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Evaluation of Phosphorus Source Coefficients as Predictors of Runoff Phosphorus Concentrations
Author(s) -
Smith Matt C.,
White John W.,
Coale Frank J.
Publication year - 2009
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2007.0669
Subject(s) - compost , surface runoff , poultry litter , phosphorus , manure , environmental science , manure management , zoology , fertilizer , nutrient , chemistry , agronomy , environmental chemistry , ecology , biology , organic chemistry
Many states have adopted a P site index (PSI) as a risk assessment tool to determine when P‐based nutrient management is required for a given agricultural field. Some PSIs use a weighting factor, the phosphorus source coefficient (PSC), to account for differences in P solubility between organic P sources. Information relating to appropriate values of PSC for various organic P sources is limited. The objectives of this study were to determine PSCs for organic P sources and to examine the relationship between PSCs and P concentrations measured in simulated rainfall runoff. An incubation study was used to calculate PSCs based on the extractability of P from organic P sources (separated and unseparated liquid dairy manure, digested dairy manure, dairy manure solids, poultry litter, and compost) relative to P from triple superphosphate fertilizer. The PSCs from the 14‐d incubations were the best predictors of runoff P after 14 d soil equilibration in the runoff boxes. The values for iron‐oxide strip phosphorus (FeO‐P) PSC ranged from 78% for compost to 28% for poultry litter and were significantly related to runoff DR‐P ( r 2 = 0.80***) and FeO‐P ( r 2 = 0.76***) during the 14‐d runoff event. Mehlich 3 PSCs ranged from 59% for compost to 30% for unseparated dairy manure and were better predictors of DR‐P and FeO‐P during the 56‐d event ( r 2 = 0.73*** and 0.65***, respectively). The results of this study indicate that PSCs based on soil incubations may improve the ability of PSCs to predict the risk of runoff transport, particularly after manure incorporation.