Submitted to: International Symposium on Foliar Nutrition of Perennial Fruit Plants
Publication Type: Proceedings
Publication Acceptance Date: September 30, 2001
Publication Date: November 1, 2002
Citation: Swietlik, D. Zinc Nutrition of Fruit Trees by Foliar Sprays. Proceedings of the International Symposium on Foliar nutrition of Perennial Fruit Plants. 2002. Acta Hort N. 594. p. 123-129. Technical Abstract: Foliar or dormant Zn sprays have become a method of choice of supplying this element to fruit trees due to poor mobility of Zn in the soil & a large portion of a root system of woody plants occupying deep soil layers. In a majority of studies, foliar or dormant sprays have been conclusively proven to be more effective than soil treatments in alleviating Zn deficiencies & they are widely recommended by extension specialists to fruit growers in many parts of the world. The ability of foliar sprays to rapidly alleviate Zn deficiency symptoms is their main advantage whereas the limited translocation of Zn from sprayed to non-sprayed organs is the foliar sprays' major setback & the chief reason for repeated applications. Particularly tree species producing several flushes of growth, or those growing continuously during much of a growing season require repeated Zn applications. The poor mobility of foliar-absorbed Zn may be the reason why yin a number of field studies, trees with mild or even moderate Zn deficiency symptoms failed to respond to corrective Zn foliar sprays. Much still needs to be learned about when Zn foliar sprays applied in the field will improve vegetative growth, fruiting, or fruit quality. For example, in grapefruit about 15-20% of the canopy foliage must be affected by Zn deficiency before yield responses could be induced by Zn foliar sprays. Moreover, Zn application 1-2 months before anthesis was more effective than when applied at other times. Our knowledge about the mechanisms involved in foliar absorption & translocation of the foliar-absorbed Zn is quite limited. An understanding of Zn absorption and translocation will lead to more effective Zn nutrient management in crops throughout the world.