A greenhouse experiment was conducted to study the growth and chemical composition of rice (Oryza sativa L.) cv Ghasroddashti as affected by boron (B) and two zinc (Zn) sources in a calcareous soil(fine, mixed, mesic, Fluventic Haploxerepts). Treatments consisted of seven B levels (0, 2.5, 5, 10, 20, 40, and 80 mg kg-1 as boric acid), three rates of Zn (0, 5, and 10 mg Zn kg-1 soil) and two sources (ZnSO4 and ZnO). The statistical design was a completely randomized factorial one with three replicates. Zn fertilization increased the number of tillers, dry matter yield, and Zn, Cu, B, and K concentrations in the plant top. Concentrations of Mn and P decreased with application of Zn , but that of Fe was not affected. Soil B application increasesd B, Cu, P, and K concentrations, but reduced the concentration of Fe. When no Zn was supplied application of 2.5 mg B kg-1 soil, increased dry matter yields dramaticaly. In presence of optimum amounts of Zn from either source the increase in dry matter was continued up to 5 mg B kg-1 soil. The results also show that in soils with high levels of B, Zn application may reduce the adverse effects of B toxicity and consequently increase rice yield.
)