Effects of Cu, Zn, and S application to peach trees (Prunus persica (L.) Batsch.) on an east Texas soil

Abstract

Extent and severity of S deficiencies are likely to increase with expanding use of S free fertilizers and pesticides (Duke and Reisenhauer, 1986). New generation fungicides are generally Cu free which eliminates a source of the micronutrient. Recommendations for correcting Cu deficiency have not changed in the recent past. Zinc deficiency is one of the more common trace element deficiencies. Correction of Zn deficiency has been achieved on some fruit and nut crops (Smith, 19G7) and pecans (Storey et al., 1974). An effective and reliable means of correcting Zn deficiency in Texas peaches has yet to be documented. Fifteen treatments consisting of combinations of 5 rates of Cu, Zn, and S were evaluated using a central composite rotatable design. Each treatment was replicated 4 times. Sulfur and Cu treatments were applied in January followed by three separate Zn foliar sprays in March, April, and May. Responses were linear between applied Zn and foliar Zn, applied S and foliar S, and applied S and leaf area. No linear effects of applied Cu were found. No interactive effects between nutrients and growth parameters were determined. A positive correlation was noted between foliar Cu and foliar N. A supplemental greenhouse study to evaluate recommended Cu levels was implemented. A pilot study conducted prior to initiation of the larger greenhouse study revealed 12.5 and 25 ppm Cu levels to be toxic. Copper levels of 0, 2, 4, 6, 8, and 10 ppm were applied to peach seedlings. No statistical differences among treatments were found.