Foliar micronutrient application effects on citrus fruit yield, soil and leaf Zn concentrations and 65Zn mobilization within the plant

The use of foliar fertilizers has been routine practice in Brazilian citrus plantations for applying micronutrients, but little information exists on effects on yield and fruit quality. Experiments were conducted in a citrus plantation to study the effect of Zn foliar fertilization on fruit yield and quality, leaf Zn concentration and soil Zn concentration. Studies on foliar absorption and transport of Zn and the effect of different sources of this micronutrient were also conducted. A third experiment was conducted in order to study the absorption and the translocation of Zn-65 (Zn-EDTA, Zn-lignin sulfonate, ZnCl2 and ZnSO4), applied on leaves of young orange plants grown in greenhouse. The results of the experiments showed that the foliar fertilization increased leaf Zn concentration, to within the adequate range; however, there was no effect on orange fruit yield and quality. The soil Zn concentration increased under canopies; especially in the soil samples taken near the plant trunks. The chloride was more efficient Zn-65 source than sulfate, but only a small portion (less than 1%) of foliar applied Zn was translocated to other plant parts.