Colloidal phosphorus in surface runoff and water extracts from semiarid soils of the Western United States

Fósforo Coloidal en Deslaves Superficiales y Extractos de Agua de Suelos Semiáridos del Oeste de Estados Unidos

Turner, Benjamin L. and Kay, Mary A. and Westermann, Dale T. (2004) Colloidal phosphorus in surface runoff and water extracts from semiarid soils of the Western United States. Journal of Environmental Quality. 33:1464-1472.

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Abstract

Colloidal particles in runoff may have an important role in P transfer
from soils to waterbodies, but remain poorly understood. We
investigated colloidal molybdate-reactive phosphorus (MRP) in surface
runoff and water extracts of calcareous arable soils from the
semiarid western United States. Colloidal MRP was determined by
ultrafiltration and operationally defined as MRP associated with particles
between 1µm and 1 nm diameter, although a smaller pore-size
filter (0.3 nm) was used to define the lower size limit of colloids in
water extracts. In surface runoff from three calcareous soils generated
by simulated sprinkler irrigation, colloidal MRP concentrations ranged
between 0.16 and 3.07 1LM, constituting between 11 and 56% of the
MRP in the <1-gm fraction. Concentrations were strongly correlated
with agronomic and environmental soil-test P concentrations for individual
soils. Water extracts of a range of similar soils contained two
size fractions of colloidal MRP: a larger fraction (1.0-0.2um) probably
associated with fine clays, and a smaller fraction (3-0.3 nm) probably
associated with Ca–phosphate minerals. Colloidal MRP was solubilized
in the acidic medium of the colorimetric detection procedure,
suggesting that a fraction of the filterable MRP in runoff from calcareous
soils may not be as readily bioavailable as free phosphate in
waterbodies. Our results suggest that colloidal MRP is an important
but poorly understood component of P transfer in runoff from calcareous
western U.S. soils and should be given greater consideration in
mechanistic studies of the P transfer process.

Item Type:	Article
NWISRL Publication Number:	1127
Subjects:	Irrigation > Furrow irrigation > Runoff losses > Nutrients Mass Import - autoclassified (may be erroneous)
Depositing User:	Dan Stieneke
Date Deposited:	20 Nov 2010 21:49
Last Modified:	03 Nov 2016 16:11
Item ID:	1
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/1