Chloride Toxicity of Soybeans Grown on Atlantic Coast Flatwoods Soils1
- Myron B. Parker,
- G. J. Gascho and
- T. P. Gaines2
Leaf scorch, caused by CI toxicity, affected over 20,000 ha of soybeans (Glycine max (L.) Merr.) in 1980 in the poorly-drained Flatwoods soils of Georgia. This new disorder, compounded by the extended drought of 1980, resulted in Severe yield reductions of ‘Bragg’ soybeans. Field studies involving fertilizer treatments in two experiments and 15 cultivars in one experiment were conducted in 1981 to determine the cause of the problem. Phosphorus, Mg, and Cl treatments were evaluated on two problem areas—a Leefield sand (arenic Plinthaquic Paleudults) and an Alapaha sand (arenic Plinthic Paleaquults). Cultivars also were evaluated on the Alapaba sand. Leaf scorch developed on plants receiving Cl containing fertilizer and on 5 of 15 cultivars. Symptoms observed were the same as those described for Cl toxicity. Leaf and seed Cl levels averaged 0.12% and 75 µg/g, respectively, for plants receiving no KCl fertilizer compared to 0.94% and 166 µg/g for plants receiving KCl. Leaf and seed Cl levels averaged 1.67% and 682 µg/g, respectively, for five susceptible cultivars compared to 0.09% and 111 µg/g for 10 tolerant cultivars. The parent seed of each cultivar contained relatively low levels of Cl, indicating that susceptible cultivars are not high Cl accumulators when grown under low Cl soil conditions. Leaf scorch ratings were positively correlated with leaf and seed Cl and negatively correlated with seed weight and yield. The leaf scorch problem on susceptible cultivars apparently is caused by a Cl buildup in poorly-drained Flatwoods soils. The major source of Cl appears to be KCl fertilizer.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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