Department of Plant Sciences

Iron (Fe) toxicity is a widespread nutrient disorder and limit to grain yield in lowland rice. As it is, however, sometimes associated with deficiency of other nutrients, Fe toxicity might be also managed and alleviated by applications of concerned nutrients such as potassium (K) and zinc (Zn). However, the information on this topic available in literature is very limited, especially in the case of Zn. The objective of this study was to evaluate the effects of soil and foliar Zn applications on severity of Fe toxicity and grain concentrations of Zn in rice grown on a Fe-toxic soil in Laos under field conditions. Soil Zn applications have been realized in 2 forms: 1.5 % Zn-containing KCl (KCl-Zn) and ZnSO4. The results with soil Zn applications showed that plant growth at early growth stage was increased by both forms of Zn applications which in turn contributed to final grain yield. The increases in grain yield resulted from the KCl-Zn and ZnSO4 applications were similar and were around 35 % compared to the control treatment without any Zn application. Leaf Zn concentrations were also increased by Zn applications while Fe concentrations tended to decrease. In a separate experiment soil and foliar applications of ZnSO4 were examined for their effectiveness in affecting plant Zn concentration. Soil Zn application was not affective in increasing grain Zn concentration, but foliar-applied Zn increased Zn concentration of brown rice up to 34 %. This study suggested that Zn fertilizer strategy is a promising approach to contribute to both grain yield and grain Zn concentrations in rice under Fe toxic soil conditions.