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Published on: August 8, 2014
Soil and surface runoff phosphorus relationships for five typical USA midwest soils
B L Allen1, A P Mallarino, J G Klatt
1Department of Agronomy, Iowa State University, Ames, IA 50011, USA.
Journal of Environmental Quality
|March 3, 2006
Summary
High soil phosphorus (P) increases runoff P loss. Water-extractable P (WP) and Olsen P (OP) best predict runoff P, with improved accuracy for non-calcareous soils. Routine soil tests can estimate P loss risk.
Area of Science:
- Soil Science
- Environmental Chemistry
- Agronomy
Background:
- Excessive soil phosphorus (P) is a major contributor to P loss via surface runoff, impacting water quality.
- Understanding the relationship between soil P tests and runoff P is crucial for effective nutrient management.
- Different soil types and P testing methods exhibit varying correlations with P loss.
Purpose of the Study:
- To characterize the relationships between soil P tests and runoff P concentrations under simulated rainfall.
- To evaluate the effectiveness of various soil P tests and saturation indices in predicting P loss across diverse Midwest soils.
- To determine if soil P test performance differs between calcareous and non-calcareous soils.
Main Methods:
- Indoor rainfall simulations were conducted on five Midwest soils incubated with varying rates of NH4H2PO4.
- Soil samples were analyzed for Total Soil P (TPS) and Soil-Test P (STP) using Bray-P1 (BP), Mehlich-3 (M3P), Olsen (OP), Fe-oxide-impregnated paper (FeP), and water (WP) tests.
- Degree of Soil P Saturation (DPS) was calculated using different indices (DPSSTP, DPSox, DPSM3), and runoff bioavailable P (BAP) and dissolved reactive P (DRP) were measured.
Main Results:
- Runoff BAP and DRP increased linearly with P rate, STP, DPSox, and DPSM3, and curvilinearly with DPSSTP.
- FeP, OP, and WP tests showed the strongest correlations (r ≥ 0.95) with runoff DRP or BAP across soils.
- Excluding the calcareous soil improved correlations for BP, indicating differences in P behavior between soil types.
Conclusions:
- Routine soil P tests, particularly FeP, OP, and WP, can effectively estimate relationships between soil P and runoff P concentration.
- Separate calibrations for calcareous and non-calcareous soils may improve the accuracy of predicting P loss using soil tests.
- This study provides valuable insights for optimizing P management strategies to minimize environmental P losses from agricultural lands.
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