THE AMOUNT OF BORON ABSORBED BY SOYBEAN PLANTS AND ITS EFFECT ON THEIR GROWTH

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Abstract
Short-term growth studies on the soybean plant indicate that a 20-day growth period and 12-day treatment period are sufficient to demonstrate toxicity of B both by growth relationships and by foliar symptoms. Visible toxicity to the soybean plant as indicated by foliar symptoms corresponded to the presence of 200 ppm. or more B in the moisture-free plant material. Duplication of growth maxima in 4 plant series, duplicated in sand and sand-soil mixtures, and treated with varying quantities of B appears to be conclusive proof that such maxima are present at 0.4 ppm. and 0.8 ppm. added B at this stage of growth of the soybean plant. A 5th series (A) showed stimulation to growth but was treated under different conditions. Preliminary field expts. with soybeans indicate a growth change which corresponds in effect to that observed in greenhouse studies. The B conc. of field-grown soybean plants, at mid-season, showed little difference between treatments. The plant at earlier and later growth stages showed increased B conc. with treatment. This procedure offers a method for testing small quantities of soil for boron toxicity in a short time.