Effect of foliar application of humic acid and potassium nitrate on growth of okra

Introduction

Okra (Abelmoschus esculentus L. Moench), belonging to the family Malvaceae, is an important vegetable crop cultivated widely in tropical and subtropical regions. It is commonly known as bhendi or lady's finger and is primarily grown for its tender edible green pods. Okra is valued for its nutritional and economic importance and is extensively cultivated in India as well as in other major okra-growing regions of the world. The tender pods are rich in vitamins, minerals, fibre and other nutritional constituents and are consumed as a vegetable in various forms. The crop also has considerable commercial and export potential. Humic acid is an important component of organic matter and has been reported to improve plant growth by influencing physiological processes and enhancing nutrient availability and uptake. It can promote cell division and elongation and may improve the translocation of nutrients within the plant. Potassium nitrate (KNO₃) is a readily available source of nitrogen and potassium. Nitrogen promotes vegetative growth, while potassium plays an important role in enzyme activation, water regulation, photosynthesis, translocation of assimilates, fruit development and produce quality. Foliar application of humic acid and potassium nitrate may therefore improve nutrient utilization and physiological efficiency, resulting in better vegetative growth, flowering, fruit development, yield and quality of okra. However, the response of the crop may vary with the concentration and combination of foliar-applied nutrients, cultivar and prevailing environmental conditions. Hence, identification of suitable concentrations and combinations of humic acid and potassium nitrate is essential for obtaining optimum crop performance. Therefore, the present investigation entitled "Effect of foliar application of humic acid and potassium nitrate on growth, yield and quality of okra (Abelmoschus esculentus L.) cv. PDKV Pragati". was undertaken to evaluate their effect on growth, yield and quality attributes of okra and to identify suitable foliar application treatments for improved crop productivity.

Materials and Methods

The present investigation entitled "Effect of foliar application of Humic acid and potassium nitrate on growth, yield and quality of okra" was carried out during the kharif season of the year 2025-26 at the Experimental Unit, Horticultural Section, College of Agriculture, Nagpur. The experiment was laid out in a Factorial Randomized Block Design with Factor (A) comprising four concentration of Humic acid [H₁-Water spray (Control), H₂-1%, H₃-2% and H₄-3%] and Factor (B) comprising four concentration of potassium nitrate [P₁-water spray (Control), P2-1%, P3-1.5%, P4-2%], with sixteen treatment combinations replicated thrice. The experiment was carried out on a flat bed with a gross plot size of 3.6 m × 3 m. Healthy seeds were sown in the main field at a spacing of 60 cm × 45 cm. The recommended dose i.e. 100:50:50 NPK kg ha -1 of fertilizers while, half dose N and full dose of P & K and reaming N was uniformly applied to all the experimental plots to supply essential nutrients. Observations on vegetative growth parameters, viz., plant height, plant spread, branches plant⁻¹, number of internode on main stem, internodal length, days to first flower emergence, and 50 percent flowering were recorded.

Results

Growth parameters Effect of Humic acid

Foliar application of Humic acid significantly influenced the vegetative growth of okra. Humic acid significantly influenced plant height, plant spread and number of branches on main at 60 and 90 DAS. The maximum plant height was recorded with 1% humic acid (H₂), measuring 85.40 cm at 60 DAS and 151.20 cm at 90 DAS, whereas the minimum (121.10 cm) was observed under water spray at 90 DAS. at 60 and 90 DAS. The highest plant spread was recorded with 1% humic acid (H₂), with 39.77 cm at 60 DAS and 46.89 cm at 90 DAS, while the lowest (35.21) was recorded with water spray (H1) at 90 DAS. Number of branches plant -1 at 60 and 90 DAS. The maximum number of branches was recorded with 1% humic acid (H₂), i.e. 7.00 at 60 DAS and 8.40 at 90 DAS, compared with 5.50 and 6.80, respectively, under water spray. number of internodes at 50% flowering. The maximum number of internodes (10.30) was recorded with 1% humic acid (H₂), followed by 2% and 3% humic acid, while the minimum (8.69) was recorded under water spray. The maximum internodal length (10.52 cm) was recorded with 1% humic acid (H₂), followed by 2% (10.39 cm) and 3% (10.23 cm), whereas the minimum (9.29 cm) was recorded under water spray. Days to first flower emergence significantly influenced flowering. The earliest first flower emergence (39.61 days) was recorded with 1% humic acid (H₂), whereas the latest (41.94 days) was recorded under water spray. The earliest 50% flowering (46.09 days) was recorded with 1% humic acid (H₂), followed by 2% (46.63 days) and 3% (46.75 days), while the latest (47.83 days) was recorded under water spray.

Effect of potassium nitrate

Potassium nitrate significantly influenced plant height,plant spread and number of branches on main stem at 60 and 90 DAS. The maximum plant height was recorded with 1.5% potassium nitrate (P₃), with 83.76 cm at 60 DAS and 150.68 cm at 90 DAS, whereas the minimum was recorded under water spray. At 60 and 90 DAS the highest plant spread was recorded with 1.5% potassium nitrate (P₃), measuring 37.74 cm at 60 DAS and 46.81 cm at 90 DAS, while the lowest was observed under water spray. at 60 and 90 DAS The maximum number of branches was recorded with 1.5% potassium nitrate (P₃), with 7.15 and 8.44 branches plant⁻¹, respectively, whereas the minimum was recorded under water spray. the number of internodes on the main stem, with the highest number recorded under 1.5% potassium nitrate (P₃) and the lowest under water spray.The highest mean internodal length (10.41 cm) was recorded with 1.5% potassium nitrate (P₃), followed by 1% and 2% potassium nitrate (10.05 cm each), while the lowest (9.78 cm) was observed under water spray. The minimum number of days (39.76 days) was recorded with 1.5% potassium nitrate (P₃), followed by 1% (40.21 days) and 2% (40.74 days), while the maximum (42.37 days) was recorded under water spray. The earliest 50% flowering (45.28 days) was recorded with 1.5% potassium nitrate (P₃), followed by 1% (46.45 days) and 2% (47.51 days), whereas the latest (48.04 days) was observed under water spray.

Interaction effect

The interaction between Humic acid and potassium nitrate significantly influenced plant height, plant spread and number of branches at 90 DAS and number of internode, internodal length at 50 percent flowering and first flower emergence and 50 percent flowering of okra. The application of 1% humic acid and 1.5% potassium nitrate at 90 DAS (H1P3) recorded the maximum plant height (156.74 cm), whereas the maximum plant spread (51.40 cm) was obtained with 1% humic acid and 1.5% potassium nitrate at 90 DAS and maximum number of branches (9.71) was recorded. The earlier first flower emergence (38.42days) was recorded with 1% humic acid and 1.5% potassium nitrate. Performance of these treatment combinations may be attributed to complementary effect of optimum humic acid concentration and potassium nitrate application.

Conclusion

From the present investigation, it can be concluded that foliar application of humic acid and potassium nitrate significantly improved the growth and flowering performance of okra.

Among the treatment combinations, 1% humic acid + 1.5% potassium nitrate (H₂P₃) was found to be the most effective, recording maximum plant height, plant spread, number of branches, number of internodes and internodal length, along with earlier first flower emergence and 50 percent flowering. Thus, H₂P₃ was identified as the most promising treatment for improving growth and promoting early flowering in okra under the conditions of the present investigation.

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