Effect of rates of Ca(OH) 2 and ZnSO 4 on soluble zinc concentration of spray solution and absorption of 65Zn by sweet-orange leaves

Abstract

In a laboratory experiment, addition of increasing rates of Ca(OH) 2 to ZnSO 4 spray solution caused a decrease in soluble Zn concentration and an increase in its pH. The soluble Zn concentration in 0.15% neutralized ZnSO 4 solution was 7 times higher than in the 0.60% neutralized ZnSO 4 solution. The spray solutions containing 0.15 and 0.45% of 65ZnSO 4 in combination with 0.0, 0.0375, 0.0750, 0.1125 and 0.225% of Ca(OH) 2 were applied to sweet orange ( Citrus sinensis Osbeck) leaves. The increasing rates of Ca(OH) 2 in the ZnSO 4 spray solution decreased 65Zn absorption by the leaves and this effect decreased with increasing rates of 65ZnSO 4 in the solution. This has resulted from the decrease in Zn concentration in the spray solution. Thus addition or presence of any ion in the solution that forms a precipitate with Zn would cause a decrease in the efficiency of the spray solution as a result of a lower amount of Zn available from solution per unit area of the leaf.