Submitted to: HortTechnology
Publication Type: Review Article
Publication Acceptance Date: October 31, 2001
Publication Date: December 31, 2001
Citation: Swietlik, D. Zinc Nutrition of Fruit Crops. HortTechnology. 2002. v.12(1). p.45-50. Technical Abstract: Zn deficiency is widespread throughout the world causing economic losses on a number of crops. Despite the fact that much information was generated during the last twenty years on Zn soil chemistry and its organic phase equilibrium, the mechanism controlling the amount of free Zn+2 present in the soil solution is not yet completely understood. This information is critical for the development of effective techniques of supplying Zn through the soil. As Zn moves very slowly through the soil, however. and a large portion of fruit tree root system occupies deep soil layers, foliar sprays with Zn are generally more effective than soil treatments in alleviating Zn deficiency symptoms. That is why many extension specialists recommend this approach. In view of poor mobility of foliar-absorbed Zn in plants, however, we may need to re-examine this approach. Zinc foliar sprays may be effective in controlling Zn deficiency in leaves, but not in alleviating Zn deficiency in roots or subsequent flushes of growth. Also, the conditions under which fruit trees are most likely to respond to corrective Zn treatments are not well understood & the critical periods for Zn supply to assure optimal fruit set, fruit growth, & high fruit external & internal quality are not well defined. Field studies on fruit trees suggest that Zn deficiency must be quite severe to make the application of this element economically justifiable. In well-controlled greenhouse studies, however, growth responses were realized on plants only mildly affected by Zn deficiency. If considerable field variability may explain this discrepancy in the data, then future yield research must utilize improved methodologies to properly quantify the impact of various levels of Zn deficiency on tree growth, fruit yield, and fruit quality.