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Nutrient Runoff Losses as Predicted by Annual and Monthly Soil Sampling
Author(s) -
Sharpley A. N.,
Smith S. J.,
Berg W. A.,
Williams J. R.
Publication year - 1985
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/jeq1985.00472425001400030010x
Subject(s) - surface runoff , environmental science , nutrient , hydrology (agriculture) , particulates , nitrate , soil water , soil science , ecology , engineering , geotechnical engineering , biology
The transport of soluble and particulate P and N in runoff from several cropped and grassed watersheds in Oklahoma and Texas was related to the nutrient content of surface soil (0–50 mm) sampled monthly and annually (March) over a 2‐yr period in an effort to improve the prediction of nutrient transport. For both monthly and annual soil samplings, the prediction of soluble P was good for events > 0.75 mm runoff ( r values ranged from 0.57 to 0.92), but smaller events were poorly predicted. The nitrate content of runoff was not closely related to surface soil content ( r vlaues ranged from 0.17 to 0.58), precluding its accurate prediction in runoff. Prediction of both particulate P and total N concentrations of individual runoff events was improved using separate equations for grassed and cropped watersheds compared to a general equation. Even so, predicted mean annual flow‐weighted concentrations and amounts of soluble P, particulate P, and total N using either monthly or annual soil nutrient data were significantly related to measured values at the 0.01 level and above ( r values ranged from 0.57 to 0.97). Results indicate that seasonal variation in soil nutrient content had less effect on the predictive equations than rainfall and management characteristics. Consequently, these characteristics must be accounted for before the transport equations can be reliably used on an individual runoff event basis.