Iron and zinc biofortification in polished rice and accumulation in rice plant (Oryza sativa L.) as affected by nitrogen fertilization

Abstract

With focus on maximizing grain yield in rice (Oryza sativa L.) production, especially in China, information available in the literature on how nitrogen (N) fertilization of rice crops affects biofortification of iron (Fe) and (Zn) in grains is limited. The objective of the experiment was to investigate to what degree application of N fertilizer attained the optimum Fe and Zn concentration in rice grains as well as grain yield under pot conditions. Two rice cultivars of the indica ‘Zhenong 952’ and the japonica ‘Bing 98110’, grown widely in the area of the Yangtse River Delta in southern China, and fertilized with four rates of urea (0, 0.50, 1.00 and 1.50 g N pot−1), were investigated. The results showed that, in the pot trails, the optimum application of N alone on rice crops could increase the concentration of Fe in the polished rice. By considering both health and commercial reasons, when N application reached 1.00 g pot−1, the optimal Fe and Zn concentrations were attained as well as grain yield for ‘Zhenong 952’, and for ‘Bing 98110’ the optimum N application was 1.50 g pot−1. Fe appeared not to be so easily mobilized as Zn in the plant. The ratio of Zn deposited in the brown rice was about 40% of total Zn in the plant, irrespective of N application. However, deposited Fe was only about 3% of total Fe. Fe concentration in brown rice was only about ½ that in rice husk, 1/5 that in peduncles, 1/10 that in leaves, and only a little more than 1% of that in roots. These results suggested if we wanted to increase the amount of Fe in grains the translocation mechanism of Fe in rice plant must be clearly understood first.