Influence of phosphorus levels and foliar sprays on green fodder yield, quality and economics of cowpea [Vigna unguiculata (L.)]

Introduction

Leguminous crops occupy a pivotal position in sustainable agriculture owing to their ability to fix atmospheric nitrogen and enrich soil fertility. Among grain legumes, cowpea [Vigna unguiculata (L.)] is widely grown in tropical and subtropical regions for its adaptability, short duration and multiple uses as pulse, vegetable and fodder crop. Besides being a rich source of dietary protein for humans (Jayathilake et al., 2018) [1] , cowpea also provides nutritious green fodder containing 16-24 percent crude protein, making it a valuable feed resource for livestock and enhancing its utility as a dual-purpose crop in mixed croplivestock farming systems. Phosphorus is one of the most critical nutrients governing legume productivity, influencing nodulation, nitrogen fixation, root proliferation and biomass accumulation. However, its use efficiency from inorganic sources alone is often low due to fixation in soil. Integrated nutrient management (INM), which combines inorganic fertilizers with farmyard manure (FYM) and phosphorus solubilizing bacteria (PSB) offers a sustainable means of improving phosphorus availability while maintaining soil health. In addition to soil applied nutrients, foliar nutrition has emerged as an effective supplementary strategy for correcting nutrient deficiencies during critical growth stages, since foliar absorbed nutrients bypass soil related constraints such as fixation and leaching. While the effects of phosphorus management and foliar nutrition on the growth and seed yield of cowpea have been documented, information on their combined influence on fodder quality traits such as crude protein and crude fibre content along with green fodder yield and profitability, remains limited. The present study was therefore undertaken to evaluate the effect of integrated phosphorus management and foliar nutrition on green fodder yield, crude protein content, crude fibre content and economics of cowpea.

Materials and Methods

A field experiment was conducted during rabi 2025-26 at dryland farm, S. V. Agricultural College, Tirupati campus of Acharya N. G. Ranga Agricultural University. The soil of the experimental site was sandy loam in texture, neutral in reaction (pH 6.51), low in organic carbon (0.4%) and available nitrogen (207 kg ha⁻¹), and medium in available phosphorus (24.3 kg ha⁻¹) and available potassium (213 kg ha⁻¹). The experiment was laid out in randomized block design with factorial concept with three replications, comprising fifteen treatment combinations of three phosphorus levels: P₁-100% recommended dose of phosphorus (RDP) through inorganics, P₂-75% RDP through inorganics + 25% RDP through FYM + PSB @ 1.25 l ha⁻¹ and P₃-50% RDP through inorganics + 50% RDP through FYM + PSB @ 1.25 l ha⁻¹ (RDP = 50 kg P₂O₅ ha⁻¹), and five foliar sprays: F₁-control (water spray), F₂-2% urea, F₃-10% cow urine, F₄-1% potassium nitrate (KNO₃) and F₅-1% seaweed extract, applied twice at 30 and 45 days after sowing (DAS). The short-duration cowpea variety TPTC-29 was sown on 19 th November 2025 at a spacing of 45 cm × 15 cm. A uniform basal dose of 20 kg N ha⁻¹ and 25 kg K₂O ha⁻¹ was applied to all plots. All the other recommended practices were also adopted as per the crop requirement.

Results and Discussion

Green Fodder Yield Green fodder yield of cowpea was significantly influenced by phosphorus levels and foliar sprays, while their interaction effect was non-significant (Table 1). Among phosphorus levels, significantly higher green fodder yield was recorded with 100% RDP through inorganics (P₁), while 75% RDP through inorganics + 25% RDP through FYM + PSB @ 1.25 l ha -1 (P 2 ) and 50% RDP through inorganics + 50% RDP through FYM + PSB @ 1.25 l ha -1 (P 3 ) were statistically at par with each other, both recording significantly lower yield than P₁. The higher biomass accumulation under P₁ can be attributed to the immediate and complete availability of soluble inorganic phosphorus from early crop growth stages, which sustained active vegetative growth, whereas the slower mineralization of the organically sourced phosphorus fraction under P₂ and P₃ likely resulted in a transient nutrient deficit during the peak vegetative phase. Similar findings on higher fodder yield under fully inorganic phosphorus nutrition were reported by Joshi et al. (2018) [2] , Mobeena et al. (2020) [3] and Sejal et al. (2024) [4] . Among foliar sprays, 1% KNO₃ (F₄) recorded significantly the highest green fodder yield, followed by 2% urea (F₂), while 10% cow urine (F 3 ) and 1% seaweed extract (F 5 ) were statistically comparable and occupied an intermediate position, and water spray (F 1 ) recorded significantly the lowest yield. The superiority of F₄ can be ascribed to the concurrent foliar supply of nitrogen and potassium during the critical vegetative growth stages, which enhanced turgor maintenance, chlorophyll biosynthesis and net photosynthetic rate, thereby promoting greater vegetative biomass accumulation. These results corroborate the findings of Dey et al. (2017) [5] , Sakpal et al. (2021) [6] and Surender et al. (2024) [7] in cowpea.

Crude Protein Content in Green Fodder

Crude protein content in green fodder was significantly influenced by phosphorus levels and foliar sprays, with a non-significant interaction effect (Table 1). Among phosphorus levels, significantly higher crude protein content was recorded with 75% RDP through inorganics + 25% RDP through FYM + PSB @ 1.25 l ha -1 (P 2 ), while 100% RDP through inorganics (P₁) and 50% RDP through inorganics + 50% RDP through FYM + PSB @ 1.25 l ha -1 (P 3 ) were statistically at par with each other and significantly lower than P₂. The integrated supply of inorganic phosphorus, FYM and PSB under P₂ likely enhanced nodule activity and biological nitrogen fixation, leading to greater nitrogen accumulation in vegetative tissues and consequently higher crude protein content. These findings are in agreement with Rekha et al. (2018) [8] , Mobeena et al. (2020) [3] and Dharani et al. (2025) [9] . Among foliar sprays, significantly the highest crude protein content was recorded with 2% urea (F₂) and was on par with 1% KNO₃ (F₄). 10% cow urine (F 3 ) and 1% seaweed extract (F 5 ) were statistically comparable at an intermediate level and water spray (F 1 ) recorded significantly the lowest crude protein content. The direct and concentrated foliar supply of nitrogen through urea, applied during active vegetative growth, appears to have maximized nitrogen incorporation into structural and storage proteins of the fodder. These results are in conformity with Ritika et al. (2019) [10] , Mandaliya et al. (2022) [11] and Dhar et al. (2025) [12] .

Crude Fibre Content

Crude fibre content, being an inverse indicator of fodder quality, was significantly influenced by phosphorus levels and foliar sprays (Table 1). Significantly the highest crude fibre content was recorded with 50% RDP through inorganics + 50% RDP through FYM + PSB @ 1.25 l ha -1 (P 3 ), followed by 100% RDP through inorganics (P₁), while 75% RDP through inorganics + 25% RDP through FYM + PSB @ 1.25 l ha -1 (P 2 ) recorded significantly the lowest crude fibre content. The lower nutrient availability under P₃ during the active vegetative phase likely suppressed protein and chlorophyll synthesis and diverted a greater proportion of photosynthates towards structural cell wall carbohydrates, whereas the balanced integrated nutrition under P₂ favoured metabolically active tissue over structural biomass. These results support the findings of Mobeena et al. (2020) [3] and Dharani et al. (2025) [9] . Among foliar sprays, significantly the highest crude fibre content was recorded under water spray (F 1 ), while 2% urea (F₂) and 1% KNO₃ (F₄) were on par recorded lower crude fibre content, consistent with the higher crude protein performance. The absence of exogenous nitrogen under F₁ appears to have shifted plant metabolism towards structural carbohydrate synthesis, whereas the concentrated nitrogen supply from urea enhanced protein and chlorophyll biosynthesis at the expense of cell-wall fibre deposition. Similar trends were reported by Mandaliya et al. (2022) [11] and Uttamrao et al. (2022) [13] .

Economics

Gross returns, net returns and benefit-cost ratio of cowpea were significantly influenced by phosphorus levels and foliar sprays, with a non-significant interaction effect (Table 2). Among phosphorus levels, 75% RDP through inorganics + 25% RDP through FYM + PSB @ 1.25 l ha -1 (P 2 ) recorded significantly the highest gross returns, net returns and benefit-cost ratio, followed by 100% RDP through inorganics (P₁), while 50% RDP through inorganics + 50% RDP through FYM + PSB @ 1.25 l ha -1 (P 3 ) recorded the lowest values for all three economic parameters. Although P₂ involved additional expenditure on FYM and PSB, the substantial improvement in seed and fodder yield realized through the synergism of inorganic, organic and biological phosphorus sources was sufficient to outweigh this marginal cost increase, resulting in the highest profitability. These findings were in line with Rathour et al. (2015) [14] , Jangir et al. (2016) [15] and Sejal et al. (2024) [4] .

Among foliar sprays, F₄ 1% KNO₃ (F₄) recorded the highest gross and net returns, followed by 2% urea (F₂), while F₄ and F₂ were statistically at par for benefit-cost ratio. Water spray (F 1 ) recorded the lowest values for all three economic parameters. The higher gross and net returns under F₄ reflect its superior seed and fodder yield performance, which, combined with the relatively low material cost of foliar sprays, translated into the greatest monetary and efficiency advantage among the foliar treatments. Similar results were reported by Sonal et al. (2021) [16] , Mandaliya et al. (2022) [11] and Rathod et al. (2023) [17] .

Conclusion

Based on the results of the present investigation, it can be concluded that among phosphorus levels, application of 75% RDP through inorganics + 25% RDP through FYM + PSB @ 1.25 l ha⁻¹ (P₂) recorded the best combination of fodder quality (higher crude protein, lower crude fibre) and profitability (highest gross returns, net returns and benefitcost ratio), although 100% RDP through inorganics (P₁) produced the highest green fodder yield. Among foliar sprays, foliar application of 1% KNO₃ (F₄) at 30 and 45 DAS proved superior in terms of green fodder yield, fodder quality (higher crude protein, lower crude fibre) and economic returns (highest gross returns, net returns and benefit-cost ratio). Therefore, integration of 75% RDP through inorganics with FYM and PSB, combined with foliar spray of 1% KNO₃ can be recommended for improving the productivity, quality and profitability of fodder cowpea under similar agro-climatic conditions.

Acknowledgement

AcknowledgementThe authors are grateful to the Department of Agronomy, S.V. Agricultural College, Tirupati, and Acharya N.G. Ranga Agricultural University for providing the necessary facilities to carry out this research.

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