Effect of nano dap and urea phosphate on rabi onion

Introduction

Onion (Allium cepa L.), belonging to the family Alliaceae, is one of the oldest and most widely cultivated vegetable crops in the world. Commonly known as the "Queen of the Kitchen," it is an important condiment crop valued for its flavour, pungency, aroma and medicinal properties. Onion bulbs are rich in carbohydrates, proteins, minerals, vitamin C and bioactive compounds such as allicin, quercetin and organo-sulfur compounds, which exhibit antioxidant, antimicrobial, anti-inflammatory and anticancer properties (Randle et al., 2023) [18] . Globally, onion is cultivated on about 3.6 million hectares with an annual production of nearly 80 million metric tonnes. China is the leading producer, followed by India, while the Netherlands is the largest exporter of onion in the world (FAO, 2013) [9] . India is the world's second-largest onion producer. During 2024-25, onion was grown on 19.68 lakh hectares with a production of 307.67 lakh tonnes. Gujarat is one of the major onion-producing states, with 0.811 lakh hectares under cultivation and 2.62 million tonnes of production during 2025-26. Efficient nutrient management is essential for enhancing onion productivity. Due to its shallow and poorly branched root system, onion requires adequate nitrogen and phosphorus for optimum growth, bulb development and yield. However, conventional fertilizers often show low nutrient use efficiency because of nutrient losses, resulting in reduced fertilizer effectiveness and environmental pollution (Ghaffoor et al., 2003) [11] . Foliar application of nano-fertilizers offers an efficient alternative by supplying nutrients directly through the leaves, leading to rapid absorption, improved nutrient use efficiency and better crop performance. Nano DAP, with its controlled nutrient release, enhances plant growth and yield while minimizing nutrient losses and supporting sustainable onion production (Schwab et al., 2016) [20] . Nano-fertilizers are an eco-friendly and efficient alternative that enhance nutrient availability, improve fertilizer use efficiency and support sustainable crop production (Jakhar et al., 2022) [14] . Nano DAP contains 8.0% nitrogen (N w/v) and 16.0% phosphorus (P₂O₅ w/v), offering a concentrated source of essential nutrients that promotes healthy plant development, improves crop quality and contributes to higher productivity. Its efficient nutrient delivery and lower application requirement make nano DAP an economical alternative to conventional DAP. Moreover, its use can help reduce the excessive application of phosphatic fertilizers, thereby supporting more efficient nutrient management and minimizing potential environmental concerns (Chaudhary et al., 2023) [5] . Urea phosphate is a highly water-soluble fertilizer containing 17% nitrogen and 44% phosphorus (17-44-0). It provides readily available nitrogen and phosphorus, promoting vigorous root development, vegetative growth and improved nutrient uptake, particularly during the early growth stages of crops. Its acidic nature enhances phosphorus availability and improves the efficiency of other nutrients. It also helps prevent clogging of irrigation systems by dissolving bicarbonates and deposits, making it suitable for fertigation while improving crop growth and fertilizer use efficiency (Hussein et al., 2022) [13] .

Materials and Methods

The present investigation was undertaken at the Instructional Farm of the Department of Agronomy, Junagadh Agricultural University, Junagadh, Gujarat, during the rabi season of 2024-25. During the crop growth period, the maximum temperature ranged from 26.1°C to 41.1°C, while the minimum temperature varied from 12.1°C to 22.5°C. Relative humidity ranged from 65 to 78 per cent in the morning and from 22 to 30 per cent in the afternoon. Wind velocity varied between 4.6 and 7.4 km/h. No rainfall was received during the crop-growing period, with total rainfall recorded as 0.0 mm. The duration of bright sunshine ranged from 3.8 to 11.1 hours/day, whereas evaporation varied from 3.6 to 9.0 mm/day. The experimental soil was clayey in texture and had a pH of 7.7, electrical conductivity of 0.56 dS/ m at 25°C and organic carbon content of 0.48%. The soil contained 233.33 kg/ha of available nitrogen, 40.57 kg/ha of available phosphorus and 266.20 kg/ha of available potassium. The onion cultivar used in the experiment was GJRO-11 Gujarat Junagadh Red Onion-11 were transplanted on 3 rd December 2024 at a spacing of 15x10 cm using seed rate of 10 kg/ha with standard package of practices with 9 treatments and 3 replications. The treatments were as follows: T 1 (Absolute control), T 2 (100% RDF), T 3 (75% RDF + root dipping of onion seedling with nano DAP 5 ml/L), T 4 (50% RDF + Foliar spray of nano DAP 4 ml/L water at 45, 60 and 75 DAT), T 5 (75% RDF + Foliar spray of nano DAP 4 ml/L water at 45 and 60 DAT), T 6 (50% RDF + root dipping of onion seedling of Nano DAP 5 ml/L + Foliar spray of nano DAP 4 ml/L water at 45, 60 and 75 DAT), T 7 (75% RDF + root dipping of onion seedling of nano DAP 5 ml/L + Foliar spray of nano DAP 4 ml/L water at 60 and 75 DAT), T 8 (50% RDF + Foliar spray of Urea phosphate 2% at 30, 45 and 60 DAT), T 9 (75% RDF + Foliar spray of Urea phosphate 2% at 30, 45 and 60 DAT).

Results and Discussion

The highest plant height was recorded (45.47 cm) recorded under T₇ (75% RDF + root dipping of onion seedlings with Nano DAP @ 5 ml/L + foliar spray of Nano DAP @ 4 ml/L 60 and 75 DAT) may be attributed to improved nutrient availability and uptake through Nano DAP. Root dipping promoted better root establishment, while foliar application ensured timely nutrient supply during critical growth stages, resulting in enhanced cell division, elongation and photosynthetic activity. While foliar application at 60 and 75 DAT provides a quick nutrient supply during critical growth stages. Similar findings were reported by Dubey et al. (2023) [8] , Dhakar (2024) [6] and Yewale et al. (2024) [25] .

Number of Leaves per Plant at harvest

The application of 75% RDF + root dipping of onion seedling of nano DAP 5 ml/L + Foliar spray of nano DAP 4 ml/L water at 60 and 75 DAT (T 7 ) recorded significantly higher number of leaves per plant (10.56) at harvest which was found at par with treatments of T 5 (75% RDF + Foliar spray of nano DAP 4 ml/L water at 45 and 60 DAT), T 9 (75% RDF + Foliar spray of urea phosphate 2% at 30, 45 and 60 DAT), T 3 (75% RDF + root dipping of onion seedling with Nano DAP 5 ml/L) and T 2 (100% RDF) in respect of No. of leaves per plant at harvest. Results were in conformity with the findings obtained by Anup et al. (2022) [1] , Chamuah et al. (2023) [4] , Dubey et al. (2023) [8] and Dobariya (2025) [7] .

The treatment T 7 (75% RDF + root dipping of onion seedlings in nano DAP 5 ml/L + foliar spray of nano DAP 4 ml/L at 60 and 75 DAT) exhibited the maximum equatorial bulb diameter (55.74 mm) and polar diameter (43.27 mm). Application of Nano DAP improved bulb development by enhancing chlorophyll content, photosynthate production, nutrient uptake and phosphorus availability. It also promoted enzymatic activity and hormonal balance, resulting in better bulb expansion and growth. The present findings corroborated the results reported by Samiksha et al. (2024) [19] , Haripriya et al. (2025) [12] , Talpur et al. (2025) [24] and Sudarshan et al. (2026) [23] .

The treatment T 7 (75% RDF + root dipping of onion seedlings in nano DAP 5 ml/L + foliar spray of nano DAP 4 ml/L at 60 and 75 DAT) Displayed the greatest value of neck thickness of bulb (11.23 mm) at harvest. Foliar application of Nano DAP enhanced chlorophyll content, photosynthetic activity and nutrient use efficiency, leading to better assimilate accumulation and increased neck thickness. Similar findings were reported by Anup et al. (2022) [1] , Garg (2023) [10] , Dubey et al. (2023) [8] , Balamurugan et al. (2024) [2] and Haripriya et al. (2025) [12] .

Effect on yield attributes and yield parameters

Average bulb weight at harvest (kg) Application of T 7 (75% RDF + root dipping of onion seedling of nano DAP 5 ml/L + Foliar spray of nano DAP 4 ml/L water at 60 and 75 DAT) gave higher average bulb weight (63.68 gm). The findings are in agreement with those reported by Obiadalla-Ali et al. (2022) [17] , Garg (2023) [10] and Sudarshan et al. (2026) [23] .

Bulb Yield (kg/ha) Higher bulb yield under T 7 (75% RDF + root dipping of onion seedling of nano DAP 5 ml/L + Foliar spray of nano DAP 4 ml/L water at 60 and 75 DAT) was This effect was likely associated with enhanced nutrient uptake and efficient nutrient delivery through root dipping and foliar application of nano DAP. Root dipping of seedlings with nano DAP promoted better root development and initial growth, enhancing nutrient absorption. Moreover, foliar application at 60 and 75 DAT provided an immediate supply of nitrogen and phosphorus during the crucial bulb formation stage. This continuous and balanced nutrient availability improved photosynthetic efficiency, dry matter production and the translocation of assimilates towards bulb development, thereby resulting in higher bulb yield. These findings are in agreement with results obtained by Obiadalla-Ali et al. (2022) [17] , Garg (2023) [10] and Sudarshan et al. (2026) [23] .

Significantly higher dry matter yield of onion leaves (965 kg/ha) was registered with treatment T 7 (75% RDF + root dipping of onion seedling of nano DAP 5 ml/L + Foliar spray of nano DAP 4 ml/L water at 60 and 75 DAT) and T 1 (Absolute control) produced the lowest Dry matter yield of onion leaves (780 kg/ha).

It may be due to the balanced and timely supply of nitrogen and phosphorus through RDF and Nano DAP, which enhanced chlorophyll content and photosynthetic activity. This resulted in increased synthesis and accumulation of carbohydrates and other assimilates, promoting vigorous leaf growth and higher biomass production. Similar findings were reported by Bolashetti et al. (2023) [3] , Garg (2023) [10] and Sudarshan et al. (2026) [23] .

The higher marketable bulb yield observed under treatment T 7 may be attributed to the combined effect of 75% RDF and foliar application of nano DAP which facilitated improved nutrient supply and efficient nutrient absorption during critical crop growth stages. This enhanced supply of nitrogen and phosphorus likely promoted better vegetative growth and increased accumulation of assimilates, which were effectively translocated towards bulb development, resulting in improved bulb size and marketable yield. In contrast, the lowest marketable bulb yield recorded. These findings are in accordance with the results reported by Balamurugan et al. (2024) [2] , Singh et al. (2025) [21] and Sudarshan et al. (2026) [23] .

Economics

Gross Returns

Treatment T₇ (75% RDF + root dipping of onion seedlings with Nano DAP @ 5 ml/L+ foliar spray of Nano DAP @ 4 ml/L at 60 and 75 DAT) Registered the highest gross return (2,57,501 ₹/ha), followed by T₅ (2,46,586 ₹/ha) while the lowest gross return (1,76,451 ₹/ha) was observed under T₁ (absolute control). The higher gross return under T₇ was attributed to increased bulb yield and improved nutrient use efficiency, resulting in higher marketable yield and profitability. Similar results were reported by Koushik (2022) [15] , Singh et al. (2023) [22] , Dhakar (2024) [6] and Malwade et al. (2025) [16] .

Net Returns

The highest net return (1,75,278 ₹/ha) was recorded under T₇ (75% RDF + root dipping of onion seedlings with Nano DAP @ 5 ml/L+ foliar spray of Nano DAP @ 4 ml/L at 60 and 75 DAT), followed by T₅ (1,64,501₹/ha), whereas the lowest net return (1,06,306₹/ha) was observed under T₁ (absolute control). The higher net return under T₇ was mainly attributed to higher bulb yield, superior bulb quality and improved nutrient use efficiency, which enhanced market value and overall profitability. These findings are in agreement with those reported by Koushik (2022) [15] , Singh et al. (2023) [22] and Malwade et al. (2025) [16] .

Benefit: Cost Ratio (BCR)

The data pertaining to the benefit: cost ratio of the different treatments are presented in Table 4.18. Among the treatments, T 7 (75% RDF + root dipping of onion seedlings with nano DAP @ 5 ml/L + foliar application of nano DAP @ 4 ml/L at 60 and 75 DAT) recorded the highest 3.13, followed by T 5 (75% RDF + foliar application of nano DAP @ 4 ml/L at 45 and 60 DAT), which was 3.00. It may be attributed to the greater bulb yield obtained with this treatment in relation to its comparatively favourable cost of cultivation. The present findings are in agreement with those reported by Koushik (2022) [15] , Singh et al. (2023) [22] and Malwade et al. (2025) [16] .

Conclusion

On the basis of the results obtained from the present one-year field study, it can be concluded that to achieve optimum growth and higher bulb yield along with higher net realization of onion, with Under medium black calcareous soils of the South Saurashtra Agro-climatic Zone, the The crop should be treated with 75% RDF + root dipping of onion seedlings of nano DAP 5 ml/L, followed by foliar application of nano DAP @ 4 ml/L at 60 and 75 DAT.

Acknowledgement

AcknowledgementThe authors are highly thankful to the agronomy department, College of Agriculture, Junagadh Agricultural University, Junagadh, for providing the experimental field, laboratory facilities and technical guidance throughout the study. The authors also extend their sincere thanks to the faculty members, technical staff and farm workers for their valuable assistance during field experimentation, data collection and laboratory analysis.

References

1. Anup PS, Vijay B, Rajneesh S, Gaurav PS, Bhanu PS, Singh AP. Effect of zinc oxide and iron oxide nanoparticles on growth, yield and quality traits of onion (Allium cepa L.). The Pharma Innovation Journal. 2022;11(10):1722-1726.
2. Balamurugan P, Shinde S, Patil B, Durgude A, Dahatonde K. Effect of nano urea on yield and benefit cost ratio of onion in Kharif cv. Phule Samarth. International Journal of Advanced Biochemistry Research. 2024;8(10):833-837.
3. Bolashetti S, Hilli JS, Uppar DS, Hiremath SM. Influence of foliar nutrition through nano urea and boron on plant growth characters and seed yield in onion (Allium cepa L.). The Pharma Innovation Journal. 2023;12(10):1343-1346.
4. Chamuah S, Gogoi S, Dutta S, Bhattacharjee D, Sharma S, Das K. Impact of nano DAP on growth and development of cabbage. International Journal of Environment and Climate Change. 2023;13(12):1298-1304.
5. Chaudhary S, Singh R, Meena VS. Nanofertilizers for improving nutrient use efficiency and crop productivity. Journal of Soil Science and Plant Nutrition. 2023;23(2):1587-1602.
6. Dhakar A. Effect of nano fertilizers on growth, yield and quality of garlic (Allium sativum L.). Jhalawar, Rajasthan, India: College of Horticulture and Forestry, Agriculture University, Kota; 2024.
7. Dobariya M. Impact of nano DAP on growth, yield and quality of summer pearl millet. Junagadh, Gujarat, India: Junagadh Agricultural University; 2025.
8. Dubey PM, Upadhyay J, Chowdhury S, Bagare V. Response of onion (Allium cepa L.) to foliar application of nano urea and urea. International Journal of Environment and Climate Change. 2023;13(11):1816-1821.
9. Food and Agriculture Organization of the United Nations. Good agricultural practices for onion production. Rome, Italy: Food and Agriculture Organization of the United Nations; 2013.
10. Garg J. Studies on conjoint applications of conventional and nano-fertilizers in garlic. Solan, Himachal Pradesh, India: Dr. Yashwant Singh Parmar University of Horticulture and Forestry; 2023.
11. Ghaffoor A, Jilani MS, Khaliq G, Waseem K. Effect of different NPK levels on the growth and yield of onion (Allium cepa L.). Asian Journal of Plant Sciences. 2003;2(3):342-346.
12. Haripriya T, Lavanya R, Preetham G, Veena J. Effect of foliar application of nano urea plus on growth and yield of onion (Allium cepa L.) under Telangana conditions. Plant Archives. 2025;25(2):2771-2776.
13. Hussein MM, El-Sayed SAA, El-Mogy MM. Effect of fertigation with urea phosphate on growth, nutrient uptake and productivity of vegetable crops under drip irrigation. Journal of Plant Nutrition. 2022;45(6):889-901.
14. Jakhar AM, Aziz I, Kaleri AR, Hasnain M, Haider G, Abideen Z. Nano-fertilizers: a sustainable technology for improving crop nutrition and food security. NanoImpact. 2022;27:100411.
15. Malwade SS, Thaokar AK, Gawali A, Sarda A, Deshmukh P, Satwadhar A, et al. Economic and soil chemical impact of nano DAP with varied fertilizer levels in soybean production. International Journal of Advanced Biochemistry Research. 2025;9(7):1440-1443.
16. Obiadalla-Ali HA, El-Shaikh KAA, Marey RA. Effect of mineral (NPK) rates and injection with nano NPK on growth, yield and quality of onion. Journal of Sohag Agriscience. 2022;7(2):60-76.
17. Randle WM, Routledge HY. Onions. In: Processing vegetables. 2023. p. 209-228.
18. Samiksha DA, Bahadur VJ, Topno V. Effect of nanofertilizer and nano mixed micronutrients for yield and quality of onion (Allium cepa L.). International Journal of Advanced Biochemistry Research. 2024;8(2):454-457.
19. Schwab F, Zhai G, Kern M, Turner A, Schnoor JL, Wiesner MR. Barriers, pathways and processes for uptake, translocation and accumulation of nanomaterials in plants: critical review. Nanotoxicology. 2016;10(3):257-278.
20. Singh J, Singh Y, Singh GK, Chauhan A. Effect of nano urea and nano DAP alone and with different levels of N and P on growth and yield of broccoli (Brassica oleracea L.). International Journal of Advanced Biochemistry Research. 2025;9(8):1653-1655.
21. Singh YK, Singh BV, Katiyar D, Saikanth DRK, Kumar K, Singh O, et al. Efficacy of nano fertilizers on yield, attributes and economics of wheat. International Journal of Environment and Climate Change. 2023;13(7):291-297.
22. Sudarshan DB, Raghunatha RL, Sood M. Integrative effects of nano and conventional fertilizers on performance and economics of onion (Allium cepa L.). International Journal of Research in Agronomy. 2026;9(1):563-568.
23. Talpur NA, Jamali IA, Arain JA, Solangi AR, Depar N. Growth, yield and zinc accumulation of onion in relation to varying application rates of chemical and nano zinc fertilizers. Pakistan Journal of Botany. 2025;57(6):20752080.
24. Yewale SV, Ugale NS, Danawale NJ, Ghodke SK, Patil MR, Bodake PS. Response of foliar spray of nano DAP and nutrients on growth, yield and quality of chickpea (Cicer arietinum L.). International Journal of Research in Agronomy. 2025;8(1):306-310.