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Title: Quality of runoff from a small Piedmont pasture with periods of drought

Author
item Endale, Dinku
item Owens, Lloyd
item Fisher, Dwight
item Jenkins, Michael
item Schomberg, Harry
item STEVENS, CAROLINE - Us Environmental Protection Agency (EPA)
item Bonta, James - Jim

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/11/2010
Publication Date: 10/31/2010
Citation: Endale, D.M., Owens, L.B., Fisher, D.S., Jenkins, M., Schomberg, H.H., Stevens, C., Bonta, J.V. 2010. Quality of runoff from a small Piedmont pasture with periods of drought. ASA-CSSA-SSSA International Annual Meetings, October 31-November 2, 2010, Long Beach, CA. CDROM.

Interpretive Summary:

Technical Abstract: Approximately 11% of the Piedmont (1.8 million ha) is used as pastures and hay fields, mostly under low-input management. Animal manure can lead to enrichments of surface soils with nutrients leading to elevated water quality concerns. We present 11 years (1999-2009) of hydrologic and water quality data from a 7.8 ha zero-order catchment with mix of bermuda over-seeded with winter annuals used as a rotational grazing pasture near Watkinsville in the Georgia Piedmont. Mean cattle days (MCD = number of cattle x number of days) was least in December (100) and highest in Feb, Aug and Oct (900-1100), and 500-800 for the remaining months. More cattle grazed the pasture in 2002 to 2004 (MCD ~1000) than the rest of the years (400-600). Rainfall was below the 1250-mm annual average (166 to 397 mm) in 8 of the 11 years, and below the monthly normal in 65.3% of the months. Under these conditions, the statistics (mean ± standard error and range) for runoff causing rainfall, runoff and water quality were: Rainfall-mm (44.6 ± 2.9, 8-129); runoff-mm (5.3 ± 1.0, 0.01-41.1); percent runoff (8.7 ± 1.3, 0.01-65.5); flow weighted concentration (mg/L) - NO3-N (1.1 ± 0.2, 0.04-4.9); NH4-N (1.7 ± 0.7, 0.07-16.87); TN (4.4 ± 0.7, 0.72-15.63); TOC (8.9 ± 0.5, 2.74-15.8); PO4-P (2.3 ± 0.2, 0.83-7.07); TP (2.8 ± 0.3, 0.78-7.59); Fe (0.2 ± 0.02, 0.02-0.55); and Al (0.02 ± 0.01, 0.00-0.17); nutrient load (kg/ha)- NO3-N (0.05±0.01, 0.00-0.22); NH4-N (0.05 ± 0.01, 0.00-0.29); TN (0.22 ± 0.06, 0.00-1.26); TOC (4.66 ± 4.18, 0.00-134); PO4-P (0.13 ± 0.03, 0.00-0.64); TP (0.13 ± 0.03, 0.00-0.51); Fe (0.02 ± 0.02, 0.00-0.11); and Al (0.00 ± 0.00, 0.00-0.002). Only the P-release was, therefore, of concern, most of which must have come from the animal manure and not from management input.