Soil and Surface Runoff Phosphorus Relationships for Five Typical USA Midwest Soils
- B. L. Allen,
- A. P. Mallarino *,
- J. G. Klatt,
- J. L. Baker and
- M. Camara
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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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