Spatial and Temporal Variability of Phosphorus Retention in a Riparian Forest Soil
1998
Lyons, Jodi B. | Görres, Josef H. | Amador, José A.
Riparian zones remove P from surface runoff and can act as filters of nonpoint source (NPS) P pollution for surface waters. Riparian forest soils were investigated in spring and fall for their capacity to retain PO³⁻₄-P. Samples (300 on each date) were taken from a soil drainage catena from moderately well (MWD), somewhat poorly (SPD), and poorly drained (PD) soil in May and November of 1995 to examine spatial and temporal variability of P retention and its relationship to soil properties. The equilibrium P concentration at zero sorption (EPC₀) was determined for each sampling point (lower EPC₀, = higher P retention capacity). Mean (coefficient of variation, CV) EPC₀ values were 3.8 (0.49) mg P L⁻¹ in May and no P sorption was apparent in November for SPD soil, 1.0 (1.34) and 1.5 (1.03) P L⁻¹ in May and November, respectively for MWD soil, and 0.5 (1.87) and 1.3 (1.13) mg P L⁻¹, respectively for PD soil. The EPC₀ was significantly and positively correlated to organic matter (OM) for all drainage classes on both dates. Low EPC₀ values—high P retention capacity—in MWD and PD soil corresponded with high Feₒₓ and Alₒₓ values. For SPD soil, high mean EPC₀ corresponded with low mean Feₒₓ and Alₒₓ values. The relationship between EPC₀ and Feₒₓ and Alₒₓ was described by a hyperbolic function for MWD and PD soil, but not for SPD soil. The EPC₀ did not exhibit spatial structure at the sampling scale used for any of the drainage classes, even though Feₒₓ, Alₒₓ, and OM content showed spatial structure.
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