Livestock grazing effects on phosphorus cycling in watersheds

Shewmaker, Glenn E. (1999) Livestock grazing effects on phosphorus cycling in watersheds. pp. 53-60. In: Tanaka, John A. (ed.) Proc. Riparian and Watershed Management in the Interior Northwest: An Interdisplinary Perspective Symp. USA-OR-La Grande, 1998/09/10-12.

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Abstract

Elevated phosphorus (P) loading of wetlands, streams, lakes, and reservoirs can occur from nonpoint
sources such as grazing of uplands, wet meadows, and palustrine wetlands. Erosion caused by livestock grazing
or any activity will increase the total P load in streams; however, herbivores can also harvest P from forage and
export a significant amount of P from the watershed. Some land managers fail to recognize that the P taken up
by plants will continue to cycle through soil and water. Dissolved P or P attached to soil particles suspended in
water are the primary vectors of P movement in a watershed. Herbivores add another vector with more opportunities
to export P from the watershed. Using best management practices such as rotational grazing, buffer strips
next to wetlands, and proper irrigation management should reduce overland flow and streambank erosion.
Livestock grazing should harvest and remove a significant amount of P from the ecosystem by incorporation
into bone and tissue mass of growing animals and beef export from the basin. The Phosphorus Uptake and
Removal from Grazed Ecosystem (PURGE) model uses three separate methods to estimate P retention in cattle,
and using limits of the input variables, predicted a range from 4 to 50 Mg P could be removed annually from
17,700 ha of pasture in the Cascade Reservoir watershed in west-central Idaho. With proper grazing management,
cattle should be part of a long-term solution to P loading and improvement of water quality in Cascade
Reservoir.

Item Type:	Conference or Workshop Item (Paper)
NWISRL Publication Number:	0988
Additional Information:	John A. Tanaka is a compiler, not an editor **A.K.A NWISRL PUBLICATION 988a**
Subjects:	Animal > Animal health Mass Import - autoclassified (may be erroneous)
Depositing User:	Dan Stieneke
Date Deposited:	20 Nov 2010 21:56
Last Modified:	17 Nov 2016 15:52
Item ID:	915
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/915