Effects of copper,zinc, and sulfur application to peach trees on coastal plain soil

Abstract

Expanded use of sulfur (S)‐free fertilizers and copper (Cu)‐free fungicides is likely to increase plant deficiencies of these essential elements. Zinc (Zn) deficiency occurs more frequently. An effective and reliable means of correcting Zn deficiency in peach trees remains to be documented in Texas. This study was designed to evaluate S, Cu, and Zn treatments on peach trees. Fifteen treatments consisting of combinations of five rates each of S, Cu, and Zn were evaluated using a central‐composite, rotatable design. Each treatment was replicated four times. Sulfur and Cu treatments were applied in January. Zinc treatments were foliar‐applied in March, April, and May. Responses were linear between applied Zn and leaf Zn, applied S and leaf S, and applied S and leaf area. A positive correlation between leaf Cu and leaf N was found. A preliminary study in the greenhouse revealed that both the 12.5 and 25 ppm Cu treatments were toxic. In a succeeding study, no statistical differences among Cu treatments from 0 to 10 mg/kg were found.