EFFECTS OF COPPER, ZINC, AND SULFUR APPLICATION TO PEACH-TREES ON COASTAL-PLAIN SOIL

Expanded use of sulfur (S)-free fertilizers and copper (Cu)-free fungi cides is likely to increase plant deficiencies of these essential elem ents. Zinc (Zn) deficiency occurs more frequently. An effective and re liable 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 combinati ons 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 we re foliar-applied in March, April, and May. Responses were linear betw een applied Zn and leaf Zn, applied S and leaf S, and applied S and le af 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.