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This article in SSSAJ

  1. Vol. 66 No. 2, p. 652-660
    Received: Apr 2, 2001

    * Corresponding author(s): t.george@cgiar.org
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Phosphorus Fertilizer Effects on Soil Phosphorus Pools in Acid Upland Soils

  1. Achim Dobermanna,
  2. Thomas George *b and
  3. Niels Thevsc
  1. a Dept. of Agronomy and Horticulture, Univ. of Nebraska, P. O. Box 830915, Lincoln, NE 68583-0915
    b Univ. of Hawaii–IRRI Collaboration, Soil, and Water Sciences Division, International Rice Research Institute (IRRI) DAPO Box 7777, Metro Manila, Philippines
    c Flurstr. 240, 22549 Hamburg, Germany


Opinions vary on fertilization strategies in part because of uncertainties in methods assessing P supply across sites. We quantified the fate and extractability of fertilizer P after two to four crops with four to five P levels applied to upland rice (Oryza sativa L.)–soybean [Glycine max (L.) Merr.] rotations in three experiments in Asia. Soil P pools were measured by Mehlich-1 extractant, a modified Hedley fractionation and by mixed-bed resin capsules after 1 and 14 d (resin adsorption quantity, RAQ-P1 and RAQ-P14). Without P addition, 84% of the total P was in the NaOH-Po and residual-P fractions across sites. Phosphorus fertilization increased Mehlich-1 P, resin-P, NaOH-Pi, H2SO4-P, RAQ-P1, and RAQ-P14 across sites, whereas NaOH-Po and residual-P were unchanged. The sum of resin-P and NaOH-Pi increased from 10% to between 20 and 30% of the total soil P. Mehlich-1 P and resin P increased similarly across sites and fitted quadratic models: the increase in Mehlich-1 P (mg kg−1 per kg P ha−1) ranged from 0.050 at low P rates to >0.125 at >400 kg P ha−1 The increases per unit P of RAQ-P, NaOH-Pi, and H2SO4-P varied among sites. Oxalate-extractable Fe accounted for most of the variation in NaOH-Pi and RAQ-P. Changes in soil P pools in tropical upland Oxisols and Ultisols following P addition are likely better reflected by NaOH-Pi and RAQ-P than Mehlich-1 P and resin P. Improvements in soil P tests are needed to better discriminate the changes in P pools from fertilization across soils.

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Copyright © 2002. Soil Science SocietyPublished in Soil Sci. Soc. Am. J.66:652–660.