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Soil Science Society of America Journal Abstract -

Birdsfoot Trefoil Seedling Response to Soil Phosphorus and Potassium Availability Indexes


This article in SSSAJ

  1. Vol. 53 No. 3, p. 828-836
    Received: Aug 1, 1988

    * Corresponding author(s):
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  1. M. P. Russelle ,
  2. L. L. Meyers and
  3. R. L. McGraw
  1. USDA-Agricultural Research Service/U.S. Dairy Forage Research Center, Dep. of Soil Science, 439 Borlaug Hall, Univ. of Minnesota, St. Paul, MN 55108
    Agronomy Dep., Univ. of Missouri, Columbia, MO 65201



Birdsfoot trefoil (Lotus corniculatus L.) is a promising forage legume, yet little is known about its nutrient requirements during early growth. Several soil P and K indexes were evaluated for their ability to predict dry mass (DM) and P and K concentration and uptake by ‘Fergus’ and ‘Maitland’ birdsfoot trefoil seedlings grown for 6 wk in the greenhouse in four diverse soils amended to attain a broad range of plant-available P and K. Soils were extracted with 0.01 M CaCl2, neutral 1 M ammonium acetate, or H2SO4 to estimate plant-available K, and 1 mM SrCl2, Bray and Kurtz no. 1 (Bray-P), or anion exchange resin (AER) to estimate available P. Shoot DM was not influenced by soil K and increased with increasing soil P, being best predicted across soils by AER-P. Maitland DM exceeded that of Fergus at all fertility levels. Tissue concentration of P and K were best related to soil solution concentration (extracted with weak salt solutions), but only one-half the variation in tissue P concentration was explained by soil solution-P concentration. Across soils, P and K uptake were best related to Bray-P and to solution-K concentration, respectively, but exchangeable-K exhibited less sensitivity to cultivar differences than solution-K. Anion exchange resin appeared to extract a constant fraction of nonoccluded Fe- and Al-bound P (47%), regardless of the oxide content of the soil, whereas the Bray-1 reagent appeared to extract a constant proportion of P per unit mass Fe oxide present. These differences may account for the relatively poor performance of AER in predicting P uptake across soils differing in parent material.

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