Interactions of nutrients in Valencia orange leaves as affected by the composition of manganese, zinc, and urea sprays

Abstract

The main effects and interactions of foliar applications of MnSO4, ZnSO4, and urea in factorial combinations on nutrients in Valencia orange leaves were studied. The presence of MnSO4 in ZnSO4 foliar sprays containing Na2CO3 as precipitating agent significantly decreased the concentration of soluble Zn ions in solution and, as a consequence, decreased the concentration of Zn in the leaves as compared with Zn concentration found in the spray solutions and leaves of trees sprayed with ZnSO4 alone. The presence of ZnSO4 plus Na2CO3 in MnSO4-urea foliar sprays significantly increased the concentration of soluble Mn ions in solution, causing increased Mn concentration in the leaves of trees sprayed with this solution. Considering all Mn-urea treatments in this experiment, a positive interaction between Mn and urea foliar applications occurred: Mn concentration increased in the leaves of trees sprayed with MnSO4-urea mixture. This increase in Mn concentration in the leaves may have been due to better uptake of Mn by the leaves when urea was present, since the concentration of Mn in the spray solution was not affected significantly by the presence or absence of urea in Mn foliar sprays.