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This article in AJ

  1. Vol. 76 No. 2, p. 209-212
    Received: June 27, 1983

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Root Growth and Morphology, Nutrient Uptake, and Nutrient Status of Early Growth of Soybeans as Affected by Soil P and K1

  1. W. B. Hallmark and
  2. S. A. Barber2



Little information is available on the effects of levels of soil P and K on soybean [Glycine max (L.) Merr] root growth and morphology. Soybeans were grown for 9, 16, and 21 days in Raub silt loam soil (fine-silty, mixed, mesic Aquic Argiudoll) to measure the effect of increasing soil P and K on root growth and morphology and its relation to shoot growth, nutrient status of shoots, and net nutrient influx. Increasing soil P increased shoot weight, root surface area per plant, root surface area per g of root, P, K, Ca, and Mg influx and P, K, Ca, and Mg concentration of shoots. Adding P decreased the root surface area per g of shoot and increased root surface area per g of root. Increasing soil K increased shoot weight (with high P soil), P, K, and Ca influx, and P and K concentration of shoots. Potassium decreased Mg influx and Mg concentration of shoots. Significant positive P ✕ K interactions were found for secondary root radius, P, K, and Mg influx and shoot concentration showing that P and K had their greatest effect when the other nutrient concentration in the soil was high. The effect of P and K on nutrient concentration of shoots followed the same pattern as that for nutrient influx. Since adding P or K changes root surface area per g of shoot, influx of other nutrients changes when they are added. Where influx increases, a sufficient soil level of each nutrient is then needed so that soil supply does not limit influx.

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