Effect of urea spray accordance with growth phenology on yield and alternate ‎bearing of satsuma mandarin (Citrus unshiu)‎

Document Type : Full Paper


1 Assistant Professor, Soil and Water Research Department, Mazandaran Agricultural and Natural Resources Research and ‎Education Center, AREEO, Sari, Iran

2 Assistant Professor, Agronomy and Horticultural Science Department, Mazandaran Agricultural and Natural Resources Research ‎and Education Center, AREEO, Sari, Iran


To increase yield and reduce alternate bearing of satsuma mandarin trees, an experiment was performed in randomized complete block design during seven years. Treatments include: control; winter urea spraying (before flower bud differentiation); urea spraying at full bloom (at the opening of at least 50% of flowers) and summer urea spraying (after summer physiological abscission of fruitlets). Results showed that yield difference between “on” and “off” years in the first and second years was very high as from 94.19 kg for each tree in the first (on) year reached to 13.69 kg in the second (off) year which had about 80 kg difference. But yield difference in following “on” and “off” years (third and fourth years of experiment) reach to about 40 kg that was about half of previous alternate bearing cycle. Therefore, urea spraying adjusts alternate bearing during years of experiment, gradually. Treatments of urea spraying had significant difference on cumulative yield at 5% as the highest obtained from control and at flowering spray treatments. Also, effect of different urea treatments on alternate bearing index was significant. Control trees, had the most alternate bearing index and winter and spring spray treatments had the least alternate bearing index. All urea spray treatments increased fruit average weight compare to control. Therefore, based on the results of this project to modulate alternate bearing, winter and spring spraying of urea recommended.


  1. Ahyaee, M. & Behbahanizadeh, A. (1997). Methods of soil chemical analysis. Publication 1024, Soil and Water Institute, Tehran, Iran. (in Farsi)
  2. Albrigo, L.G. (1999). Effects of foliar applications of urea or nutriphite on flowering and yields of Valencia orange trees. In: Proceedings of the Florida State Horticultural Society, 112, 1- 4.
  3. Ali, A.G. & Lovatt, C.J. (1992). Winter application of foliar urea. Citrograph, 78(2), 7-9.
  4. Ali, A.G. & Lovatt, C.J. (1994). Winter application of low biuret urea to the foliage of Washington navel orange increased yield. Journal of the American Society for Horticultural Science, 119, 1144-1150.
  5. Ali, A.G. & Lovatt, C.J. (1995). Relationship of polyamines to low-temperature stress-induced flowering of the Washington navel orange. Journal Horticultural Science, 70, 491-498.
  6. Anonymous. (2015). Introduction and production of citrus cultivars and commercial rootstocks. J. No. 9441, National Citrus Research Institute, Agricultural Research, Education and Promotion Organization, Tehran, Iran. (in Farsi)
  7. Arias, M., Carbonell, J. & Agusti, M. (2005). Endogenous free polyamines and their role in fruit set of low and high parthenocarpic ability citrus cultivars. Journal of Plant Physiology, 162,845-853.
  8. Arzani, K. & Akhlaghi Amiri, N. (2000). Size and quality of Satsuma mandarin (Citrus unshiu)as affected by 2,4-D and NAA. Journal of Seed and Plant, 16(4), 450-459. (in Farsi)
  9. Asadi Kangarshahi, A., Savaghebi, Gh.R. & Akhlaghi Amiri, N. (2011). Reducing of citrus alternate bearing by managing of nitrogen using and pruning in East of Mazandaran, Iranian Journal of Horticultural Science, 42(3), 217-225. (in Farsi)
  10. Asadi Kangarshahi, A. (2019). Nutition Management of Citrus Trees (1th ed). Agricultural Extension and Education Publications. (in Farsi)
  11. Asadi Kangarshahi, A. & Akhlaghi Amiri, N. (2014 a). Advanced and Applied Citrus Nutrition. (1sted.). Agricultural Extension and Education Publications. (in Farsi)
  12. Asadi Kangarshahi, A. & Akhlaghi Amiri, N. (2014 b). Advanced and Applied Citrus Nutrition (1th ed). Agricultural Extension and Education Publications. (in Farsi)
  13. Asadi Kangarshahi, A., Basirat, M., Akhlaghi Amiri, N., Hghigatnia, H., Sheykh Ashkevari, A.R., Salimpour, S., Sabbah, A., Shahabiyan, M., Saleh, J., Ghasemi, O. & Rejali, F. (2017). Guidelines for integrated soil fertility and plant nutrition management of citrus trees in the north and south of the country. Soil and Water Research Institute, Theran, Iran. (in Farsi)
  14. Bondada, B.R., Syvertsen, J.P. & Albrigo, L.G. (2001). Urea nitrogen uptake by citrus leaves. HortScience, 36, 1061-1065.
  15. Corona, J.C. (1994). Relationship of polyamines to fruit set and growth of the Washington navel orange. MS thesis, University of California Riverside.
  16. El-Otmani, M., Ait-Oubahou, A., Zahra, F. & Lovatt, C.J. (2002). Efficacy of foliar urea as N source in sustainable citrus production systems. Acta Horticulturae, International Symposium on Foliar Nutrition of Perennial Fruit Plants, 594, 611-617.
  17. Emami, A. (1996). Methods of plant analysis. Publication 982. Soil and Water Institute, Tehran, Iran. (in Farsi)
  18. Fichtner, E., Chao, Y.Y., Verreynne, J.S., Tang, L., Ferguson, L. & Lovatt, C.J. (2017). Repeating cycles of on and off yields in alternate bearing olive, pistachio and citrus, different mechnisms, common soulution. 1st International Horticultural Science Conference of Iran, September 4-7, Tarbiat Modares University, Tehran, Iran.
  19. Goldschmidth, E.E. (2005). Regulatory aspects of alternate bearing in fruit tree. Italus Hortus, 12, 11-17.
  20. Hamid, G.A., VanGundy S.D. & Lovatt, C.J. (1988). Phenologies of the citrus nematode and citrus roots treated with oxamyl. In: Proceeding ofthe 6th International Citrus Congress, 2, 993-1004.
  21. Lovatt, C.J. (1999). Timing citrus and avocado foliar nutrient application to increase fruit set and size. Hortechnology, 9, 607-612.
  22. Lovatt, C.J., Sagee, O. & Ali, A.G. (1992). Ammonia and its metabolites influence flowering, fruit set and yield of Washington Navel orange. In: Proceedings of the International Society of Citriculture, 1, 412-416.
  23. Lovatt, C.J., Zheng, Y. & Hake, K.D. (1988a). Demonstration of a change in nitrogen metabolism influencing flower initiation in citrus. Israel Botanists, 37(3/4), 181-188.
  24. Lovatt, C.J., Zheng Y. & Hake, K.D. (1988b). A new look at the Kraus-Kraybill hypothesis and flowering of citrus. In: 6th International Citrus Congress, 1, 475-483.
  25. Mazhar, M. S., Anwar, R. & Maqbool, M. (2007). A review of alternate bearing in citrus. In: Proceedings of International Symposium on Prospects of Horticultural Industry in Pakistan, 143-149.
  26. Monselise, S.P. & Goldschmidt, E.E. (1982). Alternate bearing in fruit trees. In: Horticultural reviews, AVI Publishing Company, 4, 128-174.
  27. Monselise, S.P., Goldschmidt, E.E. & Golomb, A. (1981). Alternate bearing in citrus and ways of control. In: Proceeding of International Society of Citriculture, 1, 239-242.
  28. Raiesi, T. & Moradi, B. (2018). The effect of urea foliar spray time on yield and fruit quality of 'Thomson Navel' sweat orange trees. Iranian Journal of Horticultural Science. 50(2), 349-359. (in Farsi).
  29. Rabe, E. (1994). Yield benefits associated with pre-blossom low biuret urea sprays on citrus spp. Journal of Horticultural Science, 69, 495-500.
  30. Reuther, W. & Smith, P.F. (1954). Leaf analysis of citrus. In: N.F. Childers (Ed), Fruit nutrition. (pp. 257- 294) Rutgers University, New Jersey.
  31. Sagee, O. & Lovatt, C.J. (1991). Putrescine concentration parallels ammonia and arginine metabolism in developing flowers of Washington navel orange. Journal of the American Society for Horticultural Science, 116, 280-285.
  32. Saleem, B.A., Malik, A., Maqbool, M., Din, I., Farooq, M. & Rajwana, I.A. (2008). Early winter spray of low biuret urea improves marketable yield and fruit quality of sweet oranges. Pakistan Journal of Botany, 40(4), 1455-1465.
  33. Schalk, I. (2012). Studies on the phenology and carbohydrate status of alternate bearing mandarin trees. Thesis M.Sc., Stellenbosch University, USA.
  34. Young, Y. & Kwangchool, K. (1997). Effects of pre- and post-harvest foliar spray of urea on the flowering and fruit setting Satsuma mandarin. Journal of Korean Society for Horticultural Science, 38, 227-233.