Effect Of Foliar Micronutrient Fertilizers On The Concentration Of Trace Elements In Grains Of Japonica Rice

Micronutrients including iron, zinc, vitamin A, and iodine, play important roles in human health. Hidden hunger, micronutrient deficiency, now affects nearly one third of the world’s population, resulting in poor health of people especially in the developing areas. Staple foods crops such as rice and wheat contain relatively low iron and zinc, partially contributing to the widespread micronutrient deficiency across the world. Rice is one of the most important food crops, providing energy, protein, and minerals for nearly half of the world’s population. Increasing the content of iron and zinc in rice grain is of great importance for alleviating micronutrient malnutrition in developing areas. Foliar application is an effective way to improve micronutrient nutrition of crops and subsequently to enhance the density of micronutrients in grains. This study was performed to investigate the effect of foliar application of micronutrients including iron, zinc, copper, and manganese on grain micronutrient contents, and thereby proposing fertilization management aiming for high micronutrient quality of rice.The main results were shown as follows:(1) A pot experiment was carried out to investigate the effect of foliar application on grain micronutrients contents. Three japonica rice cultivars, Wuyujing3, Wuyunjing7, and Ningjingl were used, and four kinds of micronutrient including Fe, Mn, Cu, and Zn, three rate and three timing treatments were performed. Results showed promoting effect of foliar application on grain micronutrient contents. Fe contents in brown and milled rice increased by foliar application of Fe2(SO4)3-xH2O, being by46.6%and64.7%, respectively. And the enhancing effect of ZnSO4·7H2O foliar application on brown and milled were96.7%and80.3%. Foliar application of Cu decreased grain yield whereas the other three minerals showed no significant effect on grain yield. The depressed effect of Cu was associated with the lower filled grain rate. Overall, foliar fertilization is an effective way of increasing the contents of micronutrients in rice grain.(2) A field experiment was performed investigating the effect of the foliar fertilization of FeSO4on grain Fe contents. Two japonica rice cultivars, Wuyujing3and Wuyunjing7were used, and three forms involving inorganic iron compound(Fe2(S04)3·xH20), Fe-EDTA and Fe(Ⅱ)-amino acids, three rate and three timing treatments were performed. The results showed that Fe content in the brown and milled rice were increased by the Fe fertilizer spraying and the effect of foliar application at one week after full heading time was better than booting stage and full heading time. The0.5%inorganic iron compound was the better foliar fertilizer than the other fertilizers for increasing the content of the Fe in the rice grain. Foliar application of Fe2(SO4)3·xH2O at one week after full heading time increased grain yield whereas the other foliar application showed depressed effect on grain yield. These results indicated that foliar application of0.5%Fe2(SO4)3-xH2O at one week after full heading time was the better way to increase the iron content in rice grain.(3) The field experiment was conducted to quantify the influence foliar application of Zn on grain Zn contents. Two japonica rice cultivars, Wuyujing3and Wuyunjing7were used, and two nitrogen levels including0and270kg/ha, three rate and three timing treatments were performed. Results showed the Zn content in the brown and milled rice were increased significantly to control by spraying Zn fertilizer. The Zn content in grains was decreased with the nitrogen increasing and foliar application of Zn effectively relieve the reverse effect of the increasing nitrogen. The effect of foliar application at one week after full heading time was better than booting stage and full heading time. The0.5%ZnSO4was the better foliar fertilizer than the other fertilizers for increasing the content of the Zn in the rice grain. Foliar application of Zn at one week after full heading time increased grain yield whereas the other foliar application showed no significantly effect on grain yield. These results indicated that foliar application of0.5%ZnSO4fertilizer at one week after full heading time was the better way to increase the iron content in rice grain.