Effect of Foliar Application of Zinc and Phosphorous on Their Dynamic, Biofortification, and on Grain Protein Content of Two Rice Cultivars (Hashemi and Guilaneh)

Phosphorus (P) is the second macronutrients and zinc (Zn) is the most important micronutrients that their deficiencies are the most important global nutrient disorders in the world paddy fields. The current field study was conducted to evaluate the effect of Zn and P foliar application (each at three levels) on their content in rice tissues and grains bio-fortification (Zn and protein content). A field experiment as factorial form was conducted in a completely randomized block design with three replications in 2017-2018, at research farm of Rice Institute in Rasht, Iran. The results of the variance analysis indicated that all the applied treatments and their interactions significantly influenced the Zn and P content of rice tissues, Zn and protein contents of rice grains. The heighest zinc content increased in the leaves four times, in the stem and panicle three times and the phosphorous content increased in all organs two times, at flowering and ripening stages. The highest content of grain Zn in Hashemi and Guilaneh cultivars, treated by foliar application of Zn (using 5 ppt ZnSO4) one week before flowering and grain filling stages,  were recorded to be about 39.06 mgkg-1 (27.11% more than the control) and 35.37 mgkg-1 (27.37 % more than the control ), respectively. Also, the highest content of grain protein in Hashemi and Guilaneh cultivars with no significant difference treated by foliar application of Zn (using 5 ppt ZnSO4) one week before flowering and grain filling stages were recorded to be about 11% (32.37% more than the control) and  10.67% (38.21 % more than the control), respectively. The proposed cultivars have been similarly responded to the applied treatments. It can be concluded that the foliar application of Zn, one week before flowering and grain filling stages might be a quick and proper solution to enhance grain Zn and protein content.