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Using Simulated Rainfall to Evaluate Field and Indoor Surface Runoff Phosphorus Relationships

Guidry, A. R., Schindler, F. V., German, D. R., Gelderman, R. H., Gerwing, J. R.
Journal of environmental quality 2006 v.35 no.6 pp. 2236-2243
rainfall simulation, agricultural soils, phosphorus, chemical concentration, prediction, agricultural runoff, Mollisols, regression analysis, equations, South Dakota
While numerous studies have evaluated the efficacy of outdoor rainfall simulations to predict P concentrations in surface runoff, few studies have linked indoor rainfall simulations to P concentrations in surface runoff from agricultural fields. The objective of this study was to evaluate the capacity of indoor rainfall simulation to predict total dissolved P concentrations [TP(<0.45)] in field runoff for four dominant agricultural soils in South Dakota. Surface runoff from 10 residue-free field plots (2 m wide by 2 m long, 2–3% slope) and packed soil boxes (1 m long by 20 cm wide by 7.5 cm high, 2–3% slope) was compared. Surface runoff was generated via rainfall simulation at an intensity of 65 mm h⁻¹ and was collected for 30 min. Packed boxes produced approximately 24% more runoff (range = 2.8–3.4 cm) than field plots (range = 2.3–2.7 cm) among all soils. No statistical differences in either TP(<0.45) concentration or TP(<0.45) loss was observed in runoff from packed boxes and field plots among soil series (0.17 < P < 0.83). Three of four soils showed significantly more total P lost from packed boxes than field plots. The TP(<0.45) concentration in surface runoff from field plots can be predicted from TP(<0.45) concentration in surface runoff from the packed boxes (0.68 < r ² < 0.94). A single relationship was derived to predict field TP(<0.45) concentration in surface runoff using surface runoff TP(<0.45) concentration from packed boxes. Evidence is provided that indoor runoff can adequately predict TP(<0.45) concentration in field surface runoff for select soils.