Effect of integrated application of inorganic fertilizer, biochar and biofertilizer on soil health, growth, yield and economics of White Maize (Zea mays L.) var. Pearl white

Introduction

Soil health, defined as the continuing capacity of soil to function as a living system that sustains plants, animals and human beings, is governed jointly by its physical, chemical and biological properties, and remains the foundation of sustainable crop production (Bünemann et al., 2018) [9] . Intensive cultivation, imbalanced and continuous use of chemical fertilizers, and inadequate replenishment of organic matter have progressively degraded soil quality in many intensively cropped regions, lowering organic carbon content, disturbing microbial communities and reducing native nutrient-supplying capacity (Zhang et al., 2021) [32] . Since chemical fertilizers alone cannot sustain long-term soil fertility, greater emphasis is now being placed on integrated nutrient management (INM), in which mineral fertilizers are combined with organic amendments and microbial inoculants to build a more resilient and productive soil system (Mahajan et al., 2021) [25] . Maize (Zea mays L.) is the third most important cereal of India after rice and wheat and, being a nutrient-exhaustive crop, is particularly sensitive to the fertility status of the soil in which it is grown (ICAR-IIMR, 2024) [18] . Among the organic amendments available for INM, biochar-a stable, carbon-rich material produced by pyrolysing biomass under limited oxygen-has attracted wide attention because its porous structure and large surface area can improve soil aggregation, water retention and cation exchange capacity while providing a favourable habitat for soil microorganisms (Lehmann and Joseph, 2015) [24] . Biofertilizers containing Azospirillum and phosphate-solubilizing bacteria (PSB) complement this effect biologically, by fixing atmospheric nitrogen and solubilising fixed soil phosphorus, thereby raising nutrient-use efficiency and reducing dependence on mineral fertilizer (Bhattacharyya and Jha, 2012) [6] . Although the individual effects of biochar, biofertilizers and inorganic fertilizers on soil properties and cereal yield have been documented separately, information on their combined, graded application to white maize under the sub-tropical alluvial soils of the middle Gangetic plain is limited. The present investigation was therefore undertaken to (i) evaluate the effect of integrated nutrient management on soil physico-chemical properties, (ii) determine its influence on growth, yield attributes, yield and nutrient uptake of maize, and (iii) work out the economic feasibility of the different nutrient-management practices tested.

Materials and Methods

The field experiment was carried out during the Kharif season of 2025 at the Soil Science Research Farm, Naini Agricultural Institute, SHUATS, Prayagraj (25°27′ N, 81°51′ E; 98 m amsl), a sub-tropical location in the middle Gangetic plain with a sandy loam soil. The soil, sampled from a depth of 0-15 cm before sowing, was slightly alkaline in reaction (pH 7.60), non-saline (EC 0.32 dS m⁻¹), low in organic carbon (0.42%) and available nitrogen (215 kg ha⁻¹), and medium in available phosphorus (18.4 kg ha⁻¹), potassium (245 kg ha⁻¹) and sulphur (11.2 mg kg⁻¹). The experiment comprised nine treatment combinations arising from two factors-three levels of the recommended dose of fertilizer (RDF; I₀: 0%, I₁: 50%, I₂: 100% of 120:60:40 kg N:P₂O₅:K₂O ha⁻¹ supplied through urea, DAP and MOP) and three levels of biochar together with biofertilizer (B₀: no biochar/no biofertilizer, B₁: wheat-straw biochar @ 2.5 t ha⁻¹ + Azospirillum + PSB, B₂: biochar @ 5.0 t ha⁻¹ + Azospirillum + PSB)-laid out in a factorial randomized block design with three replications (Table 1). Each plot measured 2.0 × 2.0 m, and white maize var.

Pearl White was sown on 24 June 2025 at 60 × 20 cm spacing after seed inoculation with the respective biofertilizers using a jaggery-solution slurry. Biochar was incorporated into the surface soil during final land preparation; phosphorus and potassium were applied basally and nitrogen in two split top-dressings. All other agronomic operations were kept uniform across plots. Five randomly tagged plants per plot were used to record plant height, number of leaves and dry-matter accumulation at 30, 60 and 90 days after sowing (DAS), while cob length, grains per cob, test weight, grain yield, stover yield and biological yield were recorded at harvest. Composite post-harvest soil samples (0-15 cm) were analysed for pH and electrical conductivity in a 1:2.5 soil:water suspension (Jackson, 1973) [19] , organic carbon by wet oxidation (Walkley and Black, 1934) [31] , available nitrogen by the alkaline permanganate method (Subbiah and Asija, 1956) [29] , available phosphorus by Olsen's method (Olsen et al., 1954) [28] , available potassium by neutral normal ammonium acetate extraction followed by flame photometry (Jackson, 1973) [19] , and available sulphur by the turbidimetric method (Chesnin and Yien, 1951) [10] ; bulk density, particle density and water-holding capacity were determined by the core-sampler, pycnometer and Keen-Raczkowski methods, respectively, and soil texture by the hydrometer method (Bouyoucos, 1962) [8] . Nitrogen, phosphorus and potassium concentrations in grain and stover were used, together with the respective dry-matter yields, to compute total nutrient uptake. The cost of cultivation, gross return, net return and benefit:cost ratio were worked out using the prevailing market prices of inputs and produce. All data were subjected to analysis of variance appropriate to a randomized block design (Gomez and Gomez, 1984) [16] , and treatment means were compared using the critical difference at the 5% level of significance. [30,12] . In contrast, organic carbon and the availability of nitrogen, phosphorus, potassium and sulphur increased significantly and progressively with increasing levels of RDF and biochar, and were maximum under T [23,4,6,26] . [27,7,3,1] .

Growth parameters

Plant height, number of leaves per plant and dry-matter accumulation all increased significantly and progressively with crop age and with increasing levels of RDF, biochar and biofertilizer (Table 4). At 90 DAS, plant height ranged from 165.2 cm under T 1 to 217.9 cm under T 9 , the number of leaves per plant from 11.2 to 15.8, and dry-matter accumulation from 158.6 to 241.6 g plant⁻¹. A similar, dose-dependent increase was evident at the earlier 30 and 60 DAS stages. The larger, more vigorous canopy produced under the integrated treatments is attributable to the combined availability of balanced mineral nutrients, biocharmediated improvement in the soil physical environment, and biofertilizer-assisted nitrogen fixation and phosphorus mobilisation, all of which favour greater nutrient uptake and photosynthetic assimilation, as also reported by Hammad et al.

(2011) [17] , Fageria et al. (2011) [13] and Amanullah et al. (2016) [2] .

Yield attributes and yield

Cob length, number of grains per cob and test weight, along with grain, stover and biological yield, were significantly higher under the integrated treatments than under sole or lower levels of fertilizer (Table 5). Treatment T 9 recorded the longest cobs (19.8 cm), the most grains per cob (482), the highest test weight (282 g) and the highest grain, stover and biological yield (58.9, 98.5 and 157.4 q ha⁻¹, respectively)-an increase of about 69% in grain yield over T 1 (34.8 q ha⁻¹). This superiority follows logically from the greater plant height, leaf area and dry-matter accumulation recorded under the same treatment (Table 4), since better vegetative growth generally translates into more effective cob elongation, grain set and grain filling under adequate, balanced nutrition, as noted by Faloye et al. (2019) [14] and Amanullah et al. (2016) [2] . The corresponding gains in nitrogen, phosphorus and potassium uptake-from 82.6, 17.4 and 64.8 kg ha⁻¹ under T 1 to 143.9, 30.8 and 113.6 kg ha⁻¹ under T 9 (Table 5)-confirm that the yield advantage of the integrated treatments reflects genuinely higher nutrient acquisition rather than simple biomass dilution, in line with Ciampitti and Vyn (2012) [11] , Kizito et al. (2019) [21] and Joseph et al. (2021) [20] .

Economics of maize cultivation

The cost of cultivation rose from ₹48,200 ha⁻¹ under T 1 to ₹60,099 ha⁻¹ under T 9 on account of the added expenditure on fertilizer, biochar and biofertilizer, but this extra cost was more than offset by the accompanying gain in yield (Table 6). Gross return increased from ₹69,600 to ₹1,17,800 ha⁻¹ and net return from ₹21,400 to ₹57,701 ha⁻¹ between T 1 and T 9 , while the benefit:cost ratio improved from 1:1.44 to 1:1.96 over the same range. The superior economics of T 9 stem directly from the substantially higher grain and stover yield realised under this treatment, which comfortably compensated for the additional input cost, corroborating the findings of Gezahegn (2021) [15] and Bhandari et al. (2021) [5] that integrated nutrient management is economically advantageous for maize cultivation.

Conclusion

Integrated application of inorganic fertilizer with wheat-straw biochar and biofertilizer improved post-harvest soil fertility and physical condition, enhanced growth, yield attributes, yield and nutrient uptake, and increased profitability of white maize, without any adverse effect on soil pH or salinity. Among the nine combinations tested, 100% RDF applied together with 5.0 t ha⁻¹ wheat-straw biochar and seed inoculation with Azospirillum and phosphate-solubilizing bacteria (T 9 ) consistently gave the best performance across all the parameters studied and may be recommended as an effective and sustainable nutrientmanagement practice for white maize cultivation under agroclimatic conditions similar to those of Prayagraj. Long-term, multi-location trials are suggested to confirm the residual and cumulative benefits of this integrated nutrient-management strategy.

Acknowledgement

AcknowledgementThe authors are grateful to the Department of Soil Science and Agricultural Chemistry, Naini Agricultural Institute, Sam Higginbottom University of Agriculture, Technology and Sciences (SHUATS), Prayagraj, for providing the research farm, laboratory and other facilities used in this investigation.

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