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This article in SSSAJ

  1. Vol. 37 No. 3, p. 424-427
     
    Received: Sept 5, 1972


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doi:10.2136/sssaj1973.03615995003700030032x

Phosphorus Losses from Four Agricultural Watersheds on Missouri Valley Loess1

  1. G. E. Schuman,
  2. R. G. Spomer and
  3. R. F. Piest2

Abstract

Abstract

Phosphorus losses from four field-size experimental watersheds at Treynor, Iowa, were measured during 1969, 1970, and 1971. A contour-planted corn watershed and a pasture watershed were fertilized at the recommended P rate (39 kg/ha). A level-terraced and a second contour-planted corn watershed were fertilized at 2.5 times this rate. At the high level of P fertilization, phosphorus loss by surface runoff from the contour-planted corn watershed was 0.495 kg/ha in 1969, 1.034 kg/ha in 1970, and 2.130 kg/ha in 1971. Level terraces greatly reduced P loss by reducing runoff and erosion.

Water samples for all runoff events taken above the overfall of each watershed gully contained considerably more inorganic P in solution than samples taken at the weir site, 70 to 230 m downstream. This reduction in solution P was caused by the adsorption of P by the additional suspended soil material entering the stream from gully erosion.

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