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TECHNICAL REPORTS

Landscape and Watershed Processes

Nitrogen and Phosphorus Status of Soils and Trophic State of Lakes Associated with Forage-Based Beef Cattle Operations in Florida

^a USDA-ARS, Subtropical Agricultural Research Station, Brooksville, FL 34601
^b USDA-NRCS, 2614 NW 43rd Street, Gainesville, FL 32606-6611
^c Resources Data Section, Southwest Florida Water Management District, Tampa, FL 33637

^* Corresponding author (gcsigua{at}ifas.ufl.edu)

Received for publication June 20, 2005. Forage-based livestock systems have been implicated as major contributors to deteriorating water quality, particularly for phosphorus (P) from commercial fertilizers and manures affecting surface and ground water quality. Little information exists regarding possible magnitudes of nutrient losses from pastures that are managed for both grazing and hay production and how these might impact adjacent bodies of water. We examined the changes that have occurred in soil fertility levels of rhizoma peanut (Arachis glabrata Benth.)-based beef cattle pastures (n = 4) in Florida from 1988 to 2002. These pastures were managed for grazing in spring followed by haying in late summer and were fertilized annually with P (39 kg P₂O₅ ha^–1) and K (68 kg K₂O ha^–1). Additionally, we investigated trends in water quality parameters and trophic state index (TSI) of lakes (n = 3) associated with beef cattle operations from 1993 to 2002. Overall, there was no spatial or temporal buildup of soil P and other crop nutrients despite the annual application of fertilizers and daily in-field loading of animal waste. In fact, soil fertility levels showed a declining trend for crop nutrient levels, especially soil P (y = 146.57 – 8.14 x year; r² = 0.75), even though the fields had a history of P fertilization and the cattle were rotated into the legume fields. Our results indicate that when nutrients are not applied in excess, cow-calf systems are slight exporters of P, K, Ca, and Mg through removal of cut hay. Water quality in lakes associated with cattle production was "good" (30–46 TSI) based on the Florida Water Quality Standard. These findings indicate that properly managed livestock operations may not be major contributors to excess loads of nutrients (especially P) in surface water.

Abbreviations: DSSP, degree of soil saturation with phosphorus • RP, rhizoma peanuts • STARS, Subtropical Agricultural Research Station • TN, total nitrogen • TP, total phosphorus • TSI, trophic state index

This article has been cited by other articles:

				G. C. Sigua, W.-J. Kang, and S. W. Coleman Soil Profile Distribution of Phosphorus and Other Nutrients following Wetland Conversion to Beef Cattle Pasture J. Environ. Qual., October 27, 2006; 35(6): 2374 - 2382. [Abstract] [Full Text] [PDF]