November 22, 2018 9:48 am Published by KirstyH

Zinc (Zn) is an essential micronutrient for both plants and humans.

It is the most deficient micronutrient in the soil worldwide. It has been estimated that 49% of the world’s agriculturally important soils have inadequate levels of zinc and that one third of the worlds human population suffers from zinc deficiency (Sillanpää, 1990; Cakmak et al., 2010).

As with other cereals, zinc deficiency limits rice growth and yield (Chaudhary et al. 2007).

The main factors responsible for causing zinc deficiency in staple food crops, such as rice are soil related. They include; low zinc total value in the soil, high pH, high calcite content, high concentration of bicarbonate ions and salts and high levels of available phosphorous (Figure 2).

The most important factors affecting zinc availability to crops can be noted as follows (Chang et al., 2007; Alloway, 2008; Sillanpaa, 1990):

  • Zinc total value may be very low in highly acidic soils due to the intense soil leaching.
  • Zinc availability decreases with increasing soil pH. This is because the solubility of minerals, which help zinc uptake is reduced. These ‘uptake facilitators’ include coil colloidal particles such as clay minerals, iron and aluminium oxides, organic matter and calcium carbonate.
  • Zinc usability decreases with temperature and light intensity due to limited root development.
  • Zinc usability is decreased by high levels of phosphorous in the soil.
  • Zinc uptake by plants is inhibited by some metal cations such as Cu²+ and Fe²+ because they all use the same transport mechanisms to enter the plant roots.

The sources of phosphorous and cations limiting the availability of zinc to the crop are; excessive phosphorous fertilizer applications, inherent soil minerals and irrigation water.

Availability of zinc in submerged soils is decreased due to the formation of complexes and compounds such as insoluble franklinite (ZnFe2O4), insoluble ZnS, insoluble ZnCO3, and insoluble Zn (OH)2 (Brar and Sekon, 1976).

These findings explain why rice grown in flooded conditions have
higher requirements for zinc.  Foliar applications of zinc fertiliser
provide an appropriate solution to zinc solubility issues, as it avoids the complex soil interactions and other soil related issues.

Figure 2: Major soil chemical and physical factors effecting availability of zinc to roots (Cakmak, 2008)

Zinc is an important micronutrient for normal human growth and development. Widespread and extensive zinc deficiency has been reported in many rice producing areas.
One of the contributing factors, among many, is the high phytate content of rice and other cereal crops, which makes zinc non-bioavailable in the human digestive tract. Studies have suggested a simple way to overcome zinc deficiency in humans is by applications of zinc to crops like rice.

Various independent studies have shown that foliar fertilization is a more effective approach than base fertilisers for the correction of zinc deficiency in rice (Zhang et al., 2018; Jaksomsak et al., 2018) and at the same time fortifies the plant with zinc that is bio available for human nutrition.

Role of Zinc in Rice Plants

The importance of zinc in regulating several plant biological and physiological processes cannot be over emphasized. Zinc is involved
in more than 300 plant enzyme activities explaining why its deficiency will limit rice growth and yield (Ur et al., 2012).

These enzymes are involved in carbohydrate metabolism, maintenance of cell turgidity, protein synthesis, auxin regulation and pollen formation (Ur et al., 2012).

Regulation of gene expression linked to stress defence responses in plants is also zinc dependent; deficient plants are hence susceptible to injuries caused by excessive light, extreme temperatures and fungal pathogen invasion (Hafeez et al., 2013 and Lefevre et al., 2014).

Moreover, zinc deficiency in rice reduces pollen viability leading to reduced grain set and severe yield penalties (Yoshida et al., 1970).
Rice zinc deficiency can also occur at very early stages of development, as reported by several studies done with seedling in nurseries. Therefore, zinc deficiency in rice is a major cause of yield losses worldwide (Gao et al., 2006).

Below are conclusions of some studies that were carried out on rice production in various parts of the world especially in the areas where zinc deficiency is moderate to high in soil and the human population.

Rice cultivation benefiting from Zinc application:

  • Soil zinc application led to an increase in zinc concentration of 7% in rice grains while foliar application led to increases of 25%. (Edward et al. 2015).
  • Two-year field experiment indicated that soil zinc application has no significant effect on grain zinc concentration. In contrast, foliar zinc application increased grain zinc concentration by an average of 61%. (Ai-qing et al. 2013).
  • Amauri et al. 2014 concluded in their study that treating rice seed with zinc increased the grain yield by 5.8% and foliar application increase the 7% compared to the untreated.
  • Treating rice seed with zinc did not negatively change the germination rate or seedling emergence (Amauri et al. 2014).
  • Zinc application increases the crop growth rate of rice (Mustafa et al. 2011)
  • Application of zinc reduced phytate concentration and Phytate: zinc molar ratio in cereal (Yang et al. 2011).
  • Denre et al. 2017 concluded that the application of zinc in staple foods like rice may play a role in reducing zinc deficiency in human beings and animals.
  • Muthukumararaja and Sriramachandrasekharan (2012) observed that rice yield significantly improved with zinc fertilisation in zinc deficient soil. More so, they observed that the zinc content, uptake and zinc use efficiency had significant positive linear relationship with grain yield of rice.

OMEX  Zinc Application

For the best results to enhance crop development and increase grain zinc content, apply OMEX Kingfol Zinc at 0.5-1.0 l/ha during the tillering stage of rice.



Ai-qing Zhao Xiao-hong Tian Yu-xian Cao Xin-chun Lu Ting Liu (2013) Comparison of soil and foliar zinc application for enhancing grain zinc content of wheat when grown on potentially zinc-deficient calcareous soils.
Alloway, B.J., 2008. Zinc in soils and crop nutrition. Second edition, published by IZA and IFA, Brussels, Belgium and Paris, France.
Amauri Nelson Beutler, Vanessa Neumann Silva, Evandro Ademir Deak, Giovane Matias Burg, Marcelo Raul Schmidtand Marcos Toebe (2014) Zinc doses, sources and application times: seed physiological potential and flooded rice yield. Australian journal of Crop Science 8(11):1517-1525
Brar MS, Sekhon GS. Effect of Fe and Zinc on the availability of micronutrients under flooded and unflooded condition. J. Indian Soc. Soil Sci. 1976; 24:446-454
Cakmak I (2008) Enrichment of cereal grains with zinc: Agronomic or genetic biofortification? Plant Soil (2008) 302:1–17
Cakmak I, Kalayci M, Kaya Y, Torun AA, Aydin N, Wang Y, Arisoy Z, Erdem H, Yazici A, Gokmen O, Ozturk L, Horst WJ (2010) Biofortification and localization of zinc in wheat grain. J Agric.Food Chem 58:9092–9102
Chang, W.Y., B.Y. Lu, J.J. Yun, Y.L. Ping, Y. Zheng, X.S. Xin, L.G. An, S. Wei, Z. Chun, 2007. Sufficiency and deficiency indices of soil available zinc for rice in the alluvial soil of the coastal yellow sea. Rice Science, 14(3):223-228.
Chaudhary, S.K. and Singh, N.K. (2007). Effect of levels of nitrogen and zinc on grain yield and their uptake in transplanted rice. Oryza 44(1): 44-47
Edward J. M. Joy, Alexander J. Stein, Scott D. Young, E. Louise Ander, Michael J. Watts, Martin R. Broadley (2015) Zinc-enriched fertilisers as a potential public health intervention in Africa. Plant Soil (2015) 389:1–24
Gao X, Zou C, Fan X, Zhang F, Hoffland E (2006) From flooded to aerobic conditions in rice cultivation: consequences for zinc uptake. Plant Soil 280: 41-47.Ghulam Mustafa, Ehsanullah,Nadeem Akbar,Saeed Ahmad Qaisrani,Asif Iqbal, Haroon Zaman Khan ,khawar Jabran,Ashfaq Ahmad Chattha, Richard Trethowan,Tariq Chattha and Babar Manzoor Atta (2011) Effect of Zinc Application on Growth and Yield of Rice (Oryza sativa L.). IJAVMS, vol 5, issue 6:550-535
Hafeez B, Khanif Y, Saleem M (2013) Role of zinc in plant nutrition-a review.Am J Exp Agric 3: 374-391
Lefevre I, Vogel-Mikuš K, Jeromel L, Vavpetič P, Planchon
S, et al. (2014) Differential cadmium and zinc distribution in
relation to their physiological impact in the leaves of the accumulating Zygophyllum fabago L. Plant Cell Environ
37: 1299-1320
Jaksomsak P, Tuiwong P, Rerkasem B, Guild G, Palmer L, Stangoulis J. 2018. The impact of foliar applied zinc fertilizer on zinc and phytate accumulation in dorsal and ventral grain sections of four Thai rice varieties with different grain zinc. Journal of Cereal Science 79, 6–12
Kiekens L., Zinc, in: B.J. Alloway (Ed.), Heavy Metals in Soils, second ed., Blackie.
Academic and Professional, London, 1995, pp. 284–305
Muthukumararaja, T.M. and M.V. Sriramachandrasekharan (2012) effect of zinc on yield, zinc nutrition and zinc use efficiency of lowland rice. Journal of Agric technology vol 8(2) 551-561
Sillanpää M, Vlek PLG (1985) Micronutrients and the agroecology of tropical and Mediterranean regions. Fert Res 7:151–167
Sillanpaa, M., 1990. Micronutrient assessment at the country level an international study. FAO, Rome, 63: 208
Tye AM, Young SD, Crout NMJ, Zhang H, Preston S, BarbosaJefferson VL, Davison W, McGrath SP, Paton GI, Kilham K, Resende L (2003) Predicting the activity of Cd2+ and Zinc2+ in 22 Plant Soil (2015) 389:1–24 soil pore water from the radio-labile metal fraction. Geochim Cosmochim Acta 67:375–385
Ur Rehman H, Aziz T, Farooq M, Wakeel A, Rengel Z (2012) Zinc nutrition in rice production systems: a review. Plant Soil 361: 203-226
Waleed Khaliq Rana and Saifur Rehman Kashif (2014) Effect of different Zinc sources and methods of application on rice yield and nutrients concentration in rice grain and straw. Journal of Environmental and Agricultural Sciences ISSN: 2313-8629
Yoshida S, McLean GW, Shafi M, Mueller KE (1970) Effects of different methods of zinc application on growth and yields of rice in a calcareous soil, West Pakistan. Soil Sci Plant Nutr 16: 147-149
Zhao AQ, Tian XH, Cao YX, Lu XC, Liu T (2014) Comparison of soil and foliar zinc application for enhancing grain zinc content of wheat when grown on potentially zinc-deficient calcareous soils. J Sci Food Agric 94:2016–2022
Zhang T, Sun H, Lv Z, Cui L, Mao H, Kopittke PM. 2018. Using synchrotron-based approaches to examine the foliar application of ZincSO4 and ZincO nanoparticles for field-grown winter wheat. Journal of Agricultural and Food Chemistry.