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This article in JEQ

  1. Vol. 35 No. 2, p. 599-610
     
    Received: Apr 25, 2005


    * Corresponding author(s): apmallar@iastate.edu
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doi:10.2134/jeq2005.0135

Soil and Surface Runoff Phosphorus Relationships for Five Typical USA Midwest Soils

  1. B. L. Allen,
  2. A. P. Mallarino *,
  3. J. G. Klatt,
  4. J. L. Baker and
  5. M. Camara
  1. Department of Agronomy, Iowa State University, Ames, IA 50011

Abstract

Excessively high soil P can increase P loss with surface runoff. This study used indoor rainfall simulations to characterize soil and runoff P relationships for five Midwest soils (Argiudoll, Calciaquaoll, Hapludalf, and two Hapludolls). Topsoil (15-cm depth, 241–289 g clay kg−1 and pH 6.0–8.0) was incubated with five NH4H2PO4 rates (0–600 mg P kg−1) for 30 d. Total soil P (TPS) and soil-test P (STP) measured with Bray-P1 (BP), Mehlich-3 (M3P), Olsen (OP), Fe-oxide-impregnated paper (FeP), and water (WP) tests were 370 to 1360, 3 to 530, 10 to 675, 4 to 640, 7 to 507, and 2 to 568 mg P kg−1, respectively. Degree of soil P saturation (DPS) was estimated by indices based on P sorption index (PSI) and STP (DPSSTP) and P, Fe, and Al extracted by ammonium oxalate (DPSox) or Mehlich-3 (DPSM3). Soil was packed to 1.1 g cm−3 bulk density in triplicate boxes set at 4% slope. Surface runoff was collected during 75 min of 6.5 cm h−1 rain. Runoff bioavailable P (BAP) and dissolved reactive P (DRP) increased linearly with increased P rate, STP, DPSox, and DPSM3 but curvilinearly with DPSSTP Correlations between DRP or BAP and soil tests or saturation indices across soils were greatest (r ≥ 0.95) for FeP, OP, and WP and poorest for BP and TPS (r = 0.83–0.88). Excluding the calcareous soil (Calciaquoll) significantly improved correlations only for BP. Differences in relationships between runoff P and the soil tests were small or nonexistent among the noncalcareous soils. Routine soil P tests can estimate relationships between runoff P concentration and P application or soil P, although estimates would be improved by separate calibrations for calcareous and noncalcareous soils.

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Copyright © 2006. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyASA, CSSA, SSSA