Soil Application of Calcium, Zinc and Boron as a Safer Alternative to Foliar Application for Fruit Nutritional Quality and Human Health

Sajid Farid¹, Saadia Razzaq², Maryam Sajid³, Ruhma Sajid⁴

¹ Head of Farm Advisory Centre, FFC Pakistan.  

² Associate Professor, Department of Education, Islamabad Model College for Girls, Islamabad, Pakistan.

³ Student, Islamic International Dental College, Riphah International University, Islamabad, Pakistan.

⁴ Student, Foundation University Medical College, FUSH, Pakistan. 

Abstract

Calcium (Ca), zinc (Zn), and boron (B) are essential plant nutrients that play critical roles in cell wall stability, membrane integrity, enzyme activation, hormonal regulation, pollen tube growth, fruit set, and postharvest quality. These nutrients are supplied to crops through soil and foliar application methods, each influencing nutrient uptake, translocation, and accumulation differently. Foliar application is widely used for rapid correction of deficiencies; however, several experimental studies across crops such as tomato, citrus, strawberry, and plum have demonstrated that excessive or repeated foliar sprays can lead to localized nutrient accumulation, leaf burn, fruit surface residues, and phytotoxicity, particularly in the case of boron due to its narrow deficiency-to-toxicity range. In contrast, soil application delivers nutrients through the root system, enabling gradual uptake regulated by plant physiological demand and soil buffering capacity, resulting in more balanced distribution among roots, stems, leaves, and fruits.

Global research indicates that soil-applied Ca, Zn, and B significantly improve crop growth, fruit firmness, yield, and nutritional quality under recommended doses. For instance, soil application of Zn and B in citrus increased fruit retention and yield, while boron application in cotton and tomato improved reproductive development and fruit quality when applied within optimal ranges. In contrast, foliar treatments often produce rapid increases in tissue nutrient concentration, which, although beneficial under deficiency conditions, may elevate the risk of excessive accumulation in edible plant parts if not carefully managed.

From a food safety perspective, this distinction is critical. While Ca, Zn, and B are essential micronutrients for human health, excessive intake may result in adverse physiological effects. The tolerable upper intake level for zinc is approximately 40 mg/day, whereas boron intake should generally not exceed 20 mg/day in adults (National Institutes of Health). Therefore, uncontrolled nutrient enrichment through repeated foliar application may have implications for dietary exposure and long-term health risk.

Overall, evidence suggests that soil application provides a safer and more sustainable nutrient management strategy by promoting controlled uptake, internal partitioning, and reduced risk of excessive nutrient accumulation in fruits. Foliar application should be considered a supplementary practice for targeted deficiency correction rather than a primary fertilization approach. Integrated nutrient management, combining soil-based fertilization with carefully regulated foliar interventions, is recommended to optimize crop productivity, fruit quality, and human health safety.     

Keywords: Calcium, Zinc, Boron, Soil application, Foliar application, Nutrient partitioning, Fruit quality, Phytotoxicity, Food safety, Micronutrient toxicity

References

1. Abalist, R.O. and Ukoroije, R.B. (2026) ‘Levels and health risks of heavy metals in Oryctes owariensis larvae from gas-flaring communities in Rivers State’, International Journal of Technology, Health and Sustainability, 2(1), pp. 346-350. https://ijths.com/wp-content/uploads/S-No-49-IJTHS-020193.pdf
2. Ahmed, N., Abid, M., Ahmad, F., et al. (2008) ‘Boron toxicity in irrigated cotton (Gossypium hirsutum L.)’, Pakistan Journal of Botany, 40(6), pp. 2443–2452.
3. Alila, P., Gitari, H.I., Musyoka, M.W., et al. (2023) ‘Boron nutrition in horticultural crops: Constraint diagnosis and management’. In: Boron in plants and agriculture: Exploring the physiology of boron and its impact on plant growth; Aydin, M. IntechOpen.
4. Alloway, B.J. (2008) Zinc in soils and crop nutrition. 2^nd ed. International Zinc Association and International Fertilizer Industry Association.
5. Álvarez-Herrera, J.G., Jaime-Guerrero, M. and Fischer, G. (2025) ‘The effect of boron on fruit quality: A review’, Horticulturae, 11(8), 992. https://doi.org/10.3390/horticulturae11080992
6. Broadley, M.R., White, P.J., Hammond, J.P., et al. (2007) ‘Zinc in plants’, New Phytologist, 173(4), pp. 677–702.
7. Brown, P.H. and Shelp, B.J. (1997) ‘Boron mobility in plants’, Plant and Soil, 193, pp. 85–101.
8. Farid, S. and Razzaq, S. (2026) ‘Rectifying calcium deficiency in plants through soil and foliar application in calcareous soils: A global review’, International Journal of Technology, Health and Sustainability, 2(2), pp. 602–611. https://ijths.com/wp-content/uploads/IJTHS-0202028.pdf
9. Farid, S., Razzaq, S. and Sajid, M. (2026) ‘Impact of balanced use of fertilizer on crop production and its quality for human health’, International Journal of Technology, Health and Sustainability, 2(1), pp. 29-38. https://ijths.com/wp-content/uploads/IJTHS-020143.pdf
10. Fernández, V. and Eichert, T. (2009) ‘Uptake of foliar-applied nutrients: Mechanisms and factors influencing efficiency’, Journal of Experimental Botany, 60(1), pp. 37–49.
11. Haleema, B., Rab, A. and Hussain, S.A. (2018) ‘Effect of calcium, boron and zinc foliar application on growth and fruit production of tomato’, Sarhad Journal of Agriculture, 34(1), pp. 19–30. https://doi.org/10.17582/journal.sja/2018/34.1.19.30
12. Ibrahim, H.K.M., El-Hefnawi, N.N., Arafa, M.M.A., et al. (2021) ‘Effect of foliar application with calcium, boron and zinc on the yield and quality of strawberry fruits and post-harvest diseases’, Journal of Environmental Studies and Researches, 11(2), pp. 300–314.
13. Khan, M.M.H., Ahmed, N., Naqvi, S.A.H., et al. (2022) ‘Synchronization of zinc and boron application methods and rates for improving the quality and yield attributes of Mangifera indica L. on sustainable basis’, Journal of King Saud University – Science, 34, 102280. https://doi.org/10.1016/j.jksus.2022.102280 
14. Mal, S., Sarkar, D., Mandal, B., et al. (2025) ‘Improving quality of tomato (Solanum lycopersicum L.) fruits for fresh consumption and processing with optimised boron application’, Journal of Food Composition and Analysis, 140, 107255. https://doi.org/10.1016/j.jfca.2025.107255 
15. Marschner, P. (2012) Marschner’s mineral nutrition of higher plants. 3^rd ed. Academic Press.
16. Nable, R.O., Bañuelos, G.S. and Paull, J.G. (1997) ‘Boron toxicity’, Plant and Soil, 193, pp. 181–198.
17. Nielsen, F.H. (2014) Update on human health effects of boron’, Journal of Trace Elements in Medicine and Biology, 28(4), pp. 383–387. https://doi.org/10.1016/j.jtemb.2014.06.023   
18. NIH (2022) Boron: Fact sheet for health professionals. National Institutes of Health, Office of Dietary Supplements, U.S. Department of Health and Human Services.
19. NIH (2025) Calcium: Fact sheet for health professionals. National Institutes of Health, Office of Dietary Supplements, U.S. Department of Health and Human Services.
20. NIH (2026) Zinc: Fact sheet for health professionals. National Institutes of Health, Office of Dietary Supplements, U.S. Department of Health and Human Services.
21. Noor, Y., Shah, Z. and Tariq, M. (2019) Effect of zinc and boron using different application methods on yield of citrus (Sweet orange) in calcareous soils’, Sarhad Journal of Agriculture, 35(4), pp. 1247–1258. https://doi.org/10.17582/journal.sja/2019/35.4.1247.1258
22. Qamar, R., Hussain, A., Sardar, H., et al. (2020) ‘Soil applied boron (B) improves growth, yield and fiber quality traits of cotton grown on calcareous saline soil’, PLOS ONE, 15(8), e0231805. https://doi.org/10.1371/journal.pone.0231805
23. Roy, R.N., Finck, A., Blair, G.J., et al. (2006) Plant nutrition for food security: A guide for integrated nutrient management. FAO Fertilizer and Plant Nutrition Bulletin No. 16, Food and Agriculture Organization of the United Nations.
24. Sajid, M., Rab, A., Ali, N., et al. (2010) ‘Effect of foliar application of Zn and B on fruit production and physiological disorders in sweet orange cv. Blood Orange’, Sarhad Journal of Agriculture, 26(3), pp. 355–360.
25. Salman, M., Ullah, S., Razzaq, K., et al. (2022) ‘Combined foliar application of calcium, zinc, boron and time influence leaf nutrient status, vegetative growth, fruit yield, fruit biochemical and anti-oxidative attributes of “Chandler” strawberry’, Journal of Plant Nutrition, 45(12), pp. 1837–1850. https://doi.org/10.1080/01904167.2022.2035759
26. White, P.J. and Broadley, M.R. (2003) ‘Calcium in plants’, Annals of Botany, 92(4), pp. 487–511.
27. WHO (1998) Boron. Environmental Health Criteria 204. World Health Organization.
28. Wójcik, P. and Wójcik, M. (2003) ‘The effect of calcium and boron foliar application on postharvest plum fruit quality’, Acta Horticulturae, 594, pp. 445–451. https://doi.org/10.17660/ActaHortic.2002.594.57
29. Xu, W., Wang, P., Yuan, L., et al. (2021) ‘Effects of application methods of boron on tomato growth, fruit quality and flavor’, Horticulturae, 7(8), 223. https://doi.org/10.3390/horticulturae7080223   
30. Zhang, Y., Hu, C., Tan, Q., et al. (2015) ‘Soil application of boron and zinc influence fruit yield and quality of Satsuma mandarin in acidic soils’, Agronomy Journal, 107(1), pp. 1–8. https://doi.org/10.2134/agronj14.0122