0.34 g m −2 day −1 in the main-plot and 0.20 to 0.21, 0.31 to 0.36 and 0.25 to 0.28 g m −2 day −1 in the sub-plot during 45-60, 60-75 DAE and 75 DAE to harvesting.Crop growth rate was significantly influenced by various nutrient treatments.Maximum CGR was found under fertilizer level F 4 in the main plot, receiving higher dose of fertilizer.
Higher CGR was also recorded in B 2 sub-plot where liquid NPK bio-formulation and Zn-solubilizing bacteria was applied.The two-order interaction effect between inorganic fertilizer and bio-formulation (F × B) were found to be significant with respect to LAI and CGR in groundnut during all the growth stages in our study.Higher LAI and other growth attributes might be due to application of bio-fertilizers which helped the plant for better vegetative growth by stimulating higher light interception by the crop canopy and resulted higher LAI values (Aduloju et al. 2009).

Groundnut yield attributes
Tables 3 and 4 show variations in various yield attribution characteristics of groundnut crop with different nutrient management practices.Number of pegs per plant was found to vary from 23.8 to 29.9 and 25.9 to 27.3 in the main and sub-plot, respectively.Higher no. of pegs were recorded under treatment F 4 (29.9)followed by F 3 (27.0) in main-plot, whereas B 2 (27.3) followed by B 3 (26.3) in sub plot treatment produced higher no. of pegs where higher dose of chemical fertilizer and bio-formulations were applied.Similar results were observed in terms of the no. of pods per plant.Number of pods per plant varied significantly and highest no. of pods was observed under the plot F 4 (21.3) and B 2 (20.8).Pegs-to-pod conversion rate indicates the number of pods that were culminated from the pegs and it varied significantly under different treatments.Pegs-to-pod conversion varied from 67.1 to 72.7% and 64.6 to 73.6% in the main and sub-plot, respectively.However, conversion rate was higher in plots receiving lower dose of fertilizer (F 2 , 72.7%) when compared to higher dose (F 4 , 68.4%).Effect of bioformulation application was statistically significant within the treatments in all three experimental years.The interaction effects between the inorganic fertilizer level and bio-formulations (F × B) were found to be insignificant in respect of no of pegs and pods; however, the effect was significant for pegs-to-pod conversion, indicating possible combined effect of both inorganic-and bio-fertilizer on peg-to-pod conversion in our experiment.Similar results were reported elsewhere (Mondal et al. 2020;Kundu et al. 2022) where microbial inoculation and higher dose of inorganic fertilizer improved the groundnut yield attributes. Shelling percentage ranged from 68.4 to 71.2 and 69.1 to 70.6 in the main and sub-plot, respectively, in our experiment.Higher percentage was recorded in plots receiving higher dose of fertilizer and bio-formulations.The percentage of sound mature kernels (SMK) varied significantly with fertilizer and bio-formulation application.SMK (%) varied from 84.7 to 88.5 and 85.8 to 87.1 in the main and sub-plot, respectively.The weight of a hundred kernels (100 KW) was found to vary from 43.7 to 45.5 and 43.8 to 45.2 in the main and sub-plot, respectively.Higher 100 KW was recorded in the treatment with higher dose of fertilizer and bioformulations.Increasing shelling percentage, SMK and seed weight with increasing level of fertilizer was reported elsewhere (Nagar et al. 2019;Mondal et al. 2020).However, yield attributes like Shelling (%), SMK (%) and 100 kernel weights (g) did not vary significantly under different doses of chemical fertilizer along with or without supplementation bioformulations although treatments differences were recorded.

Groundnut yield
Variation in groundnut yield under different nutrient management practices is reported in Table 5. Groundnut pod, haulm and kernel yield increased with higher doses of chemical fertilizer and with the supplementation of bio-formulation.Highest pod yield was noted under treatment F 4 (2658.2kg ha −1 ) in the main-plot and B 2 (2282.1 kg ha −1 ) in the sub-plot and was statistically superior over the rest of the treatments.Similarly, haulm and kernel yield were found higher under treatment F 4 (3313.1 and 2891.8 kg ha −1 ) in the main-plot and B 2 (1851.9 and 1566.4 kg ha −1 ) in the sub-plot.However, haulm and kernel yield in B 2 (sub-plot) was statistically at par with treatment B 3 .Lowest pod, haulm and kernel yield was recorded when lower dose of chemical fertilizer (F 1 ) was applied without any bio-formulations (B 1 ).Crop harvest index (HI) was found to vary from 42.9 to 44.5 in the main-plot and 43.4 to 44.0 in the sub-plot with higher values under F 4 (44.5) and B 2 (44.0) treatment.However, the difference between various treatments was statistically nonsignificant.The two-order interaction effects between the inorganic fertilizer level and bio-formulations (F × B) were found to be significant in respect of groundnut pod, haulm and kernel yield in the third year of experiment, implying possible combined effect of both inorganic-and bio-fertilizer on groundnut yield.Enhanced nutrient uptake and their efficient utilization under adequate fertilization has favoured superior growth responses and yield-determining factors (Mir et al. 2013).Better translocation and accumulation of photosynthesis have boosted plant height, no. of branches, dry matter accumulation, LAI, CGR, no. of pods and hundred kernel weight, resulting higher pod, haulm and kernel yield.
Our results were in conformity with previously reported observations (Ravankar et al. 2003;Mondal et al. 2020).Groundnut seeds inoculated with microbial inoculants reported higher yields than treatments without inoculation (Basu and Bhadoria 2008;Asante et al. 2020).Favourable microclimate combined with an optimum supply of plant nutrients facilitated better growth, yielddetermining traits and ultimately groundnut yield.

Groundnut quality traits
Variation in groundnut quality in terms of oil and protein content (%) was reported in Figure 7.Both oil and protein content varied significantly with different level of fertilizer and bioformulation application.Oil content was found to vary from 39.6% to 47.6% in the main-plot   and 42.0 to 43.8% in the sub-plot.Similarly, protein content in groundnut kernel varied from 19.6 to 21.5% in the main-plot and 19.8% to 20.6% in the sub-plot.Their concentration was higher when higher amount of inorganic fertilizer was applied with bio-formulations.Maximum oil and protein content were found in plot receiving 100% of RDF (F 4 ) along with liquid NPK bio-formulation and Zn-solubilizing bacteria (B 2 ).However, the difference was not significant in the sub-plot.Nutrient especially N and P are essential component of protein and fats.Thus, higher uptake and accumulation of these nutrients has resulted in better seed quality in groundnut.Win et al. (2010) and Ahmed et al. (2018) reported similar increase in oil and protein content in ground nut under different fertilizer management.

Economic benefits
Details of economic analysis under different fertilizer management is accounted in Table 6.Several economic indices varied significantly under different treatments.Generally, plots receiving higher dose of fertilizer and bio-formulations resulted higher gross and net return and BCR in all the experimental years.Gross return was found to vary from 858.5 to 1302.2 USD in the main-plot and 1018.1 to 1115.1 USD in the sub-plot.Whereas, net return varied from 412.3 to 810.3 USD and 558.1 to 641.5 USD in the main and sub-plot, respectively.Both gross and net return was highest in F 4 and B 2 in the main and sub-plot, respectively.Similar results were obtained for BCR.It varied from 1.9 to 2.7 in the main-plot and 2.2 to 2.3 in the sub-plot.High net profit and BCR in F 4 (main-plot) and B 2 (sub-plot) was possibly due to higher groundnut growth and crop productivity under higher nutrient uptake and better soil environment.Baishya et al. (2013) and Mondal et al. (2020) reported similar high net returns with increasing application rate of fertilizer up to the full recommended dose.

Conclusion
We have studied variations in groundnut growth, yield and quality traits under different nutrient management practices in nutrient poor Alfisol (subgroup -Typic Haplustalf) soils of India.Several strains of bio-formulations were applied in conjunction with different dose of inorganic fertilizer and their response were recorded.Maximum response was recorded when full amount of recommended dose of fertilizer (100% RDF; F 4 ) was coupled with liquid NPK bio-formulation and Zn-solubilizing bacteria (B 2 ).Higher dose of fertilizer and bio-formulations have resulted in release of readily soluble nutrients from soil and higher uptake of nutrients in groundnut crops ensuring better growth and development of plant, enhanced photosynthetic activity, higher yield and quality.Economic returns (net revenue, benefit-to-cost ratio and the incremental cost-benefit ratio) was also higher under the circumstances.We concluded that groundnut crop is responsive to higher levels of inorganic fertilizers and application of liquid NPK bio-formulation + Zn-solubilizing bacteria (B 2 ) along with 100% RDF (F 4 ) have stimulated significant improvement in physiological traits, quality as well as productivity and profitability of groundnut crop and may be recommended for acid Alfisol soils of Red and Laterite Zone of India for maximum sustainable yield.

Figure 1 .
Figure 1.Mean climatic variation in our study area during the cropping season (mean of 2018, 2019 and 2020).

Table 2 .
Effect of different nutrient management practices on nutrients (NPK) uptake in groundnut kernel.

Table 3 .
Yield attributes of groundnut as influence by different nutrient management practices.

Table 4 .
Yield attributes of groundnut as influence by different nutrient management practices.

Table 5 .
Influence different nutrient management practices on groundnut yield and harvest index.