Effects of Foliar Application of Zinc on Grain Yield and Zinc Concentration of Rice in Farmers’ Fields

Three field experiments were conducted on farms in Chiang Mai, Thailand in 2015 to evaluate the effects of: (i) foliar application of Zn on the grain yield and grain Zn concentration of rice and (ii) using Zn-enriched seeds in the next cropping on growth and yield. Zn was applied by foliar spraying 0.5% ZnSO 4 at three different growth stages: booting, flowering, and early milk stages. Foliar spraying of Zn improved the grain Zn concentration by 41% in one field, and an average of 30% across the three fields. The foliar- sprayed Zn did not, however, affect the grain yield in any of the fields. The Zn-enriched seeds also did not affect the grain yield of the plants in the farmers’ fields in the next cropping, probably because of the high amount of soluble Zn already in the experimental fields. Clearly, the foliar application of Zn significantly increased grain Zn concentration, but had no effect on grain yiel