Calvin G. Lyons

Microwave digestion of plant samples for sulfur analysis

Abstract The goal was to develop an easy, fast, and economical procedure to produce plant digests that can be accurately analyzed by plasma emission spectrometry for foliar sulfur content. The closed vessel microwave procedure described requires less than 2 hours to produce 12 digested 0.5 gram samples from the point of weighing the samples to applying them to plasma emission spectrometry analysis. The procedure utilizes nitric acid and hydrogen peroxide as a predigestion. The predigested samples are then each microwaved for 2.25 minutes. With this procedure, sulfur levels are within an average of 1.27% of that reported for the NBS Citrus Standard, are within 102.25% to 99.44% of the values determined for wet ash digested materials and display recovery rates of 96 to 98% for known levels of sulfur in the range expected in plant foliage.

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 treatment...

Effectiveness of three different zinc fertilizers and two methods of application for the control of “little‐leaf’ in peach trees in south texas

Abstract Fall soil treatments of ZnEDTA and ZnSO4 at three increasing rates of 32.2, 64.4, and 128.8 g Zn/tree, and one, two, or three spring foliar treatments of NZN (0.35 g Zn/tree application) replicated four times in a randomized complete block design were tested to find the most effective Zn source, method and rate of application, and economical method for controlling Zn deficiency in three year old ‘Earligrande’ peach trees from 1989 to 1990. The Zn fertilizers had no statistical influence on the soil pH change. The high rates of ZnSO4, NZN, and ZnEDTA produced equal chlorophyll contents and had no statistical difference in tree appearance. Neither those trees which received three foliar applications of NZN nor those that received the high ZnEDTA soil treatment showed Zn‐deficiency symptoms other than a few chlorotic leaves on top of the trees as a result of Zn being a non‐mobile element. A fourth NZN application, or a delay in initiation of the three NZN spray schedule, would be necessary to compen...